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PT J
AU Arantes, GM
   Chaimovich, H
TI Thiolysis and alcoholysis of phosphate tri- and monoesters with alkyl
   and aryl leaving groups. An ab initio study in the gas phase
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID QUANTUM-MECHANICAL CALCULATIONS; MOLECULAR-ORBITAL METHODS;
   GAUSSIAN-BASIS SETS; TRIMETHYL PHOSPHATE; PHOTOELECTRON-SPECTROSCOPY;
   AQUEOUS-SOLUTION; INFRARED-SPECTROSCOPY; PROTEIN PHOSPHATASES;
   CHEMICAL-REACTIONS; ESTER HYDROLYSIS
AB Phosphate esters are important compounds in living systems. Their
   biological reactions with alcohol and thiol nucleophiles are catalyzed
   by a large superfamily,if phosphatase enzymes. However, very little is
   known about the intrinsic reactivity of these nucleophiles with
   phosphorus centers. We have performed ab initio calculations on the
   thiolysis and alcoholysis at phosphorus of trimethyl phosphate,
   dimethyl phenyl phosphate, methyl phosphate, and phenyl phosphate.
   Results in the gas phase are a reference for the study of the intrinsic
   reactivity of these compounds. Thiolysis of triesters was much slower
   and less favorable than the corresponding alcoholysis. Triesters
   reacted through an associative mechanism. Monoesters can react by both
   associative and dissociative mechanisms. The basicity of the attacking
   and leaving groups and the possibility of proton transfers can modulate
   the reaction mechanisms. Intermediates formed along associative
   reactions did not follow empirically proposed rules for ligand
   positioning. Our calculations also allow re-interpretation of some
   experimental results, and new experiments are proposed to trace
   reactions that are normally not observed, both in the gas phase and in
   solution.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Arantes, GM, Univ Sao Paulo, Inst Quim, Av Lineu Prestes 748,
   BR-05508900 Sao Paulo, Brazil.
EM gma@dinamicas.art.br
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NR 72
TC 3
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JUN 30
PY 2005
VL 109
IS 25
BP 5625
EP 5635
PG 11
SC Chemistry, Physical
GA 940CZ
UT ISI:000230122600013
ER

PT J
AU Rego, LGC
   Abuabara, SG
   Batista, VS
TI Model study of coherent quantum dynamics of hole states in
   functionalized semiconductor nanostructures
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID HETEROGENEOUS ELECTRON-TRANSFER; CHARGE-TRANSFER; FEMTOSECOND
   SPECTROSCOPY; MOLECULAR-DYNAMICS; SOLAR-CELLS; TIO2; SYSTEMS;
   DECOHERENCE; ENVIRONMENT; NANOPARTICLES
AB Functionalization of semiconductor nanocrystals can be achieved by
   anchoring organic ligands to the surface dangling bonds. The resulting
   surface complexes often introduce electronic states in the
   semiconductor band gap. These interband states sensitize the host
   material for photoabsorption at frequencies characteristic of the
   molecular adsorbates, leading to the well-known process of
   photoexcitation and subsequent femtosecond interfacial electron
   transfer. This paper investigates the relaxation dynamics of hole
   states, energetically localized deep in the semiconductor band gap,
   after the ultrafast electron-hole pair separation due to interfacial
   electron transfer. Mixed quantum-classical methods, based on mean-field
   nuclear dynamics approximated by ab initio density functional theory
   molecular dynamics simulations, reveal superexchange hole tunneling
   between adjacent adsorbate molecules in a model study of functionalized
   TiO2-anatase nanostructures. It is shown that electronic coherences can
   persist for hundreds of picoseconds under cryogenic and vacuum
   conditions, despite the partial intrinsic decoherence induced by
   thermal ionic motion, providing results of broad theoretical and
   experimental interest. (c) 2005 American Institute of Physics.
C1 Univ Fed Santa Catarina, Dept Phys, BR-88040900 Florianopolis, SC, Brazil.
   Yale Univ, Dept Chem, New Haven, CT 06520 USA.
RP Rego, LGC, Univ Fed Santa Catarina, Dept Phys, BR-88040900
   Florianopolis, SC, Brazil.
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NR 53
TC 4
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD APR 15
PY 2005
VL 122
IS 15
AR 154709
DI ARTN 154709
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 927HQ
UT ISI:000229185400044
ER

PT J
AU Zhang, PH
   Capaz, RB
   Cohen, ML
   Louie, SG
TI Theory of sodium ordering in NaxCoO2
SO PHYSICAL REVIEW B
LA English
DT Article
ID ELECTRON-GAS; SYSTEMS; COO2
AB The ordering of Na ions in NaxCoO2 is investigated systematically by
   combining detailed density functional theory (DFT) studies with model
   calculations. Various ground state ordering patterns are identified,
   and they are in excellent agreement with available experimental
   results. Our results suggest that the primary driving force for the Na
   ordering is the screened Coulomb interaction among Na ions. Possible
   effects of the Na ordering on the electronic structure of the CoO2
   layer are discussed. We propose that the nonexistence of a charge
   ordered insulating state at x=2/3 is due to the lack of a commensurate
   Na ordering pattern, whereas an extremely stable Na ordering at x=0.5
   enhances the charge ordering tendency, resulting in an insulating state
   as observed experimentally.
C1 Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Lawrence Berkeley Lab, Div Sci Mat, Berkeley, CA 94720 USA.
   Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, Brazil.
RP Zhang, PH, Univ Calif Berkeley, Dept Phys, Berkeley, CA 94720 USA.
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NR 24
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD APR
PY 2005
VL 71
IS 15
AR 153102
DI ARTN 153102
PG 4
SC Physics, Condensed Matter
GA 921KJ
UT ISI:000228762900002
ER

PT J
AU Freire, RO
   Rocha, GB
   Simas, AM
TI Sparkle model for the calculation of lanthanide complexes: AM1
   parameters for Eu(III), Gd(III), and Tb(III)
SO INORGANIC CHEMISTRY
LA English
DT Article
ID CAMBRIDGE STRUCTURAL DATABASE; IMAGING CONTRAST AGENTS; SIMPLE OVERLAP
   MODEL; RARE-EARTH ELEMENTS; AB-INITIO; GADOLINIUM COMPLEXES;
   INTERMEDIATE NEGLECT; ELECTRONIC-STRUCTURE; CRYSTAL-STRUCTURES; LU
AB Our previously defined Sparkle model (Inorg. Chem. 2004, 43, 2346) has
   been reparameterized for Eu(III) as well as newly parameterized for
   Gd(III) and Tb(III). The parameterizations have been carried out in a
   much more extensive manner, aimed at producing a new, more accurate
   model called Sparkle/AM1, mainly for the vast majority of all Eu(III),
   Gd(I I), and Tb(III) complexes, which possess oxygen or nitrogen as
   coordinating atoms. All such complexes, which comprise 80% of all
   geometries present in the Cambridge Structural Database for each of the
   three ions, were classified into seven groups. These were regarded as a
   "basis" of chemical ambiance around a lanthanide, which could span the
   various types of ligand environments the lanthanide ion could be
   subjected to in any arbitrary complex where the lanthanide ion is
   coordinated to nitrogen or oxygen atoms. From these seven groups, 15
   complexes were selected, which were defined as the parameterization set
   and then were used with a numerical multidimensional nonlinear
   optimization to find the best parameter set for reproducing chemical
   properties. The new parametorizations yielded an unsigned mean error
   for all interatomic distances between the Eu(III) ion and the ligand
   atoms of the first sphere of coordination (for the 96 complexes
   considered in the present paper) of 0.09 angstrom, an improvement over
   the value of 0.28 angstrom for the previous model and the value of 0.68
   angstrom for the first model (Chem. Phys. Lett. 1994, 227, 349).
   Similar accuracies have been achieved for Gd(III) (0.07 angstrom, 70
   complexes) and Tb(III) (0.07 A, 42 complexes). Qualitative improvements
   have been obtained as well; nitrates now coordinate correctly as
   bidentate ligands. The results, therefore, indicate that Eu(Ill),
   Gd(III), and Tb(III) Sparkle/AM1 calculations possess geometry
   prediction accuracies for lanthanide complexes with oxygen or nitrogen
   atoms in the coordination polyhedron that are competitive with present
   day ab initio/effective core potential calculations, while being
   hundreds of times faster.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540 Recife, PE, Brazil.
RP Simas, AM, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540
   Recife, PE, Brazil.
EM simas@ufpe.br
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NR 70
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0020-1669
J9 INORG CHEM
JI Inorg. Chem.
PD MAY 2
PY 2005
VL 44
IS 9
BP 3299
EP 3310
PG 12
SC Chemistry, Inorganic & Nuclear
GA 922CL
UT ISI:000228813400046
ER

PT J
AU Cabral, BJC
   Canuto, S
TI The enthalpy of the O-H bond hornolytic dissociation: Basis-set
   extrapolated density functional theory and coupled cluster calculations
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID CORRELATION-ENERGY; GAS-PHASE; WAVE-FUNCTIONS; ENERGETICS; MOLECULES;
   EXCHANGE; PHENOL; CONVERGENCE; RESPECT
AB The O-H bond homolytic dissociation of water, hydrogen peroxide,
   methanol, phenol, and cathecol is investigated by density functional
   theory (DFT) and ab initio coupled cluster calculations. DFT results
   are based on several recently proposed functionals, including B98, PBE,
   VSXC, and HCTH. The dependence of DFT results on the basis-set size is
   discussed using correlation-consistent polarized (cc-pVXZ) basis-sets
   (X = 2-5). A scheme proposed by Truhlar is used to extrapolate CCSD
   energies. Basis-set extrapolated CCSD results for the O-H bond
   homolytic dissociation enthalpies of phenol and cathecol are in
   excellent agreement with experimental information. (c) 2005 Elsevier
   B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Lisbon, Dept Quim & Bioquim, P-1649003 Lisbon, Portugal.
   Univ Lisbon, Grp Fis Matemat, P-1649003 Lisbon, Portugal.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
EM canuto@if.usp.br
CR ANGEL LA, 2004, J PHYS CHEM A, V108, P8346
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NR 35
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 2
PY 2005
VL 406
IS 4-6
BP 300
EP 305
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 920FY
UT ISI:000228676000004
ER

PT J
AU Ferretti, A
   Calzolari, A
   Di Felice, R
   Manghi, F
   Caldas, MJ
   Nardelli, MB
   Molinari, E
TI First-principles theory of correlated transport through nanojunctions
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID STATES; HOLE
AB We report the inclusion of electron-electron correlation in the
   calculation of transport properties within an ab initio scheme. A key
   step is the reformulation of Landauer's approach in terms of an
   effective transmittance for the interacting electron system. We apply
   this framework to analyze the effect of shortrange interactions on Pt
   atomic wires and discuss the coherent and incoherent correction to the
   mean-field approach.
C1 INFM, Natl Ctr NanoStruct & BioSyst Surfaces, I-41100 Modena, Italy.
   Univ Modena, Dipartimento Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
   N Carolina State Univ, Dept Phys, Raleigh, NC 27695 USA.
   Oak Ridge Natl Lab, CCS, CSM, Oak Ridge, TN 37831 USA.
RP Ferretti, A, INFM, Natl Ctr NanoStruct & BioSyst Surfaces, I-41100
   Modena, Italy.
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NR 27
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD MAR 25
PY 2005
VL 94
IS 11
AR 116802
DI ARTN 116802
PG 4
SC Physics, Multidisciplinary
GA 910IA
UT ISI:000227923200049
ER

PT S
AU Fileti, EE
   Coutinho, K
   Canuto, S
TI Is there a favorite isomer for hydrogen-bonded methanol in water?
SO ADVANCES IN QUANTUM CHEMISTRY, VOL 47
SE ADVANCES IN QUANTUM CHEMISTRY
LA English
DT Review
ID CARLO-QUANTUM-MECHANICS; SEQUENTIAL MONTE-CARLO; AB-INITIO CALCULATION;
   THERMODYNAMIC PROPERTIES; AQUEOUS-SOLUTIONS; LIQUID WATER; MIXTURES;
   SIMULATIONS; TRANSITION; ENERGIES
AB Sequential Monte Carlo/quantum-mechanical calculations of the
   interaction energy of hydrogen-bonded methanol in liquid water give the
   same result for methanol acting either as the proton donor or the
   proton acceptor. For the complex-optintized cases, methanol acting as
   the proton acceptor, CH3HO center dot center dot center dot H2O, is
   more stable than the proton donor, CH3OH center dot center dot center
   dot OH2, by similar to 0.5 kcal/mol. In the case of methanol in liquid
   water, at room temperature, statistically converged results, using
   counterpoise corrected MP2/aug-cc-pVDZ calculations, lead to the same
   binding energy in both cases.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi Das Cruzes, CIIB, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Fileti, EE, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 38
TC 3
PU ELSEVIER ACADEMIC PRESS INC
PI SAN DIEGO
PA 525 B STREET, SUITE 1900, SAN DIEGO, CA 92101-4495 USA
SN 0065-3276
J9 ADVAN QUANTUM CHEM
PY 2004
VL 47
BP 51
EP 63
PG 13
GA BBV45
UT ISI:000228024400004
ER

PT J
AU MacLeod, JM
   Miwa, RH
   Srivastava, GP
   McLean, AB
TI The electronic origin of contrast reversal in bias-dependent STM images
   of nanolines
SO SURFACE SCIENCE
LA English
DT Article
DE silicon; bismuth; density functional calculations; scanning tunneling
   microscopy; growth; low index single crystal surfaces; self-assembly;
   surface electronic phenomena
ID SCANNING-TUNNELING-MICROSCOPY; SURFACE-STRUCTURE; SI(100) SURFACE;
   AB-INITIO; BISMUTH; SI(001); LINES; NANOWIRE
AB Self-organized Bi lines that are only 1.5 nm wide can be grown without
   kinks or breaks on Si(001) surfaces to lengths of up to 500 nm.
   Constant-current topographical images of the lines, obtained with the
   scanning tunneling microscope, have a striking bias dependence.
   Although the lines appear darker than the Si terraces at biases below
   approximate to\1.2\ V, the contrast reverses at biases above
   approximate to\1.5\ V. Between these two ranges the lines and terraces
   are of comparable brightness. It has been suggested that this bias
   dependence may be due to the presence of a semiconductor-like energy
   gap within the line. Using ab initio calculations it is demonstrated
   that the energy gap is too small to explain the experimentally observed
   bias dependence. Consequently, at this time, there is no compelling
   explanation for this phenomenon. An alternative explanation is proposed
   that arises naturally from calculations of the tunneling current, using
   the Tersoff-Hamann approximation, and an examination of the electronic
   structure of the line. (C) 2004 Elsevier B.V. All rights reserved.
C1 Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada.
   Univ Fed Uberlandia, Fac Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
RP McLean, AB, Queens Univ, Dept Phys, Kingston, ON K7L 3N6, Canada.
EM mclean@physics.queensu.ca
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NR 24
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD FEB 10
PY 2005
VL 576
IS 1-3
BP 116
EP 122
PG 7
SC Chemistry, Physical
GA 895OL
UT ISI:000226872600016
ER

PT J
AU Ramalho, TC
   Buhl, M
TI Probing NMR parameters, structure and dynamics of 5-nitroimidazole
   derivatives. Density functional study of prototypical radiosensitizers
SO MAGNETIC RESONANCE IN CHEMISTRY
LA English
DT Article
DE NMR; N-15 NMR; radiosensitizers; molecular dynamics simulations;
   solvent effects; spin-spin coupling constants
ID POLARIZABLE CONTINUUM MODEL; VERTICAL ELECTRON-AFFINITY;
   CHEMICAL-SHIFTS; AB-INITIO; CORRELATION-ENERGY; SHIELDING TENSORS;
   DRUG-RESISTANCE; SPECTROSCOPY; SYSTEMS; DESIGN
AB The N-15 chemical shifts of metronidazole (1), secnidazole (2),
   nimorazole (3) and tinidazole (4), radiosensitizers based on the
   5-nitroimidazole motif, are reported. A detailed computational study of
   1 is presented, calling special attention to the performance of various
   theoretical methods in reproducing the C-13 and N-15 data observed in
   solution. The most sophisticated approach involves density
   functional-based Car-Parrinello molecular dynamics simulations (CPMD)
   of 1 in aqueous solution (BP86 level) and averaging chemical shifts
   over snapshots from the trajectory. In the NMR calculations for these
   snapshots (performed at the B3LYP level), a small number of discrete
   water molecules are retained, and the remaining bulk solution effects
   are included via a polarizable continuum model (PCM). A similarly good
   accord with experiment is obtained from much less involved, static
   geometry optimization and NMR computation of pristine 1 employing a PCM
   approach. Solvent effects on delta(N-15), which are of the order of up
   to 20 ppm, are not due to changes in geometric parameters upon
   solvation, but arise from the direct response of the electronic
   wavefunction to the presence of the solvent, which can be represented
   by discrete molecules and/or the dielectric bulk. Copyright (C) 2004
   John Wiley Sons, Ltd.
C1 Max Planck Inst Kohlenforsch, D-45470 Mulheim, Germany.
   Inst Militar Engn, Dept Quim, BR-22290270 Rio De Janeiro, RJ, Brazil.
RP Buhl, M, Max Planck Inst Kohlenforsch, Kaiser Wilhelm Pl 1, D-45470
   Mulheim, Germany.
EM buel@mpi-muelheim.mpg.de
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NR 71
TC 3
PU JOHN WILEY & SONS LTD
PI CHICHESTER
PA THE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLAND
SN 0749-1581
J9 MAGN RESON CHEM
JI Magn. Reson. Chem.
PD FEB
PY 2005
VL 43
IS 2
BP 139
EP 146
PG 8
SC Chemistry, Multidisciplinary; Chemistry, Physical; Spectroscopy
GA 892KR
UT ISI:000226650000005
ER

PT J
AU Ludwig, V
   Coutinho, K
   Canuto, S
TI Sequential classical-quantum description of the absorption spectrum of
   the hydrated electron
SO PHYSICAL REVIEW B
LA English
DT Article
ID MOLECULAR-DYNAMICS SIMULATION; MONTE-CARLO; SOLVATED ELECTRON; EXCESS
   ELECTRON; INTEGRAL-EQUATION; WATER CLUSTERS; LIQUID WATER; AB-INITIO;
   TEMPERATURE; MECHANICS
AB A localized state of the electron in water is assumed to study the
   absorption spectrum of the hydrated electron. A classical Monte Carlo
   statistical mechanics simulation is used to generate the structure of
   water in the field of the hydrated electron. These structures are used
   in quantum mechanical calculations of the absorption spectrum using
   time-dependent density-functional theory. The statistically converged
   spectral distribution is in good agreement with experiment. The value
   obtained here for the maximum of the absorption profile is 1.70 eV with
   a half-width of 0.90 eV, in comparison with the corresponding
   experimental values of 1.725 and 0.84 eV.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi das Cruzes, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
EM canuto@if.usp.br
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NR 44
TC 3
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD DEC
PY 2004
VL 70
IS 21
AR 214110
DI ARTN 214110
PG 4
SC Physics, Condensed Matter
GA 884UF
UT ISI:000226111400043
ER

PT J
AU Rossato, J
   Baierle, RJ
   Fazzio, A
   Mota, R
TI Vacancy formation process in carbon nanotubes: First-principles approach
SO NANO LETTERS
LA English
DT Article
ID ELECTRONIC-PROPERTIES; AB-INITIO; SYSTEMS; DEFORMATION; DEFECTS
AB The electronic and structural properties of a single-walled carbon
   nanotube (SWNT) under mechanical deformation are studied using
   first-principles calculations based on the density functional theory. A
   force is applied over one particular C-atom with enough strength to
   break the chemical bonds between the atom and its nearest neighbors,
   leading to a final configuration represented by one tube with a vacancy
   and an isolated C-atom inside the tube. Our investigation demonstrates
   that there is a tendency that the first bond to break is the one most
   parallel possible to the tube axis and, after, the remaining two other
   bonds are broken. The analysis of the electronic charge densities, just
   before and after the bonds breaking, helps to elucidate how the vacancy
   is formed on an atom-by-atom basis. In particular, for tubes with a
   diameter around 11 Angstrom, it is shown that the chemical bonds start
   to break only when the externally applied force is of the order of 14
   nN and it is independent of the chirality. The formation energies for
   the vacancies created using this process are almost independent of the
   chirality, otherwise the bonds broken and the reconstruction are
   dependent.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Baierle, RJ, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria,
   RS, Brazil.
EM rbaierle@smail.ufsm.br
CR AJAYAN PM, 1998, PHYS REV LETT, V81, P1437
   BAIERLE RJ, 2001, PHYS REV B, V64
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CHARLIER JC, 1996, PHYS REV B, V53, P11108
   DAI HJ, 2002, SURF SCI, V500, P218
   FAGAN SB, 2003, NANO LETT, V3, P289
   FAGAN SB, 2003, PHYS REV B, V67
   HANSSON A, 2000, PHYS REV B, V62, P7639
   KRASHENINNIKOV AV, 2001, PHYS REV B, V63
   KRASHENINNIKOVA AV, 2002, J VAC SCI TECHNOL B, V20, P728
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   TOULLIER N, 1993, PHYS REV B, V43, P1991
   ZHU YF, 1999, APPL SURF SCI, V137, P83
NR 18
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1530-6984
J9 NANO LETT
JI Nano Lett.
PD JAN
PY 2005
VL 5
IS 1
BP 197
EP 200
PG 4
SC Chemistry, Multidisciplinary; Materials Science, Multidisciplinary
GA 887TE
UT ISI:000226327600038
ER

PT J
AU Freire, RO
   Rocha, GB
   Albuquerque, RQ
   Simas, AM
TI Efficacy of the semiempirical sparkle model as compared to ECP
   ab-initio calculations for the prediction of ligand field parameters of
   europium(III) complexes
SO JOURNAL OF LUMINESCENCE
LA English
DT Article
DE sparkle model; semiempirical methods; ab-initio methods; europium (III)
   complexes
ID CAMBRIDGE STRUCTURAL DATABASE; SIMPLE OVERLAP MODEL; LANTHANIDE
   COMPLEXES; SPECTROSCOPIC PROPERTIES; SUPRAMOLECULAR DEVICES; INTENSITY
   PARAMETERS; CRYSTAL-STRUCTURES; LUMINESCENCE; CHEMISTRY; MECHANISM
AB The second version of the sparkle model for the calculation of
   lanthanide complexes (SMLC II) as well as ab-initio calculations
   (HF/STO-3G and HF/3-21G) have been used to calculate the geometries of
   a series of europium (III) complexes with different coordination
   numbers (CN = 7, 8 and 9), ligating atoms (O and N) and ligands (mono,
   bi and polydentate). The so-called ligand field parameters, B-q(k)'s,
   have been calculated from both SMLC II and ab-initio optimized
   structures and compared to the ones calculated from crystallographic
   data. The results show that the SMLC II model represents a significant
   improvement over the previous version (SMLC) and has given good results
   when compared to ab-initio methods, which demand a much higher
   computational effort. Indeed, ab-initio methods take around a hundred
   times more computing time than SMLC. As such, our results indicate that
   our sparkle model can be a very useful and a fast tool when applied to
   the prediction of both ground state geometries and ligand field
   parameters of europium (III) complexes. (C) 2004 Elsevier B.V. All
   rights reserved.
C1 UFPE, Dept Quim Fundamental, CCEN, BR-50590470 Recife, PE, Brazil.
RP Simas, AM, UFPE, Dept Quim Fundamental, CCEN, BR-50590470 Recife, PE,
   Brazil.
EM simas@ufpe.br
CR ALBUQUERQUE RQ, 2000, CHEM PHYS LETT, V331, P519
   ALLEN FH, 2002, ACTA CRYSTALLOGR B 3, V58, P380
   ALLEN FH, 2002, ACTA CRYSTALLOGR B 3, V58, P407
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   ANIKIN NA, 2003, PHYSCHEM0304005 CPS
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   BAZIN H, 2003, J FLUORESC, V12, P245
   BRUNO IJ, 2002, ACTA CRYSTALLOGR B 3, V58, P389
   CONSENTINO U, 2002, J AM CHEM SOC, V124, P4901
   COSENTINO U, 1997, J MOL STRUC-THEOCHEM, V392, P75
   DACOSTA NB, 2001, J MOL STRUC-THEOCHEM, V545, P131
   DEANDRADE AVM, 1994, CHEM PHYS LETT, V349, P227
   DEMESQUITA ME, 2002, INORG CHEM COMMUN, V5, P292
   DEMESQUITA ME, 2003, J SOLID STATE CHEM, V171, P183
   DEMESQUITA ME, 2004, J ALLOY COMPD, V366, P124
   DEMESQUITA ME, 2004, J ALLOY COMPD, V374, P320
   DESA GF, 2000, COORDIN CHEM REV, V196, P165
   DOLG M, 1989, THEOR CHIM ACTA, V75, P173
   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
   HEMMILA I, 1991, APPL FLUORESCENCE IM
   HEMMILA I, 1995, J ALLOY COMPD, V225, P480
   KURITA N, 2003, CHEM PHYS LETT, V372, P583
   LEHN JM, 1990, ANGEW CHEM INT EDIT, V29, P1304
   MALTA OL, 1982, CHEM PHYS LETT, V87, P27
   MALTA OL, 1997, J LUMIN, V75, P255
   MUKKALA VM, 1992, HELV CHIM ACTA, V75, P1578
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   OHNO K, 2001, CHEM PHYS LETT, V341, P387
   OHNO K, 2001, J AM CHEM SOC, V123, P8161
   PICHIERRI F, 2000, CHEM PHYS LETT, V322, P536
   PIETRASZKIEWICZ M, 1993, PURE APPL CHEM, V65, P563
   PORCHER P, 1999, PCCP PHYS CHEM CH PH, V1, P397
   RABBE C, 2000, THEOR CHEM ACC, V104, P280
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   ROCHA GB, 1999, MATER SCI FORUM, V315, P400
   ROCHA GB, 2002, THESIS U FEDERAL PER
   ROCHA GB, 2004, INORG CHEM, V43, P2346
   SABBATINI N, 1993, COORDIN CHEM REV, V123, P201
   STEWART JJP, 1993, MOPAC 93 00 MAN
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   TAYLOR DL, 1986, APPL FLUORESCENCE BI
   YANG W, 2003, J PHYS CHEM B, V107, P5986
NR 42
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2313
J9 J LUMINESC
JI J. Lumines.
PD JAN
PY 2005
VL 111
IS 1-2
BP 81
EP 87
PG 7
SC Optics
GA 885JQ
UT ISI:000226153300010
ER

PT J
AU Martins, JBL
   Longo, E
   Salmon, ODR
   Espinoza, VAA
   Taft, CA
TI The interaction of H-2, CO, CO2, H2O and NH3 on ZnO surfaces: an Oniom
   Study
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID LARGE CLUSTER-MODELS; ZINC-OXIDE SURFACES; PHOTOELECTRON-SPECTROSCOPY;
   AB-INITIO; COORDINATION CHEMISTRY; ELECTRONIC-STRUCTURES;
   CARBON-DIOXIDE; ADSORPTION; HYDROGEN; ZNO(10(1)OVER-BAR0)
AB We have used the Oniom method with three layers in order to study the
   interaction of CO, H-2, H2O, NH3 and CO2 molecules with the ZnO (10
   $(1) over bar $0) surfaces using a (ZnO)348 Cluster model. The layers
   are divided into the high layer at the CCSD level, the medium layer at
   the RHF level and the low level layer using the UFF force field method.
   The orbital and binding energies of the adsorbed molecules, Mulliken
   and ChelpG charges as well as geometrical parameters were analyzed and
   compared with the available experimental and theoretical data. (C) 2004
   Elsevier B.V. All rights reserved.
C1 DMF, Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
RP Taft, CA, DMF, Ctr Brasileiro Pesquisas Fis, R Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, Brazil.
EM catff@terra.com.br
CR AU CT, 1988, SURF SCI, V199, P507
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   DAPRICH S, 1999, J MOL STRUCT THEOCHE, V462, P1
   FRISCH MJ, 2003, GAUSSIAN 03
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   MARTINS JBL, 2000, J MOL STRUC-THEOCHEM, V528, P161
   MORIMOTO T, 1976, J PHYS CHEM-US, V80, P1876
   NAGAO M, 1995, THERMOCHIM ACTA, V253, P221
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   SCHAFTENAAR G, 2000, J COMPUT AID MOL DES, V14, P123
   SOLOMON EI, 1993, CHEM REV, V93, P2623
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NR 28
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD DEC 21
PY 2004
VL 400
IS 4-6
BP 481
EP 486
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 881YU
UT ISI:000225906300037
ER

PT J
AU Fileti, EE
   Chaudhuri, P
   Canuto, S
TI Relative strength of hydrogen bond interaction in alcohol-water
   complexes
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; AB-INITIO; INTERACTION ENERGIES; METHANOL
   COMPLEXES; ELECTRON CORRELATION; QUANTUM-CHEMISTRY; GAS-PHASE;
   CLUSTERS; TRIMERS; SPECTROSCOPY
AB Hydrogen binding energies are calculated for the different isomers of
   1:1 complexes of methanol, ethanol and water using ab initio methods
   from MP2 to CCSD(T). Zero-point energy vibration and counterpoise
   corrections are considered and electron correlation effects are
   analyzed. In methanol-water and ethanol-water the most stable
   heterodimer is the one where the water plays the role of proton donor.
   In methanol-ethanol the two isomers have essentially the same energy
   and no favorite heterodimer could be discerned. The interplay between
   the relative binding energy is briefly discussed in conjunction with
   the incomplete mixing of alcohol-water systems. (C) 2004 Elsevier B.V.
   All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Indian Assoc Cultivat Sci, Dept Theoret Phys, Calcutta 700032, W Bengal, India.
RP Canuto, S, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
EM canuto@if.usp.br
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NR 35
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD DEC 21
PY 2004
VL 400
IS 4-6
BP 494
EP 499
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 881YU
UT ISI:000225906300039
ER

PT J
AU da Silva, AJR
   Fazzio, A
   dos Santos, RR
   Oliveira, LE
TI First principles study of the ferromagnetism in Ga1-xMnxAs
   semiconductors
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID III-V SEMICONDUCTORS; ELECTRONIC-STRUCTURE; TRANSPORT-PROPERTIES; HOLE
   CONCENTRATION; GALLIUM-ARSENIDE; (GA,MN)AS; PSEUDOPOTENTIALS;
   ACCEPTORS; ORIGIN
AB We have performed ab initio calculations within the density-functional
   theory for Ga1-xMnxAs diluted semiconductors. Total energy results
   unambiguously show that a quasi-localized hole, with predominant p-like
   character, surrounds the fully polarized Mn up arrow d(5)-electrons.
   The calculations indicate that the holes form a relatively
   dispersionless impurity band, thus rendering effective-mass
   descriptions of hole states open to challenge. We obtain estimates both
   for the s = 1/2 hole and S = 5/2 Mn exchange coupling, and for the
   distance dependence of the effective Mn-Mn exchange interaction. The
   results demonstrate that the effective Mn-Mn coupling is always
   ferromagnetic, and thus non-RKKY, and is intermediated by the
   antiferromagnetic coupling of each Mn spin to the holes.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
   Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, RJ, Brazil.
   UNICAMP, Inst Fis, BR-13083970 Campinas, SP, Brazil.
RP da Silva, AJR, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, SP, Brazil.
CR ABOLFATH M, 2001, PHYS REV B, V63
   ASKLUND H, 2002, PHYS REV B, V66
   BOUZERAR G, 2003, PHYS REV B, V68
   CHAPMAN RA, 1967, PHYS REV LETT, V18, P443
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   DIETL T, 2001, PHYS REV B, V63
   DOSSANTOS RR, 2002, J PHYS-CONDENS MAT, V14, P3751
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   HAYASHI T, 2001, APPL PHYS LETT, V78, P1691
   KRESSE G, 1993, PHYS REV B, V47, P558
   KRESSE G, 1996, PHYS REV B, V54, P11169
   KRESSE G, 1999, PHYS REV B, V59, P1758
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   MATSUKURA F, 1998, PHYS REV B, V57, R2037
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   SANDRATSKII LM, 2002, PHYS REV B, V66
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   ZHAO YJ, 2004, APPL PHYS LETT, V84, P3753
NR 36
TC 3
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD NOV 24
PY 2004
VL 16
IS 46
BP 8243
EP 8250
PG 8
SC Physics, Condensed Matter
GA 879HC
UT ISI:000225706000014
ER

PT J
AU Coutinho, K
   Cabral, BJC
   Canuto, S
TI Can larger dipoles solvate less? solute-solvent hydrogen bond and the
   differential solvation of phenol and phenoxy
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID CARLO-QUANTUM-MECHANICS; SEQUENTIAL MONTE-CARLO; O-H BOND; AB-INITIO;
   WATER; DENSITY; ACETONITRILE; ENERGETICS; HYDRATION; LIQUIDS
AB Quantum mechanical calculations of the dipole moments and binding
   energies of phenol and phenoxy radical in liquid acetonitrile and water
   are made using hydrogen-bonded configurations extracted from Monte
   Carlo simulations. We contend that the preferential solvation of phenol
   (the lower dipole moment solute) over phenoxy derives from the
   hydrogen-bond shell. The reconciliation with the usual understanding,
   that larger dipole solvates better, is obtained if we consider not the
   dipole moment of the isolated solute but, instead, the average dipole
   moment in solution of the solute-solvent hydrogen-bonded solvation
   shell. (C) 2004 Elsevier B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi Cruzes, CIIB, BR-08701970 Mogi Das Cruzes, SP, Brazil.
   Univ Lisbon, Fac Ciencias, Dept Quim & Bioquim, P-1749016 Lisbon, Portugal.
   Univ Lisbon, Grp Fis Matemat, P-1649003 Lisbon, Portugal.
RP Canuto, S, Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
EM canuto@if.usp.br
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NR 30
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD DEC 1
PY 2004
VL 399
IS 4-6
BP 534
EP 538
PG 5
SC Physics, Atomic, Molecular & Chemical
GA 874ZS
UT ISI:000225389800045
ER

PT J
AU Alvarez-Puebla, RA
   Dos Santos, DS
   Aroca, RF
TI Surface-enhanced Raman scattering for ultrasensitive chemical analysis
   of 1 and 2-naphthalenethiols
SO ANALYST
LA English
DT Article
ID SINGLE-MOLECULE DETECTION; SILVER ISLANDS; SERS; SPECTROSCOPY;
   COLLOIDS; SPECTRA; MONOLAYERS
AB The results of the search for the optimal experimental conditions for
   ultrasentitive chemical analysis of 1-naphthalenethiol (1-NAT) and
   2-naphthalenethiol (2-NAT) using surface-enhanced Raman scattering
   (SERS) are discussed. The report begins with a review of the
   vibrational spectra, including infrared and Raman spectra of the target
   molecules, and the interpretation of the observed frequencies aided by
   local density functional theory (DFT) calculations at the
   B3LYP/6-311G(d,p) level of theory. Several metal nanostructures were
   tested for SERS activity, including island films and colloids of
   silver, gold and copper. Correspondingly, the most effective laser line
   for excitation in the visible and near infrared region was sought. The
   achieved detection limit for 1-naphthalenethiol, and for
   2-naphthalenethiol, on silver nanostructures is in the zeptomole regime.
C1 Univ Windsor, Sch Phys Sci, Mat & Surface Sci Grp, Windsor, ON N9B 3P4, Canada.
   Univ Sao Paulo, Inst Fis Sao Carlos, Dept Fis & Ciencia Mat, BR-13562 Sao Carlos, SP, Brazil.
RP Aroca, RF, Univ Windsor, Sch Phys Sci, Mat & Surface Sci Grp, Windsor,
   ON N9B 3P4, Canada.
EM raroca1@cogeco.ca
CR ABUEITTAH RH, 1972, APPL SPECTROSC, V26, P270
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NR 27
TC 6
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
   ENGLAND
SN 0003-2654
J9 ANALYST
JI Analyst
PY 2004
VL 129
IS 12
BP 1251
EP 1256
PG 6
SC Chemistry, Analytical
GA 874FE
UT ISI:000225335500017
ER

PT J
AU Legoas, SB
   Rodrigues, V
   Ugarte, D
   Galvao, DS
TI Contaminants in suspended gold chains: An ab initio molecular dynamics
   study
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID NANOWIRES; CONDUCTANCE; ATOMS; MICROSCOPY; CLUSTERS; BULK
AB Recently, we have proposed that the origin of anomalously long
   interatomic distances in suspended gold chains could be the result of
   carbon contamination during sample manipulation [S. B. Legoas et al.,
   Phys. Rev. Lett. 88, 076105 (2002)]. More recently, however, other
   works have proposed that hydrogen instead of carbon should be the most
   probable contaminant. We report ab initio molecular dynamics results
   for different temperatures considering different possible contaminants.
   Our results show that at nonzero temperatures (more realistic to
   simulate the experimental conditions) hydrogen may be ruled out and
   carbon atoms remain the best candidate for contamination.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Fed Amazonas, Dept Fis, BR-69077000 Manaus, Amazonas, Brazil.
   Lab Nacl Luz Sincrotron, BR-13084971 Campinas, SP, Brazil.
RP Galvao, DS, Univ Estadual Campinas, Inst Fis Gleb Wataghin, CP 6165,
   BR-13083970 Campinas, SP, Brazil.
EM galvao@ifi.unicamp.br
CR *EPAPS, EPRLTAO93071447 EPAP
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NR 26
TC 5
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD NOV 19
PY 2004
VL 93
IS 21
AR 216103
DI ARTN 216103
PG 4
SC Physics, Multidisciplinary
GA 872PU
UT ISI:000225220500052
ER

PT J
AU Cucinotta, CS
   Ruini, A
   Caldas, MJ
   Molinari, E
TI Ab initio study of chemisorption reactions for carboxylic acids on
   hydrogenated silicon surfaces
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Letter
ID FORMATION MECHANISMS; ALKYL MONOLAYERS; SPECTROSCOPY; CHEMISTRY;
   MOLECULES
AB We study chemisorbed configurations of C3H6O2 on the extended H:Si(100)
   surface, through first-principles density-functional calculations in a
   supercell approach. We demonstrate that oxygen-bonded organic
   monolayers on this silicon substrate is thermodynamically very stable,
   and comparing several Si-O-C and Si-C linked configurations, we find
   that the doubly-O-bonded configuration is favored and should lead to
   ordered SAMs. We find, moreover, that the Si-O-C bridge in this case
   does not block charge transfer from surface to molecule.
C1 Univ Modena, INFM, Natl Ctr NanoStruct & BioSystems Surfaces S3, I-41100 Modena, Italy.
   Univ Modena, Dept Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
RP Cucinotta, CS, Univ Modena, INFM, Natl Ctr NanoStruct & BioSystems
   Surfaces S3, Via Campi 213-A, I-41100 Modena, Italy.
EM c.cucinotta@unimo.it
CR BOUKHERROUB R, 2000, LANGMUIR, V16, P7429
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NR 20
TC 3
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD NOV 11
PY 2004
VL 108
IS 45
BP 17278
EP 17280
PG 3
SC Chemistry, Physical
GA 869OM
UT ISI:000224993900003
ER

PT J
AU Nascimento, CS
   Dos Santos, HF
   De Almeida, WB
TI Theoretical study of the formation of the alpha-cyclodextrin hexahydrate
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID BETA-CYCLODEXTRIN; INCLUSION COMPLEXES; MOLECULAR-STRUCTURE; AB-INITIO;
   WATER; ENERGY; TOPOGRAPHY; CRYSTAL; EQUILIBRIUM; HYDRATION
AB The alpha-ciclodextrin (alpha-CD) consist of six glucopyranose units.
   The crystalline form I of alpha-CD is obtained in the solid state as
   the hexahydrate structure (alpha-CD . 6H(2)O) containing two water
   molecules inside and four outside the cavity. In this Letter, we report
   a quantum chemical study of the formation of the alpha-cyclodextrin
   hexahydrate using the semiempirical PM3 method and Density Functional
   Theory (BLYP/6-31G(d,p) calculation). Distinct chemical processes are
   considered for the calculation of the thermodynamic properties. We
   found a good agreement with experimental data for entropy, enthalpy and
   Gibbs free energy, which add support to the theoretical approach we
   used. (C) 2004 Elsevier B.V. All rights reserved.
C1 Univ Fed Minas Gerais, Dept Quim, ICEx, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
   UFJF, Dept Quim, ICE, NEQC, BR-36036330 Juiz De Fora, MG, Brazil.
RP De Almeida, WB, Univ Fed Minas Gerais, Dept Quim, ICEx, LQCMM, Campus
   Univ, BR-31270901 Belo Horizonte, MG, Brazil.
EM wagnar@netuno.qui.ufmg.br
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NR 35
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD OCT 21
PY 2004
VL 397
IS 4-6
BP 422
EP 428
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 863DN
UT ISI:000224541000027
ER

PT J
AU Pliego, JR
TI Basic hydrolysis of formamide in aqueous solution: a reliable
   theoretical calculation of the activation free energy using the
   cluster-continuum model
SO CHEMICAL PHYSICS
LA English
DT Article
ID SOLVATION FREE-ENERGY; QUANTUM-MECHANICAL CALCULATIONS;
   DIMETHYL-SULFOXIDE SOLUTIONS; DENSITY-FUNCTIONAL THEORY; BETA-LACTAM
   ANTIBIOTICS; MONTE-CARLO SIMULATIONS; AB-INITIO; MOLECULAR-DYNAMICS;
   HYDROXIDE ION; GAS-PHASE
AB The first step of the reaction of the hydroxide ion with formamide in
   aqueous solution was studied by high level ab initio calculations and
   including the solvent effect through the cluster-continuum model. This
   hybrid discrete/continuum solvation model considers the ion explicitly
   solvated by some solvent molecules and the bulk solvent is described by
   a dielectric continuum (PCM). Two and three explicit water molecules
   solvating the hydroxide ion were included to describe the transition
   states. Our theoretical activation free energy barrier at 25 degreesC
   is 23.4 kcal mol(-1), only 2.2 kcal mol(-1) higher than the
   experimental value of 21.2 kcal mol(-1). We have also investigated a
   general basic catalysis mechanism, where the hydroxide ion acts as a
   base and one water molecule in its solvation shell is the nucleophile.
   Our results indicate that this mechanism does not take place and the
   real process is the direct nucleophilic attack of the hydroxide ion to
   the carbonyl carbon. (C) 2004 Elsevier B.V. All rights reserved.
C1 Univ Fed Santa Catarina, Dept Quim, BR-88040900 Florianopolis, SC, Brazil.
RP Pliego, JR, Univ Fed Santa Catarina, Dept Quim, BR-88040900
   Florianopolis, SC, Brazil.
EM josef@qmc.ufsc.br
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NR 94
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD NOV 15
PY 2004
VL 306
IS 1-3
BP 273
EP 280
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 865AG
UT ISI:000224674000026
ER

PT J
AU Koiller, B
   Capaz, RB
   Hu, XD
   Das Sarma, S
TI Shallow-donor wave functions and donor-pair exchange in silicon: Ab
   initio theory and floating-phase Heitler-London approach
SO PHYSICAL REVIEW B
LA English
DT Article
ID TOTAL-ENERGY CALCULATIONS; ELECTRONIC-STRUCTURE; QUANTUM COMPUTER;
   GROUND-STATE; SEMICONDUCTORS; SI; PSEUDOPOTENTIALS; GERMANIUM; SYSTEMS
AB Electronic and nuclear spins of shallow donors in silicon are
   attractive candidates for qubits in quantum computer proposals. Shallow
   donor exchange gates are frequently invoked to perform two-qubit
   operations in such proposals. We study shallow donor electron
   properties in Si within the Kohn-Luttinger envelope function approach,
   incorporating the full Bloch states of the six band edges of the Si
   conduction band, obtained from ab initio calculations within the
   density-functional and pseudopotential frameworks. Intervalley
   interference between the conduction-band-edge states of Si leads to
   oscillatory behavior in the charge distribution of one-electron bound
   states and in the exchange coupling in two-electron states. The
   behavior in the donor electron charge distribution is strongly
   influenced by interference from the plane wave and periodic parts of
   the Bloch functions. For two donors, oscillations in the exchange
   coupling calculated within the Heitler-London (HL) approach are due to
   the plane-wave parts of the Bloch functions alone, which are pinned to
   the impurity sites. The robustness of this result is assessed by
   relaxing the phase pinning to the donor sites. We introduce a more
   general theoretical scheme, the floating-phase HL, from which the
   previously reported donor exchange oscillatory behavior is
   qualitatively and quantitatively confirmed. The floating-phase
   formalism provides a "handle" on how to theoretically anticipate the
   occurrence of oscillatory behavior in electronic properties associated
   with electron bound states in more general confining potentials, such
   as in quantum dots.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21945 Rio De Janeiro, Brazil.
   SUNY Buffalo, Dept Phys, Buffalo, NY 14260 USA.
   Univ Maryland, Condensed Matter Theory Ctr, Dept Phys, College Pk, MD 20742 USA.
RP Koiller, B, Univ Fed Rio de Janeiro, Inst Fis, Caixa Postal 68528,
   BR-21945 Rio De Janeiro, Brazil.
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NR 43
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD SEP
PY 2004
VL 70
IS 11
AR 115207
DI ARTN 115207
PG 8
SC Physics, Condensed Matter
GA 858RN
UT ISI:000224209500040
ER

PT J
AU Tormena, CF
   Rittner, R
   Contreras, RH
   Peralta, JE
TI Anomeric effect on geminal and vicinal J(HH) NMR coupling constants
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; CONFORMATIONAL-ANALYSIS; NEGATIVE
   HYPERCONJUGATION; MOLECULAR-STRUCTURE; KARPLUS EQUATION; DOUBLE
   RESONANCE; RELATIVE SIGNS; BOND LENGTHS; SOLVATION; CYCLOHEXANE
AB Trends for geminal ((2)J(HH)) and vicinal ((3)J(HH)) nuclear magnetic
   resonance indirect spin-spin coupling constants, SSCCs, for
   2-methylthiirane (5) and 2-methyloxirane (6) are studied both from
   experimental and theoretical points of view to determine the influence
   of hyperconjugative interactions on these couplings. These two
   analogous compounds were chosen because it was expected that they
   exhibit quite different anomeric effects. Hyperconjugative interactions
   are investigated using the "natural bond orbital" method. Coupling
   constants are calculated within the density functional theory including
   all four scalar contributions, that is, the Fermi contact, the
   spin-dipolar, and the paramagnetic and diamagnetic spin-orbital
   contributions. Solvent dielectric effects are taken into account using
   Tomasi's polarizable continuum model. Results for geminal couplings are
   consistent with linear correlations connecting (2)J(HH) with the
   coupling pathway occupation numbers taken from the literature. The
   present analysis suggests that both (2)J(HH) and (2)J(HH) coupling
   constants are sensitive probes to gauge the anomeric effect, as well as
   other hyperconjugative interactions.
C1 Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Pret, Dept Quim, BR-14040901 Ribeirao Preto, SP, Brazil.
   Univ Estadual Campinas, Inst Quim, Phys Organ Chem Lab, BR-13084971 Campinas, SP, Brazil.
   Univ Buenos Aires, Dept Phys, RA-1428 Buenos Aires, DF, Argentina.
RP Tormena, CF, Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao
   Pret, Dept Quim, Av Bandeirantes 3900, BR-14040901 Ribeirao Preto, SP,
   Brazil.
EM tormena@ffclrp.usp.br
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NR 71
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD SEP 23
PY 2004
VL 108
IS 38
BP 7762
EP 7768
PG 7
SC Chemistry, Physical
GA 854RX
UT ISI:000223922100018
ER

PT J
AU Ramalho, TC
   da Cunha, EFF
   de Alencastro, RB
TI Solvent effects on C-13 and N-15 shielding tensors of nitroimidazoles
   in the condensed phase: a sequential molecular dynamics/quantum
   mechanics study
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID VERTICAL ELECTRON-AFFINITY; NMR CHEMICAL-SHIFTS; AB-INITIO;
   COMPUTER-SIMULATION; NUCLEAR SHIELDINGS; MAGNETIC-RESONANCE;
   HYDROGEN-BOND; LIQUID WATER; SPECTROSCOPY; RELAXATION
AB N-15-and C-13 NMR chemical shifts for three nitroimidazoles have been
   calculated and compared with experimental data. The solvent effects on
   NMR spectra were simulated with the polarizable continuum model (PCM)
   and an alternative sequential molecular dynamics/quantum mechanics
   methodology (S-MD/QM). The sampling of the structures for the quantum
   mechanical calculations is made by using the interval of statistical
   correlation obtained from the autocorrelation function of the energy.
   Magnetic shielding tensors were evaluated at the GIAO-B3LYP level using
   II' basis set. It has been shown that it is essential to incorporate
   the dynamics and solvent effects in NMR calculations in the condensed
   phase.
C1 Max Planck Inst Kohlenforsch, D-45470 Mulheim, Germany.
   Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, Phys Organ Chem Grp, BR-21949900 Rio De Janeiro, Brazil.
RP Ramalho, TC, Max Planck Inst Kohlenforsch, Kaiser Wilhelm Pl 1, D-45470
   Mulheim, Germany.
EM teo@ime.eb.br
CR *INRIA ENPC, 1989, SCIL V 2 7
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NR 57
TC 5
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD SEP 1
PY 2004
VL 16
IS 34
BP 6159
EP 6170
PG 12
SC Physics, Condensed Matter
GA 854LI
UT ISI:000223904000017
ER

PT J
AU Marques, M
   Teles, LK
   Scolfaro, LMR
   Ferreira, LG
   Leite, JR
TI Microscopic description of the phase separation process in
   AlxGayIn1-x-yN quaternary alloys
SO PHYSICAL REVIEW B
LA English
DT Article
ID LIGHT-EMITTING-DIODES; SEMICONDUCTORS; INXALYGA1-X-YN; LUMINESCENCE;
   EMISSION; GAP
AB Ab initio total energy electronic structure calculations are combined
   with Monte Carlo simulations to study the thermodynamic properties of
   AlxGayIn1-x-yN quaternary alloys. We provide a microscopic description
   of the phase separation process by analyzing the thermodynamic behavior
   of the different atoms with respect to the temperature and cation
   contents. We obtained, at growth temperatures, the range of
   compositions for the stable and unstable phases. The presence of Al in
   InGaN is proven to "catalyze" the phase separation process for the
   formation of the In-rich phase. Based on our results, we propose that
   the ultraviolet emission currently seen in samples containing AlInGaN
   quaternaries arises from the matrix of a random alloy, in which
   composition fluctuations toward InGaN- and AlGaN-like alloys formation
   may be present, and that a coexisting emission in the green-blue region
   results from the In-rich segregated clusters.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
RP Marques, M, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR ADIVARAHAN V, 2001, APPL PHYS LETT, V79, P4240
   CHEN CH, 2004, APPL PHYS LETT, V84, P1480
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   MARQUES M, UNPUB
   MARQUES M, 2003, APPL PHYS LETT, V83, P890
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   YASAN A, 2002, APPL PHYS LETT, V81, P2151
NR 21
TC 3
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD AUG
PY 2004
VL 70
IS 7
AR 073202
DI ARTN 073202
PG 4
SC Physics, Condensed Matter
GA 851WG
UT ISI:000223716600007
ER

PT J
AU Pereira, RP
   Rocco, AM
   Bielschowsky, CE
TI Poly(ethylene oxide): Electronic structure, energetics, and vibrational
   spectrum
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID AB-INITIO CALCULATIONS; POLY(METHYL METHACRYLATE) BLENDS; POLYMER
   ELECTROLYTES; COMPLEXES; PEO; BEHAVIOR; LICLO4; ETHER
AB The electronic structure, energetics, and vibrational spectrum of
   poly(ethylene oxide) (PEO) are determined from density functional
   theoretical calculations on model systems (CH2CH2O)(n)X-2,
   ((EO)(n)X-2), where X is a termination group, such as methyl or
   hydroxyl, and n varies from 2 to 8. Geometry optimization was performed
   on these linear model systems chosen to represent the noncrystalline
   conformer of PEO, and the convergence of selected properties (total
   energy, vibrational spectra) was studied. To simulate the crystalline
   conformer, geometry optimization and vibrational spectrum calculations
   were carried out on a helical (EO)(6)(CH3)(2) model system.
   Differential scanning calorimetry data were employed to determine the
   crystalline fraction, used as weight for the simulation of total
   vibrational spectra, based on the spectra of the two conformers. The
   high resolution simulated spectra exhibited the contribution of
   individual vibrational modes to the experimentally observed broad peaks
   (or envelopes), while the simulated spectra with low resolution
   exhibited good agreement with experimental data, indicating a strong
   influence of the line width on the simulated spectra, caused by the
   distribution of chain conformations in the experimental PEO sample. The
   electronic structure of the linear (EO)(6)(CH3)(2) model system
   exhibited localization of the frontier orbitals on the oxygen atoms,
   where the border effect is highly pronounced, the orbitals localized on
   the oxygen atoms closer to the termination being highly energetic. The
   simulation of PEO by the finite size cluster approach utilizing
   oligo(ethylene oxide) model systems with six units was shown to be a
   good approximation to the calculation of electronic structure and
   vibrational spectra.
C1 Univ Fed Rio de Janeiro, Inst Quim, Grp Espectroscopia Teor, BR-21945970 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, Grp Mat Condutores, BR-21945970 Rio De Janeiro, Brazil.
RP Pereira, RP, Univ Fed Rio de Janeiro, Inst Quim, Grp Espectroscopia
   Teor, CT,Bloco A,Cidade Univ, BR-21945970 Rio De Janeiro, Brazil.
EM rpacheco@iq.ufrj.br
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NR 28
TC 3
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD AUG 26
PY 2004
VL 108
IS 34
BP 12677
EP 12684
PG 8
SC Chemistry, Physical
GA 847XG
UT ISI:000223430800011
ER

PT J
AU Brewer, WD
   Scherz, A
   Sorg, C
   Wende, H
   Baberschke, K
   Bencok, P
   Frota-Pessoa, S
TI Direct observation of orbital magnetism in cubic solids
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID RAY CIRCULAR-DICHROISM; 3D IMPURITIES; DILUTE AUCO; FE; MAGNETIZATION;
   FIELDS; COBALT; ATOMS
AB We present x-ray magnetic circular dichroism determinations of the
   orbital/spin magnetic moment ratios of dilute 3d-series impurities in
   Au (and Cu) host matrices. This is the first direct measurement of
   considerable orbital moments in cubic symmetry for a localized impurity
   in a bulk metal host. It is shown that the unquenching of orbital
   magnetism depends on a delicate balance of hybridization effects
   between the local impurity with the host and the filling of the 3d
   states of the impurity. The results are accompanied by ab initio
   calculations that support our experimental findings.
C1 Free Univ Berlin, Inst Expt Phys, D-14195 Berlin, Germany.
   European Synchrotron Radiat Facil, F-38043 Grenoble, France.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Brewer, WD, Free Univ Berlin, Inst Expt Phys, Arnimallee 14, D-14195
   Berlin, Germany.
EM brewer@physik.fu-berlin.de
CR BOYSEN J, 1973, SOLID STATE COMMUN, V12, P1095
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NR 21
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD AUG 13
PY 2004
VL 93
IS 7
AR 077205
DI ARTN 077205
PG 4
SC Physics, Multidisciplinary
GA 845VL
UT ISI:000223273300057
ER

PT J
AU Rino, JP
   Ebbsjo, I
   Branicio, PS
   Kalia, RK
   Nakano, A
   Shimojo, F
   Vashishta, P
TI Short- and intermediate-range structural correlations in amorphous
   silicon carbide: A molecular dynamics study
SO PHYSICAL REVIEW B
LA English
DT Article
ID DENSITY-FUNCTIONAL-THEORY; X-RAY-ABSORPTION; CARBON ALLOYS; CHEMICAL
   ORDER; NEUTRON-SCATTERING; PHOSPHATE-GLASSES; ATOMIC-STRUCTURE;
   FINE-STRUCTURE; A-SI1-XCX-H; ICE
AB Short- and intermediate-range structural correlations in amorphous
   silicon carbide (a-SiC) are studied in terms of partial pair
   distributions, bond angle distribution functions, and shortest-path
   ring statistics. A well relaxed sample is prepared following a slow
   annealing schedule of the simulation at the experimental density of the
   amorphous phase. The short-range correlation functions indicate a
   locally ordered amorphous structure with heteronuclear bonds, Si-C,
   with no phase separation, and no graphitic or diamond structures
   present. The bond distances and coordination numbers are similar to
   those in the crystalline phase. The rings statistics indicate an
   intermediate-range topology formed by the rearrangement of tetrahedra
   with the occurrence of corner and edge sharing units connecting two-
   (similar to5% of total), three-, four-, and five-fold rings. The
   presence of large size rings indicates the existence of nano-voids in
   the structure, which explains the low density compared with the crystal
   phase while keeping the same coordination number and bond distance.
   These simulation results agree well with experimental results.
C1 Univ So Calif, Dept Mat Sci & Engn, Collab Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Phys & Astron, Collab Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Comp Sci, Collab Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Biomed Engn, Collab Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ Fed Sao Carlos, Dept Phys, BR-13560 Sao Carlos, SP, Brazil.
   Univ Uppsala, Studsvik Neutron Res Lab, Nykoping, Sweden.
   Kumamoto Univ, Dept Phys, Kumamoto, Japan.
RP Rino, JP, Univ So Calif, Dept Mat Sci & Engn, Collab Adv Comp &
   Simulat, Los Angeles, CA 90089 USA.
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NR 55
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD JUL
PY 2004
VL 70
IS 4
AR 045207
DI ARTN 045207
PG 11
SC Physics, Condensed Matter
GA 843CO
UT ISI:000223053300026
ER

PT J
AU Bugs, MR
   Forato, LA
   Bortoleto-Bugs, RK
   Fischer, H
   Mascarenhas, YP
   Ward, RJ
   Colnago, LA
TI Spectroscopic characterization and structural modeling of prolamin from
   maize and pearl millet
SO EUROPEAN BIOPHYSICS JOURNAL WITH BIOPHYSICS LETTERS
LA English
DT Article
DE pennisetin molecular model; zein molecular model; circular dichroism;
   dynamic light scattering; small-angle X-ray scattering
ID PROTEIN SECONDARY STRUCTURE; NUCLEAR-MAGNETIC-RESONANCE; ALPHA-ZEIN
   PROTEINS; X-RAY-SCATTERING; 3-DIMENSIONAL STRUCTURE;
   CIRCULAR-DICHROISM; SEQUENCE-ANALYSIS; SPECTRA; EVOLUTION; GENES
AB Biophysical methods and structural modeling techniques have been used
   to characterize the prolamins from maize (Zea mays) and pearl millet
   (Pennisetum americanum). The alcohol-soluble prolamin from maize,
   called zein, was extracted using a simple protocol and purified by gel
   filtration in a 70% ethanol solution. Two protein fractions were
   petrified from seed extracts of pearl millet with molecular weights of
   25.5 and 7 kDa, as estimated by SDS-PAGE. The high molecular weight
   protein corresponds to pennisetin, which has a high alpha-helical
   content both in solution and the solid state, as demonstrated by
   circular dichroism and Fourier transform infrared spectra. Fluorescence
   spectroscopy of both fractions indicated changes in the tryptophan
   microenvironments with increasing water content of the buffer.
   Low-resolution envelopes of both fractions were retrieved by ab initio
   procedures from small-angle X-ray scattering data, which yielded
   maximum molecular dimensions of about 14 nm and 1 nm for pennisetin and
   the low molecular weight protein, respectively, and similar values were
   observed by dynamic light scattering experiments. Furthermore, H-1
   nuclear magnetic resonance spectra of zein and pennisetin do not show
   any signal below 0.9 ppm, which is compatible with more extended
   solution structures. The molecular models for zein and pennisetin in
   solution suggest that both proteins have an elongated molecular
   structure which is approximately a prolate ellipsoid composed of
   ribbons of folded alpha-helical segments with a length of about 14 run,
   resulting in a structure that permits efficient packing within the seed
   endosperm.
C1 Embrapa Instrumentacao Agropecuaria, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Sao Paulo, Inst Fis Sao Carlos, Grp Cristalog, BR-13566590 Sao Carlos, SP, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14049901 Ribeirao Preto, SP, Brazil.
RP Colnago, LA, Embrapa Instrumentacao Agropecuaria, Rua 15 Novembro 1452,
   BR-13560970 Sao Carlos, SP, Brazil.
EM colnago@cnpdia.embrapa.br
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NR 30
TC 3
PU SPRINGER
PI NEW YORK
PA 233 SPRING STREET, NEW YORK, NY 10013 USA
SN 0175-7571
J9 EUR BIOPHYS J BIOPHYS LETT
JI Eur. Biophys. J. Biophys. Lett.
PD JUL
PY 2004
VL 33
IS 4
BP 335
EP 343
PG 9
SC Biophysics
GA 841OU
UT ISI:000222941000007
ER

PT J
AU Fagan, SB
   Souza, AG
   Lima, JOG
   Mendes, J
   Ferreira, OP
   Mazali, IO
   Alves, OL
   Dresselhaus, MS
TI 1,2-dichlorobenzene interacting with carbon nanotubes
SO NANO LETTERS
LA English
DT Article
ID AB-INITIO; RAMAN-SPECTROSCOPY; LARGE SYSTEMS; WATER
AB The interaction of 1,2-dichlorobenzene (DCB) with carbon nanotubes is
   analyzed by experimental and theoretical methods. Using
   first-principles calculations we studied the structural and electronic
   behavior of DCB interacting with a semiconductor (8,10) single-wall
   carbon nanotube (SWNT). We have found that the DCB weakly interacts
   with a perfect SWNT surface, but this interaction is slightly stronger
   when the SWNT surface has structural vacancies. Resonant Raman
   experiments performed on DCB-adsorbed SWNTs confirm the weak DCB-SWNT
   interaction, as suggested by the ab initio simulations.
C1 Univ Fed Ceara, Dept Fis, BR-60455900 Fortaleza, Ceara, Brazil.
   Univ Estadual Campinas, Inst Quim, LQES, BR-13081970 Campinas, SP, Brazil.
   MIT, Dept Elect Engn & Comp Sci, Cambridge, MA 02139 USA.
   MIT, Dept Phys, Cambridge, MA 02139 USA.
RP Fagan, SB, Univ Fed Ceara, Dept Fis, Caixa Postal 6030,Campus Pici,
   BR-60455900 Fortaleza, Ceara, Brazil.
EM solange@fisica.ufc.br
CR ARTACHO E, 1999, PHYS STATUS SOLIDI B, V215, P809
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NR 20
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1530-6984
J9 NANO LETT
JI Nano Lett.
PD JUL
PY 2004
VL 4
IS 7
BP 1285
EP 1288
PG 4
SC Chemistry, Multidisciplinary; Materials Science, Multidisciplinary
GA 839CX
UT ISI:000222762000022
ER

PT J
AU Kleinpeter, E
   Seidl, PR
TI The gamma- and the delta-effects in C-13 NMR spectroscopy in terms of
   nuclear chemical shielding (NCS) analysis
SO JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
LA English
DT Article
DE C-13 NMR spectroscopy; gamma- and delta-effects; steric hindrance;
   partitions to natural chemical shieldings
ID AB-INITIO IGLO; MAGNETIC-RESONANCE; SUBSTITUENT DEPENDENCIES; SHIFTS;
   SPECTRA; TENSORS; ANGLE
AB Carbon-13 NMR is widely used in the determination of the
   stereochemistry of organic compounds. Changes in chemical shifts caused
   by interactions of groups that are close in space normally result in
   shielding of the carbon and deshielding of the hydrogen nuclei that are
   involved. This is not always the case, however, and further work on the
   origin of these effects would be desirable. Early applications of
   theoretical methods to the study of NMR shielding parameters were not
   particularly successful, but in recent years, the calculation of NMR
   shielding parameters by theoretical methods has developed into a useful
   and popular tool for structural studies by NMR. A promising approach to
   the problem of distinguishing and evaluating stereochemical influences
   on carbon and hydrogen chemical shifts is provided by natural chemical
   shielding (NCS) analysis. This method allows a partitioning of
   theoretical NMR shieldings into magnetic contributions from bonds and
   lone pairs of the molecule using the natural bond orbital (NBO) method.
   In order to investigate the origins of steric effects, we employed the
   NCS analysis to axial/equatorial-Me-cyclohexane, norbornane and
   exo/endo-Me-norbornane, in addition to n-pentane in the anti, gauche
   and g(P) g(M) conformations. Our results indicate that distortions in
   molecular structure due to steric effects can result in bond stretching
   or compression or in angular distortions. Changes in bond lengths
   result in the predictable shielding or deshielding of the nuclei that
   are involved. Where the molecular framework may be distorted to
   alleviate strain, chemical shifts appear to reflect changes in angles.
   Copyright (C) 2004 John Wiley Sons, Ltd.
C1 Univ Potsdam, Inst Chem, D-14415 Potsdam, Germany.
   Univ Fed Fluminense, Programa Posgrad Quim Organ, BR-24020150 Niteroi, RJ, Brazil.
RP Kleinpeter, E, Univ Potsdam, Inst Chem, POB 60 15 53, D-14415 Potsdam,
   Germany.
EM kp@chem.uni-potsdam.de
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NR 31
TC 3
PU JOHN WILEY & SONS LTD
PI CHICHESTER
PA THE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLAND
SN 0894-3230
J9 J PHYS ORG CHEM
JI J. Phys. Org. Chem.
PD AUG
PY 2004
VL 17
IS 8
BP 680
EP 685
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 840TV
UT ISI:000222883700005
ER

PT J
AU Ramalho, TC
   de Alencastro, RB
   La-Scalea, MA
   Figueroa-Villar, JD
TI Theoretical evaluation of adiabatic and vertical electron affinity of
   some radiosensitizers in solution using FEP, ab initio and DFT methods
SO BIOPHYSICAL CHEMISTRY
LA English
DT Article
DE radiosensitizers; electron affinity; HF and DFT calculations
ID HYPOXIC CELL RADIOSENSITIZERS; DIFFERENCE THERMODYNAMIC INTEGRATION;
   MOLECULAR-DYNAMICS SIMULATION; MST-SCRF CALCULATIONS; FREE-ENERGY;
   BIOLOGICAL-ACTIVITY; PHOTOELECTRON-SPECTROSCOPY; VOLTAMMETRIC BEHAVIOR;
   IONIZATION-POTENTIALS; DRUG-RESISTANCE
AB The biological activity of radiosensitizers is associated to their
   electron affinity (EA), which can be divided in two main processes:
   vertical and adiabatic. In this work, we calculated the EAs of
   nitrofurans and nitroimidazoles (Fig. 2) using Hartree-Fock (HF) and
   density functional theory (DFT) methods and evaluated solvent effects
   (water and carbon tetrachloride) on EAs. For water, we combined the
   polarized continuum model (PCM) and free energy perturbation (FEP)
   (finite difference thermodynamic integration, FDTI) methods. For carbon
   tetrachloride, we used the FDTI method. The values of adiabatic EA
   obtained are in agreement with experimental data (deviations of 0.013
   eV). The vertical EAs were calculated according to Cederbaum's outer
   valence Green function (OVGF) method. This methodology, which relies on
   theoretical aspects of free energy calculations on charged molecules in
   solution, was used to select potential selective radiosensitizers from
   recently reported compounds and could be helpful in the rational design
   of new and more selective bioreductive anticancer drugs. (C) 2004
   Elsevier B.V. All rights reserved.
C1 Inst Mil Engn, Dept Quim, BR-22290270 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, Grp Fisicoquim Organ, BR-21949900 Rio De Janeiro, Brazil.
   Univ Sao Paulo, Fac Ciencias Farmaceut, Dept Farm, BR-05508900 Sao Paulo, Brazil.
RP Figueroa-Villar, JD, Inst Mil Engn, Dept Quim, Praca Gen Tiburcio 80,
   BR-22290270 Rio De Janeiro, Brazil.
EM figueroa@ime.eb.br
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   LISTER SG, 1992, INT J QUANTUM CHEM, V41, P293
   LISTER SG, 1997, INT QUANTUM CHEM, V59, P135
   LUQUE FJ, 1996, J COMPUT CHEM, V17, P806
   MEZEI M, 1987, J CHEM PHYS, V86, P7084
   MIERTUS S, 1981, CHEM PHYS, V55, P117
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   PIRES JR, 2001, J MED CHEM, V44, P3673
   PRAMANN A, 2001, CHEM PHYS LETT, V343, P99
   PRESS WH, 1986, NUMERICAL RECIPES AR
   REYNOLDS CA, 1988, J CHEM SOC CHEM COMM, P1434
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NR 71
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-4622
J9 BIOPHYS CHEM
JI Biophys. Chem.
PD AUG 1
PY 2004
VL 110
IS 3
BP 267
EP 279
PG 13
SC Chemistry, Physical; Biochemistry & Molecular Biology; Biophysics
GA 836XM
UT ISI:000222589500008
ER

PT J
AU Orhan, E
   Pontes, FM
   Santos, MA
   Leite, ER
   Beltran, A
   Andres, J
   Boschi, TM
   Pizani, PS
   Varela, JA
   Taft, CA
   Longo, E
TI Combined experimental and theoretical study to understand the
   photoluminescence of Sr1-xTiO3-x
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID THIN-FILMS; ABO(3) PEROVSKITES; STRONTIUM-TITANATE; ROOM-TEMPERATURE;
   VISIBLE PHOTOLUMINESCENCE; AMORPHOUS SRTIO3; ABSORPTION EDGE; CHEMICAL
   ROUTE; LEAD TITANATE; ENERGY-BANDS
AB A joint experimental and theoretical study has been carried out to
   rationalize the results of visible photoluminescence measurements at
   room temperature on Sr1-xTiO3-x (ST) perovskite thin films. From the
   experimental side, ST thin films, x = 0 to 0.9, have been synthesized
   following soft chemical processing, and the corresponding
   photoluminescence properties have been measured. First principles
   quantum mechanical techniques, based on density functional theory at
   the B3LYP level, have been employed to study the electronic structure
   of a crystalline, stoichiometric (x = 0) ST-s model and a
   nonstoichiometric (SrO-deficient, x not equal 0) and structurally
   disordered ST-d model. The relevance of the present theoretical and
   experimental results of the photoluminescence behavior of ST is
   discussed. The optical spectra and the calculations indicate that the
   symmetry-breaking process on going from ST-s to ST-d creates electronic
   levels in the valence band. Moreover, an analysis of the Mulliken
   charge distribution reveals a charge gradient in the structure. These
   combined effects seem to be responsible for the photoluminescence
   behavior of deficient Sr1-xTiO3-x.
C1 Univ Estadual Paulista, Inst Quim, BR-14801907 Araraquara, SP, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Jaume I, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
RP Orhan, E, Univ Estadual Paulista, Inst Quim, BR-14801907 Araraquara,
   SP, Brazil.
EM emmanuelle.orhan@liec.ufscar.br
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NR 40
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD JUL 1
PY 2004
VL 108
IS 26
BP 9221
EP 9227
PG 7
SC Chemistry, Physical
GA 832PJ
UT ISI:000222279100067
ER

PT J
AU Ferretti, A
   Ruini, A
   Bussi, G
   Molinari, E
   Caldas, MJ
TI Ab initio study of transport parameters in polymer crystals
SO PHYSICAL REVIEW B
LA English
DT Article
ID CONJUGATED POLYMERS; CHARGE-TRANSPORT; INTERCHAIN INTERACTIONS;
   POLYTHIOPHENE CRYSTALS; CONDUCTING POLYMERS; CHAINS;
   POLY(3-ALKYLTHIOPHENES); POLY(3-OCTYLTHIOPHENE); 1ST-PRINCIPLES;
   COHERENT
AB Transfer integrals (TI's) are essential parameters in the calculation
   of electron transport both in coherent and incoherent regimes. We show
   that TI's for polymer crystals can be obtained from first principles,
   starting from plane-wave density-functional calculations of the
   electronic structure in the local-density approximation, and propose
   methods at different levels of approximation. We demonstrate that
   special choices of single-chain states can be used very effectively as
   building blocks for the crystal electronic structure, thus allowing a
   deeper insight into the transport properties of molecular crystals. We
   apply this approach to polymer systems of great interest to molecular
   electronics, such as poly-para-phenylene-vinylene and polythiophene in
   different crystal packing morphologies, and show that it offers a very
   powerful tool to understand and design the impact of intermolecular
   interactions on conduction of organic crystals.
C1 Univ Modena & Reggio Emilia, INFM Natl Ctr Nanostruct & Biosyst Surface S3, I-41100 Modena, Italy.
   Univ Modena & Reggio Emilia, Dipartimento Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
RP Ferretti, A, Univ Modena & Reggio Emilia, INFM Natl Ctr Nanostruct &
   Biosyst Surface S3, Via Campi 213-A, I-41100 Modena, Italy.
EM ferretti.andrea@unimo.it
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NR 43
TC 3
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAY
PY 2004
VL 69
IS 20
AR 205205
DI ARTN 205205
PG 10
SC Physics, Condensed Matter
GA 830BD
UT ISI:000222095700036
ER

PT J
AU Da Cunha, EFF
   De Alencastro, RB
   Ramalho, TC
TI Theoretical study of adiabatic and vertical electron affinity of
   radiosensitizers in solution Part 2: Analogues of tirapazamine
SO JOURNAL OF THEORETICAL & COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE radiosensitizers; electron affinity; HF and DFT calculations
ID HYPOXIC CELL RADIOSENSITIZERS; MOLECULAR-DYNAMICS SIMULATION;
   FREE-ENERGY; THERMODYNAMIC INTEGRATION; VOLTAMMETRIC BEHAVIOR;
   AQUEOUS-SOLUTION; ANTICANCER DRUG; SOLID TUMORS; AB-INITIO; POTENTIALS
AB Tirapazamine is a radiosensitizer, whose biological activity is
   associated to its electron affinity (EA). The electron affinity can be
   divided in two main processes: Vertical and Adiabatic. In this work, we
   calculated the EAs of nitroimidazoles (Fig. 2) using HF and DFT methods
   and evaluated solvent effects (water and carbon tetrachloride) on EAs.
   For water, we combined the Polarized Continuum Model (PCM) and free
   energy perturbation (Finite Difference Thermodynamic Integration, FDTI)
   methods. For carbon tetrachloride, we used the FDTI method. The values
   of adiabatic EA obtained axe in agreement with experimental data
   (deviations of 13.25 meV). The vertical EA were calculated according to
   Cederbaum's Outer Valence Green Function (OVGF) method. This study,
   which relays on theoretical aspects of free energy calculations on
   charged molecules in solution, could be helpful in the rational design
   of new and more selective bioreductive anticancer drugs.
C1 Inst Militar Engn, Dept Quim, BR-22290270 Rio De Janeiro, Brazil.
   Fed Univ Rio De Janeiro, Inst Quim, Dept Quim Organ, Grp Fis Quim, BR-21949900 Rio De Janeiro, Brazil.
RP Da Cunha, EFF, Inst Militar Engn, Dept Quim, Praca Gen Tiburcio 80,
   BR-22290270 Rio De Janeiro, Brazil.
CR ADAMS GE, 1976, RADIAT RES, V67, P550
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   BRETT AMO, 1997, ELECTROANAL, V9, P1132
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   BROWN JM, 1999, CANCER RES, V59, P1391
   CAMMI R, 1997, THEORETICAL ASPECTS
   CANCES E, 1997, J CHEM PHYS, V107, P3032
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   MEZEI M, 1987, J CHEM PHYS, V86, P7084
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   VIODE C, 1999, BIOCHEM PHARMACOL, V57, P549
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NR 64
TC 4
PU WORLD SCIENTIFIC PUBL CO PTE LTD
PI SINGAPORE
PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE
SN 0219-6336
J9 J THEOR COMPUT CHEM
JI J. Theor. Comput. Chem.
PD MAR
PY 2004
VL 3
IS 1
BP 1
EP 13
PG 13
SC Chemistry, Multidisciplinary
GA 820UD
UT ISI:000221414000001
ER

PT J
AU Ramalho, TC
   da Cunha, EFF
   de Alencastro, RB
TI A density functional study on the complexation of ethambutol with
   divalent cations
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE ethambutol-metal complexes; mycobacterium tuberculosis; DFT
ID POLARIZABLE CONTINUUM MODEL; AB-INITIO; MYCOBACTERIUM-TUBERCULOSIS;
   ENERGY; METAL; ARABINOGALACTAN; APPROXIMATION; SMEGMATIS; IRON
AB The influence of non-bonded interactions on the formation of ethambutol
   (EMB) complexes with divalent cations was studied by DFT
   (B3LYP/6-311++G**). An analysis of the natural bond order provided a
   possible explanation for the difference in stability on (S, S), (R, R)
   and (meso) EMB complexes as well as an evaluation of the structural and
   electronic effects, applying non-bonded interactions. Due to
   n(O7)/sigma*(C3-H) interactions, Gibbs energies can be rationalized in
   terms of the stabilization of the complexes. Our results are in
   agreement with experimental studies which show that the (S,
   S)-configuration of EMB complexes is essential for activity against
   Mycobacterium tuberculosis. (C) 2004 Elsevier B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, Lab Fisicoquim Organ, BR-21949900 Rio De Janeiro, Brazil.
   Inst Militar Engn, Dept Quim, BR-22290270 Rio De Janeiro, Brazil.
RP de Alencastro, RB, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ,
   Lab Fisicoquim Organ, Ilha Fundao,CT,Bloco A,Sala 609, BR-21949900 Rio
   De Janeiro, Brazil.
EM bicca@iq.ufrj.br
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   CAMMI R, 1997, THEORETICAL ASPECTS
   CANCES E, 1997, J CHEM PHYS, V107, P3032
   CAROLINE P, 1996, J PHYS CHEM-US, V100, P17797
   CHO SG, 2000, J MOL STRUC-THEOCHEM, V532, P279
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NR 39
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAY 14
PY 2004
VL 676
IS 1-3
BP 149
EP 153
PG 5
SC Chemistry, Physical
GA 819YB
UT ISI:000221351100023
ER

PT J
AU Jalbout, AF
   Basso, EA
   Pontes, RM
   Das, D
TI Hyperconjugative interactions in vinylic systems: the problem of the
   barrier to methyl rotation in acetone
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE hyperconjugation; acetone; rotational barrier; natural bond orbital
ID SET MODEL CHEMISTRY; INTERNAL-ROTATION; ALIPHATIC-ALDEHYDES; TORSIONAL
   SPECTRA; AB-INITIO; ENERGIES; MOLECULES; KETONES; ROTORS; ETHANE
AB The origin of the barrier to methyl rotation in acetone has been
   studied through natural bond orbital theory. The analysis is divided in
   two parts, one involving the stability of bonds and lone pairs and
   other involving hyperconjugative donor-acceptor interactions. In the
   first part, we observed that the carbon-carbon bond of the rotor is
   destabilized upon rotation, and it represents the largest contribution
   to the barrier among bond energy and lone pair components, in
   accordance to studies of similar molecules. In addition, lone pairs
   were found to play an important role. The analysis of hyperconjugation
   effects showed that interactions involving the out-of-plane sigma CH
   orbitals and sigma and pi CO orbitals contribute to increase the
   rotational barrier, while analogous interactions involving the in-plane
   CH bond are either null or antibarrier forming. By excluding the
   mentioned donor-acceptor interactions during geometry optimization, it
   was possible to estimate their influence on bond and lone pair
   stabilities. From this analysis, it was observed that the
   destabilization of bonds and lone pairs upon rotation is determined by
   some of the considered hyperconjugative interactions, which led us to
   conclude that the latter are the primary source of the rotational
   barrier. Finally, a simple set of canonical structures is proposed to
   describe this effect. The model showed to be useful in the qualitative
   understanding of the rotational barrier in similar systems and even of
   conformational preferences. (C) 2004 Elsevier B.V. All rights reserved.
C1 Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana, Brazil.
   Univ New Orleans, Dept Chem, New Orleans, LA 70148 USA.
   Dillard Univ, Dept Phys, New Orleans, LA 70112 USA.
RP Basso, EA, Univ Estadual Maringa, Dept Quim, Av Colombo 5790,
   BR-87020900 Maringa, Parana, Brazil.
EM eabasso@uem.br
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NR 41
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAY 31
PY 2004
VL 677
IS 1-3
BP 167
EP 171
PG 5
SC Chemistry, Physical
GA 820WR
UT ISI:000221420900024
ER

PT J
AU Longo, E
   Orhan, E
   Pontes, FM
   Pinheiro, CD
   Leite, ER
   Varela, JA
   Pizani, PS
   Boschi, TM
   Lanciotti, F
   Beltran, A
   Andres, J
TI Density functional theory calculation of the electronic structure of
   Ba0.5Sr0.5TiO3: Photoluminescent properties and structural disorder
SO PHYSICAL REVIEW B
LA English
DT Article
ID THIN-FILM; ABO(3) PEROVSKITES; OPTICAL-PROPERTIES; LUMINESCENCE;
   BATIO3; SRTIO3; MICROSTRUCTURE; ABSORPTION; TITANATE
AB First-principles quantum-mechanical techniques, based on density
   functional theory (B3LYP level) were employed to study the electronic
   structure of ordered and deformed asymmetric models for Ba0.5Sr0.5TiO3.
   Electronic properties are analyzed and the relevance of the present
   theoretical and experimental results on the photoluminescence behavior
   is discussed. The presence of localized electronic levels in the band
   gap, due to the symmetry break, would be responsible for the visible
   photoluminescence of the amorphous state at room temperature. Thin
   films were synthesized following a soft chemical processing. Their
   structure was confirmed by x-ray data and the corresponding
   photoluminescence properties measured.
C1 Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Estadual Paulista, Inst Quim, BR-14801907 Araraquara, SP, Brazil.
   Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Jaume I, Dept Ciencies Expt, Castello 12080, Spain.
RP Longo, E, Univ Fed Sao Carlos, Dept Quim, Caixa Postal 676, BR-13565905
   Sao Carlos, SP, Brazil.
EM liec@dq.ufscar.br
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NR 34
TC 12
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAR
PY 2004
VL 69
IS 12
AR 125115
DI ARTN 125115
PG 7
SC Physics, Condensed Matter
GA 818QG
UT ISI:000221259000041
ER

PT J
AU da Silva, EZ
   Novaes, FD
   da Silva, AJR
   Fazzio, A
TI Theoretical study of the formation, evolution, and breaking of gold
   nanowires
SO PHYSICAL REVIEW B
LA English
DT Article
ID QUANTIZED CONDUCTANCE; LARGE SYSTEMS; ELECTRON-GAS; ENERGY;
   PSEUDOPOTENTIALS; OSCILLATIONS; METALS; WIRES; ATOMS
AB Real time imaging experiments with metal nanowires (NWs), in particular
   gold under stress, that show their formation, evolution, and breaking,
   were obtained with high resolution electron microscopy. In order to
   understand these results, we use density functional theory (DFT) based
   methods to simulate the evolution of Au NWs. First we use a
   tight-binding molecular dynamics (TBMD) method to understand the
   mechanisms of formation of very thin gold NWs. We present realistic
   simulations for the breaking of these NWs, whose main features are very
   similar to the experimental results. We show how defects lead to the
   formation of one-atom constrictions in the Au NW, which evolves into a
   one-atom-thick necklace chain. Similarly to the experimental results,
   we obtain that these necklaces can get as long as five-atoms from apex
   to apex. Before breaking, we obtain relatively large Au-Au bond
   distances, of the order of 3.0-3.1 Angstrom. A further pull of the wire
   causes a sudden increase of one of the bond distances, indicating the
   breaking of the NW. To get some more insight into the electronic
   structure aspects of this problem, we considered several of our
   tight-binding structures before breaking and studied them in detail
   using an ab initio method based on the DFT. By pulling the wire
   quasi-statically in this case, we also observed the breaking of the
   wire at similar distances as in the TBMD. This result was independent
   of the exchange-correlation potential used-either the local density
   approximation (LDA) or the generalized gradient approximation (GGA).
   The pulling force before rupture was obtained as 2.4 nN for the LDA,
   and 1.9 nN for the GGA. Finally, we also present a detailed analysis of
   the electronic structure properties for the Au neck atoms, such as the
   density of states and charge densities, for some configurations before
   the rupture.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP da Silva, EZ, Univ Estadual Campinas, Inst Fis Gleb Wataghin, CP 6165,
   BR-13083970 Campinas, SP, Brazil.
EM zacarias@ifi.unicamp.br
   ajrsilva@if.usp.br
   fazzio@if.usp.br
CR AGRAIT N, 1993, PHYS REV B, V47
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NR 50
TC 14
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAR
PY 2004
VL 69
IS 11
AR 115411
DI ARTN 115411
PG 11
SC Physics, Condensed Matter
GA 812BC
UT ISI:000220814000125
ER

PT J
AU Shimizu, K
   Chaimovich, H
   Farah, JPS
   Dias, LG
   Bostick, DL
TI Calculation of the dipole moment for polypeptides using the generalized
   born-electronegativity equalization method: Results in vacuum and
   continuum-dielectric solvent
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID INITIO QUANTUM-CHEMISTRY; POLARIZABLE FORCE-FIELD; ATOMIC CHARGES;
   FLUCTUATING CHARGE; MODEL; SOLVATION; PARAMETERIZATION; DISTRIBUTIONS;
   POTENTIALS; MOLECULES
AB The electronegativity equalization methodology, EEM, is frequently used
   to calculate the charge distribution and reactivity index (e.g., local
   softness and hardness, condensed Fukui function) of molecules. However,
   recent work (Chelli, R. et al., J. Chem. Phys. 1999, 111, 8569) has
   shown a serious shortcoming of EEM in the prediction of the
   polarizability for large molecules. In this paper, our goal is to show
   that we can obtain a reliable dipole moment for polypeptides in vacuum
   and continuum-dielectric solvent using the constrained charge
   approximation and the generalized Born-electronegativity equalization
   method. Different EEM parameterizations were tested and compared to the
   expected values of the dipole moment vector operator as calculated at
   the ab initio B3LYP/6-311G(d,p) level. One EEM parameterization
   (Bakowies, D., Thiel, W., J. Comput. Chem. 1996, 17, 87) when used with
   the constrained charge approximation and the generalized
   Born-electronegativity equalization method was comparable to the CM1
   charge model (Storer et al., J. Comput.-Aided Mol. Des. 1995, 9, 87) in
   the prediction of the dipole moment vector in vacuum and
   continuum-dielectric solvent, but was calculated with a much greater
   computational efficiency.
C1 Univ N Carolina, Dept Chem, Chapel Hill, NC 27599 USA.
   Univ Sao Paulo, Inst Chem, Dept Chem, Sao Paulo, SP, Brazil.
   Univ Sao Paulo, Inst Chem, Dept Biochem, Sao Paulo, SP, Brazil.
   Univ N Carolina, Dept Phys, Chapel Hill, NC 27599 USA.
   Univ N Carolina, Program Mol & Cell Biophys, Chapel Hill, NC 27599 USA.
RP Dias, LG, Univ N Carolina, Dept Chem, Venable Hall CB 3290, Chapel
   Hill, NC 27599 USA.
EM lgdias@email.unc.edu
CR BAKOWIES D, 1996, J COMPUT CHEM, V17, P87
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NR 32
TC 3
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD APR 1
PY 2004
VL 108
IS 13
BP 4171
EP 4177
PG 7
SC Chemistry, Physical
GA 807TT
UT ISI:000220524500033
ER

PT J
AU Pliego, JR
   Riveros, JM
TI Free energy profile of the reaction between the hydroxide ion and ethyl
   acetate in aqueous and dimethyl sulfoxide solutions: A theoretical
   analysis of the changes induced by the solvent on the different
   reaction pathways
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID POLARIZABLE CONTINUUM MODEL; CARBOXYLIC-ACID ESTERS; GAS-PHASE
   REACTION; BASE-CATALYZED-HYDROLYSIS; CARBONYL OXYGEN EXCHANGE;
   SOLVATION FREE-ENERGY; ALKALINE-HYDROLYSIS; AB-INITIO; METHYL FORMATE;
   REACTION-MECHANISMS
AB An extensive analysis of the free energy profile for the reaction of
   the hydroxide ion with ethyl acetate in both aqueous and dimethyl
   sulfoxide (DMSO) solutions has been carried out using ab initio
   calculations and including the solvent effect by the polarizable
   continuum model. Different reaction pathways were investigated, such as
   the usual B(AC)2 mechanism, the carbanion mechanism, the elimination
   mechanism, and the S(N)2 mechanism. Our calculation agrees with the
   view that in aqueous and DMSO solution basic hydrolysis occurs by the
   B(AC)2 mechanism. In water, the predicted activation free energy value
   is 17.6 kcal mol(-1), which is in very good agreement with the
   experimental value of 18.8 kcal mol(-1). Using a new parametrization of
   the polarizable continuum model adequate to describe anions and neutral
   species in DMSO, the present study predicts a rate enhancement by a
   factor of 435 in the reaction when going from water (protic solvent) to
   DMSO (dipolar aprotic solvent). In this solvent, the activation free
   energy is predicted to drop to 14.0 kcal mol(-1). Furthermore, our
   results point out that the elimination mechanism is only 6.0 kcal
   mol(-1) (DeltaG(Sol)(double dagger) = 20.0 kcal mol(-1)) less favorable
   than the B(AC)2 mechanism in DMSO solution, and 8.4 kcal mol(-1) less
   favorable in water. The S(N)2 and the carbanion mechanisms have
   barriers above 30 kcal mol(-1) in water and DMSO and are thus highly
   unfavorable. These results suggest the elimination mechanism can become
   the dominant pathway in the basic hydrolysis of sterically crowded
   esters at the carbonyl center.
C1 Univ Fed Santa Catarina, Dept Quim, CFM, BR-88040900 Florianopolis, SC, Brazil.
   Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Pliego, JR, Univ Fed Santa Catarina, Dept Quim, CFM, BR-88040900
   Florianopolis, SC, Brazil.
EM josef@qmc.ufsc.br
   jmmigra@iq.usp.br
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NR 60
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD APR 1
PY 2004
VL 108
IS 13
BP 2520
EP 2526
PG 7
SC Chemistry, Physical
GA 807TR
UT ISI:000220524300024
ER

PT J
AU Machado, AM
   Masili, M
TI Variationally stable calculations for molecular systems:
   Polarizabilities and two-photon ionization cross section for the
   hydrogen molecule
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MATRIX-FLOQUET THEORY; INTENSE LASER FIELDS; MULTIPHOTON IONIZATION;
   H-2 MOLECULE; DYNAMIC POLARIZABILITIES; DIPOLE POLARIZABILITIES;
   OPTICAL-PROPERTIES; WAVE-FUNCTIONS; H-ATOM; HYPERPOLARIZABILITIES
AB The variationally stable method of Gao and Starace [B. Gao and A. F.
   Starace, Phys. Rev. Lett. 61, 404 (1988); Phys. Rev. A 39, 4550 (1989)]
   has been applied for the first time to the study of multiphoton
   processes in molecular systems. The generalization in theory is
   presented, as well as the calculation of properties such as the static
   and dynamic polarizabilities of the hydrogen molecule and the
   generalized two-photon ionization cross section. The Schwinger
   variational iterative method [R. R. Lucchese and V. McKoy, Phys. Rev. A
   21, 112 (1980)] has been applied in the achievement of the
   photoelectron wave function, while a Hartree-Fock representation has
   been used for the target. This research has been motivated by the
   scarceness of ab initio calculations of molecular multiphoton
   ionization cross sections in the literature. (C) 2004 American
   Institute of Physics.
C1 Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Ctr Univ Cent Paulista, BR-13563470 Sao Carlos, SP, Brazil.
RP Machado, AM, Univ Sao Paulo, Inst Fis Sao Carlos, Caixa Postal 369,
   BR-13560970 Sao Carlos, SP, Brazil.
CR APALATEGUI A, 2002, J PHYS B-AT MOL OPT, V35, P1909
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NR 44
TC 3
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD APR 22
PY 2004
VL 120
IS 16
BP 7505
EP 7511
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 810AA
UT ISI:000220676000032
ER

PT J
AU Costa, LAS
   Rocha, WR
   De Almeida, WB
   Dos Santos, HF
TI The solvent effect on the aquation processes of the
   cis-dichloro(ethylenediammine)platinum(II) using continuum solvation
   models
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-TYPE BASIS; ORGANIC-MOLECULES;
   AB-INITIO; APPROXIMATION; DNA
AB The present Letter describes a systematic analysis of the solvent
   effect on the hydrolysis process of an important cisplatin analogue
   (cis-DEP). Self-consistent reaction field continuum models were used to
   include the solvent effect at the HF, DFT and MP2 levels of theory. A
   disagreement between the gas phase calculated (k(2) = 1.92 x 10(-11)
   M-1 s(-1)) and experimental (k(2) = 4.4 x 10(-5) M-1 s(-1)) rate
   constant for the second aquation reaction of cis-DEP was recently
   reported by us. The value calculated in aqueous solution at the PCM-MP2
   level was 2.87 x 10(-5) M-1 s(-1) in perfect accordance with
   experiment. Calculations using spherical cavity SCRF model require
   inclusion of high order multipole terms (up to octupole). (C) 2004
   Elsevier B.V. All rights reserved.
C1 Univ Fed Juiz Fora, ICE, Dept Quim, NEQC, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Minas Gerais, Dept Quim, ICEx, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
   EPCAR, DEPENS, Dept Ensino Aeronaut, Comando Aeronaut, BR-36200000 Barbacena, MG, Brazil.
   Univ Fed Pernambuco, CCEN, Dept Quim Fundamental, BR-50670901 Recife, PE, Brazil.
RP Dos Santos, HF, Univ Fed Juiz Fora, ICE, Dept Quim, NEQC, Campus Univ
   Martelos, BR-36036330 Juiz De Fora, MG, Brazil.
EM helius@quimica.ufjf.br
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NR 21
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAR 21
PY 2004
VL 387
IS 1-3
BP 182
EP 187
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 804AV
UT ISI:000220272500032
ER

PT J
AU de Lazaro, S
   Longo, E
   Sambrano, JR
   Beltran, A
TI Structural and electronic properties of PbTiO3 slabs: a DFT periodic
   study
SO SURFACE SCIENCE
LA English
DT Article
DE lead; titanium oxide; density functional calculations; surface
   electronic phenomena (work function; surface potential, surface states,
   etc.); semiconducting surfaces
ID THIN-FILMS; VISIBLE PHOTOLUMINESCENCE; FERROELECTRIC MEMORIES;
   PEROVSKITE TITANATES; SURFACE RELAXATION; ABO(3) PEROVSKITES;
   FUNCTIONAL THEORY; DENSITY; BATIO3; BULK
AB Structural and electronic properties of the bulk and relaxed surfaces
   (TiO2 and PbO terminated) of cubic PbTiO3 are investigated by means of
   periodic quantum-mechanical calculations based on density functional
   theory. It is observed that the difference in surface energies is small
   and relaxations effects are most prominent for Ti and Ph surface atoms.
   The electronic structure shows a splitting of the lowest conduction
   bands for the TiO2 terminated surface and of the highest valence bands
   for the PbO terminated slab. The calculated indirect band gap is: 3.18,
   2.99 and 3.03 eV for bulk, TiO2 and PbO terminations, respectively. The
   electron density maps show that the Ti-O bond has a partial covalent
   character, whereas the Pb-O bonds present a very low covalency. (C)
   2004 Elsevier B.V. All rights reserved.
C1 Univ Jaume I, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Estadual Paulista, Lab Simulacao Mol, BR-17033360 Bauru, SP, Brazil.
RP Sambrano, JR, Univ Jaume I, Dept Ciencies Expt, POB 6029, Castello
   12080, Spain.
EM sambrano@fc.unesp.br
   beltran@exp.uji.es
CR BECKE AD, 1993, J CHEM PHYS, V98, P5648
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NR 42
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD MAR 10
PY 2004
VL 552
IS 1-3
BP 149
EP 159
PG 11
SC Chemistry, Physical
GA 801VI
UT ISI:000220123000019
ER

PT J
AU Scopel, WL
   da Silva, AJR
   Orellana, W
   Fazzio, A
TI Comparative study of defect energetics in HfO2 and SiO2
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID CHEMICAL-VAPOR-DEPOSITION; THERMAL-STABILITY; THIN-FILMS;
   MOLECULAR-DYNAMICS; METALS; SUBSTRATE; SI(100); HAFNIUM; OXIDES; ZRO2
AB We perform ab initio calculations, based on density functional theory,
   for substitutional and vacancy defects in the monoclinic hafnium oxide
   (m-HfO2) and alpha-quartz (SiO2). The neutral oxygen vacancies and
   substitutional Si and Hf defects in HfO2 and SiO2, respectively, are
   investigated. Our calculations show that, for a large range of Hf
   chemical potential, Si substitutional defects are most likely to form
   in HfO2, leading to the formation of a silicate layer at the HfO2/Si
   interface. We also find that it is energetically more favorable to form
   oxygen vacancies in SiO2 than in HfO2, which implies that
   oxygen-deficient HfO2 grown on top of SiO2 will consume oxygen from the
   SiO2. (C) 2004 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Scopel, WL, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
EM fazzio@if.usp.br
CR BASTOS KP, 2002, APPL PHYS LETT, V81, P1669
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   KANG J, 2003, PHYS REV B, V68
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NR 25
TC 6
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD MAR 1
PY 2004
VL 84
IS 9
BP 1492
EP 1494
PG 3
SC Physics, Applied
GA 778WJ
UT ISI:000189264100020
ER

PT J
AU Silva, CHTP
   Almeida, P
   Taft, CA
TI Density functional and docking studies of retinoids for cancer treatment
SO JOURNAL OF MOLECULAR MODELING
LA English
DT Article
DE density functional; docking; cancer treatment
ID NUCLEAR RECEPTOR; AB-INITIO; ACID; GAMMA; SELECTIVITY; ANALOGS;
   BINDING; ALPHA
AB The retinoic acid receptor (RAR) and retinoid X receptor (RXR) are
   members of the nuclear receptor superfamily. The ligand-binding domain
   contains the ligand-dependent activation function. The isotypes
   RARalpha,beta and gamma are distinct pharmacological targets for
   retinoids involved in the treatment of various cancers and skin
   diseases. There is thus considerable interest in synthetic retinoids
   with isotype selectivity and reduced side effects. In this work we have
   focused on the retinoid acid receptor and three of its panagonists. We
   have carried out density functional geometry optimizations at the
   B3LYP/6-31G* level, computed two types of atomic charges and also
   electrostatic potentials. A docking program was used to investigate the
   interactions between the receptor and the three ligands. A
   theoretically more potent inhibitor, which was obtained by modifying
   one of the retinoic acids investigated, is proposed.
C1 Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Univ Sao Paulo, Inst Fis Sao Carlos, Sao Carlos, SP, Brazil.
   Inst Ciencias Saude, Dept Ciencias Biointeracao, Lab Biotecnol & Ecol Microrganismos, Salvador, BA, Brazil.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Rua Dr Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, Brazil.
EM taft@cbpf.br
CR *ACC, 2000, INS 2 US GUID VERS 2
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   FORESMAN JB, 1996, J PHYS CHEM-US, V100, P16098
   FRISCH MJ, 2002, GAUSSIAN 98 REVISION
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NR 24
TC 5
PU SPRINGER-VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 0948-5023
J9 J MOL MODEL
JI J. Mol. Model.
PD FEB
PY 2004
VL 10
IS 1
BP 38
EP 43
PG 6
SC Chemistry, Multidisciplinary; Computer Science, Interdisciplinary
   Applications; Biochemistry & Molecular Biology; Biophysics
GA 774RK
UT ISI:000188998200007
ER

PT J
AU Gracia, L
   Andres, J
   Safont, VS
   Beltran, A
TI DFT study of the reaction between VO2+ and C2H6
SO ORGANOMETALLICS
LA English
DT Review
ID POTENTIAL-ENERGY SURFACES; OXIDE CLUSTER CATIONS; GAS-PHASE CHEMISTRY;
   ELECTRONIC-STRUCTURE ASPECTS; C-H BOND; SPIN-FORBIDDEN PROCESSES;
   VANADIUM-OXIDE; AB-INITIO; TRANSITION-STATES; CROSSING POINTS
AB The molecular mechanisms of the reaction VO2+ ((1)A(1)/(3)A'') + C2H6
   ((1)A(g)) to yield V(OH)(2)(+) ((1)Sigma(+)/(3)Sigma(-)) + C2H4
   ((1)A(g)) and/or VO+ ((1)Delta/(3)Sigma) + H2O ((1)A(1)) + C2H4 (Ag-1)
   have been investigated with density functional theory (DFT) at the
   B3LYP/6-311G(2d,p) level. Calculations including geometry optimization,
   vibrational analysis, and Gibbs free energy for the stationary points
   on the reactive potential energy surfaces at both the singlet (s) and
   first excited triplet (t) electronic states have been carried out. The
   most thermodynamically and kinetically favorable pathway is the
   formation of t-V(OH)(2)(+) + C2H4 along a four-step molecular mechanism
   (insertion, two consecutive hydrogen transfers, and elimination). A
   crossing point between s and t electronic states has been
   characterized. A comparison with previous works on VO2+ + C2H4 (Gracia
   et al. J. Phys. Chem. A 2003, 107, 3107-3120) and VO2+ + C3H8 (Engeser
   et al. Organometallics 2003, 22, 3933-3943) reactions allows us a
   rationalization of the different reactivity patterns. The catalytic
   role of water molecules in the tautomerization process between hydrated
   oxide cation, VO(H2O)(+,) and dihydroxide cation, V(OH)(2)(+), is
   achieved by a water-assisted mechanism.
C1 Univ Jaume I, Dept Ciencias Expt, Castello 12080, Spain.
   Univ Estadual Paulista, Lab Simulacao Mol, BR-17033360 Bauru, SP, Brazil.
RP Andres, J, Univ Jaume I, Dept Ciencias Expt, Box 224, Castello 12080,
   Spain.
EM andres@exp.uji.es
CR ANGLADA JM, 1996, J AM CHEM SOC, V118, P4636
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   ASCHI M, 1998, CHEM COMMUN     0307, P531
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   ASCHI M, 2001, CHEM PHYS, V265, P251
   ASMIS KR, 2002, PHYS CHEM CHEM PHYS, V4, P1101
   BARRIENTOS C, 1999, CHEM PHYS LETT, V306, P168
   BEARPARK MJ, 1994, CHEM PHYS LETT, V223, P269
   BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BELL RC, 1998, J PHYS CHEM A, V102, P1733
   BELL RC, 1998, J PHYS CHEM A, V102, P8293
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NR 113
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0276-7333
J9 ORGANOMETALLICS
JI Organometallics
PD FEB 16
PY 2004
VL 23
IS 4
BP 730
EP 739
PG 10
SC Chemistry, Inorganic & Nuclear; Chemistry, Organic
GA 772ZF
UT ISI:000188872700015
ER

PT J
AU Larico, R
   Justo, JF
   Machado, WVM
   Assali, LVC
TI An ab initio investigation on nickel impurities in diamond
SO PHYSICA B-CONDENSED MATTER
LA English
DT Article
DE diamond; synthetic diamond; transition metals; nickel impurities
ID SYNTHETIC DIAMOND; POINT-DEFECTS; NI; CENTERS; TRANSITION; EPR
AB We carried out a theoretical investigation on the electronic and
   structural properties of substitutional and interstitial nickel
   impurities in diamond. The atomic structures, symmetries, acceptor and
   donor transition energies, and formation energies of isolated Ni in
   diamond were computed using a total energy all electron ab initio
   methodology. Compared to available experimental data on the
   electrically and optically active centers in synthetic diamond, our
   results provide a new interpretation for the microscopic structure of
   those active centers. (C) 2003 Elsevier B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Sao Paulo, Escola Politecn, BR-05424970 Sao Paulo, Brazil.
RP Assali, LVC, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
EM lassali@if.usp.br
CR BARBOSA KO, 2001, PHYSICA B, V308, P726
   BEELER F, 1990, PHYS REV B, V41, P1603
   BLAHA P, 1999, WIEN97 FULL POTENTIA
   GERSTMANN U, 1999, PHYSICA B, V274, P632
   HOFMANN DM, 1994, PHYS REV B, V50, P17618
   HOFMANN DM, 1995, MATER SCI FORUM, V196, P79
   ISOYA J, 1990, PHYS REV B, V41, P3905
   ISOYA J, 1990, PHYS REV B, V42, P9843
   JINLONG Y, 1994, PHYS REV B, V49, P15525
   KOHN W, 1965, PHYS REV, V140, A1133
   LOWTHER JE, 1995, PHYS REV B, V51, P91
   LUDWIG GW, 1962, SOLID STATE PHYS, V13, P223
   MASON PW, 1999, PHYS REV B, V60, P5417
   MONKHORST HJ, 1976, PHYS REV B, V13, P5188
   NAZARE MH, 1991, PHYS REV B, V43, P14196
   NAZARE MH, 2001, PHYSICA B, V308, P616
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
NR 17
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0921-4526
J9 PHYSICA B
JI Physica B
PD DEC 31
PY 2003
VL 340
BP 84
EP 88
PG 5
SC Physics, Condensed Matter
GA 765TR
UT ISI:000188300200012
ER

PT J
AU Assali, LVC
   Machado, WVM
   Justo, JF
TI Transition metal impurities in 3C-SiC and 2H-SiC
SO PHYSICA B-CONDENSED MATTER
LA English
DT Article
DE silicon carbide; transition metals; LAPW methods
ID ELECTRONIC-PROPERTIES; SIC POLYTYPES; SILICON-CARBIDE; BAND-GAP; LEVEL;
   TI; CENTERS; STATES; PAIRS; CR
AB The electronic and structural properties of 3d transition metal (TM)
   impurities in 3C-SiC and 2H-SiC have been investigated by ab initio
   calculations. The stability, spin states, formation and transition
   energies of isolated Ti, V, and Cr impurities in several charge states
   were computed. Our results were compared to available experimental
   data. (C) 2003 Elsevier B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Sao Paulo, Escola Politecn, BR-05424970 Sao Paulo, Brazil.
RP Assali, LVC, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
EM lassali@if.usp.br
CR ACHTZIGER N, 1998, PHYS REV B, V57, P12181
   ASSALI LVC, 1998, PHYS REV B, V58, P3870
   BARANOV PG, 1999, PHYS SOLID STATE+, V41, P783
   BARBOSA KO, 2001, PHYSICA B, V308, P726
   BARBOSA KO, 2003, THESIS U SAO PAULO
   BAUR J, 1997, PHYS STATUS SOLIDI A, V162, P153
   BLAHA P, 1999, WIEN97 FULL POTENTIA
   DALIBOR T, 1997, PHYS STATUS SOLIDI A, V162, P199
   EVWARAYE AO, 1995, APPL PHYS LETT, V67, P3319
   HOHENBERG P, 1964, PHYS REV B, V136, P864
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   RESHANOV SA, 2001, DIAM RELAT MATER, V10, P2035
   SULEIMANOV YM, 2001, PHYSICA B, V308, P714
NR 20
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0921-4526
J9 PHYSICA B
JI Physica B
PD DEC 31
PY 2003
VL 340
BP 116
EP 120
PG 5
SC Physics, Condensed Matter
GA 765TR
UT ISI:000188300200018
ER

PT J
AU Trasferetti, BC
   Davanzo, CU
   de Moraes, MAB
TI Infrared and Raman studies on films of organosiloxane networks produced
   by PECVD
SO MACROMOLECULES
LA English
DT Article
ID CHEMICAL-VAPOR-DEPOSITION; THIN-FILMS; VIBRATIONAL-SPECTRA; PLASMA
   POLYMERIZATION; SILICA FILM; AB-INITIO; OXYGEN; SPECTROSCOPY;
   ABSORPTION; NITROGEN
AB The effect of the incorporation of oxygen and nitrogen on the structure
   of films obtained by PECVD of hexamethyldisiloxane (HMDSO)-He-N-2 and
   HMDSO-He-O-2 mixtures is investigated using infrared and Raman
   spectroscopies. From transmittance spectra of films deposited onto
   single-crystal KBr disks, the transverse optical (TO) and longitudinal
   optical (LO) functions in the mid-infrared region were calculated. To
   correlate structural aspects with the observed LO-TO splittings, an
   identification analysis of functional group based on the infrared and
   Raman literature was made. It was concluded that the structure of the
   films deposited from HMDSO-He-O-2 discharges was strongly dependent on
   the proportion of oxygen in the gas feed. In the absence of oxygen,
   i.e., for a discharge of a HMDSO-He mixture, the resulting film
   consisted of a network of interconnected siloxane and carbosilane
   units. Addition of O-2 precluded the formation of methylene bridges and
   induced the formation of a material enriched with Si-O-Si groups. Films
   formed from the HMDSO-He-N-2 plasmas, on the other hand, consisted
   mainly of interconnected siloxane and carbosilane units in addition to
   a small quantity of silazane units. On the basis of these results, we
   propose an interpretation for the variation of the LO-TO splitting
   amplitude for the asymmetrical stretching mode (AS1) of Si-O in Si-O-Si
   groups as a function of the oxygen or nitrogen incorporation into the
   films.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
RP Davanzo, CU, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083970 Campinas, SP, Brazil.
EM celso@iqm.unicamp.br
CR ALEXANDER MR, 1997, J PHYS CHEM B, V101, P3614
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   TEN YS, 1989, J PHYS CHEM-US, V93, P7208
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   TSU DV, 1989, PHYS REV B, V40, P1795
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NR 50
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0024-9297
J9 MACROMOLECULES
JI Macromolecules
PD JAN 27
PY 2004
VL 37
IS 2
BP 459
EP 466
PG 8
SC Polymer Science
GA 766NU
UT ISI:000188383100034
ER

PT J
AU Larico, R
   Assali, LVC
   Machado, WVM
   Justo, JF
TI Isolated nickel impurities in diamond: A microscopic model for the
   electrically active centers
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID SYNTHETIC DIAMOND; NI; EPR; ABSORPTION; PRESSURE; SITE
AB We present a theoretical investigation on the structural and electronic
   properties of isolated nickel impurities in diamond. The atomic
   structures, symmetries, formation and transition energies, and
   hyperfine parameters of isolated interstitial and substitutional Ni
   were computed using ab initio total energy methods. Based on our
   results, we ultimately propose a consistent microscopic model which
   explains several experimentally identified nickel-related active
   centers in diamond. (C) 2004 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Sao Paulo, Escola Politecn, BR-05424970 Sao Paulo, Brazil.
RP Assali, LVC, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
EM lassali@if.usp.br
CR ANGUS JC, 1988, SCIENCE, V241, P913
   BARBOSA KO, 2001, PHYSICA B, V308, P726
   BLAHA P, 1999, WIEN97 FULL POTENTIA
   COLLINS AT, 1989, J PHYS-CONDENS MAT, V1, P439
   DAVIES G, 1989, EUROPHYS LETT, V9, P47
   GOSS J, 1995, MATER SCI FORUM, V196, P67
   HOFMANN DM, 1994, PHYS REV B, V50, P17618
   HOFMANN DM, 1995, MATER SCI FORUM, V196, P79
   HOHENBERG P, 1964, PHYS REV, V136, B864
   ISOYA J, 1990, PHYS REV B, V41, P3905
   ISOYA J, 1990, PHYS REV B, V42, P9843
   JINLONG Y, 1994, PHYS REV B, V49, P15525
   KOHN W, 1965, PHYS REV, V140, A1133
   LOWTHER JE, 1995, PHYS REV B, V51, P91
   LUDWIG GW, 1962, SOLID STATE PHYS, V13, P223
   MASON PW, 1999, PHYS REV B, V60, P5417
   MONKHORST HJ, 1976, PHYS REV B, V13, P5188
   NADOLINNY VA, 1999, J PHYS-CONDENS MAT, V11, P7357
   NAZARE MH, 1991, PHYS REV B, V43, P14196
   NAZARE MH, 2001, PHYSICA B, V308, P616
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
   SINGH DJ, 1994, PLANEWAVES PSEUDOPOT
   TWITCHEN DJ, 2000, PHYS REV B, V61, P9
NR 23
TC 8
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 2
PY 2004
VL 84
IS 5
BP 720
EP 722
PG 3
SC Physics, Applied
GA 767WX
UT ISI:000188497800026
ER

PT J
AU da Silva, LB
   Fagan, SB
   Mota, R
TI Ab initio study of deformed carbon nanotube sensors for carbon monoxide
   molecules
SO NANO LETTERS
LA English
DT Article
ID LARGE SYSTEMS; ENERGETICS
AB Deformed single-wall carbon nanotubes (SWCNT) are investigated through
   ab initio simulations as sensors to detect the presence of chemical
   gases. Although the viability of using undeformed SWCNT devices has
   been demonstrated for many molecules, there are important exceptions of
   toxic gases, such as carbon monoxide, which are not detectable by these
   sensors. To overcome this problem, recent interesting propositions have
   been presented based on doping of impurity atoms into SWCNT. In this
   paper, an alternative method is proposed using radial deformation,
   which induces fundamental changes on the electronic properties of
   SWCNT, allowing functionalization of the tube surface to detect the
   presence of CO molecules.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Univ Fed Ceara, Dept Fis, BR-60455900 Fortaleza, Ceara, Brazil.
RP Mota, R, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
EM mota@ccne.ufsm.br
CR ARTACHO E, 1999, PHYS STATUS SOLIDI B, V215, P809
   BAIERLE RJ, 2001, PHYS REV B, V64
   FAGAN SB, 2003, DIAM RELAT MATER, V12, P861
   FAGAN SB, 2003, MATER CHARACT, V50, P183
   FAGAN SB, 2003, NANO LETT, V3, P289
   FAGAN SB, 2003, PHYS REV B, V67
   KONG J, 2001, ADV MATER, V13, P1384
   ORDEJON P, 1996, PHYS REV B, V53
   PENG S, 2003, NANO LETT, V3, P513
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
   SANCHEZPORTAL D, 1997, INT J QUANTUM CHEM, V65, P453
   SANKEY OF, 1989, PHYS REV B, V40, P3979
   TROULLIER N, 1991, PHYS REV B, V43, P1993
NR 13
TC 6
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1530-6984
J9 NANO LETT
JI Nano Lett.
PD JAN
PY 2004
VL 4
IS 1
BP 65
EP 67
PG 3
SC Chemistry, Multidisciplinary; Materials Science, Multidisciplinary
GA 764YA
UT ISI:000188233200013
ER

PT J
AU Almerindo, GI
   Tondo, DW
   Pliego, JR
TI Ionization of organic acids in dimethyl sulfoxide solution: A
   theoretical ab initio calculation of the pK(a) using a new
   parametrization of the polarizable continuum model
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID COMPLETE BASIS-SET; DENSITY-FUNCTIONAL THEORY; QUANTUM-MECHANICAL
   CALCULATIONS; SOLVATION FREE-ENERGY; CARBOXYLIC-ACIDS;
   AQUEOUS-SOLUTION; GAS-PHASE; THERMODYNAMIC CYCLES; ALIPHATIC-ALCOHOLS;
   HALOACETIC ACIDS
AB The pK(a) values of over 41 organic acids in dimethyl sulfoxide (DMSO)
   solution were calculated using ab initio electronic structure methods
   at MP2 and MP4 levels of electron correlation and including basis set
   of 6-31+G(d) and 6-311+G(2df,2p) quality. The solvation was included
   through the polarizable continuum model (PCM), using the recent
   parametrization of Pliego and Riveros. The root-mean-square (RMS) error
   over this set of molecules having different functional groups is only
   2.2 units. A linear fit on this data set decreases this error by only
   0.2 units, indicating that this empirical correction is not necessary.
   The major error in the calculated pK(a) value was -5.3 units for the
   CH3SO3H solute. Halogenated carboxylic acids have also presented a high
   deviation (similar to4 units). An explanation for these high deviations
   is the possibility of strong hydrogen-bond formation involving the
   neutral acid molecule and DMSO. The pK(a) values were also calculated
   using a combination of theoretical solvation data with experimental
   gas-phase data. In this case, the RMS error increased to 2.3 units for
   a set of 36 acids. Our results show that the performance of the PCM
   model with a fixed atomic radius in DMSO solution is very superior to
   its performance in aqueous solution, which is a behavior that can be
   attributed to the presence of strong and specific solute-solvent
   interactions of ionic solutes with water molecules. In addition, no
   extensive parametrization of the PCM model is needed to describe the
   solvation of anions in DMSO solution.
C1 Univ Fed Santa Catarina, Dept Quim, BR-88040900 Florianopolis, SC, Brazil.
RP Pliego, JR, Univ Fed Santa Catarina, Dept Quim, BR-88040900
   Florianopolis, SC, Brazil.
EM josef@qmc.ufsc.br
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NR 52
TC 13
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JAN 8
PY 2004
VL 108
IS 1
BP 166
EP 171
PG 6
SC Chemistry, Physical
GA 760MU
UT ISI:000187838500024
ER

PT J
AU Jorge, FE
   Autschbach, J
   Ziegler, T
TI On the origin of the optical activity in the d-d transition region of
   tris-bidentate Co(III) and Rh(III) complexes
SO INORGANIC CHEMISTRY
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; CIRCULAR-DICHROISM SPECTRA; CO-ORDINATION
   COMPOUNDS; METAL-COMPLEXES; CRYSTAL-STRUCTURE; COBALT(III) COMPLEXES;
   RESPONSE THEORY; ROTATORY POWER; ABSOLUTE-CONFIGURATIONS; CHIROPTICAL
   PROPERTIES
AB Time-dependent density functional theory (TD-DFT) has been employed to
   calculate the rotatory strengths in the d-d transition region for
   various tris-bidentate Co(III) and Rh(III) complexes. Optimized
   structural parameters are also reported. Our results confirm a
   previously proposed relationship between the azimuthal distortion of a
   complex containing saturated tris(diamine) and its optical activity.
   Formally d-d transitions are forbidden and should not exhibit optical
   activity. However, it is shown here that the intensity of these bands
   originates from a coupling of even ligand combination (participating in
   the e(g) type LUMO) and an odd ligand combination (participating in the
   t(2g) HOMO). For complexes containing planar unsaturated ligands, the
   signs of the d-d bands observed from the single-crystal circular and
   linear dichroisms are in accordance with the TD-DFT predictions. It is
   shown that by using hypothetical Co(NH3)(6)(3+) complexes it is
   possible to estimate the contribution from the azimuthal distortion to
   the total rotatory strengths of the saturated tris(diamine) complexes.
   A discussion is also provided of previous theoretical studies and the
   way in which these investigations rationalized the optical activity.
C1 Univ Calgary, Dept Chem, Calgary, AB T2N 1N4, Canada.
   Univ Fed Espirito Santo, Dept Fis, BR-29060900 Vitoria, ES, Brazil.
   SUNY Buffalo, Dept Chem, Buffalo, NY 14260 USA.
RP Ziegler, T, Univ Calgary, Dept Chem, Calgary, AB T2N 1N4, Canada.
EM ziegler@ucalgary.ca
CR AUTSCHBACH J, 2002, J CHEM PHYS, V116, P6930
   AUTSCHBACH J, 2002, J CHEM PHYS, V116, P891
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NR 59
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0020-1669
J9 INORG CHEM
JI Inorg. Chem.
PD DEC 29
PY 2003
VL 42
IS 26
BP 8902
EP 8910
PG 9
SC Chemistry, Inorganic & Nuclear
GA 759LX
UT ISI:000187740100044
ER

PT J
AU Carauta, ANM
   de Souza, V
   Hollauer, E
   Tellez, CA
TI Vibrational study of dialkylphosphonates: di-n-propyl- and
   di-i-propylphosphonates by semiempirical and ab initio methods
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE dialkylphosphonates; vibrational spectra; semiempirical AM1; ab initio
   RHF/6-31G
ID ORGANOPHOSPHORUS COMPOUNDS; CONFORMATIONAL STABILITY; INFRARED-SPECTRA;
   FORCE-FIELD; PHOSPHONATE; COMPLEXES; FREQUENCIES; RAMAN; ASSIGNMENTS;
   DIESTER
AB Fourier transform infrared and Fourier transform Raman spectra of
   n-C3H7 and i-C3H7 dialkylphosphonates have been obtained. Semiempirical
   AM1 and the ab initio orbital molecular RHF/6-31G* theories have been
   used to study the molecular geometry, and the harmonic vibrational
   spectra with the purpose to assist the experimental assignments of
   these compounds. An extensive discussion on the assignment of the C-C,
   C-O, P-O and P=O stretching is carried out based on experimental data
   of compounds which have the propyl and isopropyl groups, as well as
   comparing the vibrational spectra of propane. Most of the RHF/6-31G*
   and AM1 results, once applied the appropriate scaling factor, showed an
   excellent agreement with the experimental wavenumbers. A few calculated
   frequencies related to CC and CO stretching do not agree well with the
   experimental trends. (C) 2003 Elsevier B.V. All rights reserved.
C1 Univ Fed Fluminense, Inst Quim, Dept Quim Geral & Inorgan, BR-24210150 Rio De Janeiro, Brazil.
   INMETRO, Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Dept Quim Fis, Inst Quim, BR-24210150 Rio De Janeiro, Brazil.
RP Tellez, CA, Univ Fed Fluminense, Inst Quim, Dept Quim Geral & Inorgan,
   Morro do Valonguinho S-N,Niteroi Ctr, BR-24210150 Rio De Janeiro,
   Brazil.
CR BEELAMY LJ, 1952, J CHEM SOC, P475
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NR 42
TC 3
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JAN
PY 2004
VL 60
IS 1-2
BP 41
EP 51
PG 11
SC Spectroscopy
GA 759RK
UT ISI:000187750500006
ER

PT J
AU De Abreu, HA
   De Almeida, WB
   Duarte, HA
TI pK(a) calculation of poliprotic acid: histamine
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID POLARIZABLE CONTINUUM MODEL; COMPLETE BASIS-SET; CORRELATION-ENERGY;
   AB-INITIO; N-HYDROXYACETAMIDE; SOLVATION METHODS; GAS-PHASE; DENSITY;
   IONS; APPROXIMATION
AB Various theoretical studies have been reported addressing the
   performance of solvation models available to estimate pK(a) values.
   However, no attention has been paid so far to the role played by the
   electronic, thermal and solvation energy individual contributions to
   the Gibbs free energy of the deprotonation process. In this work, we
   decompose the total Gibbs free energy into three distinct terms and
   then evaluate the dependence of each contribution on the level of
   theory employed for its determination using different levels of theory.
   The three possible pK(a)s of histamine have been estimated and compared
   with available experimental data. We found that the electronic energy
   term is sensitive to the level of theory and basis set, and, therefore,
   could be also a source of error in the theoretical calculation of
   pK(a)s. (C) 2003 Elsevier B.V. All rights reserved.
C1 UFMG, ICEx, Dept Quim, LQC MM, BR-31270901 Belo Horizonte, MG, Brazil.
RP Duarte, HA, UFMG, ICEx, Dept Quim, LQC MM, Av Antonio Carlos 6627,
   BR-31270901 Belo Horizonte, MG, Brazil.
CR 1992, HDB CHEM PHYS
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NR 33
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD JAN 1
PY 2004
VL 383
IS 1-2
BP 47
EP 52
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 759TL
UT ISI:000187752900010
ER

PT J
AU Schimpl, J
   Petrilli, HM
   Blochl, PE
TI Nitrogen binding to the FeMo-cofactor of nitrogenase
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID AUGMENTED-WAVE METHOD; AZOTOBACTER-VINELANDII NITROGENASE;
   DENSITY-FUNCTIONAL THEORY; IRON-MOLYBDENUM COFACTOR; ATOMIC-LEVEL
   MECHANISM; MOFE-PROTEIN; KLEBSIELLA-PNEUMONIAE; MOLECULAR-DYNAMICS;
   CENTRAL LIGAND; CRYSTALLOGRAPHIC STRUCTURE
AB Density functional calculations are presented to unravel the first
   steps of nitrogen fixation of nitrogenase. The individual steps leading
   from the resting state to nitrogen binding at the FeMo-cofactor with a
   central nitrogen ligand are characterized. The calculations indicate
   that the Fe-Mo cage opens as dinitrogen binds to the cluster. In the
   resting state, the central cage is overall neutral. Electrons and
   protons are transferred in an alternating manner. Upon dinitrogen
   binding, one protonated sulfur bridge is broken. An axial and a bridged
   binding mode of dinitrogen have been identified. Adsorption at the Mo
   site has been investigated but appears to be less favorable than
   binding at Fe sites.
C1 Tech Univ Clausthal, Inst Theoret Phys, D-38678 Clausthal Zellerfeld, Germany.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
RP Blochl, PE, Tech Univ Clausthal, Inst Theoret Phys, D-38678 Clausthal
   Zellerfeld, Germany.
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NR 61
TC 26
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AM CHEM SOC
JI J. Am. Chem. Soc.
PD DEC 24
PY 2003
VL 125
IS 51
BP 15772
EP 15778
PG 7
SC Chemistry, Multidisciplinary
GA 755XF
UT ISI:000187436200042
ER

PT J
AU Pereira, MS
   Nascimento, MAC
TI Theoretical study on reactions catalyzed by gallium-substituted zeolites
SO THEORETICAL CHEMISTRY ACCOUNTS
LA English
DT Article
DE zeolite; gallium; catalysis by zeolites
ID DEHYDROGENATION REACTION; AROMATIZATION; ZSM-5; GA; GALLOSILICATES;
   ISOBUTANE; ACIDITY; PROPANE; ALKANES; STATE
AB The dehydrogenation and cracking reactions of light alkanes in
   gallium-containing zeolites were studied using density functional
   theory. Gallium isomorphically substituted, generating Bronsted acid
   sites, was used in the computations. The following reactions were
   examined: dehydrogenation of methane, ethane, propane, isobutane and
   cracking of ethane, propane and isobutene, all catalyzed by the
   framework gallium species. The cracking reaction seems to be favored
   relative to the dehydrogenation when framework gallium species are
   used. This behavior is also observed in aluminum-containing zeolites
   (H-ZSM5). The geometries and energetics of the transition states found
   for the gallium zeolites were compared with theoretical data for the
   same transition states in aluminum zeolites. There seems to be no
   significant difference between framework gallium and framework aluminum
   species. Therefore the framework gallium should not be the species
   responsible for the catalytic enhancement observed in
   gallium-containing zeolites.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis,
   Cidade Univ,CT,Bloco A,Sala 412, BR-21949900 Rio De Janeiro, Brazil.
CR *GAUSS INC, 1995, GAUSS 98
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NR 33
TC 3
PU SPRINGER-VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1432-881X
J9 THEOR CHEM ACC
JI Theor. Chem. Acc.
PD DEC
PY 2003
VL 110
IS 6
BP 441
EP 445
PG 5
SC Chemistry, Physical
GA 749YU
UT ISI:000186958300014
ER

PT J
AU Martins, TLC
   Ramalho, TC
   Figueroa-Villar, JD
   Flores, AFC
   Pereira, CMP
TI Theoretical and experimental C-13 and N-15 NMR investigation of
   guanylhydrazones in solution
SO MAGNETIC RESONANCE IN CHEMISTRY
LA English
DT Article
DE NMR; N-15 NMR; C-13 NMR; chemical shifts; molecular dynamics; GIAO;
   DFT; guanylhydrazones
ID SEQUENTIAL MONTE-CARLO; CHEMICAL-SHIFTS; AB-INITIO; SOLVENT;
   DERIVATIVES; SIMULATION; CONTINUUM; AGENTS; RELAXATION; MOLECULES
AB Experimental and theoretical N-15 and C-13 NMR data for the three
   nitrobenzaldehyde guanylhydrazones are reported. The theoretical data
   were obtained using sequential molecular dynamics/quantum mechanics
   methodology for the calculation of flexible molecules in a condensed
   phase, followed by the use of the GIAO/DFT method with the 6-311G**
   basis set. The experimental N-15 chemical shifts for the
   guanylhydrazones are compared with the calculated shifts. Copyright (C)
   2003 John Wiley Sons, Ltd.
C1 Inst Militar Engn, Dept Quim, BR-22290270 Rio De Janeiro, RJ, Brazil.
   Univ Fed Santa Maria, Dept Quim, BR-97105900 Santa Maria, RS, Brazil.
RP Figueroa-Villar, JD, Inst Militar Engn, Dept Quim, BR-22290270 Rio De
   Janeiro, RJ, Brazil.
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NR 46
TC 3
PU JOHN WILEY & SONS LTD
PI CHICHESTER
PA THE ATRIUM, SOUTHERN GATE, CHICHESTER PO19 8SQ, W SUSSEX, ENGLAND
SN 0749-1581
J9 MAGN RESON CHEM
JI Magn. Reson. Chem.
PD DEC
PY 2003
VL 41
IS 12
BP 983
EP 988
PG 6
SC Chemistry, Multidisciplinary; Chemistry, Physical; Spectroscopy
GA 747CW
UT ISI:000186788500002
ER

PT J
AU Barbosa, PHR
   Raposo, EP
   Coutinho, MD
TI Microscopic description of an ising spin glass near the percolation
   threshold
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID RANDOM-FIELD; RANDOM-EXCHANGE; ORDERED PHASE; MONTE-CARLO;
   NONEQUILIBRIUM DYNAMICS; DILUTED ANTIFERROMAGNET; NEUTRON-SCATTERING;
   SYSTEM FEXZN1-XF2; CRITICAL-BEHAVIOR; FE0.25ZN0.75F2
AB Monte Carlo results using a microscopic model to describe FexZn1-xF2
   indicate that its spin-glass phase at x=0.25 and zero magnetic field is
   characterized by the presence of antiferromagnetic fractal domains,
   separated by random vacancies and strongly correlated in time. The
   effective local random-field distribution corroborates this glassy
   behavior, which emerges irrespective of ab initio competing
   interactions and is a consequence of the fractal domain structure near
   the percolation threshold, x(p)=0.24. The aging properties of the
   system are in agreement with predictions of short-range stochastic
   spin-glass models and with the droplets model for spin glass close to
   percolation.
C1 Univ Fed Pernambuco, Dept Fis, Lab Fis Teor & Computac, BR-50670901 Recife, PE, Brazil.
   Univ Fed Piaui, Dept Fis, BR-64048550 Teresina, PI, Brazil.
RP Barbosa, PHR, Univ Fed Pernambuco, Dept Fis, Lab Fis Teor & Computac,
   BR-50670901 Recife, PE, Brazil.
CR BALLESTEROS HG, 1998, PHYS REV B, V58, P2740
   BARBER WC, 2000, PHYS REV B, V61, P8960
   BARBOSA PHR, 2000, J APPL PHYS 3, V87, P6531
   BARBOSA PHR, 2001, J MAGN MAGN MATER 2, V226, P1293
   BARBOSA PHR, 2001, MATER SCI FORUM, V373, P705
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   BARRAT A, 2001, PHYS REV LETT, V87
   BARRETT PH, 1986, PHYS REV B, V34, P3513
   BELANGER DP, 1986, PHYS REV B, V34, P452
   BELANGER DP, 1991, PHYS REV B, V44, P2161
   BELANGER DP, 1993, PHYS REV B, V47, P5051
   BELANGER DP, 2000, BRAZ J PHYS, V30, P682
   BERNARDI LW, 2001, PHYS REV LETT, V86, P720
   BIRGENEAU RJ, 1983, PHYS REV B, V27, P6747
   BRAY AJ, 1988, COMMENTS CONDENS MAT, V14, P21
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NR 53
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD NOV 7
PY 2003
VL 91
IS 19
AR 197207
DI ARTN 197207
PG 4
SC Physics, Multidisciplinary
GA 740VR
UT ISI:000186422700045
ER

PT J
AU Sensato, FR
   Custodio, R
   Longo, E
   Beltran, A
   Andres, J
TI Electronic and structural properties of SnxTi1-xO2 solid solutions: a
   periodic DFT study
SO CATALYSIS TODAY
LA English
DT Article
DE oxidation-reduction potential; electron-hole recombination; Fermi
   level; SnO2-TiO2; periodic DFT calculation; photocatalysis
ID DENSITY-FUNCTIONAL THEORY; GAS-SENSING PROPERTIES; THIN-FILMS;
   1ST-PRINCIPLES CALCULATIONS; THEORETICAL-ANALYSIS; SNO2(110) SURFACES;
   TIO2-SNO2 SYSTEM; TIO2; ADSORPTION; SENSORS
AB The structural and electronic properties of selected compositions of
   SnxTi1-xO2 solid solutions (x = 0, 1/24, 1/16, 1/12, 1/8, 1/6, 1/4,
   1/2, 3/4, 5/6, 7/8, 11/12, 15/16, 23/24 and 1) were investigated by
   means of periodic density functional theory (DFT) calculations at B3LYP
   level. The calculations show that the corresponding lattice parameters
   vary non-linearly with composition, supporting positive deviations from
   Vegard's law in the SnxTi1-xO2 system. Our results also account for the
   fact that chemical decomposition in SnxTi1-xO2 system is dominated by
   composition fluctuations along [0 0 1] direction. A nearly continuous
   evolution of the direct band gap and the Fermi level with the growing
   value of x is predicted. Ti 3d states dominate the lower portion of the
   conduction band of SnxTi1-xO2 solid solutions. Sn substitution for Ti
   in TiO2 increases the oxidation-reduction potential of the oxide as
   well as it renders the lowest energy transition to be indirect. These
   two effects can be the key factors controlling the rate for the
   photogenerated electron-hole recombination. These theoretical results
   are capable to explain the enhancement of photoactivity in SnxTi1-xO2
   solid solutions. (C) 2003 Elsevier B.V All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello, Spain.
RP Sensato, FR, Univ Estadual Campinas, Inst Quim, CP 6154, BR-13083970
   Campinas, SP, Brazil.
CR ABEE MW, 2002, SURF SCI, V520, P65
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NR 49
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0920-5861
J9 CATAL TODAY
JI Catal. Today
PD OCT 15
PY 2003
VL 85
IS 2-4
BP 145
EP 152
PG 8
SC Chemistry, Applied; Chemistry, Physical; Engineering, Chemical
GA 738FG
UT ISI:000186275600007
ER

PT J
AU Machado, M
   Piquini, P
   Mota, R
TI Electronic properties of selected BN nanocones
SO MATERIALS CHARACTERIZATION
LA English
DT Article
DE apex; BN; nanocones; atoms
ID BORON-NITRIDE NANOTUBES; CARBON NANOTUBES; DENSITY; FRUSTRATION;
   STATES; GROWTH; CONES
AB The electronic properties of selected BN nanocones are investigated. In
   particular, we have proposed one configuration for BN nanocones
   associated with the 240degrees disclination as the most stable one
   presenting as characteristic four pentagons at the apex and termination
   in two atoms. This structure is simulated by clusters containing 58 B
   plus N atoms and additional 12 H atoms to saturate the dangling bonds
   at the edge. The geometric structure is obtained through molecular
   mechanics optimization calculations. The density-functional theory is
   employed to perform total energy calculations. The most stable
   termination is obtained when the two terminating atoms are one B and
   one N. For those cases where the two apex atoms are of the same kind,
   the apex with B atoms is determined to present lower binding energy
   than with N atoms. For the topologies studied, the local densities of
   states are investigated near the apex of the nanocones and sharp
   resonant states are found to dominate the electronic structure in the
   region close to the Fermi energy. These BN nanocones with pentagonal
   sites at their apex are proposed as good candidates for nanoprobes in
   scanning microscopy and also for electron field emitters. (C) 2003
   Elsevier Inc. All rights reserved.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Machado, M, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria,
   RS, Brazil.
CR BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BENGU E, 2001, PHYS REV LETT, V86, P2385
   BLASE X, 1998, PHYS REV LETT, V80, P1666
   BOURGEOIS L, 2000, PHYS REV B, V61, P7686
   CARROLL DL, 1997, PHYS REV LETT, V78, P2811
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   FRISCH MJ, 1998, GAUSSIAN 98
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NR 21
TC 5
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA
SN 1044-5803
J9 MATER CHARACT
JI Mater. Charact.
PD MAR
PY 2003
VL 50
IS 2-3
BP 179
EP 182
PG 4
SC Materials Science, Characterization & Testing
GA 737UJ
UT ISI:000186249900015
ER

PT J
AU Fagan, SB
   Mota, R
   Baierle, RJ
   da Silva, AJR
   Fazzio, A
TI Energetics and structural properties of adsorbed atoms and molecules on
   silicon-doped carbon nanotubes
SO MATERIALS CHARACTERIZATION
LA English
DT Article
DE energetics; structural properties; silicon-doped carbon nanotubes
ID LARGE SYSTEMS; CLUSTERS; GAS
AB The energetics and structural properties of atoms and molecules on a
   substitutional Si atom in single wall carbon nanotubes (SWCN) are
   investigated using first principle calculations based on
   density-functional theory. A detailed analysis is performed for the
   geometry and the electronic structures of a Si-doped semiconducting
   (10,0) carbon nanotube interacting with F, Cl, H, CH3, and SiH3. A
   common feature for the systems with these atoms or molecules is the
   presence of one half-filled level close to the top of the valence band.
   The specific position of this level in the gap depends on the
   chemisorbed species and the binding energy between this species and the
   Si atom. (C) 2003 Elsevier Inc. All rights reserved.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Ctr Univ Franciscano, Dept Ciencias Exatas, BR-97101032 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
RP Fagan, SB, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
EM sfagan@mail.ufsm.br
CR ALRUBAIEY N, 1998, J PHYS CHEM A, V102, P8564
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NR 22
TC 3
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA
SN 1044-5803
J9 MATER CHARACT
JI Mater. Charact.
PD MAR
PY 2003
VL 50
IS 2-3
BP 183
EP 187
PG 5
SC Materials Science, Characterization & Testing
GA 737UJ
UT ISI:000186249900016
ER

PT J
AU Guedes, RC
   Coutinho, K
   Cabral, BJC
   Canuto, S
   Correia, CF
   dos Santos, RMB
   Simoes, JAM
TI Solvent effects on the energetics of the phenol O-H bond: Differential
   solvation of phenol and phenoxy radical in benzene and acetonitrile
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID SUBSTITUTED CYCLOPENTADIENYL RADICALS; CARLO-QUANTUM-MECHANICS; SMALL
   CLUSTERS; BASIS-SET; PHOTOACOUSTIC CALORIMETRY; THERMAL-DECOMPOSITION;
   TOTAL ENERGIES; AB-INITIO; HYDRATION; WATER
AB Monte Carlo statistical mechanics simulations, density-functional
   theory calculations, time-resolved photoacoustic calorimetry, and
   isoperibol reaction-solution calorimetry experiments were carried out
   to investigate the solvation enthalpies and solvent effects on the
   energetics of the phenol O-H bond in benzene and acetonitrile. A good
   agreement between theoretical and experimental results is obtained for
   the solvation enthalpies of phenol in benzene and acetonitrile. The
   theoretical calculations also indicate that the differences between the
   solvation enthalpies of phenol (PhOH) and phenoxy radical (PhO*) in
   both benzene and acetonitrile are significantly smaller than previous
   estimations based on the ECW model. The results for the solvation
   enthalpies are used to obtain the O-H bond dissociation enthalpies in
   benzene and acetonitrile. For benzene and acetonitrile, the theoretical
   results of 89.4 +/- 1.2 and 90.5 +/- 1.7 kcal mol(-1), respectively,
   are in good agreement with the experimental values (90.9 +/- 1.3 and
   92.9 +/- 0.9 kcal mol(-1)), obtained by photoacoustic calorimetry. The
   solute-solvent interaction energies of phenol and phenoxy radical with
   both acetonitrile and benzene differ by less than 2 kcal mol-1. A
   detailed analysis of the solvent contributions to the differential
   solvation enthalpy is made in terms of the hydrogen bonds and the
   solute-solvent interactions. Both PhOH and PhO* induce a significant,
   although equivalent, solvent reorganization enthalpy. Finally, the
   convergence of the solute-solvent interaction is analyzed as a function
   of the distance to the solute and illustrates the advantages and
   limitations of local models such as microsolvation and
   hydrogen-bond-only models.
C1 Univ Lisbon, Fac Ciencias, Dept Quim & Bioquim, P-1749016 Lisbon, Portugal.
   Univ Lisbon, Grp Fis Matemat, P-1649003 Lisbon, Portugal.
   Univ Mogi Cruzes, BR-08701970 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Algarve, Fac Engn Recursos Nat, P-8005139 Faro, Portugal.
RP Cabral, BJC, Univ Lisbon, Fac Ciencias, Dept Quim & Bioquim, P-1749016
   Lisbon, Portugal.
CR BECKE AD, 1993, J CHEM PHYS, V98, P5648
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   CORREIA CF, 2003, UNPUB J PHYS CHEM A
   COUTINHO K, 2000, DICE GEN MONTE CARLO
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NR 57
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD OCT 30
PY 2003
VL 107
IS 43
BP 9197
EP 9207
PG 11
SC Chemistry, Physical
GA 736DQ
UT ISI:000186156000018
ER

PT J
AU Souza-Neto, NM
   Ramos, AY
   Tolentino, HCN
   Favre-Nicolin, E
   Ranno, L
TI Local anisotropy in strained manganite thin films
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID MAGNETIC-ANISOTROPY; MAGNETORESISTANCE; SPECTROSCOPY; DEPENDENCE
AB We report on an angular resolved x-ray absorption spectroscopy study of
   the local atomic structure around the manganese ions in La0.7Sr0.3MnO3
   thin films epitaxially grown on tensile and compressive substrates. Ab
   initio calculations provide strong support to the analysis of the
   experimental data and make possible the unambiguous derivation of a
   model of local distortion around the manganese atoms, without
   modification of the tilt angle Mn-O-Mn, among the octahedra. This
   distortion, tending to localize the charge carriers, is the driving
   parameter in the modifications of the magnetic and transport properties
   observed in thin films with respect to bulk systems. (C) 2003 American
   Institute of Physics.
C1 LNLS, BR-13084971 Campinas, Brazil.
   UNICAMP, Inst Fis Gleb Wataghin, BR-13083970 Campinas, Brazil.
   LMCP, CNRS, UMR 7590, Paris, France.
   Univ Grenoble 1, CNRS, UPR 5051, Lab Louis Neel, Grenoble, France.
RP Souza-Neto, NM, LNLS, CP 6192, BR-13084971 Campinas, Brazil.
CR ANKUDINOV AL, 2002, PHYS REV B, V65
   DHO J, 2003, APPL PHYS LETT, V82, P1434
   MANCEAU A, 1992, AM MINERAL, V77, P1133
   MILLIS AJ, 1998, J APPL PHYS, V83, P1588
   MILLIS AJ, 1998, NATURE, V392, P147
   MINIOTAS A, 2001, J APPL PHYS, V89, P2134
   PRELLIER W, 2001, J PHYS-CONDENS MAT, V13, R915
   QIAN Q, 2001, PHYS REV B, V63
   RAMOS AY, 2003, AIP CONF PROC, V652, P456
   RANNO L, 2002, APPL SURF SCI, V188, P170
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   TYSON TA, 1996, PHYS REV B, V53, P13985
   URUSHIBARA A, 1995, PHYS REV B, V51, P14103
   WU XW, 2000, PHYS REV B, V61, P501
NR 15
TC 4
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD OCT 27
PY 2003
VL 83
IS 17
BP 3587
EP 3589
PG 3
SC Physics, Applied
GA 734QQ
UT ISI:000186068400048
ER

PT J
AU de Oliveira, HCB
   Fonseca, TL
   Castro, MA
   Amaral, OAV
   Cunha, S
TI Theoretical study of the static first hyperpolarizability of
   azo-enaminone compounds
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID CONJUGATED ORGANIC-MOLECULES; NONLINEAR-OPTICAL-PROPERTIES; BOND-LENGTH
   ALTERNATION; AB-INITIO; ELECTRON CORRELATION; AROMATIC-COMPOUNDS;
   DIPOLE-MOMENT; FIRST-ORDER; POLARIZABILITIES; DERIVATIVES
AB In this work the static electric properties of azo-enaminones, with
   special emphasis to the vector component of the first
   hyperpolarizability beta(vec), are determined at the Hartree-Fock (HF)
   level with the electron correlation (EC) effects included through the
   second-order Moller-Plesset perturbation theory (MP2). The ab initio
   results, in accordance with previous semiempirical calculations, show
   that appropriate choices of substituents to be incorporated to the
   molecular structure can have a marked influence on the first
   hyperpolarizability. An initial study about the changes on the
   beta(vec) values of these compounds, as a result of the incorporation
   of different donor groups, indicates that this property increases as
   function of the donor group strength tending to a saturated value. A
   comparison between our HF and MP2 results, for all compounds studied
   here, show that the beta(vec) values are strongly affected by the
   effects of the electron correlation correction. (C) 2003 American
   Institute of Physics.
C1 Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
   Univ Fed Bahia, Inst Quim, BR-41170290 Salvador, BA, Brazil.
RP de Oliveira, HCB, Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go,
   Brazil.
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NR 43
TC 3
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD OCT 22
PY 2003
VL 119
IS 16
BP 8417
EP 8423
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 731BW
UT ISI:000185865500024
ER

PT J
AU Perpetuo, GJ
   Janczak, J
TI Three-dimensional self-assembly supramolecular structure of hydrogen
   bonded melaminium citrate
SO POLISH JOURNAL OF CHEMISTRY
LA English
DT Article
DE melaminium; citrate; crystal structure; self-assembling; conformation;
   hydrogen bond
ID ANHYDROUS CITRIC ACID; RAY CRYSTAL ANALYSIS; X-RAY; SOLID-STATE; TAPES;
   TETRAHYDRATE; ARCHITECTURE; SECONDARY; ACONITASE; COMPLEXES
AB The melaminium dihydrogencitrate,
   (C3H7N6)(HOOC-CH2-C(OH)(COOH)-CH2-COO), crystallizes from water
   solution at room temperature in the P2(1)/c space group of the
   monoclinic system with the lattice parameters of a = 5.531(1), b =
   20.869(4), c = 11.282(2) Angstrom and beta = 99.96(3)degrees and Z = 4.
   The crystals are built up from singly protonated at the one N-ring atom
   melaminium cations that interact in a near linear fashion through a
   pair of N-(HN)-N-... hydrogen bonds to form the centrosymmetric dimeric
   structure. The dihydrogencitrate(-) anions interact in the head-to-tail
   fashion via the terminal dissociated (COO-) and non-dissociated (COOH)
   carboxyl groups to form O-(HO)-O-... hydrogen bonded zigzag infinite
   chains. The hydroxyl group of dihydrogencitrate(-) ions is involved
   into O-(HO)-O-... hydrogen bonds that linked together the
   dihydrogencitrate(-) chains into two-dimensional network. The
   centrosymmetric dimers of melaminiurn moieties interact with the sheets
   of dihydrogencitrate(-) to form the three-dimensional hydrogen bonded
   network. The conformation of the dihydrogencitrate(-) ion in the
   crystal is compared with the conformation in the gas-phase obtained by
   the ab-initio molecular orbital calculation.
C1 Polish Acad Sci, Inst Low Temp & Struct Res, PL-50950 Wroclaw, Poland.
   Univ Fed Ouro Preto, Inst Ciencias Exatas & Biol, Dept Fis, BR-35400000 Ouro Preto, MG, Brazil.
RP Janczak, J, Polish Acad Sci, Inst Low Temp & Struct Res, POB 1410,
   PL-50950 Wroclaw, Poland.
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   JANCZAK J, 2003, ACTA CRYSTALLOGR C 6, V59, O349
   KRISCHE MJ, 2000, STRUCT BOND, V96, P3
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NR 39
TC 4
PU POLISH CHEMICAL SOCIETY
PI WARSAW
PA C/O POLISH ACAD SCIENCES, INST PHYSICAL CHEMISTRY, UL KASPRZAKA 44/52,
   01-224 WARSAW, POLAND
SN 0137-5083
J9 POLISH J CHEM
JI Pol. J. Chem.
PD OCT
PY 2003
VL 77
IS 10
BP 1323
EP 1337
PG 15
SC Chemistry, Multidisciplinary
GA 730VK
UT ISI:000185850700012
ER

PT J
AU Trasferetti, BC
   Davanzo, CU
   de Moraes, MAB
TI LO-TO splittings in plasma-deposited siloxane films
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID INFRARED-REFLECTANCE SPECTRA; CHEMICAL-VAPOR-DEPOSITION; GEL-DERIVED
   SILICA; THIN-FILMS; VIBRATIONAL-SPECTRA; SI/SIO2 INTERFACE; AB-INITIO;
   SPECTROSCOPY; OXYGEN; ABSORPTION
AB The present work presents LO and TO functions in the mid-infrared
   region for thin films deposited from glow discharge plasmas of
   tetramethylsilane (TMS) diluted either in Ar or O-2 or in mixtures of
   these two gases. These functions were calculated through the
   Kramers-Kronig analysis of transmittance spectra of the films supported
   on KBr disks. To correlate structural aspects of the films with the
   observed LO-TO splittings, a group frequency analysis based on the
   literature was made. Such an analysis indicated that the films
   deposited from the TMS Ar mixture were formed mainly by a
   polycarbosilane skeleton, whereas those deposited from TMS-O-2 and
   TMS-O-2-Ar were formed by a random network of four types of distorted
   tetrahedra: (CH3)(3)SiO0.5, (CH3)(2)SiO, (CH3SiO1.5), and SiO2. From
   the LO-TO splitting for the asymmetrical stretching mode of Si-O-Si
   groups, the density and the presence of defects in samples obtained
   from TMS-O-2 and TMS-O-2-Ar mixtures were evaluated. The number of
   defects increased as the Ar-to-O-2 flow rate decreased. We also report
   for the first time LO-TO splittings for bands related to the bending of
   CH3 and to the stretching of the Si-C bond in Si(CH3)(x) groups. The
   knowledge of such splittings is very important for a correct evaluation
   of the infrared reflection -absorption spectra taken at oblique
   incidence of thin films containing Si-O bonds and Si(CH3)(x) groups
   deposited on metals.
C1 Univ Estadual Campinas, Inst Quim, BR-13083862 Campinas, SP, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13087970 Campinas, SP, Brazil.
RP Davanzo, CU, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083862 Campinas, SP, Brazil.
CR ALLARA DL, 1985, LANGMUIR, V1, P52
   ALMEIDA RM, 1992, PHYS REV B, V45, P161
   ALMEIDA RM, 1996, PHYS REV B, V53, P14656
   ANDERSON DR, 1974, ANAL SILICONES
   BELLAMY LJ, 1975, INFRARED SPECTRA COM
   BERREMAN DW, 1963, PHYS REV, V130, P2193
   BLAKEMORE JS, 1995, SOLID STATE PHYSICS
   DACRUZ NC, 1998, J POLYM SCI POL PHYS, V36, P1873
   DECIUS JC, 1968, J CHEM PHYS, V49, P1387
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NR 53
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD OCT 2
PY 2003
VL 107
IS 39
BP 10699
EP 10708
PG 10
SC Chemistry, Physical
GA 726QC
UT ISI:000185609600005
ER

PT J
AU Ramalho, TC
   Martins, TLC
   Borges, LEP
   Figueroa-Villar, JD
TI Influence of nonbonded interactions in the kinetics of formation of
   chalcogenol esters from chalcogenoacetylenes
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE chalcogenoacetylene; chalcogenol ester; DFT; kinetics of formation;
   nonbonded interactions; transition state
ID POLARIZABLE CONTINUUM MODEL; SELENAZOFURIN; TIAZOFURIN; CONTACTS;
   THIAZOLE; SOLVENT; ENERGY; SULFUR; AGENT
AB The influence of nonbonded interactions in the kinetics of formation of
   chalcogenol (thiol and selenol) esters from chalcogenoacetylenes was
   studied by molecular modeling. Using semiempirical and density
   functional theory methods it was possible to explain the differences
   between the reaction rates for the analogous sulfur and selenium
   chalcogenoacetylenes as well as evaluate the structural and electronic
   effects (nonbonded interactions) on the formation of the esters. The
   differences in the reaction rates can be explained in terms of the
   carbocation stabilization by the chalcogen atom. It is proposed that
   these differences are due to the differences in the intensity of the
   dominant interaction pi(CO)(*)/n(Y) between the nonbonding orbitals of
   sulfur and selenium with the vacant orbital of carbon in the cationic
   transition state. (C) 2003 Wiley Periodicals, Inc.
C1 Inst Militar Engn, Dept Quim, BR-22290270 Rio De Janeiro, Brazil.
RP Figueroa-Villar, JD, Inst Militar Engn, Dept Quim, Praca Gen Tiburcio
   80, BR-22290270 Rio De Janeiro, Brazil.
CR BACA M, 1995, J AM CHEM SOC, V117, P1881
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NR 33
TC 4
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD NOV 5
PY 2003
VL 95
IS 3
BP 267
EP 273
PG 7
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 728CF
UT ISI:000185697100009
ER

PT J
AU Laschuk, EF
   Martins, MM
   Evangelisti, S
TI Ab initio potentials for weakly interacting systems: Homonuclear rare
   gas dimers
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE ab initio; rare gas dimers; rovibrational spectroscopy; second virial
   coefficient
ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS; WAVE-FUNCTIONS;
   ENERGY CURVES; INTERMOLECULAR INTERACTIONS; BENCHMARK CALCULATIONS;
   SCHRODINGER-EQUATION; ELECTRIC PROPERTIES; NEON DIMER; AR-2
AB A series of high-level ab initio interatomic potentials for the
   homonuclear rare gas dimers He-2, Ne-2, and Ar-2 is presented, with
   predictions of rovibrational spectroscopic parameters and second virial
   coefficients. These potentials were created by using d-aug-cc-pVnZ, n =
   D,T,Q basis sets, NP4 and CCSD(T) correlation energy treatments, the
   counterpoise correction to the basis set superposition error, and
   extrapolation schemes for estimating complete basis set (CBS) limits. A
   careful FCI correction was added to our best He-2 CCSD(T) potential.
   The characteristic parameters D-e, R-e, k, and sigma of the ab initio
   potentials were compared with those of reliable empirical and ab initio
   potentials. Our best results for He-2 recovered 99.9% of Janzen's SAPT2
   well depth. In the case of Ar-2, we recovered 99.8% of Aziz's HFDID1
   well depth. For neon, second virial coefficients typically came to
   within 0.5-1.0 cm(3)mol(-1) of experimental values and rovibrational
   energy levels exhibited errors of about 1.4 cm(-1). Our best argon
   results exhibited second virial coefficients in agreement of 0.25
   cm(3)mol(-1) with experiment and rovibrational energy level errors
   around 0.2 cm(-1). (C) 2003 Wiley Periodicals, Inc.
C1 Univ Fed Rio Grande Sul, Theoret Chem Grp, BR-91501970 Porto Alegre, RS, Brazil.
   Univ Bologna, Theoret & Inorgan Chem Dept, Bologna, Italy.
RP Laschuk, EF, Univ Fed Rio Grande Sul, Theoret Chem Grp, BR-91501970
   Porto Alegre, RS, Brazil.
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NR 30
TC 3
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD NOV 5
PY 2003
VL 95
IS 3
BP 303
EP 312
PG 10
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 728CF
UT ISI:000185697100014
ER

PT J
AU Alexandre, SS
   Artacho, E
   Soler, JM
   Chacham, H
TI Small polarons in dry DNA
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID CHARGE MIGRATION; DOUBLE HELIX; LAMBDA-DNA; TRANSPORT; MODEL;
   PSEUDOPOTENTIALS; CONDUCTIVITY; MOLECULES; DAMAGE; MOTION
AB We report ab initio calculations for positively charged fragments of
   dry poly(dC)-poly(dG) DNA, with up to 4 C-G pairs. We find a strong
   hole-lattice coupling and clear evidence for the formation of small
   polarons. The largest geometry distortions occur in only one or two
   base pairs. They involve the stretching of weak bonds within each base
   pair, increasing the distance of positive hydrogens, and decreasing
   that of negative oxygens, to the region in which the hole localizes. We
   obtain an energy of similar to0.30 eV for the polaron formation, nearly
   independent of the chain size. From it, we can estimate an activation
   energy for polaron hopping of similar to0.15 eV, consistent with the
   available experimental value.
C1 Univ Fed Minas Gerais, Dept Fis, ICEx, BR-30123970 Belo Horizonte, MG, Brazil.
   Univ Cambridge, Dept Earth Sci, Cambridge CB2 3EQ, England.
   Univ Autonoma Madrid, Dept Fis Mat Condensada, E-28049 Madrid, Spain.
RP Alexandre, SS, Univ Fed Minas Gerais, Dept Fis, ICEx, CP 702,
   BR-30123970 Belo Horizonte, MG, Brazil.
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NR 32
TC 18
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD SEP 5
PY 2003
VL 91
IS 10
AR 108105
DI ARTN 108105
PG 4
SC Physics, Multidisciplinary
GA 724KA
UT ISI:000185485700048
ER

PT J
AU Coutinho, K
   Canuto, S
TI The sequential Monte Carlo-quantum mechanics methodology. Application
   to the solvent effects in the Stokes shift of acetone in water
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Monte Carlo-quantum mechanics methodology; super-molecular calculation;
   solvent effects
ID POLARIZABLE CONTINUUM MODEL; MOLECULAR-DYNAMICS SIMULATIONS;
   INTEGRAL-EQUATION FORMALISM; FORBIDDEN VIBRONIC SPECTRA; PI-ASTERISK
   TRANSITION; SELF-CONSISTENT-FIELD; LIQUID WATER; AQUEOUS-SOLUTION;
   AB-INITIO; CONFIGURATION-INTERACTION
AB The sequential Monte Carlo quantum mechanics methodology is used to
   obtain the solvent effects on the Stokes shift of acetone in water. One
   of the great advantages of this methodology is that all the important
   statistical information is known before running into the costly quantum
   mechanical calculations. This advantage is discussed not only with
   respect to the statistical correlation between the different structures
   generated by the simulation but also in the proper identification of
   hydrogen bonds in liquids. To obtain the solvent effects in the Stokes
   shift of the n-pi* absorption transition of acetone in water,
   quantum-mechanical calculations are performed in super-molecular
   structures generated by NVT Monte Carlo simulation. The statistical
   correlation between configurations is analyzed using the
   auto-correlation function of the energy. The largest calculations
   include one acetone and 170 water molecules. One-hundred INDO/CIS
   super-molecular calculations are performed for each solvation shell to
   obtain the statistical average value. The calculated solvatochromic
   shift of the n-pi* absorption transition of acetone in water, compared
   to gas phase, is similar to 1310 cm(-1) in good agreement with the
   experimental blue shift of 1500 +/- 200 cm(-1). For the emission of the
   relaxed excited state, the calculated shift is similar to 1850 cm(-1).
   The total calculated solvent effect on the Stokes shift of acetone in
   aqueous solution is thus 540 cm(-1). A detailed analysis of the
   sampling of the configurations obtained in the Monte Carlo simulation
   is made and it is shown that all results represent statistically
   converged values. (C) 2003 Elsevier B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi das Cruzes, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 85
TC 15
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD AUG 1
PY 2003
VL 632
SI Sp. Iss. SI
BP 235
EP 246
PG 12
SC Chemistry, Physical
GA 722VQ
UT ISI:000185399100019
ER

PT J
AU Branicio, PS
   Rino, JP
   Shimojo, F
   Kalia, RK
   Nakano, A
   Vashishta, P
TI Molecular dynamics study of structural, mechanical, and vibrational
   properties of crystalline and amorphous Gal-xInxAs alloys
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID SILICON-NITRIDE; PHONON DISPERSIONS; GALLIUM-ARSENIDE; SQUARE
   NANOMESAS; SOLID-SOLUTIONS; GA1-XINXAS; FRACTURE; AMORPHIZATION;
   BEHAVIOR; SIMULATION
AB Using an interaction potential scheme, molecular dynamics (MD)
   simulations are performed to investigate structural, mechanical, and
   vibrational properties of Ga1-xInxAs alloys in the crystalline and
   amorphous phases. For the crystalline phase we find that: (i) Ga-As and
   In-As bond lengths vary only slightly for different compositions; (ii)
   the nearest-neighbor cation-cation distribution has a broad peak; and
   (iii) there are two nearest-neighbor As-As distances in the As (anion)
   sublattice. These MD results are in excellent agreement with extended
   x-ray absorption fine structure and high-energy x-ray diffraction data
   and also with ab initio MD simulation results. The calculated lattice
   constant deviates less than 0.18% from Vegard's law. The calculated
   phonon density of states exhibits a two-mode behavior for
   high-frequency optical phonons with peaks close to those in binary
   alloys (GaAs and InAs), which agrees well with a recent Raman study.
   Calculated elastic constants show a significant nonlinear dependence on
   the composition. For the amorphous phase, MD results show that: (i) the
   nearest-neighbor cation-anion distribution splits into well-defined
   As-Ga and As-In peaks as in the crystal phase; (ii) the cation-cation
   distribution is similar to that in the crystal phase; and (iii) the
   As-As distribution is quite different from that in the crystal, having
   only one nearest-neighbor distance. (C) 2003 American Institute of
   Physics.
C1 Univ So Calif, Dept Mat Sci & Engn, Collab Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Phys & Astron, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Comp Sci, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Biomed Engn, Los Angeles, CA 90089 USA.
   Univ Fed Sao Carlos, Dept Fis, Sao Paulo, Brazil.
   Kumamoto Univ, Dept Phys, Kumamoto 860, Japan.
RP Branicio, PS, Univ So Calif, Dept Mat Sci & Engn, Collab Adv Comp &
   Simulat, Los Angeles, CA 90089 USA.
CR ALLEN MP, 1987, COMPUTER SIMULATION
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NR 43
TC 7
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD SEP 15
PY 2003
VL 94
IS 6
BP 3840
EP 3848
PG 9
SC Physics, Applied
GA 723EN
UT ISI:000185419600023
ER

PT J
AU Meurer, EC
   Gozzo, FC
   Augusti, R
   Eberlin, MN
TI The kinetic method as a structural diagnostic tool: ionized
   alpha-diketones as loosely one-electron bonded diacylium ion dimers
SO EUROPEAN JOURNAL OF MASS SPECTROMETRY
LA English
DT Article
ID POLYCYCLIC AROMATIC-HYDROCARBONS; QUADRUPOLE MASS SPECTROMETERS;
   PROTON-BOUND DIMERS; GAS-PHASE ACIDITIES; RADICAL CATIONS;
   THERMOCHEMICAL DETERMINATIONS; DISSOCIATION ENERGIES; IONIZATION
   ENERGIES; ATTACHMENT SITES; CHIRAL ANALYSIS
AB The kinetic method is used to corroborate the description of ground
   state ionized alpha-diketones as loosely electron-bonded acylium ion
   dimers: R'-C=O+---e(-)---O+=C-R-2. The abundance ratio of both the
   acylium ion fragments (RCO)-C-1* and (RCO+)-C-2 (summed to those of
   their respective secondary fragments) formed upon low energy (5 eV)
   collision-induced dissociation of several ionized alpha-diketones is
   found to correlate linearly with the ionization energies (IEs) of the
   corresponding (RCO.)-C-1 and (RCO.)-C-2 free radicals as predicted by
   density functional theory calculations at the B3LY/P/6-311++G(d,p)
   level. However, when these abundances are taken from 70 eV electron
   ionization mass spectra, lower and sometimes inverted ratios
   (2,3-pentanedione and 2,3-hexanedione) are observed. Inverted ratios
   are also observed via charge-exchange mass spectrometry/mass
   spectrometry (MS/MS) experiments for ionized 2,3-pentanodione formed
   with relatively high internal energies. Ionized alpha-diketones are
   found to display an effective temperature of 1705 K, which indicates an
   intermediate loosely-bonded nature. B3LY/P/6-311++G(d,p) optimized
   geometries and charge and spin densities also corroborate the
   description of ground state ionized alpha-diketones as loosely
   electron-bonded diacylium ion dimers.
C1 UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
   UFMG, Dept Chem, BR-31270901 Belo Horizonte, MG, Brazil.
RP Eberlin, MN, UNICAMP, Inst Chem, CP154, BR-13083970 Campinas, SP,
   Brazil.
CR AUGUSTI DV, 2002, ANAL CHEM, V74, P3458
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NR 63
TC 4
PU IM PUBLICATIONS
PI W SUSSEX
PA 6 CHARLTON MILL, CHARLTON, CHICHESTER,, W SUSSEX PO18 0HY, ENGLAND
SN 1469-0667
J9 EUR J MASS SPECTROM
JI Eur. J. Mass Spectrom.
PY 2003
VL 9
IS 4
BP 295
EP 304
PG 10
SC Physics, Atomic, Molecular & Chemical; Spectroscopy
GA 723XD
UT ISI:000185456100009
ER

PT J
AU Ruini, A
   Bussi, G
   Ferretti, A
   Caldas, MJ
   Molinari, E
TI Charge transport and radiative recombination in polythiophene crystals:
   a first-principles study
SO SYNTHETIC METALS
LA English
DT Article
DE density-functional theory; optical absorption; charge transport;
   polythiophene
ID ORGANIC SEMICONDUCTORS; SINGLE-CRYSTALS; AB-INITIO; GROWTH
AB We investigate two phases of polythiophene crystals by means of
   first-principles calculations, focusing on the effect of the different
   structure on charge transport parameters and luminescence quantum
   yield. The resulting microscopic interpretation highlights the impact
   of solid-state interchain coupling on both transport and emissive
   properties of semiconducting polymer crystals. (C) 2003 Elsevier B.V.
   All rights reserved.
C1 INFM, Natl Ctr NanoStruct & BioSyst Surfaces S3, Modena, Italy.
   Univ Modena, Dipartimento Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-01498 Sao Paulo, Brazil.
RP Ruini, A, INFM, Natl Ctr NanoStruct & BioSyst Surfaces S3, Modena,
   Italy.
CR ACKERMANN J, 2002, THIN SOLID FILMS, V403, P157
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NR 23
TC 3
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD OCT 9
PY 2003
VL 139
IS 3
BP 755
EP 757
PG 3
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA 721EG
UT ISI:000185303600050
ER

PT J
AU Coluci, VR
   Braga, SF
   Legoas, SB
   Galvao, DS
   Baughman, RH
TI Families of carbon nanotubes: Graphyne-based nanotubes
SO PHYSICAL REVIEW B
LA English
DT Article
ID GRAPHDIYNE SUBSTRUCTURES; ELECTRONIC-STRUCTURE; DEHYDROBENZOANNULENES;
   MICROTUBULES; SYSTEM
AB New families of carbon single-walled nanotubes are proposed and their
   electronic structures are investigated. These nanotubes, called
   graphynes, result from the elongation of covalent interconnections of
   graphite-based nanotubes by the introduction of yne groups. Analogously
   to ordinary nanotubes, armchair, zigzag, and chiral graphyne nanotubes
   are possible. We here predict the electronic properties of these
   unusual nanotubes using tight-binding and ab initio density functional
   methods. Of the three graphyne nanotube families analyzed here, two
   provide metallic behavior for armchair tubes and either metallic or
   semiconducting behavior for zigzag nanotubes. A diameter- and
   chirality-independent band gap is predicted for the other investigated
   graphyne family, as well as an oscillatory dependence of the effective
   mass on nanotube diameter.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Texas, NanoTech Inst, Richardson, TX USA.
   Univ Texas, Dept Chem, Richardson, TX 75083 USA.
RP Coluci, VR, Univ Estadual Campinas, Inst Fis Gleb Wataghin, CP 6165,
   BR-13083970 Campinas, SP, Brazil.
CR ANTHONY JE, 1997, TETRAHEDRON LETT, V38, P3499
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   LEGOAS SB, 2003, PHYS REV LETT, V90
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   ZHOU YF, 2002, SOLID STATE COMMUN, V122, P307
NR 34
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD JUL 15
PY 2003
VL 68
IS 3
AR 035430
DI ARTN 035430
PG 6
SC Physics, Condensed Matter
GA 719XD
UT ISI:000185229600144
ER

PT J
AU Orestes, E
   Marcasso, T
   Capelle, K
TI Density-functional calculation of ionization energies of
   current-carrying atomic states
SO PHYSICAL REVIEW A
LA English
DT Article
ID INHOMOGENEOUS ELECTRON-GAS; STRONG MAGNETIC-FIELDS; EXCHANGE; SYSTEMS;
   POTENTIALS; SUPERCONDUCTORS; APPROXIMATIONS; FORMALISM; SOLIDS
AB Current-density-functional theory is used to calculate ionization
   energies of current-carrying atomic states. A recently proposed
   perturbative approximation to full current-density-functional theory is
   implemented and found to be numerically feasible. Different
   parametrizations for the current-dependence of the density functional
   are critically compared. Orbital currents in open-shell atoms turn out
   to produce a small shift in the ionization energies. We find that
   modern density functionals have reached an accuracy at which small
   current-related terms appearing in open-shell configurations are not
   negligible anymore, compared to the remaining difference to experiment.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, BR-13560970 Sao Carlos, SP, Brazil.
RP Orestes, E, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol,
   Caixa Postal 780, BR-13560970 Sao Carlos, SP, Brazil.
CR BAERENDS EJ, 1997, CHEM PHYS LETT, V265, P481
   BECKE AD, 1988, PHYS REV A, V38, P3098
   BECKE AD, 2002, J CHEM PHYS, V117, P6935
   CAPELLE K, 1997, PHYS REV LETT, V78, P1872
   CAPELLE K, 1999, PHYS REV A, V60, P733
   CAPELLE K, 2000, EUROPHYS LETT, V49, P376
   CAPELLE K, 2000, PHYS REV B, V61, P15228
   CHEN JQ, 1996, PHYS REV A, V54, P3939
   CHONG DP, 2002, J CHEM PHYS, V116, P1760
   COLWELL SM, 1994, CHEM PHYS LETT, V217, P271
   DREIZLER RM, 1990, DENSITY FUNCTIONAL T
   EBERT H, 1997, EUROPHYS LETT, V40, P545
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   HOHENBERG P, 1964, PHYS REV, V136, B864
   KOHN W, 1996, J PHYS CHEM-US, V100, P12974
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   KURTH S, 1999, PHYS REV LETT, V83, P2628
   LEE AM, 1994, CHEM PHYS LETT, V229, P225
   LEE AM, 1995, J CHEM PHYS, V103, P10095
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   PARR RG, 1989, DENSITY FUNCTIONAL T
   PERDEW JP, 1981, PHYS REV B, V23, P5048
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NR 35
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD AUG
PY 2003
VL 68
IS 2
AR 022105
DI ARTN 022105
PG 6
SC Physics, Atomic, Molecular & Chemical; Optics
GA 719FC
UT ISI:000185192100011
ER

PT J
AU Borges, JC
   Fischer, H
   Craievich, AF
   Hansen, LD
   Ramos, CHI
TI Free human mitochondrial GrpE is a symmetric dimer in solution
SO JOURNAL OF BIOLOGICAL CHEMISTRY
LA English
DT Article
ID HEAT-SHOCK PROTEINS; LAMBDA-DNA REPLICATION; NUCLEOTIDE EXCHANGE
   FACTOR; ESCHERICHIA-COLI DNAK; SOLUTION SCATTERING; BIOLOGICAL
   MACROMOLECULES; SWISS-MODEL; SYSTEM; GENE; BACTERIOPHAGE
AB The co-chaperone GrpE is essential for the activities of the Hsp70
   system, which assists protein folding. GrpE is present in several
   organisms, and characterization of homologous GrpEs is important for
   developing structure-function relationships. Cloning, producing, and
   conformational studies of the recombinant human mitochondrial GrpE are
   reported here. Circular dichroism measurements demonstrate that the
   purified protein is folded. Thermal unfolding of human GrpE measured
   both by circular dichroism and differential scanning calorimetry
   differs from that of prokaryotic GrpE. Analytical ultracentrifugation
   data indicate that human GrpE is a dimer, and the sedimentation
   coefficient agrees with an elongated shape model. Small angle x-ray
   scattering analysis shows that the protein possesses an elongated shape
   in solution and demonstrates that its envelope, determined by an ab
   initio method, is similar to the high resolution envelope of
   Escherichia coli GrpE bound to DnaK obtained from single crystal x-ray
   diffraction. However, in these conditions, the E. coli GrpE dimer is
   asymmetric because the monomer that binds DnaK adopts an open
   conformation. It is of considerable importance for structural GrpE
   research to answer the question of whether the GrpE dimer is only
   asymmetric while bound to DnaK or also as a free dimer in solution. The
   low resolution structure of human GrpE presented here suggests that
   GrpE is a symmetric dimer when not bound to DnaK. This information is
   important for understanding the conformational changes GrpE undergoes
   on binding to DnaK.
C1 Lab Nacl Luz Sincroton, Ctr Biol Mol Estrutural, BR-13084971 Campinas, SP, Brazil.
   UNICAMP, Inst Biol, Dept Bioquim, BR-13084971 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Fis, Dept Fis Aplicada, BR-05389970 Sao Paulo, Brazil.
   Brigham Young Univ, Dept Chem & Biochem, Provo, UT 84602 USA.
RP Ramos, CHI, Lab Nacl Luz Sincroton, Ctr Biol Mol Estrutural, POB 6192,
   BR-13084971 Campinas, SP, Brazil.
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NR 49
TC 3
PU AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
PI BETHESDA
PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3996 USA
SN 0021-9258
J9 J BIOL CHEM
JI J. Biol. Chem.
PD SEP 12
PY 2003
VL 278
IS 37
BP 35337
EP 35344
PG 8
SC Biochemistry & Molecular Biology
GA 718UG
UT ISI:000185164400073
ER

PT J
AU da Silva, CO
   Mennucci, B
   Vreven, T
TI Combining microsolvation and polarizable continuum studies: New
   insights in the rotation mechanism of amides in water
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID N BOND ROTATION; AB-INITIO; ELECTRON-DIFFRACTION; MOLECULAR-STRUCTURE;
   INTERNAL-ROTATION; HYDROGEN-BOND; BARRIER; MODEL;
   N,N-DIMETHYLAMINOACRYLONITRILE; N,N-DIMETHYLFORMAMIDE
AB We present a quantum mechanical investigation of the rotation
   mechanisms of N,N-dimethylformamide (DMF) and NN-dimethylacetamide
   (DMA) in water. This rotation can happen through two distinct
   transition states known as TS1 and TS2, where the nitrogen lone pair is
   on the opposite side of the oxygen atom or on the same side,
   respectively. The analysis is focused on complementary descriptions of
   the solvent, either represented by a limited number of explicit solvent
   molecules (microsolvation), by an implicit (or continuum) solvation, or
   by combinations of these two approaches. The combined approach
   (microsolvation + continuum) can provide quantitative agreement with
   the experimental results for the gas to solution shift of the
   rotational barrier. For both amides, continuum effects alone are
   sufficient to select the correct channels. However, hydrogen-bond
   effects (via the explicit solvent molecules) are necessary to obtain
   quantitative agreement with experiment, provided this is combined with
   a continuum description. In the rotation in DMF, it seems that a single
   water molecule is directly involved, while the other solvent molecules
   act as a "mean field" (the bulk), which is well reproduced by a
   polarizable continuum medium. The mechanism in DMA is less clear. In
   gas phase the steric repulsive interactions between methyl groups make
   TS1 clearly favored with respect to TS2. In water, the larger dipole
   moment of TS2 produces an opposite effect with respect to the repulsion
   interactions, making the corresponding channel less disfavored than in
   gas phase. The results are compared with previous Monte Carlo
   simulations, and this comparison is used to draw a more general picture
   about how different descriptions of the solvent can take into account
   long-range and mediated effects on one side and shorter-range and
   dynamic effects on the other side.
C1 Univ Pisa, Dipartimento Chim & Chim Ind, Pisa, Italy.
   Univ Fed Rio de Janeiro, Dept Quim, Rio De Janeiro, Brazil.
   Gaussian Inc, N Haven, CT 06473 USA.
RP Vreven, T, Univ Pisa, Dipartimento Chim & Chim Ind, Via Risorgimento
   35, Pisa, Italy.
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NR 29
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 28
PY 2003
VL 107
IS 34
BP 6630
EP 6637
PG 8
SC Chemistry, Physical
GA 715JD
UT ISI:000184967600019
ER

PT J
AU Treu, O
   Pinheiro, JC
   Kondo, RT
   Marques, RFC
   Paiva-Santos, CO
   Davolos, MR
   Jafelicci, M
TI Development of basis sets to calculations of the electronic structure
   of YMnO3
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Gaussian basis sets; contracted basis sets; dipole moments; total
   energy; total atomic charges; YMnO3
ID COORDINATE HARTREE-FOCK; MOLECULAR-SYSTEMS; WAVE-FUNCTIONS;
   GAUSSIAN-BASIS; AB-INITIO; FORMALISM; ATOMS
AB The generator coordinate Hartree-Fock method was used to develop
   20s17p, 30s20p14d, and 30s21p16d Gaussian basis sets for the O ((3)p),
   Mn (S-6), and Y (D-2) atoms, respectively. The Gaussian basis sets were
   contracted to 20s17p/9s7p, 30s20p14d/11s7p7d, and 30s21p16d/14s7p7d and
   utilized in calculations of total energy and orbital energies of the
   (MnO1+)-Mn-5 and (YO1+)-Y-3 fragments to evaluate its quality in
   molecular studies. Finally, the contracted basis set for O atom was
   supplemented with one polarization function of d symmetry and used
   along with the other contracted basis sets (for Mn and Y) to calculate
   dipole moments, total energy, and total atomic charges in YMnO3 in
   space group D-6h. The analysis of those properties showed that is
   reasonable to believe that YMnO3 present behavior of piezoelectric
   material. (C) 2003 Elsevier B.V. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab Quim Teor & Computac, BR-66075110 Belem, Para, Brazil.
   UNESP, Inst Quim, Araraquara, SP, Brazil.
   Cooperat Ctr Educ Cient & Empreendedora Amazonia, BR-66601306 Belem, Para, Brazil.
   Univ Sao Paulo, Ctr Informat Sao Carlos, Seccao Tecn Suporte, BR-13560970 Sao Carlos, SP, Brazil.
RP Pinheiro, JC, Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab
   Quim Teor & Computac, CP 101101, BR-66075110 Belem, Para, Brazil.
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   TREU O, UNPUB
NR 20
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD JUL 4
PY 2003
VL 629
BP 21
EP 26
PG 6
SC Chemistry, Physical
GA 714CT
UT ISI:000184895300004
ER

PT J
AU Sambrano, JR
   Vasconcellos, LA
   Martins, JBL
   Santos, MRC
   Longo, E
   Beltran, A
TI A theoretical analysis on electronic structure of the (110) surface of
   TiO2-SnO2 mixed oxide
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE mixed oxide; titanium oxide; surface defects; clusters; ab initio
ID TIO2 THIN-FILMS; TITANIUM-DIOXIDE; ELECTRICAL-PROPERTIES; GAS SENSORS;
   OPTICAL-PROPERTIES; OXYGEN VACANCIES; VARISTOR SYSTEM; PHOTOCATALYTIC
   DEGRADATION; SOLID-SOLUTIONS; DOPING PROCESS
AB Mixed oxide compounds, such as TiO2-SnO2 system are widely used as gas
   sensors and should also provide varistor properties modifying the TiO2
   surface. Therefore, a theoretical investigation has been carried out
   characterizing the effect of SnO2 on TiO2 addition on the electronic
   structure by means of ab initio SCF-LCAO calculations using all
   electrons. In order to take into account the finite size of the
   cluster, we have used the point charge model for the (TiO2)(15) cluster
   to study the effect on electronic structure of doping the TiO2 (110)
   Surface. The contracted basis set for titanium (4322/42/3), oxygen
   (33/3) and tin (43333/4333/43) atoms were used. The charge
   distributions, dipole moments, and density of states of doping TiO2 and
   vacancy formation are reported and analysed. (C) 2003 Elsevier B.V. All
   rights reserved.
C1 Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
   Univ Estadual Paulista, Lab Simulacao Mol, BR-17033360 Bauru, SP, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Jaume I, Dept Ciencies Expt, Castello 12080, Spain.
RP Martins, JBL, Univ Brasilia, Inst Quim, Campus Univ,LQC Caixa Postal
   04478, BR-70919970 Brasilia, DF, Brazil.
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NR 72
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD JUL 4
PY 2003
VL 629
BP 307
EP 314
PG 8
SC Chemistry, Physical
GA 714CT
UT ISI:000184895300032
ER

PT J
AU Gordon, ML
   Cooper, G
   Morin, C
   Araki, T
   Turci, CC
   Kaznatcheev, K
   Hitchcock, AP
TI Inner-shell excitation spectroscopy of the peptide bond: Comparison of
   the C 1s, N 1s, and O 1s spectra of glycine, glycyl-glycine, and
   glycyl-glycyl-glycine
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID X-RAY-ABSORPTION; MILLIMETER WAVE SPECTRUM; EDGE XANES SPECTROSCOPY;
   ADVANCED LIGHT-SOURCE; AMINO-ACIDS; PHOTOELECTRON-SPECTROSCOPY;
   ELECTRONIC-STRUCTURE; GASEOUS GLYCINE; GAS-PHASE; MOLECULES
AB Oscillator strengths for C 1s, N 1s, and O 1s excitation spectra of
   gaseous glycine and the dipeptide, glycyl glycine, have been derived
   from inner-shell electron energy-loss spectroscopy recorded under
   scattering conditions where electric dipole transitions dominate (2.5
   keV residual energy, theta approximate to 2degrees). X-ray absorption
   spectra of solid glycine, glycyl-glycine, glycyl-glycyl-glycine, and a
   large protein, fibrinogen, were recorded in a scanning transmission
   X-ray microscope. The experimental spectra are assigned through
   interspecies comparisons and by comparison to ab initio computed
   spectra of various conformations of glycine and glycylglycine.
   Inner-shell excitation spectral features characteristic of the peptide
   bond are readily identified by comparison of the spectra of gas-phase
   glycine and glycyl-glycine. They include a clear broadening and a
   similar to0.3 eV shift of the C 1s - pi*(C=O) peak and introduction of
   a new pre-edge feature in the N 1s spectrum. These effects are due to
   1s --> pi*(amide) transitions introduced with formation of the peptide
   bond. Similar changes occur in the spectra of the solids. The
   computational results support the interpretation of the experimental
   inner-shell spectra and provide insight into electron density
   distributions in the core excited states. Possible conformational
   dependence of the inner-shell excitation spectra was explored by
   computing the spectra of neutral glycine in its four most common
   conformations, and of glycyl-glycine in planar and two twisted
   conformations. A strong dependence of the computed C 1s, N 1s, and O 1s
   spectra of glycylglycine on the conformation about the amide linkage
   was confirmed by additional ab initio calculations of the
   conformational dependence of the spectra of formamide.
C1 McMaster Univ, Dept Chem, Hamilton, ON L8S 4M1, Canada.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21910 Rio De Janeiro, Brazil.
   Univ Saskatchewan, Canadian Light Source, Saskatoon, SK S7N 5C6, Canada.
RP Hitchcock, AP, McMaster Univ, Dept Chem, 1280 Main St W, Hamilton, ON
   L8S 4M1, Canada.
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NR 57
TC 18
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 14
PY 2003
VL 107
IS 32
BP 6144
EP 6159
PG 16
SC Chemistry, Physical
GA 710DC
UT ISI:000184664700004
ER

PT J
AU Treu, O
   Pinheiro, JC
   Kondo, RT
   Marques, RFC
   Paiva-Santos, CO
   Davolos, MR
   Jafelicci, M
TI Gaussian basis sets to the theoretical study of the electronic
   structure of perovskite (LaMnO3)
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Gaussian basis sets; Generator Coordinate Hartree-Fock method;
   perovskite; LaMnO3; piezoelectric
ID COORDINATE HARTREE-FOCK; DIATOMIC-MOLECULES; 2ND-ROW ATOMS; AB-INITIO;
   OPTIMIZATION; CHOICE
AB The Generator Coordinate Hartree-Fock (GCHF) method is applied to
   generate extended (20s14p), (30s19p13d), and (31s23p18d) Gaussian basis
   sets for the 0, Mn, and La atoms, respectively. The role of the weight
   functions (WFs) in the assessment of the numerical integration range of
   the GCHF equations is shown. These basis sets are then contracted to
   [5s3p] and [11s6p6d] for 0 and Mn atoms, respectively, and [17s11p7d]
   for La atom by a standard procedure. For quality evaluation of
   contracted basis sets in molecular calculations, we have accomplished
   calculations of total and orbital energies in the Hartree-Fock-Roothaan
   (HFR) method for (MnO1+)-Mn-5 and (LaO1+)-La-1 fragments. The results
   obtained with the contracted basis sets are compared with values
   obtained with the extended basis sets. The addition of one d
   polarization function in the contracted basis set for 0 atom and its
   utilization with the contracted basis sets for Mn and La atoms leads to
   the calculations of dipole moment and total atomic charges of
   perovskite (LaMnO3). The calculations were performed at the HFR level
   with the crystal [LaMnO3](2) fragment in space group C-2v The values of
   dipole moment, total energy, and total atomic charges showed that it is
   reasonable to believe that LaMnO3 presents behaviour of piezoelectric
   material. (C) 2003 Elsevier B.V. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Naturais, Dept Quim, Lab Quim Teor & Computac, BR-66075110 Belem, Para, Brazil.
   UNESP, Inst Quim, Araraquara, SP, Brazil.
   Cooperat Ctr Educ Cientifica & Empreendedora Amaz, BR-66013060 Belem, Para, Brazil.
   Univ Sao Paulo, Ctr Informat Sao Carlos, Seccao Tecn Suporte, BR-13560970 Sao Carlos, SP, Brazil.
RP Pinheiro, JC, Fed Univ Para, Ctr Ciencias Exatas & Naturais, Dept Quim,
   Lab Quim Teor & Computac, CP 101101, BR-66075110 Belem, Para, Brazil.
CR CADY WG, 1964, PIEZOELECTRICITY
   CUSTODIO R, 1992, INT J QUANTUM CHEM, V42, P411
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   GERLOCH M, 1994, TRANSITION METAL CHE
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NR 23
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD AUG 1
PY 2003
VL 631
BP 93
EP 99
PG 7
SC Chemistry, Physical
GA 707PD
UT ISI:000184518300011
ER

PT J
AU Beltran, A
   Andres, J
   Longo, E
   Leite, ER
TI Thermodynamic argument about SnO2 nanoribbon growth
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID OXIDE NANOWIRES; CRYSTAL-GROWTH; TIN OXIDE; NANOTUBES; SURFACES;
   MICROSTRUCTURE; TEMPERATURE; ENERGETICS; MECHANISM; DENSITY
AB Calculations based on density functional theory at Becke's
   three-parameter exchange functional combined with the Lee-Yang-Parr
   correlation functional (B3LYP) level and periodic slab models have been
   done to obtain: (i) the surface energy per unit area of different
   stoichiometric SnO2 surfaces, and (ii) by using a simple Wulff
   construction equation-type, the thermodynamic stability associated to
   the formation of nanoribbons from these surfaces has been obtained. In
   agreement with previous theoretical studies, the (110) face is the
   thermodynamically most stable surface. The present theoretical results
   and high-resolution transmission electron microscopy data reveal that
   the nanoribbons preferentially grow along the [101] crystal direction.
   (C) 2003 American Institute of Physics.
C1 Univ Jaume I, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Fed Sao Carlos, Dept Chem, BR-13565905 Sao Carlos, SP, Brazil.
RP Beltran, A, Univ Jaume I, Dept Ciencies Expt, POB 6029 AP, Castello
   12080, Spain.
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NR 33
TC 13
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD JUL 28
PY 2003
VL 83
IS 4
BP 635
EP 637
PG 3
SC Physics, Applied
GA 704JM
UT ISI:000184336600015
ER

PT J
AU deAzevedo, ER
   Franco, RWA
   Marletta, A
   Faria, RM
   Bonagamba, TJ
TI Conformational dynamics of phenylene rings in poly(p-phenylene
   vinylene) as revealed by C-13 magic-angle-spinning exchange nuclear
   magnetic resonance experiments
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID CENTERBAND-ONLY DETECTION; NMR CHARACTERIZATION; MOLECULAR MOTIONS; MAS
   NMR; FILMS; SOLIDS; MORPHOLOGY; DEPENDENCE; RELAXATION; PRINCIPLES
AB Poly(p-phenylene vinylene) (PPV) has shown a great potential for
   electro-optical applications due to its electroluminescent and
   semiconducting properties. Such properties are directly related with
   the polymer chain conformation and dynamics. Then, it is important to
   understand in detail the local chain motions. In this work, three C-13
   solid-state magic-angle-spinning (MAS) exchange NMR techniques were
   used to study conformational dynamics of phenylene rings in PPV. The
   standard 2D MAS exchange experiment was used to identify exchange
   processes between equivalent and nonequivalent sites. Centerband-only
   detection of exchange (CODEX) experiments were applied to determine the
   amplitude of the phenylene ring flips and small-angle oscillations.
   Additionally, a new version of the CODEX technique, which allows for
   the selective observation of segments executing exchange between
   non-equivalent sites, is demonstrated and applied to determine the
   flipping fractions and the activation energies of the phenylene ring
   rotations. It was found that, at -15 degreesC, (26+/-3)% of the rings
   undergo 180degrees flips in the millisecond time scale, with average
   imprecision of (30+/-5)degrees and activation energies of (23+/-3)
   kJ/mol. Other (31+/-10)% of the rings perform only small-angle
   oscillations with an average amplitude of (9+/-2)degrees. These results
   corroborate previous experimental data and agree with recent ab initio
   calculations of potential energies barriers in phenylenevinylene
   oligomers. (C) 2003 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
RP Bonagamba, TJ, Univ Sao Paulo, Inst Fis Sao Carlos, Caixa Postal 369,
   BR-13560970 Sao Carlos, SP, Brazil.
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NR 43
TC 5
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD AUG 1
PY 2003
VL 119
IS 5
BP 2923
EP 2934
PG 12
SC Physics, Atomic, Molecular & Chemical
GA 702UE
UT ISI:000184242100050
ER

PT J
AU Fileti, EE
   Coutinho, K
   Malaspina, T
   Canuto, S
TI Electronic changes due to thermal disorder of hydrogen bonds in
   liquids: Pyridine in an aqueous environment
SO PHYSICAL REVIEW E
LA English
DT Article
ID CARLO-QUANTUM-MECHANICS; QUADRUPOLE COUPLING-CONSTANTS; AB-INITIO;
   VANDERWAALS MOLECULES; (HCN)(N) CLUSTERS; INTERMOLECULAR FORCES; WATER
   DIMER; SPECTROSCOPY; POLARIZABILITIES; FORMALDEHYDE
AB Combined Metropolis Monte Carlo computer simulation and
   first-principles quantum mechanical calculations of pyridine in water
   are performed to analyze the role of thermal disorder in the electronic
   properties of hydrogen bonds in an aqueous environment. The simulation
   uses the NVT ensemble and includes one pyridine and 400 water
   molecules. Using a very efficient geometric-energetic criterion, the
   hydrogen bonds between pyridine and water C5H5N---H2O are identified
   and separated for subsequent quantum mechanical calculations of the
   electronic and spectroscopic properties. Statistically uncorrelated
   configurations composed of one pyridine and one water molecule are used
   to represent the configuration space of the hydrogen bonds in the
   liquid. The quantum mechanical calculations on these structures are
   performed at the correlated second-order perturbation theory level and
   all results are corrected for basis-set superposition error. The
   results are compared with the equivalent electronic properties of the
   hydrogen bond in the minimum-energy configuration. Charge transfer,
   dipole moment, and dipole polarizabilities are calculated for the
   thermally disordered and minimum-energy structures. In addition, using
   the mean and anisotropic polarizabilities, the Rayleigh depolarizations
   are obtained. All properties obtained for the thermally disordered
   structures are represented by a statistical distribution and a
   convergence of the average values is obtained. The results indicate
   that the charge transfer, dipole moment, and average depolarization
   ratios are systematically decreased in the liquid compared to the
   optimized cluster. This study quantifies, using ab initio quantum
   mechanics and statistical analysis, the important aspect of the thermal
   disorder of the hydrogen bond in a liquid system.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi Cruzed, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
CR ABDURAHMAN A, 2002, PHYS REV B, V66
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NR 60
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1063-651X
J9 PHYS REV E
JI Phys. Rev. E
PD JUN
PY 2003
VL 67
IS 6
PN Part 1
AR 061504
DI ARTN 061504
PG 7
SC Physics, Fluids & Plasmas; Physics, Mathematical
GA 699XD
UT ISI:000184081000046
ER

PT J
AU Skaf, MS
   Vechi, SM
TI Polarizability anisotropy relaxation in pure and aqueous
   dimethylsulfoxide
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MOLECULAR-DYNAMICS SIMULATIONS; SULFOXIDE-WATER MIXTURES; DEPOLARIZED
   LIGHT-SCATTERING; FEMTOSECOND OPTICAL KERR; PERIODIC
   BOUNDARY-CONDITIONS; LIQUID DIMETHYL-SULFOXIDE; INTERMOLECULAR
   DYNAMICS; DIELECTRIC-PROPERTIES; COMPUTER-SIMULATION; ULTRAFAST DYNAMICS
AB A molecular dynamics simulation study is presented for the relaxation
   of the polarizability anisotropy of liquid dimethylsulfoxide (DMSO) and
   DMSO-water mixtures of DMSO mole fractions x(D)=0.05, 0.10, 0.25, 0.50,
   and 0.75. The system's collective polarizability is computed through a
   dipolar induction mechanism involving the intrinsic polarizability and
   first hyperpolarizability tensors for water and DMSO, obtained from ab
   initio quantum chemical calculations at the MP2/6-311++G(d,p) level.
   The rotational-diffusion components of the anisotropy relaxation of the
   pure liquids increase upon mixing to a maximum near 25% DMSO, showing
   consistency with other dynamical properties of these mixtures. Features
   of the optical Kerr effect (OKE) nuclear response of liquid water,
   previously ascribed to hydrogen bonding distortions, show significant
   enhancement upon addition of DMSO due to the formation of strong
   DMSO-water H-bonds. The OKE spectrum for DMSO is in close agreement
   with experimental measurements, but there are discrepancies for pure
   water in the vicinity of 60 cm(-1), pointing to the existence of
   inaccuracies in our description of OKE sensitive polarizability
   fluctuations of water. The mixtures OKE spectra feature an enhancement
   in the high frequency water librational band. (C) 2003 American
   Institute of Physics.
C1 Univ Estadual Campinas, Inst Quim, BR-13084971 Campinas, SP, Brazil.
RP Skaf, MS, Univ Estadual Campinas, Inst Quim, Cx P 6154, BR-13084971
   Campinas, SP, Brazil.
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NR 82
TC 7
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUL 22
PY 2003
VL 119
IS 4
BP 2181
EP 2187
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 700FY
UT ISI:000184103000035
ER

PT J
AU Dardenne, LE
   Werneck, AS
   Neto, MD
   Bisch, PM
TI Electrostatic properties in the catalytic site of papain: A possible
   regulatory mechanism for the reactivity of the ion pair
SO PROTEINS-STRUCTURE FUNCTION AND GENETICS
LA English
DT Article
DE papain; cysteine proteinases; electrostatic properties; enzymatic
   catalysis; ab initio calculations; multicenter multipolar expansions
ID CYSTEINE PROTEASE PAPAIN; DISTRIBUTED MULTIPOLE ANALYSIS; MOLECULAR
   CHARGE-DISTRIBUTION; ACTIVE-SITE; QUANTUM-CHEMISTRY; ENZYME CATALYSIS;
   IONIZATION CHARACTERISTICS; DIELECTRIC-CONSTANTS; PROTEINASE ACTIVITY;
   SERINE PROTEINASES
AB We present an analysis of the electrostatic properties in the catalytic
   site of papain (EC 3.4.22.2), an archetype enzyme of the C1 cysteine
   proteinase family, and we investigate their possible role in the
   formation, stabilization and regulation of the Cys25((-))...His159((+))
   catalytic ion pair. The electrostatic properties were computed using a
   reassociation method based in multicentered multipolar expansions
   obtained from ab initio quantum calculations of overlapping protein
   fragments. Solvent effects were introduced by coupling the use of
   multicentered multipolar expansions to two continuum boundary element
   methods to solve the Poisson and the linearized Poisson-Boltzmann
   equations. The electrostatic profile found in the proton transfer
   region of papain showed that this enzyme has a well-defined
   electrostatic environment to favor the formation and stabilization of
   the catalytic ion pair. The papain catalytic site electrostatic profile
   can be considered as an electrostatic fingerprint of the papain family
   with the following characteristics: (i) the presence of a net electric
   field highly aligned in the (Cys25)-SG-->(His159)-ND1 direction; (ii)
   the electrostatic profile has a saddle-point character; (iii) it is
   basically a local environmental effect. Furthermore, our analysis
   describes a possible regulatory mechanism (the ESG-->ND1 attenuation
   effect) controlling the ion pair reactivity and permits to infer the
   Asp57 acidic residue as the most probable candidate to act as the
   electrostatic modulator. (C) 2003 Wiley-Liss, Inc.
C1 Fed Univ Rio De Janeiro, Lab Fis Biol, Inst Biofis Carlos Chagas Filho, BR-21949900 Rio De Janeiro, RJ, Brazil.
   LNCC, BR-25651070 Petropolis, RJ, Brazil.
   UCB, Dept Fis, BR-72030170 Taguatinga, DF, Brazil.
   Univ Brasilia, Inst Quim, BR-70910900 Brasilia, DF, Brazil.
RP Bisch, PM, Fed Univ Rio De Janeiro, Lab Fis Biol, Inst Biofis Carlos
   Chagas Filho, CCS,Bloco G Ilha Fundao, BR-21949900 Rio De Janeiro, RJ,
   Brazil.
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NR 94
TC 6
PU WILEY-LISS
PI NEW YORK
PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0887-3585
J9 PROTEIN-STRUCT FUNCT GENET
JI Proteins
PD AUG 1
PY 2003
VL 52
IS 2
BP 236
EP 253
PG 18
SC Biochemistry & Molecular Biology; Genetics & Heredity
GA 697BW
UT ISI:000183923200012
ER

PT J
AU Arenzon, JJ
   Levin, Y
   Sellitto, M
TI Slow dynamics under gravity: a nonlinear diffusion model
SO PHYSICA A-STATISTICAL MECHANICS AND ITS APPLICATIONS
LA English
DT Article
DE granular matter; structural arrest; glass transition; compaction
   dynamics
ID VIBRATED GRANULAR MATERIAL; LATTICE-GAS MODEL; GLASS-TRANSITION;
   DENSITY-FLUCTUATIONS; COMPACTION; RELAXATION; MATTER; LIQUIDS; MEDIA;
   CRYSTALLIZATION
AB We present an analytical and numerical study of a nonlinear diffusion
   model which describes density relaxation of densely packed particles
   under gravity and weak random (thermal) vibration, and compare the
   results with Monte Carlo simulations of a lattice gas under gravity.
   The dynamical equation can be thought of as a local density functional
   theory for a class of lattice gases used to model slow relaxation of
   glassy and granular materials. The theory predicts a jamming transition
   line between a low-density fluid phase and a high-density glassy
   regime, characterized by diverging relaxation time and logarithmic or
   power-law compaction according to the specific form of the diffusion
   coefficient. In particular, we show that the model exhibits
   history-dependent properties, such as quasi-reversible-irreversible
   cycle and memory effects-as observed in recent experiments, and
   dynamical heterogeneities. (C) 2003 Elsevier Science B.V. All rights
   reserved.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
   Abdus Salam Int Ctr Theoret Phys, I-34100 Trieste, Italy.
RP Arenzon, JJ, Univ Fed Rio Grande Sul, Inst Fis, CP 15051, BR-91501970
   Porto Alegre, RS, Brazil.
CR BARRAT A, 2000, J PHYS A-MATH GEN, V33, P4401
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NR 51
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0378-4371
J9 PHYSICA A
JI Physica A
PD JUL 15
PY 2003
VL 325
IS 3-4
BP 371
EP 395
PG 25
SC Physics, Multidisciplinary
GA 696VZ
UT ISI:000183909400006
ER

PT J
AU Capelle, K
TI Variational calculation of many-body wave functions and energies from
   density functional theory
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID GENERATOR-COORDINATE METHOD; NONORTHOGONAL SLATER DETERMINANTS;
   EXCITATION-ENERGIES; ELECTRON-GAS; DISCRETIZATION; SUPERPOSITION;
   APPROXIMATION; STATES; ATOMS
AB A generating coordinate is introduced into the exchange-correlation
   functional of density functional theory (DFT). The many-body wave
   function is represented as a superposition of Kohn-Sham (KS) Slater
   determinants arising from different values of the generating
   coordinate. This superposition is used to variationally calculate
   many-body energies and wave functions from solutions of the KS equation
   of DFT. The method works for ground and excited states, and does not
   depend on identifying the KS orbitals and energies with physical ones.
   Numerical application to the Helium isoelectronic series illustrates
   the method's viability and potential. (C) 2003 American Institute of
   Physics.
C1 Univ Sao Paulo, Dept Quim & Fis Mol, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
RP Capelle, K, Univ Sao Paulo, Dept Quim & Fis Mol, Inst Quim Sao Carlos,
   Caixa Postal 780, BR-13560970 Sao Carlos, SP, Brazil.
CR ANDREJKOVICS I, 1998, CHEM PHYS LETT, V296, P489
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   DEUMENS E, 1984, INT J QUANTUM CHEM, V18, P339
   FUKUTOME H, 1988, PROG THEOR PHYS, V80, P417
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   TOMITA N, 1996, CHEM PHYS LETT, V263, P687
NR 24
TC 3
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUL 15
PY 2003
VL 119
IS 3
BP 1285
EP 1288
PG 4
SC Physics, Atomic, Molecular & Chemical
GA 696YL
UT ISI:000183915100001
ER

PT J
AU Capaz, RB
   Caldas, MJ
TI Ab initio calculations of structural and dynamical properties of
   poly(p-phenylene) and poly(p-phenylene vinylene)
SO PHYSICAL REVIEW B
LA English
DT Article
ID VIBRATIONAL-SPECTRA; DOPED POLYPARAPHENYLENE; CRYSTAL-STRUCTURE;
   PHASE-TRANSITION; X-RAY; PERDEUTERATED BIPHENYL; OPTICAL
   INVESTIGATIONS; ELECTRONIC-STRUCTURE; CONJUGATED POLYMERS; PHENYLENE
   VINYLENE
AB We perform ab initio calculations within the local density
   approximation for infinite, isolated chains of poly(para-phenylene)
   (PPP) and poly(para-phenylene-vinylene) (PPV). Phonon frequencies at
   (k) over right arrow = (0) over right arrow and structural properties
   are investigated with special focus on the ring-torsion barriers. Our
   results for PPV indicate a planar geometry, while for PPP we find a
   ring-torsion potential that is not affected by next-nearest-neighbor
   rings. This suggests the existence of a multiply degenerate ground
   state for PPP, with chiral, ordered, or random angle-alternating
   configurations having the same energy. In addition, we couple these
   results to a simple molecular-dynamics simulation in order to
   investigate the finite temperature behavior of the systems.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05389970 Sao Paulo, Brazil.
RP Capaz, RB, Univ Fed Rio de Janeiro, Inst Fis, Caixa Postal 68528,
   BR-21941972 Rio De Janeiro, Brazil.
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NR 46
TC 8
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 15
PY 2003
VL 67
IS 20
AR 205205
DI ARTN 205205
PG 9
SC Physics, Condensed Matter
GA 689GL
UT ISI:000183483200032
ER

PT J
AU Fagan, SB
   Mota, R
   da Silva, AJR
   Fazzio, A
TI Ab initio study of an iron atom interacting with single-wall carbon
   nanotubes
SO PHYSICAL REVIEW B
LA English
DT Article
ID TRANSITION-METAL ADATOMS; MOLECULAR-DYNAMICS; LARGE SYSTEMS; GRAPHITE;
   MAGNETISM; GROWTH; IMPURITIES; ADSORPTION; PARTICLES; SPECTRA
AB The interaction of an iron atom with a single-wall carbon nanotube is
   investigated using spin-polarized total-energy first-principles
   calculations. A systematic study for the atom approaching the tube
   surface, both from outside and inside, is presented for several
   configurations to determine the equilibrium distances and the binding
   energies. It is shown that when the atom interacts with the tube from
   outside, a 3d(7) 4s(1) effective configuration is obtained and the
   total magnetization is close to the atomic value. For the inside case,
   as a consequence of higher hybridization and a confinement effect, the
   magnetization decreases and the finally obtained effective
   configuration is 3d(8) 4s(0).
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Fagan, SB, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
CR ANDRIOTIS AN, 2000, APPL PHYS LETT, V76, P3890
   ANDRIOTIS AN, 2000, PHYS REV B, V61, P13393
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   JOURNET C, 1997, NATURE, V388, P756
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NR 33
TC 13
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 15
PY 2003
VL 67
IS 20
AR 205414
DI ARTN 205414
PG 5
SC Physics, Condensed Matter
GA 689GL
UT ISI:000183483200087
ER

PT J
AU Guerini, S
   Piquini, P
TI Theoretical investigation of TiB2 nanotubes
SO MICROELECTRONICS JOURNAL
LA English
DT Article
DE TiB2 nanotubes; density of states; strain energy
ID HARTREE-FOCK
AB We investigated the energetic and electronic properties of zig-zag
   titanium diboride (TiB2) nanotubes through ab initio density functional
   theory. It is determined that an isolated (6,0) bilayered TiB2 nanotube
   has a semiconductor character, with an energy gap of 1.32 eV. The
   strain energy to form the (6,0) TiB2 nanotube is calculated to be 0.26
   eV per unit formula. The electronic density of states of a three-layer
   tube ((6,0) TiB2 + (12,0) B tube) shows a metallic behavior for this
   system, which is consistent with previous calculations on similar
   hypothetical nanotubes. (C) 2003 Elsevier Science Ltd. All rights
   reserved.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Piquini, P, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria,
   RS, Brazil.
CR BARTHELAT JC, 1977, MOL PHYS, V33, P159
   BLASE X, 1994, EUROPHYS LETT, V28, P225
   CAUSA M, 1991, PHYS REV B, V43, P11937
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   HARRIS PJF, 1999, CARBON NANOTUBES REL
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NR 19
TC 3
PU ELSEVIER ADVANCED TECHNOLOGY
PI OXFORD
PA OXFORD FULFILLMENT CENTRE THE BOULEVARD, LANGFORD LANE, KIDLINGTON,
   OXFORD OX5 1GB, OXON, ENGLAND
SN 0026-2692
J9 MICROELECTR J
JI Microelectron. J.
PD MAY-AUG
PY 2003
VL 34
IS 5-8
BP 495
EP 497
PG 3
SC Engineering, Electrical & Electronic
GA 691LH
UT ISI:000183607400039
ER

PT J
AU Machado, M
   Mota, R
   Piquini, P
TI Electronic properties of BN nanocones under electric fields
SO MICROELECTRONICS JOURNAL
LA English
DT Article
DE electronic structures of nanoscale materials; nanocones; BN
ID EMISSION PROPERTIES; CARBON NANOTUBES; LARGE SYSTEMS; CONES
AB The electronic properties of BN nanocones with 240degrees disclination
   under electric fields are investigated using first-principles
   calculations based on the density-functional theory. The cones are
   studied under the influence of electric fields, up to 1.13 V/Angstrom,
   applied along the cone axis. The densities of states (DOS) of these BN
   nanocones show different patterns depending on the termination two
   atoms (BN, BB or NN) and the electric field strength. A decreasing of
   the gap is observed with increasing field. The field emission
   properties are very sensitive to the DOS and we show that the
   termination atoms, as well as the electric field, contribute to enhance
   the electron field emission. (C) 2003 Elsevier Science Ltd. All rights
   reserved.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Machado, M, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria,
   RS, Brazil.
CR BAIERLE RJ, 2001, PHYS REV B, V64
   BOURGEOIS L, 2000, PHYS REV B, V61, P7686
   CHARLIER JC, 2001, PHYS REV LETT, V86, P5970
   CHARLIER JC, 2002, NANO LETT, V2, P1191
   MACHADO, 2003, EUR PHYS J D, V23, P91
   MEUNIER V, 2002, APPL PHYS LETT, V81, P46
   MOTA R, 2003, PHYS STATUS SOLIDI C, P799
   ORDEJON P, 1996, PHYS REV B, V53
   RUBIO A, 1994, PHYS REV B, V49, P5081
   SANCHEZPORTAL D, 1997, INT J QUANTUM CHEM, V65, P453
   TERAUCHI M, 2000, CHEM PHYS LETT, V324, P359
   ZHANG G, 2002, APPL PHYS LETT, V80, P2589
NR 12
TC 5
PU ELSEVIER ADVANCED TECHNOLOGY
PI OXFORD
PA OXFORD FULFILLMENT CENTRE THE BOULEVARD, LANGFORD LANE, KIDLINGTON,
   OXFORD OX5 1GB, OXON, ENGLAND
SN 0026-2692
J9 MICROELECTR J
JI Microelectron. J.
PD MAY-AUG
PY 2003
VL 34
IS 5-8
BP 545
EP 547
PG 3
SC Engineering, Electrical & Electronic
GA 691LH
UT ISI:000183607400051
ER

PT J
AU Arissawa, M
   Taft, CA
   Felcman, J
TI Investigation of nucleoside analogs with anti-HIV activity
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE HIV; reverse transcriptase; drug-DNA interaction; nucleoside analogs
ID HUMAN-IMMUNODEFICIENCY-VIRUS; TYPE-1 REVERSE-TRANSCRIPTASE; BLOOD
   MONONUCLEAR-CELLS; DRUG-RESISTANCE; AB-INITIO; 2',3'-DIDEOXYNUCLEOSIDE
   ANALOGS; POPULATION ANALYSIS; ANTI-HIV-1 ACTIVITY; HUMAN-LYMPHOCYTES;
   LAMIVUDINE 3TC
AB Although a relatively large number of drugs that inhibit human
   immunodeficiency syndrome (HIV)-1 reverse transcriptase have been
   developed-such as AZT, d4T, ddI, 3TC, and ddC, which are chain
   terminating nucleoside analogs-resistance is still a major problem.
   Atomic charges, regioselective patterns of chemical reactivity, and
   other indices of biochemical activity may help us acquire a better
   understanding of how the drugs work and the mechanism of drug
   resistance. In this work, we investigated the above-mentioned
   nucleoside analogs using the ab initio Hartree-Fock method with 3-21G,
   3-21G*, 6-31G, 6-31G*, 6-31G**, and 6-31+G** basis sets as well as
   B3LYP/6-31G**, including thus diffusion, polarization, and correlation
   effects to obtain fully optimized geometric parameters. Vibrational
   frequencies were calculated and we also investigated the effects of
   solvents, Mulliken, and natural bond orbital charge distribution, as
   well as hydrogen bond effects. We tried to correlate very low and very
   high anti-HIV activity with charges, vibrational stretching
   frequencies, interatomic distances, and the effect of solvents. (C)
   2003 Wiley Periodicals, Inc.
C1 Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estatist, BR-22290 Rio De Janeiro, Brazil.
   Pontificia Univ Catolica Rio de Janeiro, Dept Quim, Rio De Janeiro, Brazil.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis
   Estatist, Rua Dr Xavier Sigaud,150, BR-22290 Rio De Janeiro, Brazil.
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   COLACINO E, 2001, TETRAHEDRON, V57, P8551
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   PERACH M, 1997, J MOL BIOL, V268, P648
   PLAVEC J, 1992, J BIOCHEM BIOPH METH, V25, P253
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   WEINHOLD H, 1988, STRUCTURE SMALL MOL, P227
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   ZHANG XG, 2002, J ORG CHEM, V67, P1016
NR 63
TC 5
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD JUL 5
PY 2003
VL 93
IS 6
BP 422
EP 432
PG 11
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 689WH
UT ISI:000183515600006
ER

PT J
AU Janczak, J
   Perpetuo, GJ
TI Bis(melaminium) DL-malate tetrahydrate
SO ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS
LA English
DT Article
ID HYDROGEN; DIHYDRATE; SECONDARY; TAPES; ACID
AB The crystal structure of the title melaminium salt, bis(2,4,6-
   triamino-1,3,5-triazin-1-ium) DL-malate tetrahydrate,
   2C(3)H(7)N(6)(+).C4H4O52-.4H(2)O, consists of singly protonated
   melaminium residues, DL-malate dianions and water molecules. The
   melaminium residues are connected into chains by four N-H...N hydrogen
   bonds, and these chains form a stacking structure along the c axis. The
   DL-malate dianions form hydrogen-bonded chains and, together with
   hydrogen-bonded water molecules, form a layer parallel to the ( 100)
   plane. The conformation of the malate ion is compared with an ab initio
   molecular-orbital calculation. The oppositely charged moieties, i.e.
   the stacks of melaminium chains and hydrogen-bonded DL-malate anions
   and water molecules, form a three-dimensional polymeric structure, in
   which N-H...O hydrogen bonds stabilize the stacking.
C1 Polish Acad Sci, Inst Low Temp & Struct Res, PL-50950 Wroclaw, Poland.
   Univ Fed Ouro Preto, Dept Fis, Inst Ciencias Exatas & Biolog, BR-35400000 Ouro Preto, MG, Brazil.
RP Janczak, J, Polish Acad Sci, Inst Low Temp & Struct Res, POB 1410,
   PL-50950 Wroclaw, Poland.
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   JANCZAK J, 2001, ACTA CRYSTALLOGR C 1, V57, P123
   JANCZAK J, 2001, ACTA CRYSTALLOGR C 7, V57, P873
   JANCZAK J, 2001, ACTA CRYSTALLOGR C 9, V57, P1120
   JANCZAK J, 2002, ACTA CRYSTALLOGR C 6, V58, O339
   JANCZAK J, 2002, ACTA CRYSTALLOGR C 8, V58, O455
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NR 26
TC 8
PU BLACKWELL MUNKSGAARD
PI COPENHAGEN
PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK
SN 0108-2701
J9 ACTA CRYSTALLOGR C-CRYST STR
JI Acta Crystallogr. Sect. C-Cryst. Struct. Commun.
PD JUN
PY 2003
VL 59
PN Part 6
BP O349
EP O352
PG 4
SC Crystallography
GA 686WZ
UT ISI:000183345100047
ER

PT J
AU Costa, LAS
   Rocha, WR
   De Almeida, WB
   Dos Santos, HF
TI The hydrolysis process of the
   cis-dichloro(ethylenediamine)platinum(II): A theoretical study
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-TYPE BASIS; AB-INITIO;
   CONFORMATIONAL-ANALYSIS; ORGANIC-MOLECULES; ANTITUMOR DRUGS; CISPLATIN;
   DNA; COMPLEXES; PATH
AB The hydrolysis process of the cisplatin analog
   cis-dichloro(ethylenediamine)platinum(II) (cis-DEP) was theoretically
   investigated at the Hartree-Fock, density functional theory and the
   second order Moller-Plesset perturbation theory levels of calculation.
   The stationary points on the gas phase potential energy surface for the
   first and second hydrolysis steps were fully optimized and
   characterized. For the first aquation process the gas phase results are
   in satisfactory agreement with the experimental data. However in order
   to reproduce the observed rate constant for the second hydrolysis step
   it is essential to include the solvent effect. The structures and
   energetic properties are similar to the values found for the parent
   compound cisplatin, showing that the cis-DEP analog should be
   considered as a potential drug concerning its hydrolysis process. (C)
   2003 American Institute of Physics.
C1 Univ Fed Juiz de Fora, NEQC, Dept Quim, ICE, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Minas Gerais, LQC MM, Dept Quim, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
   EPCAR, DEPENS, BR-36200000 Barbacena, MG, Brazil.
   Univ Fed Pernambuco, Dept Quim Fundamental, CCEN, BR-50740901 Recife, PE, Brazil.
RP Dos Santos, HF, Univ Fed Juiz de Fora, NEQC, Dept Quim, ICE, Campus
   Univ Martelos, BR-36036330 Juiz De Fora, MG, Brazil.
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NR 36
TC 8
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUN 15
PY 2003
VL 118
IS 23
BP 10584
EP 10592
PG 9
SC Physics, Atomic, Molecular & Chemical
GA 683AJ
UT ISI:000183124300025
ER

PT J
AU Rivelino, R
   Chaudhuri, P
   Canuto, S
TI Quantifying multiple-body interaction terms in H-bonded HCN chains with
   many-body perturbation/coupled-cluster theories
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID AB-INITIO; QUANTUM-CHEMISTRY; (HCN)(N) CLUSTERS; HYDROGEN-CYANIDE;
   WATER CLUSTERS; COMPLEXES; DELOCALIZATION; COOPERATIVITY; SPECTROSCOPY;
   MOLECULE
AB Many-body perturbation/coupled-cluster calculations have been carried
   out to investigate the multiple-body energy terms and their
   contribution to the interaction energy of linear (HCN)(N) chains. All
   minimum energy geometries of the clusters (N = 2-7) are obtained at the
   second-order many-body perturbation (MP2) levels of theory. Electron
   correlation and cooperative effects in the C-H...N hydrogen bonds are
   also quantitatively characterized during the aggregation process. It is
   found that the two- and three-body terms account for nearly all of the
   total interaction energy, but all high-body terms increase with the
   size of the cluster. Detailed numerical values are given for all the
   many-body contributions of the (HCN)(N) chains. Electron correlation
   effects are found to be important for the two- and three-body terms but
   have decreased importance for the higher-body terms. Cooperative
   effects are also investigated for the binding energy and dipole moment.
   The dipole moments of the HCN oligomers are larger than the sum of the
   individual monomers with differences ranging between 12% (N = 2) and
   28% (N = 7). The limiting values for the binding energy and dipole
   moment of (HCN)(N), per monomer, corresponding to very large N values,
   are estimated to be 22.9 kJ/mol and 3.87 D, per monomer, respectively.
   These results correspond to cooperative contributions of 5.8 kJ/mol to
   the energy, and 1.0 D to the dipole moment. (C) 2003 American Institute
   of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 33
TC 7
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUN 15
PY 2003
VL 118
IS 23
BP 10593
EP 10601
PG 9
SC Physics, Atomic, Molecular & Chemical
GA 683AJ
UT ISI:000183124300026
ER

PT J
AU Freitas, MP
   Tormena, CF
   Rittner, R
   Abraham, RJ
TI The utility of infrared spectroscopy for quantitative conformational
   analysis at a single temperature
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE infrared spectroscopy; conformational analysis; molar absorption
   coefficients; 2-bromocyclohexanone
ID R(0) STRUCTURAL PARAMETERS; AB-INITIO CALCULATIONS; VIBRATIONAL
   ASSIGNMENT; RAMAN-SPECTRA; ELECTRONIC INTERACTION; NMR; SOLVATION;
   STABILITY; ISOMERISM
AB The carbonyl stretching vibration of 2-bromocyclohexanone (1) has been
   measured in a variety of solvents. It is shown that its component
   intensities are not only dependent on the populations of the axial and
   equatorial conformers, but are also dependent on the molar
   absorptivities (epsilon) which are specific for each conformer in each
   solvent. In CCl4, the axial and equatorial conformers have, values of
   417 and 818 1 mol(-1) cm(-1), respectively, while in CH3CN solution,
   the values were 664 and 293 1 mol(-1) cm(-1). These results are
   supported by results of theoretical calculations of frequencies, which
   gave an intensity of 223.8 kM mol(-1) (1782 cm(-1)) for the axial and
   174.4 kM mol(-1) (1802 cm(-1)) for the equatorial conformer, indicating
   that the axial conformer presents a larger molar absorptivity than the
   equatorial one in the vapor phase. Moreover, the results presented here
   clearly demonstrate that although infrared spectroscopy at a single
   temperature can be an important auxiliary technique for conformational
   analysis, it must not be used to quantify conformational preferences of
   a molecule if the absorption molar coefficients for each conformer are
   not known or not amenable to experimental determination. (C) 2003
   Elsevier Science B.V. All rights reserved.
C1 UNICAMP, Inst Quim, Chim Organ Phys Lab, BR-13083862 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
RP Rittner, R, UNICAMP, Inst Quim, Chim Organ Phys Lab, Cx Postal 6154,
   BR-13083862 Campinas, SP, Brazil.
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NR 22
TC 4
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JUN
PY 2003
VL 59
IS 8
BP 1783
EP 1789
PG 7
SC Spectroscopy
GA 680YB
UT ISI:000183006700014
ER

PT J
AU Milas, I
   Nascimento, MAC
TI The dehydrogenation and cracking reactions of isobutane over the ZSM-5
   zeolite
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; LIGHT ALKANES; AB-INITIO; ACIDIC CATALYSTS;
   ISOMERIZATION; EXCHANGE; PROTON; HZSM-5; RATES
AB The dehydrogenation and cracking reactions of isobutane over zeolite
   HZMS-5 were studied at the DFT/B3LYP level of calculation. The zeolite
   was represented by the 'double-ring' 20T cluster. The activation
   energies for the reactions were 9-12 kcal/mol lower than those obtained
   with the linear 5T cluster. In both cases the attack of the acid site
   proton was directly on a carbon atom of the substrate, and not on the
   C-H and C-C bonds, evidencing carbonium-ion-type transition states. The
   results suggest that the reactions should be competitive, although the
   more hindered acid sites should favor the dehydrogenation over the
   cracking reaction. (C) 2003 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Dept Quim Fis, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Dept Quim Fis, Inst Quim,
   Cidade Univ,CT Bloco A,Sala 412, BR-21949900 Rio De Janeiro, Brazil.
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NR 28
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 20
PY 2003
VL 373
IS 3-4
BP 379
EP 384
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 681BG
UT ISI:000183016300023
ER

PT J
AU Verissimo-Alves, M
   Koiller, B
   Chacham, H
   Capaz, RB
TI Electromechanical effects in carbon nanotubes: Ab initio and analytical
   tight-binding calculations
SO PHYSICAL REVIEW B
LA English
DT Article
ID ELECTRONIC-STRUCTURE; LARGE SYSTEMS; MICROTUBULES; JUNCTIONS
AB We perform ab initio calculations of charged graphene and single-wall
   carbon nanotubes (CNTs). A wealth of electromechanical behaviors is
   obtained. (1) Both nanotubes and graphene expand upon electron
   injection. (2) Upon hole injection, metallic nanotubes and graphene
   display a nonmonotonic behavior. Upon increasing hole densities, the
   lattice constant initially contracts, reaches a minimum, and then
   starts to expand. The hole densities at minimum lattice constants are
   0.3 \e\/atom for graphene and between 0.1 and 0.3\e\/atom for the
   metallic nanotubes studied. (3) Semiconducting CNT's with small
   diameters (dless than or similar to20 Angstrom) always expand upon hole
   injection. (4) Semiconducting CNT's with large diameters (dgreater than
   or similar to20 Angstrom) display a behavior intermediate between those
   of metallic and large-gap CNT's. (5) The strain versus extra charge
   displays a linear plus power-law behavior, with characteristic
   exponents for graphene, metallic, and semiconducting CNT's. All these
   features are physically understood within a simple tight-binding
   total-energy model.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio De Janeiro, Brazil.
   Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Fed Minas Gerais, Dept Fis, ICEx, BR-30123970 Belo Horizonte, MG, Brazil.
RP Verissimo-Alves, M, Univ Fed Rio de Janeiro, Inst Fis, BR-21941972 Rio
   De Janeiro, Brazil.
CR BAUGHMAN RH, 1999, SCIENCE, V284, P1340
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   HAMADA N, 1992, PHYS REV LETT, V68, P1579
   IIJIMA S, 1991, NATURE, V354, P56
   KERTESZ M, 1983, MATERIALS RES SOC P, V20, P141
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   SAITO R, 1998, PHYSICAL PROPERTIES
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   YOON YG, 2001, PHYS REV LETT, V86, P688
NR 26
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD APR 15
PY 2003
VL 67
IS 16
AR 161401
DI ARTN 161401
PG 4
SC Physics, Condensed Matter
GA 677TT
UT ISI:000182824200017
ER

PT J
AU Machado, MP
   Piquini, P
   Mota, R
TI Energetics and electronic properties of BN nanocones with pentagonal
   rings at their apexes
SO EUROPEAN PHYSICAL JOURNAL D
LA English
DT Article
ID BORON-NITRIDE NANOTUBES; CARBON NANOTUBES; CONES; GROWTH; FRUSTRATION;
   STATES
AB The geometric structures, energetics and electronic properties of the
   recently discovered BN nanocones are investigated using
   first-principles calculations based on the density-functional theory.
   We have proposed one particular structure for BN nanocones associated
   with the 240degrees disclination, derived by the extraction of four
   60degrees segments, presenting as characteristic four pentagons at the
   apex and termination in two atoms. The cones are simulated by three
   clusters containing 58 B plus N atoms and additional 12 H atoms to
   saturate the dangling bonds at the edge. The most stable configuration
   is obtained when the two terminating atoms are one B and one N. For the
   cases where the two terminating atoms are of the same kind, the tip
   with B atoms is determined to have lower binding energy than with N
   atoms. The local densities of states of these BN nanocones are
   investigated and sharp states are found in the regions close (below and
   above) to the Fermi energy.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Machado, MP, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria,
   RS, Brazil.
CR AHLRICHS R, 1989, CHEM PHYS LETT, V162, P165
   BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BLASE X, 1998, PHYS REV LETT, V80, P1666
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   BOURGEOIS L, 2000, PHYS REV B, V61, P7686
   CARROLL DL, 1997, PHYS REV LETT, V78, P2811
   CHARLIER JC, 2001, PHYS REV LETT, V86, P5970
   CHOI WB, 1999, APPL PHYS LETT, V75, P3129
   FOWLER PW, 1999, CHEM PHYS LETT, V299, P359
   GE M, 1994, CHEM PHYS LETT, V220, P192
   GE MH, 1994, APPL PHYS LETT, V64, P710
   IIJIMA S, 1992, NATURE, V356, P776
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   KRISHNAN A, 1997, NATURE, V388, P451
   MARTIN JML, 1996, CHEM PHYS LETT, V248, P95
   MENON M, 1999, CHEM PHYS LETT, V307, P407
   MOTA R, 2003, PHYS STAT SOL C
   ROGERS KM, 2000, CHEM PHYS LETT, V332, P43
   RUBIO A, 1994, PHYS REV B, V49, P5081
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   TREACY MMJ, 2001, MAT RES S P, V673
NR 22
TC 5
PU SPRINGER-VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1434-6060
J9 EUR PHYS J D
JI Eur. Phys. J. D
PD APR
PY 2003
VL 23
IS 1
BP 91
EP 93
PG 3
SC Physics, Atomic, Molecular & Chemical
GA 679HN
UT ISI:000182914800012
ER

PT J
AU Bhering, DL
   Ramirez-Solis, A
   Mota, CJA
TI A density functional theory based approach to extraframework aluminum
   species in zeolites
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID COMPACT EFFECTIVE POTENTIALS; EXTRA-FRAMEWORK ALUMINUM; EXPONENT
   BASIS-SETS; Y-TYPE ZEOLITES; H-Y; LEWIS ACIDITY; DEALUMINATION;
   CRACKING; MODELS; SITES
AB The structures of six different extraframework aluminum (EFAL) species,
   possibly present in zeolites, were studied by density functional theory
   methods. A T-6 cluster (T = Si, Al), with different Si/Al ratios, was
   used to simulate the real zeolite Y structure and the coordination of
   the chosen EFAL species (Al3+, Al(OH)(2+), AlO+, AI(OH)(2)(+), AlO(OH),
   and Al(OH)(3)) The monovalent cations prefer to attain bicoordination
   with the framework AlO4- moiety, while di- and trivalent cations
   usually achieve tetracoordination. One important result is that, in all
   cases, coordination occurs with the oxygen atoms nearest to the
   framework aluminum ones. A single water molecule addition to the
   optimized Al3+.T-6 cluster produces a strongly exothermic reaction,
   leading to formation of a hydroxyaluminum cation and an acidic site on
   the zeolite. The addition of a second water molecule produces only
   minor energetic and structural changes.
C1 Fed Univ Rio De Janeiro, Inst Quim, Dept Quim Organ, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Dept Fis, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Fed Univ Rio De Janeiro, Inst Quim, Dept Quim Organ, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
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NR 44
TC 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD MAY 8
PY 2003
VL 107
IS 18
BP 4342
EP 4347
PG 6
SC Chemistry, Physical
GA 676BX
UT ISI:000182733000018
ER

PT J
AU Fischer, H
   Dias, SMG
   Santos, MAM
   Alves, AC
   Zanchin, N
   Craievich, AF
   Apriletti, JW
   Baxter, JD
   Webb, P
   Neves, FAR
   Ribeiro, RCJ
   Polikarpov, I
TI Low resolution structures of the retinoid X receptor DNA-binding and
   ligand-binding domains revealed by synchrotron x-ray solution scattering
SO JOURNAL OF BIOLOGICAL CHEMISTRY
LA English
DT Article
ID DIRECT SHAPE DETERMINATION; THYROID-HORMONE RECEPTORS; SMALL-ANGLE
   SCATTERING; NUCLEAR RECEPTORS; BIOLOGICAL MACROMOLECULES; TETRAMER
   FORMATION; CRYSTAL-STRUCTURE; RXR-ALPHA; ACID; HETERODIMERS
AB Nuclear receptors are ligand-inducible transcription factors that share
   structurally related DNA-binding (DBD) and ligand-binding (LBD)
   domains. Biochemical and structural studies have revealed the modular
   nature of DBD and LBD. Nevertheless, the domains function in concert in
   vivo. While high-resolution crystal structures of nuclear receptor DBDs
   and LBDs are available, there are no x-ray structural studies of
   nuclear receptor proteins containing multiple domains. We report the
   solution structures of the human retinoid X receptor DBD-LBD
   (hRXRalphaDeltaAB) region. We obtained ab initio shapes of
   hRXRalphaDeltaAB dimer and tetramer to 3.3 and 1.7 nm resolutions,
   respectively, and established the position and orientation of the DBD
   and LBD by fitting atomic coordinates of hRXRalpha DBD and LBD. The
   dimer is U-shaped with DBDs spaced at similar to2 nm in a head to head
   orientation forming an angle of about 10degrees with respect to each
   other and with an extensive interface area provided by the LBD. The
   tetramer is a more elongated X-shaped molecule formed by two dimers in
   head to head arrangement in which the DBDs are extended from the
   structure and spaced at about 6 nm. The close proximity of DBDs in
   dimers may facilitate homodimer formation on DNA, however, for the
   homodimer to bind to a DNA element containing two directly repeated
   half-sites, one of the DBDs would need to rotate with respect to the
   other element. By contrast, the separation of DBDs in the tetramers may
   account for their decreased ability to recognize DNA.
C1 Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
   Lab Nacl Luz Sincrotron, BR-13084971 Campinas, SP, Brazil.
   Univ Calif San Francisco, Ctr Diabet, Metab Res Unit, San Francisco, CA 94143 USA.
   Univ Calif San Francisco, Dept Med, San Francisco, CA 94143 USA.
   Univ Brasilia, Dept Ciencias Farmaceut, BR-70900910 Brasilia, DF, Brazil.
RP Polikarpov, I, Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao
   Carlos, Av Trabalhador Sao Carlense 400, BR-13560970 Sao Carlos, SP,
   Brazil.
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NR 49
TC 3
PU AMER SOC BIOCHEMISTRY MOLECULAR BIOLOGY INC
PI BETHESDA
PA 9650 ROCKVILLE PIKE, BETHESDA, MD 20814-3996 USA
SN 0021-9258
J9 J BIOL CHEM
JI J. Biol. Chem.
PD MAY 2
PY 2003
VL 278
IS 18
BP 16030
EP 16038
PG 9
SC Biochemistry & Molecular Biology
GA 675EL
UT ISI:000182680000074
ER

PT J
AU Autschbach, J
   Jorge, FE
   Zlegler, T
TI Density functional calculations on electronic circular dichroism
   spectra of chiral transition metal complexes
SO INORGANIC CHEMISTRY
LA English
DT Article
ID EXCHANGE-CORRELATION POTENTIALS; D-3 LANTHANIDE(III) COMPLEXES; F-F
   TRANSITIONS; EXCITATION-ENERGIES; RESPONSE THEORY; OPTICAL-ACTIVITY;
   CHIROPTICAL PROPERTIES; MAGNETIC-PROPERTIES; ORGANIC-MOLECULES; MODEL
AB Time-dependent density functional theory (TD-DFT) has for the first
   time been applied to the computation of circular dichroism (CD) spectra
   of transition metal complexes, and a detailed comparison with
   experimental spectra has been made. Absorption spectra are also
   reported. Various Co-III complexes as well as [Rh(en)(3)](3+) are
   studied in this work. The resulting simulated CD spectra are generally
   in good agreement with experimental spectra after corrections for
   systematic errors in a few of the lowest excitation energies are
   applied. This allows for an interpretation and assignment of the
   spectra for the whole experimentally accessible energy range (UV/vis).
   Solvent effects on the excitations are estimated via inclusion of a
   continuum solvent model. This significantly improves the computed
   excitation energies for charge-transfer bands for complexes of charge
   +3, but has only a small effect on those for neutral or singly charged
   complexes. The energies of the weak d-to-d transitions of the Co
   complexes are systematically overestimated due to deficiencies of the
   density functionals. These errors are much smaller for the 4d metal
   complex. Taking these systematic errors and the effect of a solvent
   into consideration, TD-DFT computations are demonstrated to be a
   reliable tool in order to assist with the assignment and interpretation
   of CD spectra of chiral transition metal complexes.
C1 Univ Calgary, Dept Chem, Calgary, AB T2N 1N4, Canada.
   Univ Fed Espirito Santo, Dept Fis, BR-29060900 Vitoria, ES, Brazil.
RP Autschbach, J, Univ Erlangen Nurnberg, Lehrstuhl Theoret Chem,
   Egerlandstr 3, D-91058 Erlangen, Germany.
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NR 87
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0020-1669
J9 INORG CHEM
JI Inorg. Chem.
PD MAY 5
PY 2003
VL 42
IS 9
BP 2867
EP 2877
PG 11
SC Chemistry, Inorganic & Nuclear
GA 674RU
UT ISI:000182650400012
ER

PT J
AU Lima, NA
   Silva, MF
   Oliveira, LN
   Capelle, K
TI Density functionals not based on the electron gas: Local-density
   approximation for a luttinger liquid
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID SOLVABLE SEMICONDUCTOR MODEL; DIMENSIONAL HUBBARD-MODEL; FORMALISM
AB By shifting the reference system for the local-density approximation
   (LDA) from the electron gas to other model systems, one obtains a new
   class of density functionals, which by design account for the
   correlations present in the chosen reference system. This strategy is
   illustrated by constructing an explicit LDA for the one-dimensional
   Hubbard model. While the traditional ab initio LDA is based on a Fermi
   liquid (the three-dimensional interacting electron gas), this one is
   based on a Luttinger liquid. First applications to inhomogeneous
   Hubbard models, including one containing a localized impurity, are
   reported.
C1 Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, Sao Paulo, Brazil.
   Univ Sao Paulo, Dept Quim & Fis Mol, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, Sao Paulo, Brazil.
RP Lima, NA, Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao Carlos,
   Caixa Postal 369, BR-13560970 Sao Carlos, Sao Paulo, Brazil.
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NR 27
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD APR 11
PY 2003
VL 90
IS 14
AR 146402
DI ARTN 146402
PG 4
SC Physics, Multidisciplinary
GA 668XH
UT ISI:000182320100037
ER

PT J
AU Jellinek, J
   Acioli, PH
TI Converting Kohn-Sham eigenenergies into electron binding energies
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; SELF-INTERACTION CORRECTION; TO-METAL
   TRANSITION; PHOTOELECTRON-SPECTROSCOPY; MAGNESIUM CLUSTERS; REMOVAL
   ENERGIES; APPROXIMATION; EIGENVALUE; BEHAVIOR; NEON
AB A new accurate scheme for converting the Kohn-Sham eigenenergies into
   electron binding energies is formulated. The accuracy of the scheme is
   illustrated in applications to ten atoms and three molecules. (C) 2003
   American Institute of Physics.
C1 Argonne Natl Lab, Div Chem, Argonne, IL 60439 USA.
   Univ Brasilia, Inst Fis, BR-70919970 Brasilia, DF, Brazil.
RP Jellinek, J, Argonne Natl Lab, Div Chem, 9700 S Cass Ave, Argonne, IL
   60439 USA.
CR ACIOLI PH, IN PRESS EUR PHYS D
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NR 33
TC 4
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD MAY 1
PY 2003
VL 118
IS 17
BP 7783
EP 7796
PG 14
SC Physics, Atomic, Molecular & Chemical
GA 668DY
UT ISI:000182276100008
ER

PT J
AU Treu, O
   Kondo, RT
   Pinheiro, JC
TI Contracted GTF basis sets applied to the theoretical interpretation of
   the Raman spectrum of hexaaquachromium(III) ion
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE contracted basis sets; GTF basis sets; generator coordinate
   Hartree-Fock method; vibrational properties of molecular species;
   theoretical interpretation of the Raman spectrum
ID COORDINATE HARTREE-FOCK; GAUSSIAN-BASIS; AB-INITIO; ATOMS; CHOICE
AB Contracted GTF basis sets designed with aid of the Generator Coordinate
   Hartree-Fock (GCHF) method for H(S-2), O2-(IS), and Cr3+(F-4) atomic
   species are applied to perform theoretical interpretation of the Raman
   spectrum of hexaaquachromium(III) ion. The 16s, 16s10p, and 24s17p13d
   GTF basis sets were contracted to [4s] for H atom, [6s4p], and [9s6p3d]
   for O2- and Cr3+, respectively, by Dunning's scheme. For Cr3+, the
   [9s6p3d] basis set was enriched with f polarization function and used
   in combination com [4s] and [6s4p] in the study of our interest. The
   results obtained in this report show that the contracted GTF basis sets
   used are a useful alternative for the theoretical interpretation of
   Raman spectrum of hexaaquachromium(III) ion and that GCHF method is an
   effective alternative to selection of GTF basis sets for theoretical
   study of vibrational properties of poliatomic species. (C) 2003
   Elsevier Science B.V. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab Quim Teor & Computac, BR-66075110 Belem, Para, Brazil.
   UNESP, Inst Quim, Araraquara, SP, Brazil.
   Univ Sao Paulo, Ctr Informat Sao Carlos, Secao Suporte, BR-13560970 Sao Carlos, SP, Brazil.
   Cooperat Ctr Educ Cient & Empreendedore Amazonia, BR-66013060 Belem, Para, Brazil.
RP Pinheiro, JC, Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab
   Quim Teor & Computac, CP 10101, BR-66075110 Belem, Para, Brazil.
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NR 18
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 25
PY 2003
VL 624
BP 153
EP 157
PG 5
SC Chemistry, Physical
GA 666HC
UT ISI:000182170700019
ER

PT J
AU Zamora, MA
   Masman, MF
   Bombasaro, JA
   Freile, ML
   Cechinel, V
   Lopez, SN
   Zacchino, SA
   Enriz, RD
TI Conformational and electronic study of
   N-phenylalkyl-3,4-dichloromaleimides: Ab initio and DFT study
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE maleimides; ab initio and DFT calculations; conformational study;
   antifungal activity
ID FUNGAL CELL-WALL; GEOMETRICAL ALGORITHM; SPACE GASCOS; SEARCH;
   ELECTROSTATICS; RECOGNITION; MECHANISM; MOLECULES
AB A conformational and electronic study on
   N-phenylalkyl-3,4-dichloromaleimides, a new series of antifungal
   compounds, was carried out. In this study ab initio [RHF/3-21G and
   RHF/6-31G(d)] and density functional theory (B3LYP/6-31G(d))
   calculations were performed. The effect of solvent (water) was taken
   into account by performing calculations with the isodensity polarizable
   continuum model method. The electronic study of the compounds was
   carried out using molecular electrostatic potentials. The presence of
   two symmetrical aromatic systems reduces notably the conformational
   possibilities of these maleimides. The results permit the recognition
   of the minimal structural requirements for the production of the
   antifungal response; a 3,4-dichloroimido ring and a benzene ring appear
   to be indispensable. Also, theoretical calculations suggest that the
   optimum interatomic distance between these moieties is about 3.5-5.0
   Angstrom. (C) 2003 Wiley Periodicals, Inc.
C1 Univ Nacl San Luis, Fac Quim Bioquim & Farm, Dept Quim, RA-5700 San Luis, Argentina.
   UNPSJB, Fac Ciencias Nat, Dept Quim, RA-9000 Comodoro Rivadavia, Chubut, Argentina.
   Univ Vale Itajai, CCS, NIQFAR, Itajai, SC, Brazil.
   Univ Nacl Rosario, Fac Ciencias Bioquim & Farmaceut, RA-2000 Rosario, Santa Fe, Argentina.
RP Enriz, RD, Univ Nacl San Luis, Fac Quim Bioquim & Farm, Dept Quim,
   Chacabuco 917, RA-5700 San Luis, Argentina.
CR *WAV INC, 1996, PC SPARTAN PRO
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NR 42
TC 5
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD MAY 15
PY 2003
VL 93
IS 1
BP 32
EP 46
PG 15
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 667HY
UT ISI:000182226700004
ER

PT J
AU Oliveira, LN
   Amaral, OAV
   Castro, MA
   Fonseca, TL
TI Static polarizabilities of doubly charged polyacetylene oligomers:
   basis set and electron correlation effects
SO CHEMICAL PHYSICS
LA English
DT Article
DE polarizabilities; polyacetylene oligomers; charged bipolarons
ID VARIATIONAL PERTURBATIONAL TREATMENT; DYNAMIC DIPOLE POLARIZABILITIES;
   NONLINEAR-OPTICAL PROPERTIES; BOND-LENGTH ALTERNATION; STABLE ATOMIC
   ANIONS; PUSH-PULL POLYENES; CONJUGATED CHAINS; FIRST
   HYPERPOLARIZABILITY; LINEAR-POLARIZABILITIES; POLARONS
AB Ab initio calculations, carried out with different basis sets, for the
   static longitudinal linear polarizability, alpha(L), and second order
   hyperpolarizability, gamma(L), Of Small doubly charged polyacetylene
   (PA) chains, are presented. The polarizabilities were calculated using
   the Hartree-Fock (HF) method while the electron correlation effects
   were included through the second-order Moller-Plesset perturbation
   theory (MP2). Positively and negatively charged bipolarons were
   studied. The results obtained for positive and negative chains show
   that the ionization state effect decreases more rapidly, as the chain
   length is increased, for alpha(L) than for gamma(L). For both types of
   charged chains, the incorporation of the electron correlation increases
   the alpha(L) and gamma(L) values, as compared to the HF values. A
   comparison between the results obtained using the standard 6-31G basis
   set and augmented versions of this set, obtained by the addition of
   diffuse and polarization functions, shows that 6-31G basis set does not
   provide a good description of the negative chains studied here and that
   the addition of extra diffuse functions on the basis set is needed in
   order to obtain reliable estimates for polarizabilities, specially for
   gamma(L). (C) 2003 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
RP Fonseca, TL, Univ Fed Goias, Inst Fis, Campus 2,Caixa Postal 131,
   BR-74001970 Goiania, Go, Brazil.
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NR 41
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD APR 15
PY 2003
VL 289
IS 2-3
BP 221
EP 230
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 665DH
UT ISI:000182104000004
ER

PT J
AU Gonzales-Ormeno, PG
   Petrilli, HM
   Schon, CG
TI Ab-initio calculations of the formation energies of BCC-based
   superlattices in the Fe-Al system
SO CALPHAD-COMPUTER COUPLING OF PHASE DIAGRAMS AND THERMOCHEMISTRY
LA English
DT Article
ID ROOM-TEMPERATURE DUCTILITY; FE3AL-BASED ALLOYS; IRON ALUMINIDES;
   PHASE-DIAGRAMS; GROUND-STATE; ORDER; TENSILE; NICKEL; FE3AL; FCC
AB First-principles calculations of the total energies of A2 iron and
   Aluminum, B2 (FeAl), B32 (FeAl) and D0(3) (Fe3Al and FeAl3) compounds
   were performed in the frame of density functional theory (DFT) using
   the Full Potential - Linear Augmented Plane Wave method (FP-LAPW).
   These results have been used to obtain formation energies of the
   respective ground states. The calculated formation energies of the
   D0(3) (Fe3Al) and B2 (FeAl) compounds show excellent agreement with
   available calorimetric data on standard enthalpies of formation of
   Fe-Al alloys up to 50 at.% aluminum. As the Fe-Al system has a
   controversial magnetic behavior when described by ab-initio methods in
   the DFT, this agreement is remarkable. (C) 2003 Elsevier Science Ltd.
   All rights reserved.
C1 Univ Sao Paulo, Escola Politecn, Dept Met & Mat Engn, Computat Mat Sci Lab, BR-05508900 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Fis, Dept Fis Mat & Mecan, BR-05508900 Sao Paulo, Brazil.
RP Schon, CG, Univ Sao Paulo, Escola Politecn, Dept Met & Mat Engn,
   Computat Mat Sci Lab, Av Prof Mello Moraes 2463, BR-05508900 Sao Paulo,
   Brazil.
EM schoen@usp.br
CR ALEXANDER DJ, 1998, MAT SCI ENG A-STRUCT, V258, P276
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   HUANG YD, 2001, INTERMETALLICS, V9, P331
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   VILLARS P, 1985, PEARSONS HDB CRYSTAL
NR 34
TC 6
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0364-5916
J9 CALPHAD-COMPUT COUP PHASE DIA
JI Calphad-Comput. Coupling Ph. Diagrams Thermochem.
PD DEC
PY 2002
VL 26
IS 4
BP 573
EP 582
PG 10
SC Chemistry, Physical; Thermodynamics
GA 657TK
UT ISI:000181682300007
ER

PT J
AU Bechstedt, F
   Furthmuller, J
   Ferhat, M
   Teles, LK
   Scolfaro, LMR
   Leite, JR
   Davydov, VY
   Ambacher, O
   Goldhahn, R
TI Energy gap and optical properties of In(x)Gal(1-x)N
SO PHYSICA STATUS SOLIDI A-APPLICATIONS AND MATERIALS SCIENCE
LA English
DT Article
ID CHEMICAL-VAPOR-DEPOSITION; BAND-GAP; INXGA1-XN ALLOYS;
   STRUCTURAL-PROPERTIES; EPITAXIAL LAYERS; INDIUM NITRIDE; INN;
   SEMICONDUCTORS; 1ST-PRINCIPLES; CRYSTALS
AB We present ab initio calculations of the electronic structure and the
   optical properties of InxGa1-xN. They are completed by studies of the
   strain influence on the alloys. The results are critically discussed in
   the light of recent experiments. We find an energy gap of InN < 1 eV
   and a nonparabolic absorption edge. The strong variation of the alloy
   gap with the In molar fraction is described by a composition-dependent
   bowing parameter. The tendency of spinodal decomposition is suppressed
   by biaxial strain. Its extent depends on the realization of strain
   accommodation.
C1 Univ Jena, Inst Festkorpertheorie & Theoret Opt, D-07743 Jena, Germany.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Carlos, SP, Brazil.
   Russian Acad Sci, AF Ioffe Phys Tech Inst, St Petersburg 194021, Russia.
   Tech Univ, Ctr Micro & Nanotechnol, D-98693 Ilmenau, Germany.
   Tech Univ Ilmenau, Inst Phys, D-98684 Ilmenau, Germany.
RP Bechstedt, F, Univ Jena, Inst Festkorpertheorie & Theoret Opt, Max Wien
   Pl 1, D-07743 Jena, Germany.
EM bechstedt@ifto.physik.uni-jena.de
CR ADOLPH B, 2001, PHYS REV B, V63
   BECHSTEDT F, 1988, PHYS REV B, V38, P7710
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   BU Y, 1993, J VAC SCI TECHNOL A, V11, P2931
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   DAVYDOV VY, 2002, PHYS STATUS SOLIDI B, V230, R4
   FERHAT M, 2002, APPL PHYS LETT, V80, P1394
   FERHAT M, 2002, PHYS REV B, V65
   GROSSNER U, 1998, PHYS REV B, V58, R1722
   GUO Q, 1997, SOLID STATE COMMUN, V83, P721
   GUO QX, 1994, JPN J APPL PHYS PT 1, V33, P2453
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   LAMBRECHT WRL, 1997, SOLID STATE ELECTRON, V41, P195
   LAMBRECHT WRL, 2002, SOLID STATE COMMUN, V121, P549
   LISCHKA K, 2002, APPL PHYS LETT, V88, P769
   ODONNELL KP, 2000, MAT RES SOC S, V595
   PERSSON C, 2001, J PHYS-CONDENS MAT, V13, P8945
   RIEGER MM, 1995, PHYS REV B, V52, P16567
   SHAN W, 1996, APPL PHYS LETT, V69, P3315
   STAMPFL C, 1999, PHYS REV B, V59, P5529
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   TABATA A, 2002, APPL PHYS LETT, V80, P769
   TANSLEY TL, 1986, J APPL PHYS, V59, P3241
   TELES LK, UNPUB
   TELES LK, 2000, PHYS REV B, V62, P2475
   TELES LK, 2001, PHYS REV B, V63
   WENZIEN B, 1995, PHYS REV B, V51, P14701
NR 30
TC 29
PU WILEY-V C H VERLAG GMBH
PI WEINHEIM
PA PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY
SN 0031-8965
J9 PHYS STATUS SOLIDI A-APPL RES
JI Phys. Status Solidi A-Appl. Res.
PD FEB
PY 2003
VL 195
IS 3
BP 628
EP 633
PG 6
SC Physics, Condensed Matter
GA 656GA
UT ISI:000181599300027
ER

PT J
AU Fagan, SB
   da Silva, LB
   Mota, R
TI Ab initio study of radial deformation plus vacancy on carbon nanotubes:
   Energetics and electronic properties
SO NANO LETTERS
LA English
DT Article
ID LARGE SYSTEMS; CONDUCTANCE
AB The effects of radial deformation and single vacancy on the electronic
   properties of a single-wall carbon nanotube are studied through ab
   initio method. Different paths are considered: the tube is deformed and
   subsequently a vacancy is produced, or a vacancy is created and the
   tube is deformed later. The involved energies, band structures, and
   densities of states following several paths are discussed, and a simple
   way to induce fundamental changes on the electronic properties is
   proposed.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Mota, R, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
EM mota@ccne.ufsm.br
CR ARTACHO E, 1999, PHYS STATUS SOLIDI B, V215, P809
   BAIERLE RJ, 2001, PHYS REV B, V64
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   DRESSELHAUS MS, 2000, CARBON NANOTUBES SYN
   FAGAN SB, 2003, PHYS REV B, V67
   GULSEREN O, 2001, PHYS REV LETT, V87
   GULSEREN O, 2002, PHYS REV B, V65
   HANSSON A, 2000, PHYS REV B, V62, P7639
   IGAMI M, 1999, J PHYS SOC JPN, V68, P716
   MAITI A, 2002, PHYS REV LETT, V88
   ORDEJON P, 1996, PHYS REV B, V53
   PERDEW JP, 1981, PHYS REV B, V23, P5048
   ROCHEFORT A, 1999, PHYS REV B, V60, P13824
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   SANKEY OF, 1989, PHYS REV B, V40, P3979
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NR 17
TC 6
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1530-6984
J9 NANO LETT
JI Nano Lett.
PD MAR
PY 2003
VL 3
IS 3
BP 289
EP 291
PG 3
SC Chemistry, Multidisciplinary; Materials Science, Multidisciplinary
GA 656AN
UT ISI:000181586600004
ER

PT J
AU Schiwietz, G
   Grande, PL
TI The role of basic energy-loss processes in layer-resolved surface
   investigations with ions
SO CURRENT APPLIED PHYSICS
LA English
DT Article
DE electronic energy-loss distribution; stopping power; backscattering;
   coupled-channel calculations; protons; aluminum surface; innershell
   ionizaton
ID SCATTERING EXPERIMENTS; ANGULAR-DEPENDENCE; HE; INCIDENT; BARE
AB Ab initio quantum mechanical calculations have been performed for the
   energy loss of protons backscattered from an Al surface. Results from
   first-order perturbation theory are compared to full numerical
   atomic-orbital coupled-channel calculations. It is shown that both
   inner shells and non-perturbative effects are important for the
   understanding of ion energy-loss spectra. (C) 2002 Elsevier Science
   B.V. All rights reserved.
C1 Hahn Meitner Inst Berlin GmbH, Abt SF4, Bereich Strukturforsch, D-14109 Berlin, Germany.
   Univ Fed Rio Grande Sul, Inst Fis, BR-91501470 Porto Alegre, RS, Brazil.
RP Schiwietz, G, Hahn Meitner Inst Berlin GmbH, Abt SF4, Bereich
   Strukturforsch, Glienicker Str 100, D-14109 Berlin, Germany.
CR DOSSANTOS JHR, 1997, PHYS REV B, V55, P4332
   FRENKEN JWM, 1986, NUCL INSTRUM METH B, V17, P334
   GRANDE PL, UNPUB
   GRANDE PL, 1991, PHYS REV A, V44, P2984
   GRANDE PL, 1993, PHYS REV A, V47, P1119
   GRNDE PL, 1998, NUCL INSTRUM METH B, V136, P125
   SCHIWIETZ G, 1990, PHYS REV A, V42, P296
   SCHIWIETZ G, 1992, NUCL INSTRUM METH B, V69, P10
   SCHIWIETZ G, 1994, PHYS REV LETT, V72, P2159
   SCHULTE WH, 2001, NUCL INSTRUM METH B, V183, P16
NR 10
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 1567-1739
J9 CURR APPL PHYS
JI Curr. Appl. Phys.
PD FEB
PY 2003
VL 3
IS 1
BP 35
EP 37
PG 3
SC Materials Science, Multidisciplinary; Physics, Applied
GA 657FV
UT ISI:000181656100008
ER

PT J
AU Ornellas, FR
   Resende, SM
   Machado, FBC
   Roberto-Neto, O
TI A high level theoretical investigation of the N2O4 -> 2 NO2
   dissociation reaction: Is there a transition state?
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID POTENTIAL-ENERGY FUNCTION; DINITROGEN TETROXIDE; AB-INITIO;
   ELECTRON-DIFFRACTION; GAS; TEMPERATURE; DYNAMICS; ABINITIO
AB The N2O4-->2 NO2 dissociation reaction was investigated at a high level
   of theory using the couple cluster with all single and double
   excitations and connected triples [CCSD(T)] and complete active space
   self-consistent field approaches, and the cc-pVDZ, aug-cc-pVDZ, and
   cc-pVTZ basis sets. Only at the coupled cluster level a first-order
   saddle point was found connecting reactant and products. Collectively,
   structural, vibrational, and thermodynamic data for the three
   stationary points represent the best theoretical description of this
   reaction system to date, and are in good agreement with available
   experimental results. Unimolecular transition state theory rate
   constants (k(infinity)) were also evaluated at 250, 298.15, and 350 K.
   At the CCSD(T)/cc-pVTZ level of calculation these results are
   0.62x10(1), 1.90x10(3), and 1.66x10(5) s(-1), respectively. Known
   experimental results at 298 K vary from 1.7x10(5) to 1.0x10(6) s(-1).
   Including an estimate for basis set superposition error, we predict
   DeltaH(298)(0) for the dissociation reaction to be 12.76 kcal/mol
   (Expt. 13.1-13.7 kcal/mol). (C) 2003 American Institute of Physics.
C1 Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05513970 Sao Paulo, Brazil.
   Ctr Tecn Aeroesp, Dept Quim, Inst Tecnol Aeronaut, BR-12228900 Sao Paulo, Brazil.
   Inst Estudos Avancados, BR-1228840 Sao Jose Dos Campos, Brazil.
RP Ornellas, FR, Univ Sao Paulo, Inst Quim, Dept Quim Fundamental,
   BR-05513970 Sao Paulo, Brazil.
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NR 42
TC 3
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD MAR 1
PY 2003
VL 118
IS 9
BP 4060
EP 4065
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 646DC
UT ISI:000181018700018
ER

PT J
AU Branicio, PS
   Kalia, RK
   Nakano, A
   Rino, JP
   Shimojo, F
   Vashishta, P
TI Structural, mechanical, and vibrational properties of Ga1-xInxAs
   alloys: A molecular dynamics study
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID ABSORPTION FINE-STRUCTURE; RANDOM SOLID-SOLUTIONS
AB Structural, mechanical, and vibrational properties of Ga1-xInxAs (0less
   than or equal toxless than or equal to1) random solid solutions are
   investigated with classical and ab initio molecular-dynamics
   simulations. We find that the Ga-As and In-As bond lengths change only
   slightly as a function of x, despite the large lattice mismatch
   (similar to7%) between GaAs and InAs crystals. The nearest
   cation-cation distance has a broad distribution, whereas the nearest
   neighbor anion-anion distance distribution has two distinct peaks. The
   elastic constants exhibit a significant nonlinear dependence on x. The
   phonon density-of-states exhibits two high-frequency optical modes.
   These results are in excellent agreement with experiments. (C) 2003
   American Institute of Physics.
C1 Univ So Calif, Dept Phys & Astron, Collaboratory Adv Comp & Simulat, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Comp Sci, Los Angeles, CA 90089 USA.
   Univ So Calif, Dept Mat Sci & Engn, Los Angeles, CA 90089 USA.
   Univ Fed Sao Carlos, BR-13560 Sao Carlos, SP, Brazil.
   Kumamoto Univ, Kumamoto, Japan.
RP Branicio, PS, Univ So Calif, Dept Phys & Astron, Collaboratory Adv Comp
   & Simulat, Los Angeles, CA 90089 USA.
CR BAZANT MZ, 1997, PHYS REV B, V56, P8542
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   VEGARD L, 1921, Z PHYS, V5, P17
NR 21
TC 5
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 17
PY 2003
VL 82
IS 7
BP 1057
EP 1059
PG 3
SC Physics, Applied
GA 644KR
UT ISI:000180917000019
ER

PT J
AU Fileti, EE
   Rivelino, R
   Canuto, S
TI Rayleigh light scattering of hydrogen bonded clusters investigated by
   means of ab initio calculations
SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
LA English
DT Article
ID WATER-METHANOL COMPLEXES; MATRIX-ISOLATION; BASIS-SET;
   ELECTRON-CORRELATION; INTERACTION ENERGY; DIMER; POLARIZABILITIES;
   HYPERPOLARIZABILITY; SPECTRA; HCN-H2O
AB Ab initio calculations of depolarization ratios and intensities of
   classically scattered light, in terms of dipole polarizabilities and
   polarizability anisotropies, are reported for different hydrogen bonded
   molecular clusters. Five different groups of organic heterodimers
   formed with water are considered: HCHO...H2O, CH3HO...H2O, HCOOH...H2O,
   CH3CN...H2O, and (CH3)(2)CO...H2O, together with the water dimer
   H2O...H2O. The geometries of all complexes have been optimized by means
   of the second-order Moller-Plesset many-body perturbation theory (MP2),
   using the augmented correlation-consistent basis set with polarized
   valence of double-zeta quality (aug-cc-pVDZ). The calculated average
   dipole polarizabilities of the isolated molecules are in good agreement
   with available experimental results. The calculations are then extended
   to the complexes and, from these, the Rayleigh scattering activities
   and depolarization ratio changes, upon hydrogen bond formation, are
   obtained and analysed. The differences in activity and depolarization
   for Rayleigh scattered radiation between two groups of isomers, (i)
   HCN...H2O and H2O...HCN and (ii) CH3HO...H2O and CH3OH...OH2, have also
   been investigated.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Fileti, EE, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 51
TC 7
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-4075
J9 J PHYS-B-AT MOL OPT PHYS
JI J. Phys. B-At. Mol. Opt. Phys.
PD JAN 28
PY 2003
VL 36
IS 2
BP 399
EP 408
PG 10
SC Physics, Atomic, Molecular & Chemical; Optics
GA 642YT
UT ISI:000180835500021
ER

PT J
AU Borges, I
   Varandas, AM
   Rocha, AB
   Bielschowsky, CE
TI Forbidden transitions in benzene
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Herzberg-Teller effect; vibronic coupling; complete active space self
   consistent field wavefunctions
ID JET-COOLED BENZENE; ELECTRONIC-TRANSITION; AB-INITIO; SPECTRA; ACETONE;
   STATES
AB We have computed the optical oscillator strengths for the
   symmetry-forbidden transitions 1 B-1(2u) <-- (X) over tilde and 1
   B-1(1u) <-- (X) over tilde for benzene through vibronic coupling.
   Electronic transition dipole moments were calculated at the complete
   active space self consistent field level along the normal coordinates.
   Optical oscillator strengths for the sum of the total vibronic
   excitations are compared with available theoretical and experimental
   results. (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Dept Fisicoquim, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Coimbra, Dept Quim, P-3049 Coimbra, Portugal.
   Univ Fed Rio de Janeiro, Inst Fis, BR-21945 Rio De Janeiro, Brazil.
RP Borges, I, Univ Fed Rio de Janeiro, Dept Fisicoquim, Inst Quim, Cidade
   Univ,CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR ALBRECHT AC, 1960, J CHEM PHYS, V33, P169
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NR 29
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD FEB 3
PY 2003
VL 621
IS 1-2
BP 99
EP 105
PG 7
SC Chemistry, Physical
GA 640FE
UT ISI:000180677000012
ER

PT J
AU Capelle, K
   Gyorffy, BL
TI Exploring dynamical magnetism with time-dependent density-functional
   theory: From spin fluctuations to Gilbert damping
SO EUROPHYSICS LETTERS
LA English
DT Article
ID FERROMAGNETS; STATE
AB We use time-dependent spin-density-functional theory to study dynamical
   magnetic phenomena. First, we recall that the local-spin-density
   approximation (LSDA) fails to account correctly for magnetic
   fluctuations in the paramagnetic state of iron and other itinerant
   ferromagnets. Next, we construct a gradient-dependent density
   functional that does not suffer from this problem of the LSDA. This
   functional is then used to derive, for the first time, the
   phenomenological Gilbert equation of micromagnetics directly from
   time-dependent density-functional theory. Limitations and extensions of
   Gilbert damping are discussed on this basis, and some comparisons with
   phenomenological theories and experiments are made.
C1 Univ Sao Paulo, Dept Quim & Fis Mol, Inst Quim, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England.
RP Capelle, K, Univ Sao Paulo, Dept Quim & Fis Mol, Inst Quim, Caixa
   Postal 780, BR-13560970 Sao Carlos, SP, Brazil.
CR ANTROPOV VP, 1995, PHYS REV LETT, V75, P729
   BROWN WF, 1978, MICROMAGNETICS
   CAPELLE K, 2001, PHYS REV LETT, V87
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   VANLEEUWEN R, 1999, PHYS REV LETT, V82, P3863
   WOLF SA, 2001, SCIENCE, V294, P1488
NR 23
TC 5
PU E D P SCIENCES
PI LES ULIS CEDEXA
PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES
   ULIS CEDEXA, FRANCE
SN 0295-5075
J9 EUROPHYS LETT
JI Europhys. Lett.
PD FEB
PY 2003
VL 61
IS 3
BP 354
EP 360
PG 7
SC Physics, Multidisciplinary
GA 639PN
UT ISI:000180638600011
ER

PT J
AU Freedman, TB
   Cao, XL
   Oliveira, RV
   Cass, QB
   Nafie, LA
TI Determination of the absolute configuration and solution conformation
   of gossypol by vibrational circular dichroism
SO CHIRALITY
LA English
DT Article
DE vibrational circular dichroism; gossypol; DFT calculations; absolute
   configuration; solution conformation
ID TUMOR-CELL LINES; BREAST-CANCER; ENANTIOMERS
AB Vibrational circular dichroism (VCD) measurements and density
   functional theory (DFT) calculations were used to obtain the first
   definitive assignment of the absolute configuration for the
   polyphenolic binaphpthyl dialdehyde gossypol and a determination of the
   solution conformation in CDCl3. VCD spectra recorded for the two
   resolved enantiomers are near mirror images and excellent agreement
   between the observed IR and VCD spectra and intensity calculations
   carried out at the DFT (B3LYP/6-31G*) level establish the absolute
   configurations of (+)-gossypol as P and (-)-gossypol as M, with two
   conformations in CDCl3 solution that differ in isopropyl group
   orientation.
C1 Syracuse Univ, Dept Chem, Ctr Sci & Technol 1 014, Syracuse, NY 13244 USA.
   Univ Fed Sao Carlos, Dept Chem, BR-13565905 Sao Carlos, SP, Brazil.
RP Freedman, TB, Syracuse Univ, Dept Chem, Ctr Sci & Technol 1 014,
   Syracuse, NY 13244 USA.
CR BRZEZINSKI B, 1990, J MOL STRUCT, V220, P261
   BUSHUNOW P, 1999, J NEURO-ONCOL, V43, P79
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   CASS QB, 2002, J LIQ CHROMATOGR R T, V25, P819
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   DYATKIN AB, 2002, CHIRALITY, V14, P215
   FISH RG, 1995, TETRAHEDRON-ASYMMETR, V6, P873
   FREEDMAN TB, 2002, HELV CHIM ACTA, V85, P1160
   FRISCH MJ, 1998, GAUSSIAN 98
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   MEYERS AI, 1998, TETRAHEDRON, V54, P10493
   NAFIE LA, 2000, APPL SPECTROSC, V54, P1634
   NAFIE LA, 2000, CIRCULAR DICHROISM P, P97
   NAFIE LA, 2000, ENCY SPECTROSCOPY, P2391
   NAFIE LA, 2001, INFRARED RAMAN SPECT, P15
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   SCHMIDT JH, 1990, J AGR FOOD CHEM, V38, P505
   SEGAL SJ, 1985, GOSSYPOL POTENTIAL A
   SEIDMAN AD, 1998, INVEST MED, V46, A213
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   SHELLEY MD, 1999, CANCER LETT, V135, P171
   SHELLEY MD, 2000, ANTI-CANCER DRUG, V11, P209
   SOLLADIECAVALLO A, 2001, TETRAHEDRON-ASYMMETR, V12, P2605
   SOLLADIECAVALLO A, 2001, TETRAHEDRON-ASYMMETR, V12, P2703
   SOLLADIECAVALLO A, 2002, EUR J ORG CHEM   JUN, P1788
   SONENBERG M, 1988, CONTRACEPTION, V37, P247
   STEPHENS PJ, 2000, CHIRALITY, V12, P172
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NR 41
TC 16
PU WILEY-LISS
PI NEW YORK
PA DIV JOHN WILEY & SONS INC, 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0899-0042
J9 CHIRALITY
JI Chirality
PD FEB
PY 2003
VL 15
IS 2
BP 196
EP 200
PG 5
SC Chemistry, Analytical; Chemistry, Medicinal; Chemistry, Organic;
   Pharmacology & Pharmacy
GA 640PH
UT ISI:000180696800014
ER

PT J
AU Duarte, HA
   Duani, H
   De Almeida, WB
TI Ab initio correlated comparative study of the torsional potentials for
   2,2-bipyrrole and 2,2 '-bifuran five membered heterocyclic dimers
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID GAUSSIAN-BASIS SETS; MOLECULAR CALCULATIONS; CONDUCTING POLYMERS;
   INTERNAL-ROTATION; POLYPYRROLE; ATOMS; 2,2'-BITHIOPHENE; APPROXIMATION;
   BITHIOPHENE; EXCHANGE
AB This Letter reports an MP4(SDQ) ab initio investigation of the electron
   correlation and basis set effects on the torsional potentials for
   2,2'-bipyrrole and 2,2'-bifuran. Pople's standard basis sets and
   Dunning's double-zeta (D95**) and correlated consistent basis sets
   (aug-cc-pVDZ) were employed. We also included for the first time
   thermal corrections to the ab initio relative energies. The torsional
   potentials were fitted to a truncated Fourier expansion. Our
   MP4(SDQ)/6-311++G** and MP4(SDQ)/aug-cc-pVDZ improved levels show an
   agreement within ca. 2 U mol(-1), indicating that convergence has been
   virtually achieved. Therefore, our new torsional energy data should be
   used as reference for further studies. (C) 2003 Elsevier Science B.V.
   All rights reserved.
C1 Univ Fed Minas Gerais, LQC MM, Dept Quim, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, Univ Fed Minas Gerais, LQC MM, Dept Quim, ICEx,
   BR-31270901 Belo Horizonte, MG, Brazil.
CR AYALA PY, 1998, J CHEM PHYS, V108, P2315
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NR 36
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD FEB 7
PY 2003
VL 369
IS 1-2
BP 114
EP 124
PG 11
SC Physics, Atomic, Molecular & Chemical
GA 642GE
UT ISI:000180795200017
ER

PT J
AU Novaes, FD
   da Silva, AJR
   da Silva, EZ
   Fazzio, A
TI Effect of impurities in the large Au-Au distances in gold nanowires
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID LARGE SYSTEMS; ATOMS; MICROSCOPY; WIRE
AB Experimentally obtained atomically thin gold nanowires have presented
   exceedingly large Au-Au interatomic distances before they break. Since
   no theoretical calculations of pure gold nanowires have been able to
   produce such large distances, we have investigated, through ab initio
   calculations, how impurities could affect them. We have studied the
   effect of H, B, C, N, O, and S impurities on the nanowire electronic
   and structural properties, in particular how they affect the maximum
   Au-Au bond length. We find that the most likely candidates to explain
   the distances in the range of 3.6 Angstrom and 4.8 Angstromare H and S
   impurity atoms, respectively.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   UNICAMP, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
RP Novaes, FD, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR ARTACHO E, 1999, PHYS STATUS SOLIDI B, V215, P809
   BAHN SR, 2002, PHYS REV B, V66
   DASILVA EZ, UNPUB
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   HOHENBERG P, 1964, PHYS REV, V136, B864
   KOHN W, 1965, PHYS REV, V140, A1133
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   MEHREZ H, 2002, PHYS REV B, V65
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   SKORODUMOVA NV, CONDMAT0203162
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NR 24
TC 20
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD JAN 24
PY 2003
VL 90
IS 3
AR 036101
DI ARTN 036101
PG 4
SC Physics, Multidisciplinary
GA 638PJ
UT ISI:000180579200037
ER

PT J
AU Junqueira, GMA
   Rocha, WR
   De Almeida, WB
   Dos Santos, HF
TI Theoretical analysis of the oxocarbons: The solvent and counter-ion
   effects on the structure and spectroscopic properties of the squarate
   ion
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID DIFFERENTIAL-OVERLAP TECHNIQUE; MOLECULAR-ORBITAL METHODS; MONTE-CARLO;
   INTERMEDIATE NEGLECT; RAMAN-SPECTROSCOPY; CROCONATE DIANION; BASIS SET;
   TRANSITION; WATER; COMPLEXES
AB The squarate anion and their coordination compounds with Li+, Na+ and
   K+ are studied in gas phase and aqueous solution using ab initio
   quantum chemical methods and a sequential Monte Carlo/quantum
   mechanical procedure. The infrared and Raman spectra were calculated
   and the vibrational modes assigned at the second order Moller-Plesset
   perturbation (MP2) level of theory, employing standard split-valence
   basis set with inclusion of polarization and diffuse functions
   (6-31G(d), 6-31+G(d), 6-311+G(d), 6-311+G(2d), 6-311+G(2df)) on the O
   and C atoms. The vibrational analysis showed an important role played
   by the polarization functions on the low frequency vibrations. The
   solvent and counter-ions effects on the electronic spectrum are
   analyzed showing that both should be included in the calculation in
   order to reproduce the observed UV spectrum. This conclusion supports
   our previous analysis on the oxocarbon series.
C1 Univ Fed Juiz de Fora, NEQC, Dept Quim, ICE, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Pernambuco, Dept Quim Fundamental, CCEN, BR-50740901 Recife, PE, Brazil.
   Univ Fed Minas Gerais, LQC MM, Dept Quim, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
RP Dos Santos, HF, Univ Fed Juiz de Fora, NEQC, Dept Quim, ICE, Campus
   Martelos, BR-36036330 Juiz De Fora, MG, Brazil.
CR 1992, HDB CHEM PHYSICS
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   ZHAO B, 1992, CAN J CHEM, V70, P135
NR 55
TC 3
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
   ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI Phys. Chem. Chem. Phys.
PY 2003
VL 5
IS 3
BP 437
EP 445
PG 9
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 635YG
UT ISI:000180427300002
ER

PT J
AU El Akramine, O
   Lester, WA
   Krokidis, X
   Taft, CA
   Guimaraes, TC
   Pavao, AC
   Zhu, R
TI Quantum Monte Carlo study of the CO interaction with a dimer model
   surface for Cr(110)
SO MOLECULAR PHYSICS
LA English
DT Article
ID ELECTRON LOCALIZATION FUNCTION; METAL-SURFACES; EFFECTIVE POTENTIALS;
   WAVE-FUNCTIONS; CLUSTERS; ATOMS; DISSOCIATION; SIMULATIONS; MOLECULES;
   SOLIDS
AB The chemisorption of CO on a Cr( 110) surface is investigated using the
   quantum Monte Carlo method in the diffusion Monte Carlo (DMC) variant
   and a model Cr2CO cluster. The present results are consistent with the
   earlier ab initio HF study with this model that showed the tilted/
   near-parallel orientation as energetically favoured over the
   perpendicular arrangement. The DMC energy difference between the two
   orientations is larger (1.9 eV) than that computed in the previous
   study. The distribution and reorganization of electrons during CO
   adsorption on the model surface are analysed using the topological
   electron localization function method that yields electron populations,
   charge transfer and clear insight on the chemical bonding that occurs
   with CO adsorption and dissociation on the model surface.
C1 Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Dept Chem, Kenneth S Pitzer Ctr Theoret Chem, Berkeley, CA 94720 USA.
   Accelrys, Mat Sci, F-91898 Orsay, France.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540 Recife, PE, Brazil.
   Chinese Acad Sci, LNM, Inst Mech, Beijing 100864, Peoples R China.
RP Lester, WA, Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci,
   Berkeley, CA 94720 USA.
CR ANDERSON JB, 1999, REV COMP CH, V13, P133
   ASPURUGUZIK A, UNPUB
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   GROSSMAN JC, 2001, PHYS REV LETT, V86, P472
   GUIMARAES TC, 1997, PHYS REV B, V56, P7001
   HAMMOND BL, 1994, MONTE CARLO METHODS
   HARKLESS JA, 2001, J CHEM PHYS, V113, P2680
   KROKIDIS X, 1997, J PHYS CHEM A, V101, P7277
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   LESTER WS, 1997, RECENT ADV QUANTUM M
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   OVCHARENKO IV, 2001, J CHEM PHYS, V114, P9028
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   PAVAO AC, 1994, PHYS REV B, V50, P1868
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NR 50
TC 4
PU TAYLOR & FRANCIS LTD
PI ABINGDON
PA 4 PARK SQUARE, MILTON PARK, ABINGDON OX14 4RN, OXON, ENGLAND
SN 0026-8976
J9 MOL PHYS
JI Mol. Phys.
PY 2003
VL 101
IS 1-2
BP 277
EP 285
PG 9
SC Physics, Atomic, Molecular & Chemical
GA 633QC
UT ISI:000180293100030
ER

PT J
AU Freitas, MP
   Tormena, CF
   Rittner, R
   Abraham, RJ
TI Conformational analysis of trans-2-halocyclohexanols and their methyl
   ethers: a H-1 NMR, theoretical and solvation approach
SO JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
LA English
DT Article
DE trans-1,2-disubstituted cyclohexanes; conformational analysis; NMR;
   density functional theory
ID AB-INITIO; ISOMERISM; CYCLOHEXANES; OH
AB The conformational equilibria of trans-1-methoxy-2-chloro- (1),
   trans-1-methoxy-2-bromo- (2) and trans-1-methoxy-2-iodocyclohexane (3),
   and their corresponding alcohols (4-6), were studied through a combined
   method of NMR, theoretical calculations and solvation theory. They can
   be described in terms of the axial-axial and equatorial-equatorial
   conformations, taking into account the main rotamers of each of these
   conformations. From the NMR experiments at 183 K in (CDCl2)-Cl-2-CS2,
   it was possible to observe proton H-2 in the ax-ax and eq-eq conformers
   separately for 1 and 2, but not for 3, which gave directly their
   populations and conformer energies. In the alcohols the proportion of
   the ax-ax. conformer was too low to be detected by NMR under these
   conditions. Those HH couplings together with the values at room
   temperature, in a variety of solvents allowed the determination of the
   solvent dependence of the conformer energies and hence the vapor state
   energy difference. The DeltaE (E-ax-E-eq) values in the vapor state for
   1, 2 and 3 are -0.05, 0.20 and 0.55 kcal mol(-1), respectively,
   increasing to 1.10, 1.22 and 1.41 kcal mol(-1) in CD3CN solution (I
   kcal = 4.184 kJ). For 4-6 the eq-eq conformation is always much more
   stable in both non-polar and polar solvents, with energy differences
   ranging from 1.78, 1.94 and 1.86 kcal mol(-1) (in CCl4) to 1.27, 1.49
   and 1.54 kcal mol(-1) (in DMSO), respectively. Comparison of the
   hydroxy and methoxy compounds gives the intramolecular hydrogen bonding
   energy for the alcohols as 1.40, 1.36 and 1.00 kcal mol(-1) (in CCl4)
   for 4, 5 and 6, respectively. Copyright (C) 2002 John Wiley Sons, Ltd.
C1 UNICAMP, Phys Organ Chem Lab, Inst Quim, BR-13084971 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
RP Rittner, R, UNICAMP, Phys Organ Chem Lab, Inst Quim, Caixa Postal 6154,
   BR-13084971 Campinas, SP, Brazil.
CR ABRAHAM RJ, 1974, INTERNAL ROTATION MO, CH13
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   ABRAHAM RJ, 1999, J CHEM SOC PERK  AUG, P1663
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   BODOT H, 1967, B SOC CHIM FR, P870
   CARRENO MC, 1990, TETRAHEDRON, V46, P5649
   COLLIN P, 1995, MONOSACCHARIDES THEI
   CRAIG NC, 1997, J AM CHEM SOC, V119, P4789
   EPIOTIS ND, 1973, J AM CHEM SOC, V95, P3087
   FREITAS MP, 2001, J MOL STRUCT, V570, P175
   FREITAS MP, 2001, J PHYS ORG CHEM, V14, P317
   FRISCH MJ, 1998, GAUSSIAN 98
   GANGULY B, 2000, J ORG CHEM, V65, P558
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   SENDEROWITZ H, 1997, THEOCHEM-J MOL STRUC, V395, P123
   SOSNOVSKII GM, 1990, ZH ORG KHIM, V26, P911
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NR 33
TC 4
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND
SN 0894-3230
J9 J PHYS ORG CHEM
JI J. Phys. Org. Chem.
PD JAN
PY 2003
VL 16
IS 1
BP 27
EP 33
PG 7
SC Chemistry, Organic; Chemistry, Physical
GA 635PB
UT ISI:000180407000005
ER

PT J
AU Miwa, RH
   Srivastava, GP
TI Self-organized Bi lines on the Si(001) surface: A theoretical study
SO PHYSICAL REVIEW B
LA English
DT Article
ID SCANNING-TUNNELING-MICROSCOPY; ELECTRONIC-STRUCTURE; SI(100) SURFACE;
   BISMUTH; X-1); PSEUDOPOTENTIALS; NANOWIRE; GROWTH; CHAINS; STATE
AB We have performed an ab initio theoretical study of the stability,
   atomic geometry, and electronic structure of the self-organized Bi
   lines on the Si(001) surface. We have examined the two currently
   proposed models and two new hybrid models for the structure of Bi
   lines. Our results confirm the model proposed by Miki , in which the Bi
   lines are formed by Bi dimers parallel to the surrounding Si dimers,
   with a missing dimer row between the Bi dimers. However, in contrast to
   the proposal of symmetrically disposed surface Si dimers (i.e., with no
   buckling) by Miki , our total-energy calculations indicate that the
   buckling of the Si dimers is an exothermic process, reducing the
   surface total energy by 0.11 eV/dimer. Our theoretically simulated
   scanning tunneling microscopy results suggest a low density of states
   close to the valence-band maximum, localized on the Bi lines,
   supporting the recently proposed model of quantum antiwire systems for
   Bi lines on the Si(001) surface.
C1 Univ Fed Uberlandia, Fac Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
RP Miwa, RH, Univ Fed Uberlandia, Fac Fis, Caixa Postal 593, BR-38400902
   Uberlandia, MG, Brazil.
CR ABUKAWA T, 1995, SURF SCI, V325, P33
   BOWLER DR, 2000, PHYS REV B, V62, P7237
   BUNK O, 1999, PHYS REV B, V59, P12228
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CHO JH, 2001, PHYS REV B, V64
   DABROWSKI J, 1992, APPL SURF SCI, V56, P15
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   GONZE X, 1991, PHYS REV B, V44, P8503
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   MIWA RH, 2002, SURF SCI, V507, P368
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NR 27
TC 9
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD DEC 15
PY 2002
VL 66
IS 23
AR 235317
DI ARTN 235317
PG 6
SC Physics, Condensed Matter
GA 633JL
UT ISI:000180279400084
ER

PT J
AU Gomez, JA
   Guenzburger, D
TI Hyperfine fields and field gradients of thin films of
   face-centred-cubic Fe on Cu(001)
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; FCC IRON FILMS; GAMMA-FE; FE/CU(001)
   OVERLAYERS; COMPLEX RECONSTRUCTION; ELECTRONIC-STRUCTURE;
   MAGNETIC-PROPERTIES; FIRST-PRINCIPLES; ULTRATHIN FILMS; GROUND-STATE
AB The discrete variational method in density functional theory was
   employed to perform first-principles electronic structure calculations
   for embedded clusters representing thin films of face-centred-cubic Fe
   on a Cu(001) substrate. 3, 4 and 5 ML of Fe were investigated; the
   ferromagnetic and several types of antiferromagnetic spin
   configurations were considered. Layer-by-layer calculations of the
   contact and dipolar components of the magnetic hyperfine field are
   reported, as well as electric-field gradients at the surface and
   interface layers. Significant field gradients were found at the
   surfaces. Clusters modelling the interdiffusion of Fe and Cu between
   two layers at the interface were also investigated, to determine the
   effects on the properties.
C1 Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, RJ, Brazil.
RP Gomez, JA, Ctr Brasileiro Pesquisas Fis, Rua Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, RJ, Brazil.
CR ABRAGAM A, 1961, PRINCIPLES NUCL MAGN
   ALLENSPACH R, 1994, J MAGN MAGN MATER, V129, P160
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NR 58
TC 3
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD DEC 2
PY 2002
VL 14
IS 47
BP 12311
EP 12328
PG 18
SC Physics, Condensed Matter
GA 634DC
UT ISI:000180323900011
ER

PT J
AU Machado, AED
   de Miranda, JA
   Guilardi, S
   Nicodem, DE
   Severino, D
TI Photophysics and spectroscopic properties of
   3-benzoxazol-2-yl-chromen-2-one
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE photophysics; coumarin derivative; molecular structure; electronic
   structure; PM3; ZINDO/S; ab initio
ID DERIVATIVES; COUMARINS; COMPOUND; SOLVENT; STATE; AM1
AB The photophysics of 3-benzoxazol-2-yl-chromen-2-one was studied in
   different solvents. High molar absorptivities, between 14 800 and 22
   900 dm(3)/mol cm, were observed for the absorption peak related to the
   S-0 --> S-1 transition which suggests a pi --> pi*character. This
   compound presents a limited solvatochromism, attributed to the
   benzoxazole group, and high fluorescence quantum yields, Phi(f). The
   fluorescence quantum yield is lowered with the increase of solvent
   polarity, favouring the participation of internal conversion as
   deactivation path of the S, state. The Stokes shift shows that the
   excited state is stabilised with increasing solvent polarity. The
   dipole moment was estimated by ab initio calculations as being between
   5.28 and 5.62 Debye for S-1, and 4.75 Debye for S-0. Phosphorescence
   was not observed. A small but not negligible quantum yield of singlet
   oxygen generation ((Phi(Delta) = 0.15) was measured in chloroform. The
   geometric parameters obtained by semi-empirical calculation (PM3) are
   in good agreement with crystallographic data, showing a r.m.s.
   deviation of 0.153 Angstrom for the superposition of both structures.
   The predicted structure is all planar, while the crystallographic data
   reveal a dihedral angle of 6.5degrees, between the coumarin and
   benzoxazole rings. The theoretical description of the electronic
   spectra, obtained from a PM3 CI calculation, shows excellent agreement
   with the experimental data. Deviations lower than 2% are observed in
   the predicted absorption maxima, with best results when solvation is
   considered. For electronic states calculation, ZINDO/S gave a better
   prediction of excited state energies, with a deviation lower than 7%
   for the S, energy. The most probable sequence for the first four
   excited states is: T-1(npi*) < T-2(pipi*) < S-1(pipi*) < S-2(npi*). (C)
   2002 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Uberlandia, Inst Quim, Lab Fotoquim, GFQL, BR-38400089 Uberlandia, MG, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, Lab Espectroscopia Resolvida Tempo, BR-21949900 Rio De Janeiro, Brazil.
RP Machado, AED, Univ Fed Uberlandia, Inst Quim, Lab Fotoquim, GFQL, POB
   593, BR-38400089 Uberlandia, MG, Brazil.
CR 1999, HYPERCHEMISTRY 5 11
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   GAO F, 2000, DYES PIGMENTS, V47, P231
   GILBERT A, 1991, ESSENTIALS MOL PHOTO
   GUILARDI S, UNPUB
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   LAKOWICZ JR, 1999, PRINCIPLES FLUORESCE
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   LUAN XH, UNPUB ADV COLOUR SCI
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   MACHADO AEH, UNPUB
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   TURRO NJ, 1991, MODERN MOL PHOTOCHEM
   WHEELOCK CE, 1959, J AM CHEM SOC, V81, P1348
NR 27
TC 4
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JAN 1
PY 2003
VL 59
IS 2
BP 345
EP 355
PG 11
SC Spectroscopy
GA 626PY
UT ISI:000179882900017
ER

PT J
AU Bruns, RE
   Haiduke, RLA
   do Amaral, AT
TI The linear relationship between Koopmans' and hydrogen bond energies
   for some simple carbonyl molecules
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE hydrogen bonding; atomic charges; Koopmans' energy; QSAR
ID DIPOLE-MOMENT DERIVATIVES; FIELD ANALYSIS; AB-INITIO;
   CONFORMATIONAL-ANALYSIS; SEMIEMPIRICAL METHODS; INFRARED INTENSITIES;
   ATOMIC CHARGES; POLAR TENSORS; DESCRIPTORS; POTENTIALS
AB Recently Galabov and Bobadova-Parvanova have shown that the energy of
   hydrogen bond formation calculated at the HF/6-31G(d,p) level is highly
   correlated with the molecular electrostatic potential at the acceptor
   site for a number of simple carbonyl compounds. Here it is shown that
   the electrostatic potential can be replaced by Koopmans' energy. The
   correlation between this energy and the hydrogen bond formation energy
   is just as high as the one observed by Galabov and Bobadova-Parvanova.
   The Siegbahn simple potential relating Koopmans' energies and GAPT
   charges shows that the hydrogen bond energy is not simply correlated
   with the charge of the acceptor site because the charges on the
   neighboring atoms are also important in the hydrogen bonding process.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Bruns, RE, Univ Estadual Campinas, Inst Quim, CP 6154, BR-13083970
   Campinas, SP, Brazil.
CR BESLER BH, 1990, J COMPUT CHEM, V11, P431
   BIARGE JF, 1961, ANALES REAL SOC ES A, V57, P81
   BOBADOVAPARVANOVA P, 1998, J PHYS CHEM A, V102, P1815
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
   BUREAU R, 1996, QUANT STRUCT-ACT REL, V15, P373
   CIOSLOWSKI J, 1989, J AM CHEM SOC, V111, P8333
   DEOLIVEIRA AE, 2000, J PHYS CHEM A, V104, P5320
   FOLKERS G, 1993, 3D QSAR DRUG DESIGN, P583
   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
   GALABOV B, 1999, J PHYS CHEM A, V103, P6793
   GANCIA E, 2000, J COMPUT AID MOL DES, V14, P293
   GUADAGNINI PH, 1997, J AM CHEM SOC, V119, P4224
   HAIDUKE RLA, 2002, J PHYS CHEM A, V106, P1824
   KARELSON M, 1996, CHEM REV, V96, P1027
   KROEMER RT, 1996, J COMPUT CHEM, V17, P1296
   MULLIKEN RS, 1955, J CHEM PHYS, V23, P1833
   NAVAJAS C, 1996, QUANT STRUCT-ACT REL, V15, P189
   OVEREND J, 1963, INFRARED SPECTROSCOP, CH10
   PERSON WB, 1974, J CHEM PHYS, V61, P1040
   RECANATINI M, 1996, J COMPUT AID MOL DES, V10, P74
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   WALLER CL, 1993, J MED CHEM, V36, P2390
   WILSON EB, 1955, MOL VIBRATIONS
NR 23
TC 3
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PD NOV-DEC
PY 2002
VL 13
IS 6
BP 800
EP 805
PG 6
SC Chemistry, Multidisciplinary
GA 627DC
UT ISI:000179914600011
ER

PT J
AU de Andrade, J
   Boes, ES
   Stassen, H
TI Computational study of room temperature molten salts composed by
   1-alkyl-3-methylimidazolium cations-force-field proposal and validation
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID IONIC LIQUIDS; CHLOROALUMINATE MELTS; MOLECULAR-DYNAMICS; IMIDAZOLIUM
   SALTS; SIMULATIONS; CATALYSIS; SOLVENTS; SPECTROSCOPY; CHLORIDE; SEARCH
AB We present a complete force field for liquid-state simulations on ionic
   liquids containing 1-ethyl-3-methylimidazolium and
   1-n-butyl-3-methylimidazolium cations and the tetrachloroaluminate and
   tetrafluoroborate anions. The force field is compatible with the AMBER
   methodology and is easily extendable to other dialkylimidazolium salts.
   On the basis of the general AMBER procedures to develop lacking
   intramolecular parameters and the RESP approach to calculate the atomic
   point charges, we obtained an all-atom force field which was validated
   against the experimental density, diffusion coefficient, vibrational
   frequencies, as well as X-ray (crystal state) and neutron (liquid
   state) diffraction structural data. Moreover, molecular mechanics
   calculations for the developed force field produce the cation's
   structures and dipole moments in very good agreement with quantum
   mechanical ab initio calculations. In addition, a basic study
   concerning the simulated liquid structure in terms of the radial
   distribution functions has been undertaken using molecular dynamics
   simulation. In summary, we achieved a very consistent picture in the
   computed data for the four room-temperature molten salts.
C1 Univ Fed Rio Grande Sul, Inst Quim, Grp Quim Teor, BR-91540000 Porto Alegre, RS, Brazil.
RP Stassen, H, Univ Fed Rio Grande Sul, Inst Quim, Grp Quim Teor,
   BR-91540000 Porto Alegre, RS, Brazil.
CR AKDENIZ Z, 1999, Z NATURFORSCH A, V54, P180
   ALLEN MP, 1987, COMPUTER SIMULATIONS
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   BOLM C, 1999, ANGEW CHEM INT EDIT, V38, P907
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   CASE DA, 1999, AMBER, V6
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   DEANDRADE J, 2002, J PHYS CHEM B, V106, P3546
   DUDEK MJ, 1998, J COMPUT CHEM, V19, P548
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   ELAIWI A, 1995, J CHEM SOC DA, P3467
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   GORDON CM, 1998, J MATER CHEM, V8, P2627
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   HAGIWARA R, 2000, J FLUORINE CHEM, V105, P221
   HANKE CG, 2001, MOL PHYS, V99, P801
   HANKE CG, 2002, GREEN CHEM, V4, P107
   HARIHARAN PC, 1973, THEOR CHIM ACTA, V28, P213
   HUGHES DJ, 1955, US ATOMIC ENERGY COM
   JESSOP PG, 1999, CHEM REV, V99, P475
   KAUPP G, 1994, ANGEW CHEM INT EDIT, V33, P1452
   KAUPP G, 1994, ANGEW CHEM, V106, P1519
   LARIVE CK, 1995, J PHYS CHEM-US, V99, P12409
   LIDE DR, 1999, HDB CHEM PHYSICS
   LYUBARTSEV AP, 2000, COMPUT PHYS COMMUN, V128, P565
   MARTYNA GJ, 1996, MOL PHYS, V87, P1117
   MAYO SL, 1990, J PHYS CHEM-US, V94, P8897
   MENG Z, 2002, J MOL STRUC-THEOCHEM, V585, P119
   PAPPU RV, 1998, J PHYS CHEM B, V102, P9725
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
   SHAH JK, 2002, GREEN CHEM, V4, P112
   SUAREZ PAZ, 1998, J CHIM PHYS PCB, V95, P1626
   TAKAHASHI S, 1995, INORG CHEM, V34, P2990
   TAKAHASHI S, 1999, Z PHYS CHEM 2, V209, P209
   TOSI MP, 1993, ANNU REV PHYS CHEM, V44, P173
   TUCKERMAN M, 1992, J CHEM PHYS, V97, P1990
   WASSERSCHEID P, 2000, ANGEW CHEM INT EDIT, V39, P3772
   WELTON T, 1999, CHEM REV, V99, P2071
   WILKES JS, 1982, INORG CHEM, V21, P1263
NR 45
TC 32
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD DEC 26
PY 2002
VL 106
IS 51
BP 13344
EP 13351
PG 8
SC Chemistry, Physical
GA 628GQ
UT ISI:000179985100035
ER

PT J
AU Oliveira, HPM
   Camargo, AJ
   Macedo, LG
   Gehlen, MH
   da Silva, ABF
TI Synthesis, structure, electronic and vibrational spectra of
   9-(diethylamino)-benzo(a)phenoxazin-7-ium-5-N-methacrylamide
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE dye laser; Nile Blue; photophysical properties; DFT calculations
ID DENSITY-FUNCTIONAL THERMOCHEMISTRY; NILE-RED; ZIRCONIUM-PHOSPHATE;
   PROTON-TRANSFER; DYES; FLUORESCENCE; ANISOTROPY; EXCHANGE; DYNAMICS;
   BLUE
AB The electronic and vibrational spectra of
   9-(Diethylamino)-benzo(a)phenoxazin-7-ium-5-N-methacrylamide (Nile
   Blue-5-N-methacrylamide) are measured, and the results are compared
   with the theoretical values obtained by quantum chemical calculations.
   The geometry, electronic transitions, charge distribution, and the IR
   normal modes of this new dye and of its precursor Nile Blue have been
   computed by using Density Functional Theory (DFT) method with the
   functional B3LYP and the 6-31G(d) Gaussian basis set. The molecular
   properties of the two dyes, predicted and observed, are very similar in
   the electronic ground state. In the excited state, however, the longer
   lifetime and larger fluorescence quantum yield of the Nile
   Blue-5-methacrylamide is ascribed to an inhibition of the twisted
   intramolecular charge transfer (TICT) process, when the NH2 is
   substituted by the methacrylamide in the 5-position of the aromatic
   extended ring of the dye. The change in charge density of the N atom in
   5-position, as well as the difference in dipole moment and ionization
   potential of the two dyes molecules, explain the attenuation of TICT
   process. The vibration spectra of both dyes are simulated properly by
   using the DFT method. (C) 2002 Elsevier Science B.V. All rights
   reserved.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
RP Gehlen, MH, Univ Sao Paulo, Inst Quim Sao Carlos, CP 780, BR-13560970
   Sao Carlos, SP, Brazil.
CR BECKE AD, 1988, PHYS REV A, V38, P3098
   BECKE AD, 1992, J CHEM PHYS, V96, P2155
   BECKE AD, 1993, J CHEM PHYS, V98, P5648
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   DIAS LC, 1999, CHEM PHYS LETT, V302, P505
   DUNKERS J, 1995, SPECTROCHIM ACTA A, V51, P1061
   DUTT GB, 1991, J CHEM PHYS, V94, P5360
   DUTTA AK, 1996, J PHOTOCH PHOTOBIO A, V93, P57
   GHONEIM N, 2000, SPECTROCHIM ACTA A, V56, P1003
   GOLINI CM, 1998, J FLUORESC, V8, P395
   GROFCSIK A, 1996, CHEM PHYS LETT, V250, P261
   GROFCSIK A, 2000, J MOL STRUCT, V555, P15
   KICQ P, 1987, BIOELECTROCH BIOENER, V17, P277
   LEE C, 1988, PHYS REV B, V37, P785
   MALINAUSKAS A, 2000, J ELECTROANAL CHEM, V484, P55
   NAKASHIMA K, 1993, LANGMUIR, V9, P2825
   PESSOA CA, 1997, J ELECTROANAL CHEM, V431, P23
   SCOTT AP, 1996, J PHYS CHEM-US, V100, P16502
   SOMLOI J, 1992, SPECTROCHIM ACTA A, V48, P77
   SOUTAR I, 1996, J PHOTOCH PHOTOBIO A, V102, P87
   VISWANATHAN K, 1996, J PHOTOCH PHOTOBIO A, V95, P245
   WONG MW, 1996, CHEM PHYS LETT, V256, P391
NR 22
TC 4
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD DEC
PY 2002
VL 58
IS 14
BP 3103
EP 3111
PG 9
SC Spectroscopy
GA 620CD
UT ISI:000179514900007
ER

PT J
AU Menegon, G
   Shimizu, K
   Farah, JPS
   Dias, LG
   Chaimovich, H
TI Parameterization of the electronegativity equalization method based on
   the charge model 1
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID ATOMIC CHARGES; AB-INITIO; ELECTROSTATIC POTENTIALS; MOLECULES;
   HARDNESS; POLARIZABILITY; DEPENDENCE; CHEMISTRY
AB Fast calculation of charge distributions in molecules is feasible in
   the electronegativity equalization method, EEM. Atomic
   electronegativities and hardnesses, fundamental parameters in EEM, were
   obtained here by using CM1 atomic charges at semiempirical PM3 level as
   targets. A new optimization approach composed of Genetic and Simplex
   algorithms is also described. The correlation between EEM and CM1
   charges improved considerably (correlation coefficient improved from
   0.931 to 0.977, standard deviation from 0.079 to 0.032 and Fisher's F
   from 31 627 to 102 977, for 4093 data points) in comparison to previous
   EEM parameters ( L. G. Dias et al., Chem. Phys., 2002, 282, 237, ref.
   23). Atomic parameters obtained here are discussed and compared to
   other EEM schemes and to parameters derived from empirical approaches.
C1 Univ Sao Paulo, Inst Chem, Dept Biochem, Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Chem, Dept Chem, Sao Paulo, Brazil.
RP Menegon, G, Univ Sao Paulo, Inst Chem, Dept Biochem, Sao Paulo, Brazil.
CR BADER RFW, 1981, ADV QUANTUM CHEM, V14, P63
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   REED AE, 1985, J CHEM PHYS, V83, P735
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NR 33
TC 7
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
   ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI Phys. Chem. Chem. Phys.
PY 2002
VL 4
IS 24
BP 5933
EP 5936
PG 4
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 620XD
UT ISI:000179558000003
ER

PT J
AU Pereira, AS
   Perottoni, CA
   da Jornada, JAH
   Leger, JM
   Haines, J
TI Compressibility of AlB2-type transition metal diborides
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID TITANIUM DIBORIDE; STATE
AB The pressure behaviour of a series of transition metal borides has been
   studied both experimentally and by means of ab initio calculations.
   X-ray diffraction patterns measured up to similar to50 GPa for VB2 and
   ZrB2 show no obvious phase transition. Bulk moduli of 322 and 317 GPa,
   respectively, were obtained using a Murnaghan equation of state.
   Hartree-Fock LCCO (linear combination of crystal orbitals) calculations
   performed for TiB2 have allowed its compression behaviour to be
   studied. The bulk modulus obtained (292 GPa) and the proposed important
   contribution of the interlayer interaction to the elastic behaviour
   under high pressure are consistent with the experimental results for
   the other borides.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
   UFRGS, Escola Engn, BR-90035190 Porto Alegre, RS, Brazil.
   Univ Caxias Sul, Ctr Ciencias Exatas & Tecnol, BR-95070560 Caxias Do Sul, RS, Brazil.
   Inst Nacl Metrol Normalizacao & Qualidade Ind, Duque De Caxias, RJ, Brazil.
   Lab Proprietes Mecan & Thermodynam Mat, Villetaneuse, France.
   Univ Montpellier 2, Lab Phys Chim Mat Condensee, Montpellier, France.
RP Pereira, AS, Univ Fed Rio Grande Sul, Inst Fis, Caixa Postal 15051,
   BR-91501970 Porto Alegre, RS, Brazil.
CR CHEN XL, 2001, J PHYS-CONDENS MAT, V13, L723
   CUTLER RA, 1991, ENG PROPERTIES BORID
   MUNRO RG, 2000, J RES NATL INST STAN, V105, P709
   PEROTTONI CA, 2000, J PHYS-CONDENS MAT, V12, P7205
   PISANI C, 1988, SPRINGER LECT NOTES, V48
   VAJEESTON P, 2001, PHYS REV B, V63
NR 6
TC 5
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD NOV 11
PY 2002
VL 14
IS 44
BP 10615
EP 10618
PG 4
SC Physics, Condensed Matter
GA 620PL
UT ISI:000179541700043
ER

PT J
AU Rivelino, R
   Coutinho, K
   Canuto, S
TI A Monte Carlo-quantum mechanics study of the solvent-induced spectral
   shift and the specific role of hydrogen bonds in the conformational
   equilibrium of furfural in water
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID LIQUID WATER; AB-INITIO; ROTATIONAL BARRIERS; MOLECULAR-STRUCTURE;
   SPECTROSCOPY; SIMULATION; DYNAMICS; NMR; TRANSITION; ISOMERISM
AB The solvation shift of the lowest absorption transition of furfural in
   water is analyzed as a function of the rotation angle for the
   interconversion between the two conformations, OO-cis and OO-trans, of
   furfural. In total, 20 Monte Carlo NPT simulations are performed,
   corresponding to different rotation angles of the carbonyl group. The
   solvation shift of the n-pi* state is calculated to be 1230 +/- 45
   cm(-1) in the most stable OO-cis form. This calculated shift is found
   to be essentially independent of the rotation angle. The hydrogen bonds
   between furfural and water are also analyzed along the interconversion
   path. These hydrogen bonds are found to be equivalent, both in number
   and in binding energy, for all rotation angles. The results for the
   solvent-induced spectral shift and the hydrogen bond interactions
   confirm that in water they make no preference for any rotamer of
   furfural and lead to small contribution to the entropic activation
   barrier of furfural in protic solvents.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi Cruzes, CIIB, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 48
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD NOV 28
PY 2002
VL 106
IS 47
BP 12317
EP 12322
PG 6
SC Chemistry, Physical
GA 620QJ
UT ISI:000179543800035
ER

PT J
AU Teles, LK
   Scolfaro, LMR
   Leite, JR
   Furthmuller, J
   Bechstedt, F
TI Phase diagram, chemical bonds, and gap bowing of cubic InxAl1-xN
   alloys: Ab initio calculations
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID FIRST-PRINCIPLES CALCULATIONS; MOLECULAR-BEAM EPITAXY; FORCE-FIELD
   MODEL; STRUCTURAL-PROPERTIES; SEMICONDUCTOR ALLOYS; INXGA1-XN; ENERGY;
   REGION; INGAN; INN
AB Thermodynamic, structural, and electronic properties of cubic InxAl1-xN
   alloys are studied by combining first-principles total energy
   calculations and the generalized quasichemical approach. Results for
   bond-lengths, second-nearest-neighbors distances, and bond angles in
   the alloy are presented. The calculated phase diagram of the alloy
   shows a broad and asymmetric miscibility gap. The gap fluctuations in
   the alloy allow for the definition of a minimum gap and an average gap
   with different bowing parameters, that can provide an explanation for
   the discrepancies found in the experimental values for the bowing
   parameter. It is also found that lattice matched In0.2Al0.8N with GaN
   is suitable to form a barrier material for electronic and
   optoelectronic nitride based devices. (C) 2002 American Institute of
   Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Jena, Inst Festkorpertheorie & Theoret Opt, D-07743 Jena, Germany.
RP Teles, LK, Univ Sao Paulo, Inst Fis, CP66318, BR-05315970 Sao Paulo,
   Brazil.
CR ABERNATHY CR, 1995, J VAC SCI TECHNOL  1, V13, P716
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   NAKAMURA S, 1997, BLUE LASER DIODE GAN
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   PENG T, 1997, APPL PHYS LETT, V71, P243
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NR 35
TC 7
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD DEC 15
PY 2002
VL 92
IS 12
BP 7109
EP 7113
PG 5
SC Physics, Applied
GA 619UD
UT ISI:000179495100021
ER

PT J
AU Levin, Y
TI Electrostatic correlations: from plasma to biology
SO REPORTS ON PROGRESS IN PHYSICS
LA English
DT Review
ID ONE-COMPONENT PLASMA; DIPOLAR HARD-SPHERES; CHARGED COLLOIDAL
   PARTICLES; HYPERNETTED-CHAIN APPROXIMATION; 2-DIMENSIONAL COULOMB GAS;
   VAPOR-LIQUID CONDENSATION; DENSITY-FUNCTIONAL THEORY; DEBYE-HUCKEL
   THEORY; RESTRICTED PRIMITIVE MODEL; MONTE-CARLO SIMULATIONS
AB Electrostatic correlations play an important role in physics, chemistry
   and biology. In plasmas they result in thermodynamic instability
   similar to the liquid-gas phase transition of simple molecular fluids.
   For charged colloidal suspensions the electrostatic correlations are
   responsible for screening and colloidal charge renormalization. In
   aqueous solutions containing multivalent counterions they can lead to
   charge inversion and flocculation. In biological systems the
   correlations account for the organization of cytoskeleton and the
   compaction of genetic material. In spite of their ubiquity, the true
   importance of electrostatic correlations has come to be fully
   appreciated only quite recently. In this paper, we will review the
   thermodynamic consequences of electrostatic correlations in a variety
   of systems ranging from classical plasmas to molecular biology.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
RP Levin, Y, Univ Fed Rio Grande Sul, Inst Fis, Caixa Postal 15051,
   BR-91501970 Porto Alegre, RS, Brazil.
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NR 231
TC 117
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0034-4885
J9 REP PROGR PHYS
JI Rep. Prog. Phys.
PD NOV
PY 2002
VL 65
IS 11
BP 1577
EP 1632
PG 56
SC Physics, Multidisciplinary
GA 619JH
UT ISI:000179472500001
ER

PT J
AU Acioli, PH
   Jellinek, J
TI Electron binding energies of anionic magnesium clusters and the
   nonmetal-to-metal transition
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID MG CLUSTERS; DENSITY; APPROXIMATION; GAS; NA
AB The binding energies of the two most external electrons in Mg-n(-), n =
   2-22, clusters are computed using the gradient-corrected density
   functional theory and a new scheme for converting the Kohn-Sham
   eigenenergies into electron removal energies. The computations are
   performed for the anionic clusters considered in the most stable
   configurations of both Mg-n(-) and Mg-n. The results are compared with
   photoelectron spectroscopy data [O. C. Thomas et al., following Letter,
   Phys. Rev. Lett. 89, 213403 (2002)], and their implications for the
   finite-size analog of the nonmetal-to-metal transition are analyzed.
C1 Argonne Natl Lab, Div Chem, Argonne, IL 60439 USA.
   Univ Brasilia, Inst Fis, Nucleo Fis Atom Mol & Fluidos, BR-70919970 Brasilia, DF, Brazil.
RP Acioli, PH, Argonne Natl Lab, Div Chem, 9700 S Cass Ave, Argonne, IL
   60439 USA.
CR ACIOLI PH, IN PRESS
   AKOLA J, 2001, EUR PHYS J D, V16, P21
   BARAILLE I, 1998, J PHYS-CONDENS MAT, V10, P10969
   BECKE AD, 1988, PHYS REV A, V38, P3098
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   WADT WR, 1985, J CHEM PHYS, V82, P284
NR 21
TC 15
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD NOV 18
PY 2002
VL 89
IS 21
AR 213402
DI ARTN 213402
PG 4
SC Physics, Multidisciplinary
GA 612HH
UT ISI:000179068000015
ER

PT J
AU Frota-Pessoa, S
   Klautau, AB
   Legoas, SB
TI Influence of interface mixing on the magnetic properties of Ni/Pt
   multilayers
SO PHYSICAL REVIEW B
LA English
DT Article
ID REAL-SPACE; ANISOTROPY; FE; NI; IMPURITIES; MOMENTS
AB Motivated by existing experimental data, we study here the influence of
   interface mixing on the magnetic behavior of Ni-6/Pt-5(111)
   multilayers. In the present ab initio calculations the mixing,
   restricted to the interface layers, was simulated by ordered
   two-dimensional Ni-Pt lattices. Two different degrees of mixing of the
   components at the interface were considered-namely, 25% and 50%. The
   perfect interface was also calculated and for some of the systems
   orbital moments were obtained. We find that interface mixing explains
   rather well the observed magnetic moment profile for Ni sites. But even
   with the inclusion of orbital contributions, the theoretical results
   tend to underestimate the induced moment at the Pt sites found
   experimentally.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Fed Univ Para, Dept Fis, BR-66059 Belem, Para, Brazil.
   Univ Estadual Campinas, Inst Fis, Campinas, SP, Brazil.
RP Frota-Pessoa, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR ANDERSEN OK, 1975, PHYS REV B, V12, P3060
   ANDERSEN OK, 1985, HIGHLIGHTS CONDENSED
   BEER N, 1984, ELECT STRUCTURE COMP
   ERIKSSON O, 1990, PHYS REV B, V42, P2707
   FROTAPESSOA S, UNPUB
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   HAYDOCK R, 1980, SOLID STATE PHYS, V35, P215
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NR 23
TC 5
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD OCT 1
PY 2002
VL 66
IS 13
AR 132416
DI ARTN 132416
PG 4
SC Physics, Condensed Matter
GA 612HG
UT ISI:000179067900030
ER

PT J
AU Orellana, W
   Ferraz, AC
TI Stability and electronic structure of hydrogen-nitrogen complexes in
   GaAs
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID GALLIUM-ARSENIDE; AB-INITIO; PSEUDOPOTENTIALS; DEFECTS
AB We investigate the stability and electronic properties of defects
   formed by a substitutional nitrogen in GaAs (N-As) plus interstitial
   hydrogen atoms using first-principles total-energy calculations. We
   find the formation of strong N-As-H bond when a single H atom is
   incorporated in the lowest-energy bond centered (BC) position. This
   defect induces an electrically active level in the GaAs band gap. When
   two H atoms are incorporated, we find the stable N-As-H-2* complex as
   the lowest-energy configuration, with one H atom at the BC position and
   the second H atom at an antibonding position. The electronic structure
   of this complex shows the passivation of the gap level restoring the
   GaAs band gap. (C) 2002 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Orellana, W, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BALDASSARRI G, 2001, APPL PHYS LETT, V78, P3472
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BONAPASTA AA, 1995, PHYS REV B, V51, P4172
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   ESTREICHER SK, 1995, MAT SCI ENG R, V14, P319
   FRANCOEUR S, 1998, APPL PHYS LETT, V72, P1857
   HOHENBERG P, 1964, PHYS REV B, V136, P864
   JANOTTI A, 2002, PHYS REV LETT, V88
   KOHN W, 1965, PHYS REV, V140, A1133
   KOHN W, 1985, PHYS REV A, V140, P2471
   LOUIE SG, 1982, PHYS REV B, V26, P1738
   MONKHORST HJ, 1976, PHYS REV B, V13, P5188
   ORELLANA W, 1997, THESIS U SAO PAULO
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   PAVESI L, 1992, PHYS REV B, V46, P4621
   POLIMENI A, 2001, PHYSICA B, V308, P850
   TROULLIER N, 1991, PHYS REV B, V43, P1993
   ZHANG Y, 2000, PHYS REV B, V61, P7579
   ZHANG Y, 2001, PHYS REV B, V63
NR 19
TC 5
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD NOV 11
PY 2002
VL 81
IS 20
BP 3816
EP 3818
PG 3
SC Physics, Applied
GA 611XB
UT ISI:000179042200038
ER

PT J
AU Braga, SF
   Galvao, DS
TI A semiempirical study on the electronic structure of
   10-deacetylbaccatin-III
SO JOURNAL OF MOLECULAR GRAPHICS & MODELLING
LA English
DT Article
DE paclitaxel; taxoids; baccatin; semiempirical methods; molecular orbital
   calculations
ID POLYCYCLIC AROMATIC-HYDROCARBONS; IDENTIFY CARCINOGENIC ACTIVITY;
   SIDE-CHAIN; ANTIMITOTIC ACTIVITY; PACLITAXEL TAXOL(R);
   MOLECULAR-STRUCTURE; CRYSTAL-STRUCTURE; PACIFIC YEW; AB-INITIO; ANALOGS
AB We performed a conformational and electronic analysis for
   10-deacetylbaccatin-III (DBAC) using well-known semiempirical methods
   (parametric method 3 (PM3) and Zerner's intermediate neglect of
   differential overlap (ZINDO)) coupled to the concepts of total and
   local density of states (LDOS). Our results indicate that regions
   presented by paclitaxel (Taxol(R)) as important for the biological
   activity can be traced out by the electronic features present in DBAC.
   These molecules differ only by a phenylisoserine side chain. Compared
   to paclitaxel, DBAC has a simpler structure in terms of molecular size
   and number of degrees of freedom (d.f.). This makes DBAC a good
   candidate for a preliminary investigation of the taxoid family. Our
   results question the importance of the oxetane group, which seems to be
   consistent with recent experimental data. (C) 2002 Elsevier Science
   Inc. All rights reserved.
C1 Univ Estadual Campinas, UNICAMP, Inst Fis Gleb Wataghin, BR-13091970 Campinas, SP, Brazil.
RP Galvao, DS, Univ Estadual Campinas, UNICAMP, Inst Fis Gleb Wataghin, CP
   6165, BR-13091970 Campinas, SP, Brazil.
CR *EIU, 1990, EIU MARK EUR TRAD RE
   *MOPAC, MOPAC PROGR VERS 6 0
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   BARONE PMVB, 2000, J MOL STRUC-THEOCHEM, V505, P55
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   BRAGA RS, 2000, J CHEM INF COMP SCI, V40, P1377
   BRAGA SF, IN PRESS STRUCTURE A
   CAMPBELL SJ, 1995, ACS SYM SER, V583, P58
   CHEESEMAN JR, 1996, J CHEM PHYS, V104, P5497
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   EDWARDS WD, 1987, THEOR CHIM ACTA, V72, P347
   FARINA V, 1995, CHEM PHARM TAXOL
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   GAO Q, 1996, TETRAHEDRON LETT, V37, P3425
   GAO Q, 1996, TETRAHEDRON, V52, P2291
   GEORG GI, 1995, ACS SYM SER, V583, P217
   GORB L, 1998, THEOCHEM-J MOL STRUC, V425, P137
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   HOLTON RA, 1994, J AM CHEM SOC, V116, P1599
   JAYASINGHE LR, 1994, J MED CHEM, V37, P2981
   JEFFORD CW, 1995, THEOCHEM-J MOL STRUC, V337, P31
   JENKINS P, 1996, CHEM BRIT, V11, P43
   KISLOV VV, 1999, INTERNET J CHEM, V2, P1
   KOLL A, 2000, J MOL STRUCT, V552, P193
   LEVINE IN, 1991, QUANTUM CHEM
   LI YK, 2000, BIOCHEMISTRY-US, V39, P281
   LODISH H, 1995, MOL CELL BIOL
   LOZYNSKI M, 1995, TETRAHEDRON LETT, V36, P8849
   LYTHGOE B, 1968, ALKALOIDS, V10, P597
   MASTROPAOLO D, 1995, P NATL ACAD SCI USA, V92, P6920
   MCKINNEL RG, 1998, BIOL BASIS CANC
   MILANESIO M, 1999, J MED CHEM, V42, P291
   NICOLAOU KC, 1994, NATURE, V367, P630
   PALAFOX MA, 1999, J MOL STRUC-THEOCHEM, V459, P239
   RIDLEY JE, 1976, THEOR CHIM ACTA, V42, P223
   RUDDON RW, 1987, CANC BIOL
   SANTO LLD, 1999, J MOL STRUC-THEOCHEM, V464, P273
   SCANO P, 1991, J COMPUT CHEM, V12, P172
   SNYDER JP, 2000, J AM CHEM SOC, V122, P724
   SOOS ZG, 1994, J PHYS CHEM-US, V98, P1029
   STEWART JJP, 1989, J COMPUT CHEM, V10, P209
   STEWART JJP, 1989, J COMPUT CHEM, V10, P221
   STIERLE A, 1995, ACS SYM SER, V583, P81
   SUFFNESS M, 1995, ACS SYM SER, V583, P1
   SUGIMURA T, 1992, SCIENCE, V258, P603
   SWINDELL CS, 1991, J MED CHEM, V34, P1176
   VENDRAME R, IN PRESS J CHEM INF
   VENDRAME R, 1999, J CHEM INF COMP SCI, V39, P1094
   WANG MM, 2000, J ORG CHEM, V65, P1059
   WESSJOHANN L, 1994, ANGEW CHEM INT EDIT, V33, P959
   WILLIAMS HJ, 1996, J MED CHEM, V39, P1555
   ZERNER MC, 1991, REV COMPUTATIONAL CH, V2, P313
NR 66
TC 3
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 360 PARK AVE SOUTH, NEW YORK, NY 10010-1710 USA
SN 1093-3263
J9 J MOL GRAPH MODEL
JI J. Mol. Graph.
PD AUG
PY 2002
VL 21
IS 1
BP 57
EP 70
PG 14
SC Computer Science, Interdisciplinary Applications; Biochemical Research
   Methods; Biochemistry & Molecular Biology; Crystallography
GA 611LX
UT ISI:000179019900008
ER

PT J
AU Dalpian, GM
   Venezuela, P
   da Silva, AJR
   Fazzio, A
TI Ab initio calculations of vacancies in SixGe1-x
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID SILICON; ALLOYS
AB Ab initio calculations are used to investigate the structural and
   electronic properties of vacancies in SixGe1-x. The (+ +), (+), (0),
   and (-) charge states are studied and the substitutional disorder of
   the alloy is considered explicitly. We found a linear relationship
   between the effective-U for the system formed by the ( + +), ( +), and
   (0) charge states and the number of Si atoms in the first neighborhood
   of a vacancy (N-Si). The effective-U is positive when N-Si is zero, and
   it is negative when N-Si is 2 and 4. In all cases, the absolute value
   of the effective-U in the alloy is significantly smaller than its value
   for pure Si and pure Ge. (C) 2002 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Dalpian, GM, Univ Fed Fluminense, Inst Fis, BR-24210340 Niteroi, RJ,
   Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BARAFF GA, 1980, PHYS REV B, V21, P5662
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BOGUSLAWSKI P, 1999, PHYS REV B, V59, P1567
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
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NR 16
TC 5
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD OCT 28
PY 2002
VL 81
IS 18
BP 3383
EP 3385
PG 3
SC Physics, Applied
GA 609BB
UT ISI:000178881800025
ER

PT J
AU Giroldo, T
   Riveros, JM
TI Keto-enol isomerization of gas-phase 2 '-methylacetophenone molecular
   ions probed by high-temperature near-blackbody-induced dissociation,
   ion-molecule reactions, and ab initio calculations
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID INFRARED RADIATIVE DISSOCIATION; HYDRATED ALUMINUM CATIONS; TANDEM
   MASS-SPECTROMETRY; CNH2NO RADICAL CATIONS; UNIMOLECULAR DISSOCIATION;
   MULTIPHOTON DISSOCIATION; ACTIVATION-ENERGIES; LASER PHOTODISSOCIATION;
   THERMAL-DISSOCIATION; CARBONYL-COMPOUNDS
AB The thermal dissociation of several substituted acetophenone molecular
   ions induced by infrared radiation from a hot wire has been studied in
   a Fourier transform ion cyclotron resonance spectrometer. The
   temperature dependence of the dissociation rate constants reveals that
   the 2'-methylacetophenone molecular ion is characterized by a much
   higher activation energy for dissociation than other acetophenones.
   This molecular ion also exhibits a very different behavior with respect
   to charge-transfer reactions. Unlike molecular ions obtained from other
   isomeric acetophenones, the 2'-methylacetophenone M+. ion does not
   promote charge exchange with dimethyl disulfide but does undergo
   relatively slow electron transfer with ferrocene (IE = 6.74 eV). Ab
   initio calculations at the MP2/6-31G(d) level predict that the
   2-MeC6H4COCH3+. ion (1) can undergo facile tautomerization to the much
   more stable enol ion 2,2'-(CH2C6H4C+)-C-.(OH)CH3, by a 1,4-hydrogen
   migration (calculated energy barrier of 20 kJ mol(-1)). The calculated
   recombination energy of this ion is in good agreement with the
   observations from the charge-exchange experiments. A full analysis of
   the potential energy surface suggests that, at low ionizing energies
   (less than or equal to 11.5 eV), essentially all of the long-lived
   molecular ions have isomerized to 2. The present example reveals the
   versatility and some of the advantages of the high-temperature
   near-blackbody-induced dissociation (hot wire emission) for probing
   structural problems in ion chemistry.
C1 Univ Sao Paulo, Inst Quim, BR-05515970 Sao Paulo, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05515970
   Sao Paulo, Brazil.
CR AASERUD DJ, 1997, INT J MASS SPECTROM, V167, P705
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NR 77
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD OCT 24
PY 2002
VL 106
IS 42
BP 9930
EP 9938
PG 9
SC Chemistry, Physical
GA 607LA
UT ISI:000178792000038
ER

PT J
AU Basso, EA
   Pontes, RM
TI Further studies on the rotational barriers of Carbamates. An NMR and
   DFT analysis of the solvent effect for Cyclohexyl N,N-dimethylcarbamate
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE carbamates; rotational barriers; DFT calculations; SCRF theory
ID C-N BOND; INTERNAL-ROTATION; AB-INITIO; HARTREE-FOCK; AMIDES;
   N,N-DIMETHYLFORMAMIDE; RESONANCE; THIOFORMAMIDE; SUBSTITUENT; FORMAMIDE
AB The solvent effect on the Gibbs energy of activation for rotation
   around the (C=O)-N bond in cyclohexyl N,N-dimethylcarbamate was
   investigated by dynamic NMR spectroscopy and density-functional theory
   at the B3LYP/6-311 + G** level. The experimental barriers were about 15
   kcal mol(-1) with no appreciable variation when the solvent polarity
   was changed. A reaction field model was applied to theoretically
   mediate the solvent effect and the results were comparable to the
   experimental data. An analysis, based on the Onsager solvation theory,
   showed that the solvent effect on rotational barriers can be understood
   employing the total molecular dipole moment, the difference between the
   dipole moments of the ground and the transition state structures, or
   both, as appropriate. (C) 2002 Elsevier Science B.V. All rights
   reserved.
C1 Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana, Brazil.
RP Basso, EA, Univ Estadual Maringa, Dept Quim, Av Colombo 5790,
   BR-87020900 Maringa, Parana, Brazil.
CR ALLERHAND A, 1966, J AM CHEM SOC, V88, P3185
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NR 29
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD OCT 18
PY 2002
VL 594
IS 3
BP 199
EP 206
PG 8
SC Chemistry, Physical
GA 602MM
UT ISI:000178509100009
ER

PT J
AU Tutuncu, HM
   Miotto, R
   Srivastava, GP
   Tse, JS
TI Phonons on group-III nitride (110) surfaces
SO PHYSICAL REVIEW B
LA English
DT Article
ID BOND-CHARGE MODEL; DENSITY-FUNCTIONAL CALCULATIONS; AB-INITIO;
   LATTICE-DYNAMICS; FIRST-PRINCIPLES; GALLIUM NITRIDE; SEMICONDUCTOR
   SURFACES; ELECTRONIC-PROPERTIES; SI(001)(2X1) SURFACE; EPITAXIAL LAYERS
AB We have applied the adiabatic bond-charge model within a supercell
   approach to study the lattice dynamics of group-III nitride (110)
   surfaces. The structural and electronic information necessary for these
   calculations is obtained from using the ab initio pseudopotential
   method. The phonon dispersion curves for the group-III nitride (110)
   surfaces are presented and compared with each other in detail. From
   this comparison, it is found that the InN(110) and GaN(110) surfaces
   show similar dynamical behavior due to their large cation-anion mass
   differences. It is pointed out that in general surface phonon modes on
   group-III nitride (110) can be related to their counterparts on
   non-nitride III-V(110) and II-VI(110) surfaces provided that results
   are scaled with respect to the reduced mass and lattice constant
   differences. The rotational phonon mode predicted for other
   semiconductor surfaces is also identified for the group-III nitride
   (110) surfaces.
C1 Sakarya Univ, Fen Edebiyat Fak, Fiz Bolumu, Adapazari, Turkey.
   Natl Res Council Canada, Steacie Inst Mol Sci, Ottawa, ON K1A 0R6, Canada.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
RP Tutuncu, HM, Sakarya Univ, Fen Edebiyat Fak, Fiz Bolumu, Adapazari,
   Turkey.
CR AGRAWAL BK, 1998, SURF SCI, V405, P54
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NR 47
TC 5
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD SEP 15
PY 2002
VL 66
IS 11
AR 115304
DI ARTN 115304
PG 11
SC Physics, Condensed Matter
GA 601RG
UT ISI:000178461000050
ER

PT J
AU Menegon, G
   Loos, M
   Chaimovich, H
TI Ab initio study of the thiolysis of trimethyl phosphate ester in the
   gas phase
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID PROTEIN-TYROSINE-PHOSPHATASE; VIBRATIONAL FREQUENCIES;
   AQUEOUS-SOLUTION; HYDROLYSIS; REACTIVITY; MECHANISMS; CATALYSIS;
   SPECTROSCOPY; INSIGHTS; ATTACK
AB Phosphate esters are key compounds in important biological reactions,
   One family of enzymes, PTPases, catalyze the dephosphorylation of
   tyrosine residues from other proteins by a cystein side-chain
   nucleophilic attack at tyrosin phosphate. Very little is known about
   the intrinsic reactivity of thiol nucleophiles with phosphor-us
   centers. To explore this important reaction, we have performed ab
   initio calculations on the trimethyl phosphate ester (TMP) thiolysis by
   (CH3S)(-). Results in the gas phase indicate that attack at TMP carbon
   is essentially predominant over phosphorus. Mechanisms are A(n)D(n) and
   exoergic for reaction at carbon and A(n) + D-n with large activation
   barriers and endoergic reaction for attack on phosphorus. A
   trigonal-bipyramid intermediate was formed upon (CH3S)(-) reaction at
   phosphorus and two different and competitive pathways were found for
   the elimination of methoxide from this intermediate. One of the
   elimination pathways is positioned in-line to the thiol group, as
   proposed in the enzymatic mechanism. If PTPases work by the same
   mechanism as the gas-phase reaction, these enzymes should drastically
   lower the activation barriers for attack at phosphorus.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Menegon, G, Univ Sao Paulo, Inst Quim, Av Lineu Prestes 748,
   BR-05508900 Sao Paulo, Brazil.
CR ADMIRAAL SJ, 2000, J AM CHEM SOC, V122, P2145
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   CLELAND WW, 1995, FASEB J, V9, P1585
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   FLORIAN J, 1998, J AM CHEM SOC, V120, P11524
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NR 39
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD OCT 3
PY 2002
VL 106
IS 39
BP 9078
EP 9084
PG 7
SC Chemistry, Physical
GA 598JU
UT ISI:000178273400014
ER

PT J
AU Martins, JBL
   Perez, MA
   Silva, CHT
   Taft, CA
   Arissawa, M
   Longo, E
   Mello, PC
   Stamato, FMLG
   Tostes, JGR
TI Theoretical ab initio study of ranitidine
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE ab initio; ranitidine; conformation
ID HELICOBACTER-PYLORI INFECTION; CITRATE PLUS CLARITHROMYCIN;
   DUODENAL-ULCER; ACTIVATION MECHANISM; BISMUTH CITRATE; RECEPTOR MODEL;
   H-2-RECEPTOR ANTAGONISTS; HISTAMINE H-2-RECEPTOR; MOLECULAR MECHANISM;
   GASTRIC PH
AB The presence of a heterocyclic ring containing a basic center linked
   via a methylene chain to a substituted guanidine or thiourea polar side
   chain, such as found in the H2-antagonist metiamide, which has an
   imidazole heterocyclic ring, has often been identified as one of the
   requirements for H-2-antagonist activity. In ranitidine, on the other
   hand, the imidazole ring is substituted for a furan ring, yielding a
   more active biological H2 antagonist. hi this work, we have used the ab
   initio Hartree-Fock (HF) and second-order Moller-Plesset (MP2) methods
   in order to investigate the open and folded ranitidine conformations,
   of the type observed in metiamide. Five basis sets (3-21G, 3-21+G**,
   6-31G, 6-31+G**, and 6-31+G**) were used in order to obtain fully
   optimized geometric parameters that indicated good agreement with the
   experimental crystallographic data, We have also investigated in this
   work the effects of solvents in both ranitidine and metiamide.
   Monocationic ranitidine was also investigated. All our results,
   indicate that, as in metiamide, the folded conformation is also
   preferred. We have investigated Mulliken and natural bond order (NBO)
   charge distributions, electrostatic and hydrogen bond effects on
   stabilizing the conformations and discussed the interactions of
   ranitidine with the biological receptor. (C) 2002 Wiley Periodicals,
   Inc.
C1 Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estat, BR-22290180 Rio De Janeiro, Brazil.
   Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
   Univ Estadual Ponta Grossa, Dept Quim, BR-84031510 Ponta Grossa, Parana, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Estadual Norte Fluminense, Lab Ciencias Quim, Ctr Ciencias Exatas & Tecnol, BR-18015620 Campos, RJ, Brazil.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis
   Estat, R Xavier Sigaud 150, BR-22290180 Rio De Janeiro, Brazil.
CR BARDHAN KD, 1998, AM J GASTROENTEROL, V93, P380
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NR 70
TC 6
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD OCT 15
PY 2002
VL 90
IS 2
BP 575
EP 586
PG 12
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 595UE
UT ISI:000178126500011
ER

PT J
AU Rivelino, R
   Ludwig, V
   Rissi, E
   Canuto, S
TI Theoretical studies of hydrogen bonding in water-cyanides and in the
   base pair Gu-Cy
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE ab initio; hydrogen bond; water-cyanides; base pair
ID DENSITY-FUNCTIONAL-THEORY; PI-ASTERISK TRANSITION; AB-INITIO;
   MOLECULAR-INTERACTIONS; SOLVATOCHROMIC SHIFTS; ELECTRON CORRELATION;
   CORRELATION-ENERGY; QUANTUM-CHEMISTRY; BONDED COMPLEXES; ACETONE
AB Density-functional (DFF) and many-body-perturbation theories (MIBPT/CC)
   are used to study the hydrogen bonding in the water-cyanide complexes
   H-C=N...H2O, H3C-C=N...H2O and (CH3)(3)C-C=N...H2O. Structures, binding
   energies and changes in vibrational frequencies are analyzed. The
   calculated C=N stretching frequency is found to shift to the blue upon
   complexation in H-C=N...H2O and H3C-C=N...H2O. To investigate electron
   correlation effects on the binding energies of these complexes,
   single-point calculations are performed at the MBPT/CC (MP2, MP3, MP4,
   CCSD and CCSD(T)) levels using the optimized MP2 geometries. Binding
   energies are also obtained at different levels of DFT (B3LYP and PW91)
   and compared with the MBPT/CC results. All calculations include
   corrections for basis set superposition error (BSSE) and zero-point
   vibrational energies. Additionally, the triple hydrogen-bonded.
   guanine-cytosine (Gu-Cy) base pair is analyzed. The binding energy of
   the Watson-Crick model for Gu-Cy is calculated using the Hartree-Fock
   calculations and DFT (B3LYP and BP86) methods. The results for the
   hydrogen bonding distances and binding energies are in good agreement
   with experimental and recent theoretical values. The calculated dipole
   moment of the Gu-Cy complex is compared with the direct vector sum of
   the isolated bases. After taking into account the BSSE effects we find
   that the electron polarization due to the hydrogen binding leads to an
   increase of similar to20% of the calculated dipole moment of the
   complex. (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, POB 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 62
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD SEP 26
PY 2002
VL 615
IS 1-3
BP 257
EP 266
PG 10
SC Chemistry, Physical
GA 594XC
UT ISI:000178076800028
ER

PT J
AU Ramos, LE
   Furthmuller, J
   Scolfaro, LMR
   Leite, JR
   Bechstedt, F
TI Substitutional carbon in group-III nitrides: Ab initio description of
   shallow and deep levels
SO PHYSICAL REVIEW B
LA English
DT Article
ID CUBIC BORON-NITRIDE; PERIODIC BOUNDARY-CONDITIONS; TOTAL-ENERGY
   CALCULATIONS; MOLECULAR-BEAM EPITAXY; WAVE BASIS-SET; THIN-FILMS; GAN;
   RELAXATION; GROWTH; ALN
AB We present ab initio pseudopotential plane-wave calculations for the
   neutral and negatively charged carbon impurity on a nitrogen site in
   group-III nitrides. Ultrasoft non-norm-conserving Vanderbilt
   pseudopotentials allow the use of extremely large supercells up to 2744
   atoms. These supercells attenuate the defect-defect interaction and,
   hence, give an accurate description of the resulting acceptor levels in
   BN, AlN, GaN, and InN. We calculate atomic geometries and energetical
   positions of the defect levels, Franck-Condon shifts, and formation
   energies. The defect stability and the transition of the shallow-deep
   character are discussed along the series BN, AlN, GaN, and InN. For GaN
   we calculate a hole activation energy of about 0.2 eV in correspondence
   with photoluminescence and temperature-dependent Hall measurements.
C1 Univ Jena, Inst Festkorpertheorie & Theoret Opt, D-07743 Jena, Germany.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Ramos, LE, Univ Jena, Inst Festkorpertheorie & Theoret Opt, D-07743
   Jena, Germany.
CR ABERNATHY CR, 1995, APPL PHYS LETT, V66, P1969
   AMBACHER O, 1998, J PHYS D APPL PHYS, V31, P2653
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   AS DJ, 1999, MRS INT J NITRIDE SE
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NR 57
TC 8
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD AUG 15
PY 2002
VL 66
IS 7
AR 075209
DI ARTN 075209
PG 9
SC Physics, Condensed Matter
GA 593AV
UT ISI:000177969800082
ER

PT J
AU Yoshinaga, F
   Tormena, CF
   Freitas, MP
   Rittner, R
   Abraham, RJ
TI Conformational analysis of 2-halocyclohexanones: an NMR, theoretical
   and solvation study
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID STEREOCHEMICAL CONSEQUENCES; ORGANIC-MOLECULES; ISOMERISM; PAIRS
AB The conformational equilibria of 2-fluoro-, 2-chloro- and
   2-iodo-cyclohexanone have been determined in various solvents by
   measurement of the J(2-3) couplings. The observed couplings were
   analysed using theoretical and solvation calculations to give both the
   conformer energies in the solvents studied plus the vapour phase
   energies and the coupling constants in the distinct conformers. These
   plus previous results for the 2-bromo compound give the conformer
   energies and couplings of all the 2-halocyclohexanones. In the 2-fluoro
   compound the axial conformation is the most stable one in the vapour
   phase (E-eq - E-ax = 0.45 kcal mol(-1)), while the equatorial conformer
   predominates in all the solvents studied. The other haloketones show
   similar behaviour, but the energy difference in the vapour phase is
   larger (E-eq - E-ax = 1.05, 1.50 and 1.90 kcal mol(-1), for the chloro,
   bromo and iodo compounds respectively) and the axial conformer is still
   the prevailing conformer in CCl4 solution for the chloro and bromo
   ketones and is the major form in all solvents for the iodo compound.
   The vapour state conformer energies for the fluoro and chloro compounds
   are in complete agreement with the ab initio calculated energies, but
   those for the bromo and iodo are not in such good agreement. Both the
   ab initio calculations and molecular mechanics are used to discuss the
   origins of the conformer energies. It is shown that the interaction
   between the C2 halogen and the C=O oxygen in the equatorial conformer
   is strongly attractive for fluorine, much less so for chlorine, ca.
   zero for bromine and repulsive for iodine. Comparison of the conformer
   couplings obtained here with calculated values show generally good
   agreement.
C1 Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
   Inst Quim, Phys Organ Chem Lab, BR-13083970 Campinas, SP, Brazil.
RP Abraham, RJ, Univ Liverpool, Dept Chem, POB 147, Liverpool L69 3BX,
   Merseyside, England.
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   TORMENA CF, 2000, J CHEM SOC PERK T 2, P2054
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NR 28
TC 7
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
   ENGLAND
SN 1472-779X
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2002
IS 9
BP 1494
EP 1498
PG 5
SC Chemistry, Organic; Chemistry, Physical
GA 587ZQ
UT ISI:000177675300002
ER

PT J
AU Rocha, WR
   Martins, VM
   Coutinho, K
   Canuto, S
TI Solvent effects on the electronic absorption spectrum of formamide
   studied by a sequential Monte Carlo/quantum mechanical approach
SO THEORETICAL CHEMISTRY ACCOUNTS
LA English
DT Article
DE formamide; QM/MM; solvent effects; absorption spectrum; Monte Carlo
   simulation
ID CIRCULAR-DICHROISM CALCULATIONS; CARLO-QUANTUM-MECHANICS;
   N-METHYLACETAMIDE; AB-INITIO; EXCITED-STATES; HYDROGEN-BOND; LIQUID
   WATER; POTENTIAL FUNCTIONS; AMIDE CHROMOPHORE; AQUEOUS-SOLUTION
AB Sequential Monte Carlo/quantum mechanical calculations are performed to
   study the solvent effects on the electronic absorption spectrum of
   formamide (FMA) in aqueous solution, varying from hydrogen bonds to the
   outer solvation shells. Full quantum-mechanical intermediate neglect of
   differential overlap/singly excited configuration interaction
   calculations are performed in the supermolecular structures generated
   by the Monte Carlo simulation. The largest calculation involves the
   ensemble average of 75 statistically uncorrelated quantum mechanical
   results obtained with the FMA solute surrounded by 150 water solvent
   molecules. We find that the n --> pi* transition suffers a blueshift of
   1,600 cm(-1) upon solvation and the pi --> pi* transition undergoes a
   redshift of 800 cm(-1). On average, 1.5 hydrogen bonds are formed
   between FMA and water and these contribute with about 20% and about 30%
   of the total solvation shifts of the n --> pi* and pi --> pi*
   transitions, respectively. The autocorrelation function of the energy
   is used to sample configurations from the Monte Carlo simulation, and
   the solvation shifts are shown to be converged values.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Fed Juiz Fora, Dept Quim, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Mogi Cruzes, CCET, BR-08710970 Mogi das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR ALLEN MP, 1987, COMPUTER SIMULATION
   BERENDSEN HJC, 1981, INTERMOLECULAR FORCE, P331
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   ZERNER MC, ZINDO SEMIEMPIRICAL
NR 50
TC 5
PU SPRINGER-VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1432-881X
J9 THEOR CHEM ACC
JI Theor. Chem. Acc.
PD JUL
PY 2002
VL 108
IS 1
BP 31
EP 37
PG 7
SC Chemistry, Physical
GA 584XM
UT ISI:000177494100005
ER

PT J
AU Miotto, R
   Ferraz, AC
TI A theoretical study of C2H2 adsorption on the Ge(001) surface
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; surface relaxation and reconstruction;
   chemisorption; germanium; silicon
ID DENSITY-FUNCTIONAL THEORY; MOLECULAR-DYNAMICS; ORGANIC-MOLECULES;
   SI(001) SURFACE; ACETYLENE; SI(100)
AB Using a first-principles pseudopotential technique, we have
   investigated the adsorption of C2H2, on the Ge(0 01) surface. We have
   found that, at low temperatures, the di-sigma bond configuration is the
   most stable structure from the energetic point of view. According to
   our calculations, it is not possible to conclude if C2H2 adsorbs
   preferentially on alternate or adjacent dimer sites. The di-sigma
   adsorbed system is characterized by symmetric and slightly elongated
   Ge-Ge dimers, and by a symmetric C-C bond with length close to the
   double carbon bond length of the ethylene molecule. Our total energy
   calculations suggest that other meta-stable configurations, like the
   1,2-hydrogen transfer model, are also possible. This behaviour was also
   observed for the silicon based system. In addition, we present
   theoretical scanning tunneling microscopy images and calculated
   vibrational modes for the adsorbed system with a view to contribute to
   further experimental investigations. (C) 2002 Elsevier Science B.V. All
   rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Miotto, R, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR *NIST, 2000, NIST CHEM WEBB
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BOONE AJ, 1998, INT J QUANTUM CHEM, V70, P925
   DYSON AJ, 1997, SURF SCI, V375, P45
   HAMERS RJ, 1999, JPN J APPL PHYS 1, V38, P3879
   HIPPS KW, 2001, SCIENCE, V294, P536
   KITTEL C, 1996, INTRO SOLID STATE PH
   LIDE DR, 1995, HDB CHEM PHYSICS
   LIU HB, 1998, SURF SCI, V416, P354
   MEZHENNY S, 2001, CHEM PHYS LETT, V344, P7
   MIOTTO R, 2000, PHYS REV B, V62, P13623
   MIOTTO R, 2002, PHYS REV B, V65, P75401
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
   PILING MJ, 1995, REACTION KINETICS
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   SRIVASTAVA GP, 1997, REP PROG PHYS, V60, P561
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   XU SH, 2000, PHYS REV LETT, V84, P939
NR 24
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD AUG 1
PY 2002
VL 513
IS 3
BP 422
EP 430
PG 9
SC Chemistry, Physical
GA 581XH
UT ISI:000177319500007
ER

PT J
AU Pliego, JR
   Riveros, JM
TI Theoretical calculation of pK(a) using the cluster-continuum model
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID COMPLETE BASIS-SET; SOLVATION FREE-ENERGY; AB-INITIO; AQUEOUS-SOLUTION;
   CARBOXYLIC-ACIDS; ORGANIC-COMPOUNDS; HALOACETIC ACIDS; HYDROXIDE ION;
   GAS-PHASE; ABSOLUTE
AB The pK(a)'s of 17 species from - 10 to 50 were calculated using the ab
   initio MP2/6-311+G(2df,2p) level of theory and inclusion of solvent
   effects by the cluster-continuum model, a hybrid approach that combines
   gas-phase clustering by explicit solvent molecules and solvation of the
   cluster by the dielectric continuum. In addition, the pure continuum
   methods SM5.42R and PCM were also used for comparison purposes. Species
   such as alcohols, carboxylic acids, phenol, acetaldehyde and its
   hydrate, thiols, hydrochloric acid, amines, and ethane were included.
   Our results show that the cluster-continuum model yields much better
   agreement with experiment than do the above-mentioned pure continuum
   methods, with a rms error of 2.2 pK(a) units as opposed to 7 pK(a)
   units for the SM5.42R and PCM methods. The good performance of the
   cluster-continuum model can be attributed to the introduction of strong
   and specific solute-solvent interactions with the molecules in the
   first solvation shell of ions. This feature decreases the dielectric
   continuum contribution to the difference in the solvation free energy
   between ions, making the method less susceptible to error because of
   the continuum contribution to solvation. Because the method is not
   based on extensive parametrizations and it is shown to fare well for
   several functional groups, the present results suggest that this method
   could be used as a general approach for predicting reliable pK(a)
   values.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
CR *NIST, 2001, NIST CHEM WEBB
   ALBERT A, 1984, DETERMINATION IONIZA
   BARONE V, 1997, J CHEM PHYS, V107, P3210
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   FORESMAN JB, 1996, J PHYS CHEM-US, V100, P16098
   FRISCH MJ, 1995, GAUSSIAN 94
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   HILL TL, 1960, INTRO STAT THERMODYN
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NR 42
TC 38
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 15
PY 2002
VL 106
IS 32
BP 7434
EP 7439
PG 6
SC Chemistry, Physical
GA 582LZ
UT ISI:000177353700024
ER

PT J
AU Kirsch, R
   Prandolini, MJ
   Beutler, O
   Brewer, WD
   Gruyters, M
   Kapoor, J
   Riegel, D
   Ebert, H
   Frota-Pessoa, S
TI The formation of orbital moments on iron impurities in Ag1-xAux alloys
SO EUROPHYSICS LETTERS
LA English
DT Article
ID LOCAL ENVIRONMENT; HYPERFINE FIELDS; ALKALI-METALS; CO; FE; SURFACES;
   3D; MAGNETISM; SPIN; NI
AB Using the high specificity and sensitivity of the in-beam perturbed
   gamma-ray angular distribution method, we have investigated the
   magnetic behavior of very dilute Fe-54 probes in Ag1-xAux alloys. The
   nuclear damping time and local susceptibility of Fe are found to depend
   strongly on its local environment, showing inhomogeneous line
   broadening as well as discrete magnetic responses due to the different
   configurations of Ag/Au nearest neighbors. The results can be
   understood with the aid of ab initio calculations of electronic
   structure, magnetic moments and hyperfine fields. They underline the
   central importance of orbital magnetism for understanding the
   experimental results.
C1 Free Univ Berlin, Fachbereich Phys, D-14195 Berlin, Germany.
   Hahn Meitner Inst Berlin GmbH, D-14109 Berlin, Germany.
   Univ Munich, D-81377 Munich, Germany.
   USP, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Kirsch, R, Free Univ Berlin, Fachbereich Phys, Arnimallee 14, D-14195
   Berlin, Germany.
CR AKAI H, 1999, HYPERFINE INTERACT, V121, P3
   BLUGEL S, 1987, PHYS REV B, V35, P3271
   EBERT H, 1988, Z PHYS B, V73, P77
   EBERT H, 2000, LECT NOTES PHYS, V535, P191
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   FARLE M, 1998, REP PROG PHYS, V61, P755
   FROTAPESSOA S, 1992, PHYS REV B, V46, P14570
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   GUO GY, 2000, PHYS REV B, V62, P14609
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   JACCARINO V, 1965, PHYS REV LETT, V15, P258
   KIRSCH R, UNPUB
   KITCHENS TA, 1974, PHYS REV B, V9, P344
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   UBA S, 1998, PHYS REV B, V57, P1534
NR 21
TC 6
PU E D P SCIENCES
PI LES ULIS CEDEXA
PA 7, AVE DU HOGGAR, PARC D ACTIVITES COURTABOEUF, BP 112, F-91944 LES
   ULIS CEDEXA, FRANCE
SN 0295-5075
J9 EUROPHYS LETT
JI Europhys. Lett.
PD AUG
PY 2002
VL 59
IS 3
BP 430
EP 436
PG 7
SC Physics, Multidisciplinary
GA 581QP
UT ISI:000177304600018
ER

PT J
AU Davila, LYA
   Caldas, MJ
TI Applicability of MNDO techniques AM1 and PM3 to ring-structured polymers
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE structural properties; torsion angles; semiempirical models; ab initio;
   electronic structure
ID ELECTRONIC-PROPERTIES; SEMIEMPIRICAL METHODS; CONJUGATED POLYMERS;
   ADJACENT RINGS; TORSION ANGLE; POLYANILINE; PARAMETERS; OPTIMIZATION;
   EVOLUTION; VINYLENE)
AB Semiempirical Hartree-Fock techniques are widely used to study
   properties of long ring-structured chains, although these types of
   systems were not included in the original parametrization ensembles.
   These techniques are very useful for an ample class of studies, and
   their predictive power should be tested. We present here a study of the
   applicability of some techniques from the NDDO family (MNDO, AM1, and
   PM3) to the calculation of the ground state geometries of a specific
   set of molecules with the ring-structure characteristic. For this we
   have chosen to compare results against ab initio Restricted
   Hartree-Fock 6-31G(d,p) calculations, extended to Moller-Plesset 2
   perturbation theory for special cases. The systems investigated
   comprise the orthobenzoquinone (O2C6H4) molecule and dimers
   (O2C6H4)(2), as well as trimers of polyaniline, which present
   characteristics that extend to several systems of interest in the field
   of conducting polymers, such as ring structure and heterosubstitution.
   We focus on the torsion between rings, because this angle is known to
   affect strongly the electronic and optical properties of conjugated
   polymers. We find that AM1 is always in qualitative agreement with the
   ab initio results, and is thus indicated for further studies of longer,
   more complicated chains.
C1 USP, Inst Fis, BR-66318 Sao Paulo, Brazil.
RP Caldas, MJ, USP, Inst Fis, BR-66318 Sao Paulo, Brazil.
CR *IND U, MOPAC 6 0 PROGR 464
   AMBROSCHDRAXL C, 1995, PHYS REV B, V51, P9668
   BRAGA SF, IN PRESS
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NR 33
TC 11
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD SEP
PY 2002
VL 23
IS 12
BP 1135
EP 1142
PG 8
SC Chemistry, Multidisciplinary
GA 578ER
UT ISI:000177104900002
ER

PT J
AU Dabrowski, J
   Mussig, HJ
   Zavodinsky, V
   Baierle, R
   Caldas, MJ
TI Mechanism of dopant segregation to SiO2/Si(001) interfaces
SO PHYSICAL REVIEW B
LA English
DT Article
ID TRANSIENT ENHANCED DIFFUSION; PHOSPHORUS PILE-UP; POINT-DEFECTS; DOSE
   LOSS; ELECTRONIC-STRUCTURE; SI-SIO2 INTERFACE; SILICON DIOXIDE; MODEL;
   SI; PSEUDOPOTENTIALS
AB Dopant atoms can segregate to SiO2/Si(001) interfaces and be
   deactivated there. Using phosphorus as a typical example of a donor and
   guided by results of ab initio calculations, we present a model of
   donor segregation. We find that P is trapped at the interface in the
   form of threefold-coordinated atoms. The atomic detailed configuration
   and the process of P incorporation depend on P concentration C-P in the
   vicinity of the interface. At low C-P, phosphorus atoms prefer to
   substitute Si atoms with dangling bonds. At high C-P, phosphorus pairs
   are formed. At intermediate C-P, (around 10(17)-10(19) cm(-3))
   segregation occurs to sites associated with interface roughness and to
   interface Si-Si bridges, and is mediated by diffusion and annihilation
   of Si dangling bonds and by reoxidation during oxide annealing. Making
   diffusion of dangling bonds more difficult (for example, by
   nitridation) should, therefore, reduce the trapping efficiency of
   SiO2/Si(001) in the technologically important regime of intermediate
   C-P.
C1 IHP, D-15236 Frankfurt, Germany.
   Inst Automat & Control Proc, Vladivostok 690041, Russia.
   Univ Fed Santa Maria, Dept Fis, BR-9711030 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
RP Dabrowski, J, IHP, Technol Pk 25, D-15236 Frankfurt, Germany.
CR ASENOV A, 1998, P SISPAD 98, P223
   ASENOV A, 1999, IEEE T COMPUT AID D, V18, P1558
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   BAIERLE R, 1999, PHYSICA B, V273, P260
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BOTT E, 1998, J MATH PHYS, V39, P3393
   CALDAS MJ, 1990, PHYS REV LETT, V65, P2046
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CHOU NJ, 1974, APPL PHYS LETT, V24, P200
   DABROWSKI J, 1998, SURF SCI, V411, P54
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   DABROWSKI J, 2000, SILICON SURFACES FOR, P360
   DABROWSKI J, 2000, SPECIAL DEFECTS SEMI, P23
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   DUNHAM ST, 1992, J APPL PHYS, V71, P685
   DUNHAM ST, 1992, J ELECTROCHEM SOC, V139, P2628
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   HAMANN DR, 1989, PHYS REV B, V40, P2980
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   JARAIZ M, 1996, APPL PHYS LETT, V68, P409
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NR 50
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD JUN 15
PY 2002
VL 65
IS 24
AR 245305
DI ARTN 245305
PG 11
SC Physics, Condensed Matter
GA 577CA
UT ISI:000177043100064
ER

PT J
AU Savedra, RML
   Pinheiro, JC
   Treu, O
   Kondo, RT
TI Gaussian basis sets by generator coordinate Hartree-Fock method to ab
   initio calculations of electron affinities of enolates
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Gaussian basis sets; GCHFM; electron affinities; calculations of
   enolates; electron affinities of enolates
ID FIRST-ROW ATOMS; DIATOMIC-MOLECULES; 2ND-ROW ATOMS; CHOICE;
   CONTRACTION; EQUATIONS; EXCHANGE; VERSION; BASES; CO
AB The Generator Coordinate Hartree-Fock (GCHF) method is employed to
   generate uncontracted 15s and 18s11p gaussian basis sets for the H, C
   and O atoms, respectively. These basis sets are then contracted to 3s
   and 4s H atom and 6s5p, for C and O atoms by a standard procedure. For
   quality evaluation of contracted basis sets in molecular calculations,
   we have accomplished calculations of total and orbital energies in the
   Hartree-Fock-Roothaaii (HFR) approach for CH, C-2 and CO molecules. The
   results obtained with the uncontracted basis sets are compared with
   values obtained with the standard D95, 6-311G basis sets and with
   values reported in the literature. The 4s and 6s5p basis sets are
   enriched with polarization and diffuse functions for atoms of the
   parent neutral systems and of the enolates anions (cycloheptanone
   enolate, 2,5-dimethyleyelopentanone enolate, 4-heptanone enolate, and
   di-isopropyl ketone enolate) from the literature, in order to assess
   their performance in ab initio molecular calculations, and applied for
   calculations of electron affinities of the enolates. The calculations
   were performed at the DFT (BLYP and B3LYP) and HF levels and compared
   with the corresponding experimental values and with those obtained by
   using other 6-3 1 + +G((*)) and 6-311 + +G((*)) basis sets from
   literature. For the enolates studied, the differences between the
   electron affinities obtained with GCHF basis sets, at the B3LYP level,
   and the experimental values are -0.001, -0,014, -0.001, and -0.001 eV.
   (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab Quim Teor & Computac, BR-66075110 Belem, Para, Brazil.
   CEAM, Cooperat Ctr Educ Cient & Empreendedora Amazonia, BR-66013060 Belem, Para, Brazil.
   Univ Estadual Paulista, Inst Quim Araraquara, BR-14801970 Araraquara, SP, Brazil.
   Univ Sao Paulo, Ctr Informat Sao Carlos, Secao Suporte, BR-13560970 Sao Carlos, SP, Brazil.
RP Pinheiro, JC, Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, Lab
   Quim Teor & Computac, Caixa Postal 101101, BR-66075110 Belem, Para,
   Brazil.
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NR 31
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD JUL 5
PY 2002
VL 587
BP 9
EP 17
PG 9
SC Chemistry, Physical
GA 576TA
UT ISI:000177020100002
ER

PT J
AU Vilela, AFA
   Neto, JJS
   Mundim, KC
   Mundim, MSP
   Gargano, R
TI Fitting potential energy surface for reactive scattering dynamics
   through generalized simulated annealing
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID OPTIMIZATION
AB We propose a stochastic optimization technique, based on generalized
   simulated annealing (GSA), as a new option to fit potential energy
   surfaces (PES) for reactive scattering dynamics. In order to show this,
   we reproduced the PES of the Na + HF --> NaF + H reaction utilizing the
   ab initio calculation as well as the trial function published by Lagan
   et al. Topological studies were done on the Na + HF GSA PES considering
   a great number of the nuclear configurations. These studies showed that
   the quality of the Na + HF GSA PES is comparable to the Na + HF PES
   obtained by Lagan et al. (C) 2002 Published by Elsevier Science B.V.
C1 Univ Brasilia, Inst Fis, BR-70919970 Brasilia, DF, Brazil.
RP Gargano, R, Univ Brasilia, Inst Fis, Caixa Postal 04455, BR-70919970
   Brasilia, DF, Brazil.
CR AREAS EPG, 1995, J PHYS CHEM-US, V99, P14885
   BARTOSZEK FE, 1981, J CHEM PHYS, V74, P3400
   CEPERLY D, 2001, SCIENCE, V539, P215
   CURADO EMF, 1991, J PHYS A, V24, P3187
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   GARGANO R, 2001, J MOL STRUC-THEOCHEM, V539, P215
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   WEISS PS, 1988, CHEM PHYS, V126, P93
NR 19
TC 3
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD JUN 27
PY 2002
VL 359
IS 5-6
BP 420
EP 427
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 576XN
UT ISI:000177032600011
ER

PT J
AU Malaspina, T
   Coutinho, K
   Canuto, S
TI Ab initio calculation of hydrogen bonds in liquids: A sequential Monte
   Carlo quantum mechanics study of pyridine in water
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MOLECULAR-INTERACTIONS; BIOLOGICAL INTEREST; AQUEOUS-SOLUTIONS;
   AROMATIC BASES; REACTION FIELD; SOLVENT; COMPLEXES; SPECTROSCOPY;
   SIMULATION; DYNAMICS
AB A systematic procedure based on the sequential Monte Carlo quantum
   mechanics (S-MC/QM) methodology has been used to obtain hydrogen bond
   strength and structures in liquids. The system considered is pyridine
   in water. The structures are generated by NVT Monte Carlo simulation,
   of one pyridine molecule and 400 water molecules. The hydrogen bonds
   are obtained using a geometric and energetic procedure. Detailed
   analysis shows that 62% of the configurations have one hydrogen bond.
   In the average, pyridine in liquid water makes 1.1 hydrogen bonds. The
   sampling of the structures for the quantum mechanical calculations is
   made using the interval of statistical correlation obtained by the
   autocorrelation function of the energy. A detailed statistical analysis
   is presented and converged results are obtained. The QM calculations
   are performed at the ab initio MP2/6-31+G(d) level and the results are
   compared with the optimized 1:1 cluster. Our results using QM
   calculations on 155 structures making one hydrogen bond gives an
   average binding energy of 3.7 kcal/mol, after correcting for basis set
   superposition error, indicating that in the liquid the binding energy
   is about 2/3 of the corresponding binding in the optimized cluster. (C)
   2002 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Mogi das Cruzes, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 74
TC 19
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUL 22
PY 2002
VL 117
IS 4
BP 1692
EP 1699
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 572DM
UT ISI:000176758200034
ER

PT J
AU Miotto, R
   Ferraz, AC
   Srivastava, GP
TI Comparative study of the adsorption of C2H4 on the Si(001) and Ge(001)
   surfaces
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; surface relaxation and reconstruction;
   chemisorption; vibrations of adsorbed molecules; silicon; germanium
ID SI(100)-(2X1) SURFACE; ETHYLENE ADSORPTION; FIRST-PRINCIPLES;
   ACETYLENE; SPECTROSCOPY; SI(100)(2X1); BEHAVIOR; STATES; X-1
AB Using a first-principles pseudopotential method we have compared the
   interaction processes involved in the adsorption of ethylene on the
   silicon and germanium surfaces. We have found that, at low
   temperatures, the di-sigma bond configuration is the most stable
   structure from the energetic point of view. According to our
   calculations C2H4 adsorbs preferentially on the alternate dimer sites,
   corresponding to a coverage of 0.5 ML. The di-sigma adsorbed system is
   characterized by symmetric and slightly elongated Si-Si (Ge-Ge) dimers,
   and by a symmetric C-C bond close to the single carbon bond length of
   the ethane molecule. The electronic band structure derived from our
   calculations suggest that the adsorption of the C2H4 molecule leaves a
   surface state in the fundamental band gap that is mainly localized
   around the adsorbate. Finally, our ab initio vibrational spectra
   further support the di-sigma model for the ethylene adsorption on
   IV(001)-(2 x 2). (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
RP Miotto, R, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
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   CHO JH, 2001, PHYS REV B, V63
   CLEMEN L, 1992, SURF SCI, V268, P205
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NR 20
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD JUN 1
PY 2002
VL 507
BP 12
EP 17
PG 6
SC Chemistry, Physical
GA 569CV
UT ISI:000176583700004
ER

PT J
AU Miwa, RH
   Schmidt, TM
   Srivastava, GP
TI Ab initio study of the self-organised Bi-lines on the SK(001) surface
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; surface electronic phenomena (work
   function, surface potential, surface states, etc.); bismuth;
   self-assembly
ID SCANNING-TUNNELING-MICROSCOPY; ELECTRONIC-STRUCTURE; BISMUTH; SI(001);
   NANOWIRE; CHAINS; STATE; X-1)
AB We have perfomed an ab initio theoretical study of the stability,
   atomic geometry and electronic structure of the self-organised Bi-lines
   on the Si(0 0 1) surface. Our results show that the Bi-lines are formed
   by Bi-dimers parallel to the surrounding Si-dimers, with a missing
   dimer row between the Bi-dimers. In contrast to a recently proposed
   model of symmetrically disposed surface Si-dimers (i.e. with no
   buckling). our total energy calculations indicate that the buckling of
   the Si-dimers is an exothermic process, reducing the surface total
   energy by 0.11 eV/dimer. Our theoretically simulated STM results
   suggest a low density of states close to the valence band maximum,
   localized on the Bi-lines, supporting a recently proposed model of
   quantum antiwire systems for Bi-lines on the Si(0 0 1) surface. (C)
   2002 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Uberlandia, Fac Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
RP Miwa, RH, Univ Fed Uberlandia, Fac Fis, CP 593, BR-38400902 Uberlandia,
   MG, Brazil.
CR ABUKAWA T, 1995, SURF SCI, V325, P33
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   YEOM HW, 1999, PHYS REV LETT, V82, P4898
NR 21
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD JUN 1
PY 2002
VL 507
BP 368
EP 373
PG 6
SC Chemistry, Physical
GA 569CV
UT ISI:000176583700067
ER

PT J
AU Freire, HJP
   Egues, JC
TI Subband structure of II-VI modulation-doped magnetic quantum wells
SO BRAZILIAN JOURNAL OF PHYSICS
LA English
DT Article
ID ELECTRICAL SPIN INJECTION; SEMICONDUCTOR HETEROSTRUCTURE; TRANSPORT;
   MAGNETORESISTANCE; SUPERLATTICES; DENSITY
AB Here we investigate the spin-dependent subband structure of
   newly-developed Mn-based modulation-doped quantum wells. In the
   presence of an external magnetic field, the s-d exchange coupling
   between carriers and localized d electrons of the Mn impurities gives
   rise to large spin splittings resulting in a magnetic-field dependent
   subband structure. Within the framework of the effective-mass
   approximation, we self-consistently calculate the subband structure at
   zero temperature using Density Functional Theory (DFT) with a Local
   Spin Density Approximation (LSDA). We present results for the
   magnetic-field dependence of the subband structure of shallow
   ZnSe/ZnCdMnSe modulation doped quantum wells. Our results show a
   significant contribution to the self-consistent potential due to the
   exchange-correlation term. These calculations are the first step in the
   study of a variety of interesting spin-dependent phenomena, e.g.,
   spin-resolved transport and many-body effects in polarized
   two-dimensional electron gases.
C1 Univ Sao Paulo, Inst Fis Sao Carlos, Dept Fis Informat, BR-13560970 Sao Carlos, SP, Brazil.
RP Freire, HJP, Univ Sao Paulo, Inst Fis Sao Carlos, Dept Fis Informat,
   BR-13560970 Sao Carlos, SP, Brazil.
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   EGUES JC, 2001, PHYS REV B, V64
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   OHNO Y, 1999, NATURE, V402, P790
   SCHMIDT G, 2001, PHYS REV LETT, V87
   SMORCHKOVA I, 1996, APPL PHYS LETT, V69, P1640
   SMORCHKOVA IP, 1997, PHYS REV LETT, V78, P3571
   STORMER HL, 1983, SCIENCE, V220, P1241
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NR 20
TC 3
PU SOCIEDADE BRASILEIRA FISICA
PI SAO PAULO
PA CAIXA POSTAL 66328, 05315-970 SAO PAULO, BRAZIL
SN 0103-9733
J9 BRAZ J PHYS
JI Braz. J. Phys.
PD JUN
PY 2002
VL 32
IS 2
BP 327
EP 330
PG 4
SC Physics, Multidisciplinary
GA 568BF
UT ISI:000176522000021
ER

PT J
AU Perpetuo, GJ
   Janczak, J
TI 3-Amino-1,2,4-triazine
SO ACTA CRYSTALLOGRAPHICA SECTION C-CRYSTAL STRUCTURE COMMUNICATIONS
LA English
DT Article
ID HYDROGEN; DIHYDRATE; SECONDARY; COMPLEXES; TAPES
AB In the crystal structure of 3-amino-1,2,4-triazine, C3H4N4, the
   molecules form hydrogen-bonded chains that are almost parallel to the b
   axis (3.2degrees), and which are inclined to the a and c axes by
   similar to21 and similar to69degrees, respectively. The distortion of
   the 1,2,4-triazine ring in the crystal is compared with gas-phase ab
   initio molecular-orbital calculations.
C1 Univ Fed Ouro Preto, Inst Ciencias Exatas & Biol, Dept Fis, BR-35400000 Ouro Preto, MG, Brazil.
   Polish Acad Sci, Inst Low Temp & Struct Res, PL-50950 Wroclaw, Poland.
RP Janczak, J, Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Quim,
   BR-31270901 Belo Horizonte, MG, Brazil.
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NR 22
TC 3
PU BLACKWELL MUNKSGAARD
PI COPENHAGEN
PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK
SN 0108-2701
J9 ACTA CRYSTALLOGR C-CRYST STR
JI Acta Crystallogr. Sect. C-Cryst. Struct. Commun.
PD JUL
PY 2002
VL 58
PN Part 7
BP O431
EP O432
PG 2
SC Crystallography
GA 568WF
UT ISI:000176567300047
ER

PT J
AU Sensato, FR
   Custodio, R
   Calatayud, M
   Beltran, A
   Andres, J
   Sambrano, JR
   Longo, E
TI Periodic study on the structural and electronic properties of bulk,
   oxidized and reduced SnO2(110) surfaces and the interaction with O-2
SO SURFACE SCIENCE
LA English
DT Article
DE ab initio quantum chemical method and calculations; density functional
   calculations; models of surface chemical reactions; chemisorption;
   surface electronic phenomena (work function, surface potential, surface
   states. etc.); oxygen; tin oxides; semiconducting surfaces
ID OXYGEN VACANCIES; THEORETICAL-ANALYSIS; FUNCTIONAL THEORY; TIN OXIDES;
   THIN-FILM; SNO2 110; PHOTOEMISSION; ADSORPTION; ANTIMONY; METHANE
AB The structural and electronic properties of bulk and both oxidized and
   reduced SnO2(110) surfaces as well as the adsorption process of O-2 on
   the reduced surface have been investigated by periodic DFT calculations
   at B3LYP level. The lattice parameters, charge distribution, density of
   states and band structure are reported for the bulk and surfaces.
   Surface relaxation effects have been explicitly taken into account by
   optimizing slab models of nine and seven atomic layers representing the
   oxidized and reduced surfaces, respectively. The conductivity behavior
   of the reduced SnO2(110) surface is explained by a distribution of the
   electrons in the electronic states in the band gap induced by oxygen
   vacancies. Three types of adsorption approaches of O-2 on the four-fold
   tin at the reduced SuO(2)(110) surface have been considered. The most
   exothermic channel corresponds to the adsorption of O-2 parallel to the
   surface and to the four-fold tin row, and it is believed to be
   associated with the formation of a peroxo O-2(2-) species. The
   chemisorption of O-2 on reduced SnO2(110) surface causes a significant
   depopulation of states along the band gap and it is shown to trap the
   electrons in the chemisorbed complex producing an electron-depleted
   space-charge layer in the inner surface region of the material in
   agreement with some experimental evidences. (C) 2002 Elsevier Science
   B.V. All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Estadual Paulista, Dept Matemat, BR-17030360 Bauru, SP, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
RP Sensato, FR, Univ Estadual Campinas, Inst Quim, CP 6154, BR-13083970
   Campinas, SP, Brazil.
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NR 52
TC 19
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD JUN 10
PY 2002
VL 511
IS 1-3
BP 408
EP 420
PG 13
SC Chemistry, Physical
GA 569CY
UT ISI:000176584000048
ER

PT J
AU Dos Santos, HF
   Rocha, WR
   De Almeida, WB
TI On the evaluation of thermal corrections to gas phase ab initio
   relative energies: implications to the conformational analysis study of
   cyclooctane
SO CHEMICAL PHYSICS
LA English
DT Article
DE ab initio; DFT; thermal correction; conformational population; low
   frequency modes
ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-BASIS SETS; MECHANICS CALCULATIONS;
   ELECTRON-DIFFRACTION; ORGANIC-MOLECULES; APPROXIMATION; ATOMS;
   EXCHANGE; MINIMUM; SPECTRA
AB In this paper we present an investigation of the influence of the
   thermal correction on the conformational population for the boat-chair
   (BC) and CROWN forms of the cyclooctane molecule, calculated using
   quantum mechanical ab initio Hartree-Fock (HF), MP2, MP4SDQ, CCSD and
   density functional methods (B3LYP, BLYP, BP86) in conjunction with
   various basis sets. A previous experimental gas phase electron
   diffraction study pointed out that the BC is either the exclusive or at
   least the strongly predominant form in gas phase at room temperature.
   We therefore analyzed the performance of various levels of calculation
   for the evaluation of the relative conformational population and also
   the role played by the thermal correction to gas phase calculated
   relative energies. It turns out that the thermal correction is very
   sensitive to the presence of low frequency modes that are indeed
   internal rotations and need to be treated separately, in what the
   cyclooctane molecule is concerned. Once internal rotations were
   considered, it can be seen that the HF level of calculation produces
   very satisfactory values for thermal correction, compared to MP2.
   Therefore, it can be used in single-point energy calculations employing
   a high correlated level of theory (MP4SDQ, CCSD), leading to a quite
   trustable Gibbs free energy difference data. When thermal energies are
   not corrected for low frequency internal rotation modes, a range of
   contrasting results is obtained by varying both the quantum mechanical
   approach and the basis set. (C) 2002 Elsevier Science B.V. All rights
   reserved.
C1 LQC MM, BR-31270970 Belo Horizonte, MG, Brazil.
   UFMG, ICEx, Dept Quim, BR-31270970 Belo Horizonte, MG, Brazil.
   NEQC, BR-36036330 Juiz de Fora, MG, Brazil.
   UFJF, ICE, Dept Quim, BR-36036330 Juiz de Fora, MG, Brazil.
RP De Almeida, WB, LQC MM, BR-31270970 Belo Horizonte, MG, Brazil.
CR ALMENNINGEN A, 1966, ACTA CHEM SCAND, V20, P2689
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NR 50
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD JUN 15
PY 2002
VL 280
IS 1-2
BP 31
EP 42
PG 12
SC Physics, Atomic, Molecular & Chemical
GA 566UY
UT ISI:000176447700003
ER

PT J
AU Junqueira, GMA
   Rocha, WR
   De Almeida, WB
   Dos Santos, HF
TI Theoretical analysis of the oxocarbons: The role played by the solvent
   and counter-ions in the electronic spectrum of the deltate ion
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID DIFFERENTIAL-OVERLAP TECHNIQUE; MONTE-CARLO; INTERMEDIATE NEGLECT;
   CROCONATE DIANION; SPECTROSCOPY; WATER; TRANSITION; FORMALDEHYDE;
   COMPLEXES; LITHIUM
AB The structure and spectroscopic properties of the deltate anion are
   calculated in the gas phase using ab initio quantum chemical methods
   and in aqueous solution through a sequential Monte Carlo-quantum
   mechanical procedure. The effects of the solvent and counter-ions on
   the electronic spectrum are analyzed, showing that both should be
   included in the calculation in order to reproduce the observed UV
   spectrum. For the smallest cyclic oxocarbon, the deltate anion, the
   calculated electronic transitions were 254 and 246 nm considering the
   [Li-2(C3O3)(H2O)(20)] species. This is in accordance with the expected
   behavior for the oxocarbon series, predicting absorption bands close to
   200 nm for the deltate anion.
C1 Univ Fed Juiz de Fora, ICE, Dept Quim, NEQC, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Minas Gerais, ICEx, Dept Quim, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
RP Dos Santos, HF, Univ Fed Juiz de Fora, ICE, Dept Quim, NEQC, Campus
   Martelos, BR-36036330 Juiz De Fora, MG, Brazil.
CR 1992, HDB CHEM PHYSICS
   AIHARA J, 1981, J AM CHEM SOC, V103, P1633
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   DORY M, 1994, J CHEM SOC FARADAY T, V90, P2319
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NR 44
TC 4
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD, CAMBRIDGE CB4 0WF, CAMBS,
   ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI Phys. Chem. Chem. Phys.
PY 2002
VL 4
IS 12
BP 2517
EP 2523
PG 7
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 563FY
UT ISI:000176246700006
ER

PT J
AU de Paiva, R
   Alves, JLA
   Nogueira, RA
   de Oliveira, C
   Alves, HWL
   Scolfaro, LMR
   Leite, JR
TI Theoretical study of the AlxGa1-xN alloys
SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED
   TECHNOLOGY
LA English
DT Article
DE GaN; AlN; AlGaN; alloys; effective masses
ID ALUMINUM NITRIDE; ZINCBLENDE GAN; SEMICONDUCTORS; ALN
AB In this work we use a first-principles method based on the density
   functional theory, the full-potential linear augmented plane-wave
   method (FPLAPW), in order to calculate the electronic structures of the
   Al(x)Gal(1-x)N alloys in the cubic modification. We adopt a model which
   allows the simulation of the composition x = 0.0, 0.25, 0.50, 0.75 and
   1.0. We obtain the equilibrium lattice parameters, the bulk moduli, the
   formation energies, the miscibility curves and the effective masses of
   the conduction and valence bands in the [100], [111] and [110]
   directions. The results can be used in the parameterization of theories
   based on effective hamiltonians. To our knowledge, this is the first
   time such a systematic ab initio study of effective masses of these
   semiconductor alloys is accomplished. (C) 2002 Elsevier Science B.V.
   All rights reserved.
C1 UFMG, Dept Fis, BR-13081970 Belo Horizonte, MG, Brazil.
   FUNREI, Dept Ciencias Nat, BR-36300000 Sao Joao Del Rei, MG, Brazil.
   USP, LNMS, Dept Fis Mat & Mecan, BR-05389970 Sao Paulo, Brazil.
RP de Paiva, R, UFMG, Dept Fis, CP 702, BR-13081970 Belo Horizonte, MG,
   Brazil.
CR ALBANESI EA, 1993, PHYS REV B, V48, P17841
   BLAHA P, 1990, COMPUT PHYS COMMUN, V59, P399
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CHEN AB, 1996, SEMICONDUCTOR ALLOYS
   FAN WJ, 1996, J APPL PHYS, V79, P188
   FANCIULLI M, 1993, PHYS REV B, V48, P15144
   GERLICH D, 1986, J PHYS CHEM SOLIDS, V47, P437
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   WEI SH, 1988, PHYS REV B, V37, P8958
   WETTLING W, 1984, SOLID STATE COMMUN, V50, P33
   WIMMER E, 1981, PHYS REV B, V24, P864
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   YEH CY, 1992, PHYS REV B, V46, P10086
   YEH CY, 1994, PHYS REV B, V50, P2715
NR 17
TC 3
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0921-5107
J9 MATER SCI ENG B-SOLID STATE M
JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol.
PD MAY 30
PY 2002
VL 93
IS 1-3
BP 2
EP 5
PG 4
SC Materials Science, Multidisciplinary; Physics, Condensed Matter
GA 560NY
UT ISI:000176089200002
ER

PT J
AU de Oliveira, LFC
   Edwards, HGM
   Velozo, ES
   Nesbitt, M
TI Vibrational spectroscopic study of brazilin and brazilein, the main
   constituents of brazilwood from Brazil
SO VIBRATIONAL SPECTROSCOPY
LA English
DT Article
DE brazilin; brazilein; Brazilwood; FT-Raman spectroscopy
ID HARMONIC FORCE-FIELD; CAESALPINIA-SAPPAN; AB-INITIO; RAMAN-SPECTRA;
   1,4-BENZOQUINONE; NU(2); WOOD; MICE
AB In this work, the vibrational spectra (FT-Raman and infrared spectra)
   of brazilin, the major component of brazilwood Caesalpinia echinata
   (from Bahia, Brazil), and brazilein, the oxidised pigment, are
   investigated. The FT-Raman spectra of the compounds show different
   patterns in the carbonyl stretching region, where brazilein presents a
   Raman feature at 1697 cm(-1) that is tentatively assigned to a coupled
   vibrational mode described by C=O and aromatic C=C stretching. Infrared
   measurements are used to support this assignment. The spectral region
   between 1700 and 1500 cm(-1) is also proposed as a fingerprint for
   brazilin and brazilein. Comparisons with some quinones and polyalcohols
   as parent molecules and other deep red resin pigments such as "dragon's
   blood" are undertaken to assist the vibrational assignment. As a test
   of the spectroscopic protocol for the identification of these pigments
   in natural brazilwoods, an 80-year-old archival specimen of Caesalpinia
   echinata was analysed non-destructively and the feature of brazilein
   shown from the Raman spectrum. (C) 2002 Elsevier Science B.V. All
   rights reserved.
C1 Univ Bradford, Dept Chem & Forens Sci, Bradford BD7 1DP, W Yorkshire, England.
   Univ Fed Juiz De Fora, Dept Quim, Inst Ciencias Exatas, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Bahia, Fac Farm, BR-41170290 Salvador, BA, Brazil.
   Royal Bot Gardens, Ctr Econ Bot, Richmond TW9 3AE, Surrey, England.
RP de Oliveira, LFC, Univ Bradford, Dept Chem & Forens Sci, Bradford BD7
   1DP, W Yorkshire, England.
CR BAEK NI, 2000, ARCH PHARM RES, V23, P344
   BECKER ED, 1991, J PHYS CHEM-US, V95, P2818
   DEFILIPPS RA, 1998, ARCH NATURAL HIST, V25, P103
   EDWARDS HGM, 2001, IN PRESS SPECTROCH A
   FUKE C, 1985, PHYTOCHEMISTRY, V24, P2403
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   NONELLA M, 1997, CHEM PHYS LETT, V280, P91
   OH SR, 1998, PLANTA MED, V64, P140
   PERKIN AG, 1918, NATURAL ORGANIC COLO
   SPOLITI M, 1997, THEOCHEM-J MOL STRUC, V390, P139
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NR 21
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0924-2031
J9 VIB SPECTROSC
JI Vib. Spectrosc.
PD APR 26
PY 2002
VL 28
IS 2
BP 243
EP 249
PG 7
SC Chemistry, Analytical; Chemistry, Physical; Spectroscopy
GA 556LV
UT ISI:000175852000004
ER

PT J
AU Venezuela, P
   Dalpian, GM
   da Silva, AJR
   Fazzio, A
TI Vacancy-mediated diffusion in disordered alloys: Ge self-diffusion in
   Si1-xGex
SO PHYSICAL REVIEW B
LA English
DT Article
ID NATIVE POINT-DEFECTS; AB-INITIO; FIRST-PRINCIPLES; BORON-DIFFUSION;
   SILICON; PSEUDOPOTENTIALS; GERMANIUM; SYSTEMS
AB A model is proposed for vacancy mediated diffusion in disordered
   alloys, with particular application to Ge self-diffusion in Si1-xGex.
   We argue that if the vacancies formation energies (VFE) have a strong
   dependence on the configuration of nearest neighbor (NN) atoms, there
   will be preferential diffusion paths for some concentrations. For
   Si1-xGex we show that the VFE vary linearly from 2 to 3 eV as the
   number of NN Ge atoms varies from 4 to 0. Thus, the equilibrium
   population of the various kinds of vacancies changes significantly with
   x, and the diffusion proceeds by paths that do not necessarily resemble
   the concentration of the alloy.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Venezuela, P, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
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NR 23
TC 10
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 15
PY 2002
VL 65
IS 19
AR 193306
DI ARTN 193306
PG 4
SC Physics, Condensed Matter
GA 556QR
UT ISI:000175860900018
ER

PT J
AU Bussi, G
   Ruini, A
   Molinari, E
   Caldas, MJ
   Puschnig, P
   Ambrosch-Draxl, C
TI Interchain interaction and Davydov splitting in polythiophene crystals:
   An ab initio approach
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID SEXITHIOPHENE SINGLE-CRYSTALS; QUANTUM-WIRE STRUCTURES;
   OPTICAL-SPECTRA; OLIGOTHIOPHENES; EXCITATIONS; EMISSION; POLYMERS
AB The crystal-induced energy splitting of the lowest excitonic state in
   polymer crystals, the so-called Davydov splitting Delta, is calculated
   with a first-principles density-matrix scheme. We show that different
   crystalline arrangements lead to significant variations in Delta, from
   below to above the thermal energy k(B)T at room temperature, with
   relevant implications on the luminescence efficiency. This is one more
   piece of evidence supporting the fact that control of interchain
   interactions and solid-state packing is essential for the design of
   efficient optical devices. (C) 2002 American Institute of Physics.
C1 Univ Modena & Reggio Emilia, INFMS3, I-41100 Modena, Italy.
   Univ Modena & Reggio Emilia, Dipartimento Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-05508900 Sao Paulo, Brazil.
   Karl Franzens Univ Graz, Inst Theoret Phys, A-8010 Graz, Austria.
RP Bussi, G, Univ Modena & Reggio Emilia, INFMS3, Via Campi 213-A, I-41100
   Modena, Italy.
CR CALDAS MJ, 2001, APPL PHYS LETT, V79, P2505
   CORNIL J, 2001, SYNTHETIC MET, V119, P1
   DAVYDOV AS, 1962, THEORY MOL EXCITONS
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   KOHN W, 1965, PHYS REV, V140, A1133
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NR 22
TC 12
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD JUN 3
PY 2002
VL 80
IS 22
BP 4118
EP 4120
PG 3
SC Physics, Applied
GA 555BB
UT ISI:000175771800012
ER

PT J
AU Hitchcock, AP
   Johnston, S
   Tyliszczak, T
   Turci, CC
   Barbatti, M
   Rocha, AB
   Bielschowsky, CE
TI Generalized oscillator strengths for C 1s excitation of acetylene and
   ethylene
SO JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA
LA English
DT Article
DE generalized oscillator strength; electron scattering; EELS; quadrupole
   transitions
ID INNER-SHELL EXCITATION; IMPACT CORE EXCITATION; ENERGY-LOSS
   SPECTROSCOPY; ELECTRON-IMPACT; C-1S PHOTOIONIZATION; MOMENTUM-TRANSFER;
   SHAPE RESONANCES; MOLECULES; SF6; C2H2
AB The generalized oscillator strength profiles for discrete C 1s excited
   states of C2H2 and C2H4 have been derived from angle-dependent
   inelastic electron scattering cross-sections measured with 1300 eV
   final electron energy. The measured GOS profiles for the strong C
   1s-->pi* transition in each species are compared to theoretical
   calculations computed within the first Born approximation, using
   ab-initio generalized multi structural wave functions. These wave
   functions include relaxation, correlation and hole localization
   effects. Theory predicts large quadrupole contributions to the pi* GOS
   of each species, analogous to those previously reported for computed
   GOS profiles for O 1s-->pi* excitation of CO2. We find good agreement
   between experiment and theory as to the shape of the pi* GOS but, when
   the relative GOS extracted from the experimental data is normalized to
   the optical oscillator strength at K-2=0, the magnitude is in better
   agreement with the GOS computed for only the dipole channel than for
   the sum of the dipole and quadrupole channels. (C) 2002 Elsevier
   Science B.V. All rights reserved.
C1 McMaster Univ, Dept Chem, Hamilton, ON L8S 4M1, Canada.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21910900 Rio De Janeiro, Brazil.
RP Hitchcock, AP, McMaster Univ, Dept Chem, Hamilton, ON L8S 4M1, Canada.
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NR 43
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0368-2048
J9 J ELECTRON SPECTROSC RELAT PH
JI J. Electron Spectrosc. Relat. Phenom.
PD MAY
PY 2002
VL 123
IS 2-3
BP 303
EP 314
PG 12
SC Spectroscopy
GA 552WM
UT ISI:000175643100017
ER

PT J
AU Ruini, A
   Caldas, MJ
   Bussi, G
   Molinari, E
TI Solid state effects on exciton states and optical properties of PPV
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID QUANTUM-WIRE STRUCTURES; AB-INITIO CALCULATION; CONJUGATED POLYMERS;
   POLY(PHENYLENE VINYLENE); EXCITATIONS; ABSORPTION;
   POLY(P-PHENYLENEVINYLENE); SEMICONDUCTORS; SPECTRA; ENERGY
AB We perform ab initio calculations of optical properties for a typical
   semiconductor conjugated polymer, poly-para-phenylenevinylene, in both
   isolated chain and crystalline packing. In order to obtain results for
   excitonic energies and real-space wave functions we explicitly include
   electron-hole interaction within the density-matrix formalism. We find
   that the details of crystalline arrangement crucially affect the
   optical properties, leading to a richer exciton structure and opening
   nonradiative decay channels. This has implications for the optical
   activity and optoelectronic applications of polymer films.
C1 Univ Modena & Reggio Emilia, INFM S, I-41100 Modena, Italy.
   Univ Modena & Reggio Emilia, Dipartimento Fis, I-41100 Modena, Italy.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Ruini, A, Univ Modena & Reggio Emilia, INFM S, Via Campi 213A, I-41100
   Modena, Italy.
CR ALVARADO SF, 1996, PHYS REV LETT, V53, P16462
   BARTH S, 1997, PHYS REV LETT, V79, P4445
   BELJONNE D, 1999, J CHEM PHYS, V111, P2829
   BUSSI G, IN PRESS APPL PHYS L
   CAMPBELL IH, 1996, PHYS REV LETT, V76, P1900
   CAPAZ RB, IN PRESS
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   CHEN D, 1992, POLYMER, V33, P3116
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   CORNIL J, 2001, SYNTHETIC MET, V119, P1
   DACOSTA PG, 1993, PHYS REV B, V48, P1993
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   ECKHARDT H, 1989, J CHEM PHYS, V91, P1303
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   LENG JM, 1994, PHYS REV LETT, V72, P156
   MARTIN SJ, 1999, PHYS REV B, V59, P15133
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NR 37
TC 41
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD MAY 20
PY 2002
VL 88
IS 20
AR 206403
DI ARTN 206403
PG 4
SC Physics, Multidisciplinary
GA 549UY
UT ISI:000175466200034
ER

PT J
AU Boye, S
   Campos, A
   Douin, S
   Fellows, C
   Gauyacq, D
   Shafizadeh, N
   Halvick, P
   Boggio-Pasqua, M
TI Visible emission from the vibrationally hot C2H radical following
   vacuum-ultraviolet photolysis of acetylene: Experiment and theory
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID LASER-INDUCED FLUORESCENCE; POTENTIAL-ENERGY SURFACES; 193.3 NM;
   PHOTODISSOCIATION DYNAMICS; RECURSIVE EVALUATION; STATE DISTRIBUTION;
   ANGULAR MOMENTA; RYDBERG STATES; 121.6 NM; PHOTOCHEMISTRY
AB Photolysis of acetylene has been performed by vacuum-ultraviolet
   excitation with the synchrotron radiation via the Rydberg states
   converging to the first ionization potential (IP) at 11.4 eV. Only the
   visible fluorescence of the ethynyl radical was observed in the (A)
   over tilde (2)Pi-(X) over tilde (2)Sigma(+) system. Excitation of
   several Rydberg states of acetylene over a large energy range between 9
   and 11.4 eV allowed us to observe for the first time the evolution of
   this continuum with increasing Rydberg excitation. Intensity
   calculations based on accurate ab initio potential energy surfaces of
   C2H were performed by using a one-dimensional model accounting for the
   large-amplitude motion of the H atom around the C-C bond and for the
   overall rotation of the radical. These calculations successfully
   reproduce the observed visible continuum (maximum at 500 nm and blue
   side cutoff at 400 nm) and bring new information on the distribution of
   the internal energy deposited in the fragment. For most excited Rydberg
   states, predissociation occurs in a rather low time scale, leaving the
   C2H fragment in the (A) over tilde state, vibrationally hot, mostly
   with significant excitation in the bending mode around the
   isomerization barrier. (C) 2002 American Institute of Physics.
C1 Univ Paris 11, CNRS, Photophys Mol Lab, F-91405 Orsay, France.
   Univ Fed Fluminense, Inst Fis, BR-24020 Niteroi, RJ, Brazil.
   Univ Bordeaux 1, Lab Physicochim Mol, CNRS, UMR 5803, F-33405 Talence, France.
RP Boye, S, Univ Paris 11, CNRS, Photophys Mol Lab, Batiment 210, F-91405
   Orsay, France.
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NR 50
TC 6
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD MAY 22
PY 2002
VL 116
IS 20
BP 8843
EP 8855
PG 13
SC Physics, Atomic, Molecular & Chemical
GA 549EK
UT ISI:000175431400020
ER

PT J
AU Tostes, JGR
   Dias, JF
   Seidl, PR
   Carneiro, JWD
   Taft, C
TI Steric and electronic contributions to conformational effects on
   chemical shifts of acyclic alcohols
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE DFT/GIAO calculations; chemical shifts; hyperconjugation; acyclic
   alcohols; electronic effects; steric effects
ID AB-INITIO IGLO; C-13; EXCHANGE; CARBON
AB Our calculations on bi- and polycyclic alcohols reveal that the
   Mulliken charge distribution and chemical shift patterns due to
   hyperconjugation of lone pairs on oxygen with neighboring groups break
   down or are attenuated for certain spatial relationships of the
   hydroxyl group. Since in strained ring systems other effects on these
   parameters may be present, we applied a similar analysis to acyclic
   alcohols. Calculations at the B3LYP/6-31G* level on conformers of
   methanol, ethanol, 1- and 2-propanol, 2methyl- l-propanol,
   2-methyl-2-propanol, 2-butanol, 2-methyl-2-butanol, 1- 2- and
   3-pentanol and 2-methyl-3-pentanol, where hyperconjugation may be
   present, reveal steric effects as modifiers of hyperconjugative
   patterns affecting carbon-13 chemical shifts in such alcohols. Contrary
   to what is observed in bi- and policyclic systems, where electrostatic
   effects interfere with effects due to hyperconjugation, these steric
   effects may be the main cause for the attenuation of deshielding of
   nuclei that are subject to hyperconjugation. Electrostatic effects are
   also present but they do not interfere with hyperconjugation by lone
   pairs. Conformational effects fall off sharply after the third carbon
   in the chain. (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Univ Estadual Norte Fluminense, Ctr Ciencias & Tecnol, Lab Ciencias Quim, BR-28015620 Campos dos Goytacazes, RJ, Brazil.
   Inst Mil Engn, Dept Engn Quim, Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Escola Quim, Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Dept Quim Geral & Inorgan, Niteroi, RJ, Brazil.
   Ctr Brasileiro Pesquisas Fis, Rio De Janeiro, Brazil.
RP Tostes, JGR, Univ Estadual Norte Fluminense, Ctr Ciencias & Tecnol, Lab
   Ciencias Quim, Av Alberto Lamego 2000, BR-28015620 Campos dos
   Goytacazes, RJ, Brazil.
CR BARFIELD M, 1995, J AM CHEM SOC, V117, P2862
   BARFIELD M, 1998, MAGN RESON CHEM, V36, S93
   BECKE AD, 1988, PHYS REV A, V38, P3098
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NR 18
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAR 29
PY 2002
VL 580
SI Sp. Iss. SI
BP 75
EP 83
PG 9
SC Chemistry, Physical
GA 546DG
UT ISI:000175256200010
ER

PT J
AU Bauerfeldt, GF
   de Albuquerque, LMM
   Arbilla, G
   da Silva, EC
TI Unimolecular reactions on formaldehyde S0PES
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE H2CO; unimolecular reactions; direct dynamics; variational RRKM rate
   coefficients
ID TRANSITION-STATE; RATE CONSTANTS; PHOTOFRAGMENTATION DYNAMICS; INFRARED
   INTENSITIES; PHOTO-DISSOCIATION; AB-INITIO; ENERGY; DISTRIBUTIONS;
   SURFACE; H2CO
AB The competitive unimolecular reactions of formaldehyde., H2CO --> H-2 +
   CO; H2CO --> trans-HCOH and H2CO --> H + HCO, were comparatively
   studied under the direct dynamics formalism, using Density functional
   and ab initio levels of theory. In addition, the geometric
   isomerization trans-HCOH --> cis-HCOH was evaluated. Calculated
   reaction path properties were used in the determination of
   Rice-Ramsperger-Kassel-Marcus microcanonical rate coefficients. The
   reaction dynamics was evaluated for each individual process based on
   the nuclear displacements in the reaction path and normal coordinate
   analysis. Our results found are in very good agreement with
   experimental barrier heights and quantum yields trends. (C) 2002
   Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim, Ctr Tecnol, BR-21949900 Rio De Janeiro, Brazil.
RP Bauerfeldt, GF, Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim,
   Ctr Tecnol, Bloco A Cidade Univ, BR-21949900 Rio De Janeiro, Brazil.
CR BAKER J, 1986, J COMPUT CHEM, V7, P385
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   ZHU L, GEN RRKM PROGRAM
NR 54
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAR 29
PY 2002
VL 580
SI Sp. Iss. SI
BP 147
EP 160
PG 14
SC Chemistry, Physical
GA 546DG
UT ISI:000175256200018
ER

PT J
AU Roberto-Neto, O
   Machado, FBC
TI An ab initio study of the Cl(P-2)+C2H6 -> C2H5+HCl abstraction reaction
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE abstraction reaction; ethane; chlorine; ab initio; rate constants
ID DIRECT DYNAMICS CALCULATIONS; TRANSITION-STATE THEORY; HYDROGEN
   ABSTRACTION; PERTURBATION-THEORY; CHLORINE ATOMS; REACTION-RATES; C2H5
   RADICALS; ETHANE; KINETICS; PROPANE
AB Electronic energies, geometries, and harmonic vibration frequencies for
   the reactants, products, and transition state for the Cl(P-3) + C2H6
   --> C2H5 + HCl abstraction reaction were evaluated at the HF and MP2
   levels using several correlation consistent polarized-valence basis
   sets. Single-point calculations at PMP2, MP4, QCISD(T), and CCSD(T)
   levels were also carried out. The values of the forward activation
   energies obtained at the MP4/cc-pVTZ, QCISD(T)/cc-pVTZ, and
   CCSD(T)/cc-pVTZ levels using the MP2/cc-pVTZ structures are equal to
   -0.1, -0.4, and -0.3 kcal/mol, respectively. The experimental value is
   equal to 0.3 +/- 0.2 kcal/mol. We found that the MP2/aug-cc-pVTZ
   adiabatic vibration energy for the reaction (-2.4 kcal/mol) agrees well
   with the experimental value -(2.2-2.6) kcal/mol. Rate constants
   calculated with the zeroth-order interpolated variational transition
   state (IVTST-0) method are in good agreement with experiment. In
   general, the theoretical rate constants differ from experiment by, at
   most, a factor of 2.6. (C) 2002 Elsevier Science B.V. All rights
   reserved.
C1 Ctr Tecn Aeroesp, Inst Estudos Avancados, BR-12228840 Sao Jose Dos Campos, SP, Brazil.
   Ctr Aerosp Technol, Inst Tecnol Aeronaut, Dept Quim, BR-12228900 Sao Jose Dos Campos, SP, Brazil.
RP Roberto-Neto, O, Ctr Tecn Aeroesp, Inst Estudos Avancados, BR-12228840
   Sao Jose Dos Campos, SP, Brazil.
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NR 40
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAR 29
PY 2002
VL 580
SI Sp. Iss. SI
BP 161
EP 170
PG 10
SC Chemistry, Physical
GA 546DG
UT ISI:000175256200019
ER

PT J
AU Goncalves, PFB
   Stassen, H
TI New approach to free energy of solvation applying continuum models to
   molecular dynamics simulation
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE solvation free energy; molecular dynamics; continuum model; aqueous
   solutions
ID AB-INITIO; AQUEOUS-SOLUTION; SOLVENT; WATER; OPTIMIZATION; PARAMETERS;
   HYDRATION; PROFILES; DOCKING; RADII
AB A new approach to the calculation of the free energy of solvation from
   trajectories obtained by molecular dynamics simulation is presented.
   The free energy of solvation is computed as the sum of three
   contributions originated at the cavitation of the solute by the
   solvent, the solute-solvent nonpolax (repulsion and dispersion)
   interactions, and the electrostatic solvation of the solute. The
   electrostatic term is calculated based on ideas developed for the
   broadly used continuum models, the cavitational contribution from the
   excluded volume by the Claverie-Pierotti model, and the Van der Waals
   term directly from the molecular dynamics simulation. The proposed
   model is tested for diluted aqueous solutions of simple molecules
   containing a variety of chemically important functions: methanol,
   methylamine. water, methanethiol, and dichloromethane. These solutions
   were treated by molecular dynamics simulations using SPC/E water and
   the OPLS force field for the organic molecules. Obtained free energies
   of solvation a-re in very good agreement with experimental data.
C1 Univ Fed Rio Grande Sul, Inst Quim, Grp Quim Teor, BR-91540000 Porto Alegre, RS, Brazil.
RP Stassen, H, Univ Fed Rio Grande Sul, Inst Quim, Grp Quim Teor,
   BR-91540000 Porto Alegre, RS, Brazil.
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NR 51
TC 6
PU JOHN WILEY & SONS INC
PI HOBOKEN
PA 111 RIVER ST, HOBOKEN, NJ 07030 USA
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD MAY
PY 2002
VL 23
IS 7
BP 706
EP 714
PG 9
SC Chemistry, Multidisciplinary
GA 546VH
UT ISI:000175295300003
ER

PT J
AU Pliego, JR
   Riveros, JM
TI Parametrization of the PCM model for calculating solvation free energy
   of anions in dimethyl sulfoxide solutions
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID POLARIZABLE CONTINUUM MODEL; AB-INITIO; AQUEOUS SOLVATION;
   TRANSITION-STATES; ATOMIC RADII; SOLVENT; IONS; MOLECULES; WATER;
   OPTIMIZATION
AB We report the first parametrization of a continuum model for the
   solvation of anions in DMSO solution. The present parameters used in
   conjunction with the PCM method predict the solvation free energy of 21
   anions in DMSO solution with an average error of -1.2 kcal mol(-1), and
   a S.D. for the average error of only 2.2 kcal mol(-1). This low, value
   of the S.D. shows that the present parametrization is capable of
   predicting accurate differences of the solvation free energies in DMSO
   solution and is reliable for modeling liquid phase chemical reactions.
   (C) 2002 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, SP, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, SP, Brazil.
CR CANCES E, 1997, J CHEM PHYS, V107, P3032
   CHAMBERS CC, 1996, J PHYS CHEM-US, V100, P16385
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   FORESMAN JB, 1996, J PHYS CHEM-US, V100, P16098
   GIESEN DJ, 1997, THEOR CHEM ACC, V98, P85
   GONCALVES PFB, 1999, CHEM PHYS LETT, V304, P438
   GONZALEZ C, 1998, J PHYS CHEM A, V102, P2732
   HUMMER G, 1998, J PHYS CHEM A, V102, P7885
   LI JB, 1998, CHEM PHYS LETT, V288, P293
   LI JB, 1999, THEOR CHEM ACC, V103, P9
   LUQUE FJ, 1996, J COMPUT CHEM, V17, P806
   LUQUE FJ, 1996, J PHYS CHEM-US, V100, P4269
   MASSOVA I, 1999, J PHYS CHEM B, V103, P8628
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   PLIEGO JR, 2001, J PHYS CHEM A, V105, P7241
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   WIBERG KB, 1995, J AM CHEM SOC, V117, P4261
   WIBERG KB, 1995, J PHYS CHEM-US, V99, P9072
NR 34
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD APR 8
PY 2002
VL 355
IS 5-6
BP 543
EP 546
PG 4
SC Physics, Atomic, Molecular & Chemical
GA 547AT
UT ISI:000175310400023
ER

PT J
AU Tormena, CF
   Rittner, R
   Abraham, RJ
TI An NMR, IR and theoretical investigation of the methyl effect on
   conformational isomerism in 3-fluoro-3-methyl-2-butanone and
   1-fluoro-3,3-dimethyl-2-butanone
SO JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
LA English
DT Article
DE conformational analysis; fluoroketones; NMR; solvation; theoretical
   calculations
ID VIBRATIONAL ASSIGNMENT; ABINITIO CALCULATIONS; INTERNAL-ROTATION;
   SOLVATION; FLUOROACETONE; BARRIERS
AB The solvent dependence of the H-1 and C-13 NMR spectra of
   3-fluoro-3-methyl-2-butanone (FMB) and 1-fluoro-3,3-dimethyl-2-butanone
   (FDMB) was examined and the (4)J(HF), (1)J(CF) and (2)J(CF) couplings
   are reported. Density functional theory (DFT) at the B3LYP/6-311 ++
   G(2df,2p) level with ZPE (zero point energy) corrections was used to
   obtain the conformer geometries. In both FMB and FDMB, the DFT method
   gave only two minima for cis (F-C-C=O, 0degrees) and trans (F-C-C=O,
   180degrees) rotamers. Assuming the cis and trans forms, the observed
   couplings in FM B when analysed by solvation theory gave the energy
   difference E-cis-E-trans of 3.80 kcal mol(-1) (1 kcal = 4.184 kJ) in
   the vapour phase (cf. the DFT value of 3.21 kcal mol(-1)), decreasing
   to 2.6 kcal mol(-1) in CCl4 and to 0.27 kcal mol(-1) in DMSO. In FDMB
   the observed couplings when analysed similarly by solvation theory gave
   E-cis - E-trans = 1.80 kcal mol(-1) in the vapour phase, decreasing to
   0.47 kcal mol(-1) in CCl4 and to - 1.25 kcal mol(-1) in DMSO. The
   introduction of a methyl group geminal to the fluorine atom shifts the
   conformational equilibrium towards the trans rotamer, in contrast to no
   significant effect when the methyl group is introduced at the
   alpha-carbon further from the fluorine atom. Copyright (C) 2002 John
   Wiley Sons, Ltd.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
RP Rittner, R, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083970 Campinas, SP, Brazil.
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NR 20
TC 7
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND
SN 0894-3230
J9 J PHYS ORG CHEM
JI J. Phys. Org. Chem.
PD APR
PY 2002
VL 15
IS 4
BP 211
EP 217
PG 7
SC Chemistry, Organic; Chemistry, Physical
GA 544AB
UT ISI:000175135100004
ER

PT J
AU Antonelli, A
   Justo, JF
   Fazzio, A
TI Interaction of As impurities with 30 degrees partial dislocations in
   Si: An ab initio investigation
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID EXTENDED DEFECTS; SILICON; SEGREGATION; PSEUDOPOTENTIALS
AB We investigated through ab initio total energy calculations the
   interaction of arsenic impurities with the core of a 30degrees partial
   dislocation in silicon. It was found that when an arsenic atom sits in
   a crystalline position near the dislocation core, there is charge
   transfer from the arsenic towards the dislocation core. As a result,
   the arsenic becomes positively charged and the core negatively charged.
   The results indicate that the structural changes around the impurity
   are very small in both environments, namely, the crystal and the
   dislocation core. In this scenario, the interaction between arsenic and
   the core is essentially electrostatic, which eventually leads to
   arsenic segregation. The segregation energy was found to be as large as
   0.5 eV/atom. Additionally, it was found that arsenic pairing inside the
   core is not energetically favorable. (C) 2002 American Institute of
   Physics.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Sao Paulo, Escola Politecn, PSI, BR-05424970 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Antonelli, A, Univ Estadual Campinas, Inst Fis Gleb Wataghin, CP 6165,
   BR-13083970 Campinas, SP, Brazil.
CR ALEXANDER H, 1986, DISLOCATIONS SOLIDS, V7, P115
   ALEXANDER H, 1989, I PHYS C SER, V104, P281
   BACHELET GB, 1982, PHYS REV B, V26, P4199
   BAZANT MZ, 1997, PHYS REV B, V56, P8542
   BERGHOLZ W, 2000, PHYS STATUS SOLIDI B, V222, P5
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BULATOV VV, 2001, PHILOS MAG A, V81, P1257
   EBERT P, 2001, APPL PHYS LETT, V78, P480
   HIRTH JP, 1982, THEORY DISLOCATIONS
   JUSTO JF, 1998, PHYS REV B, V58, P2539
   JUSTO JF, 1999, PHYSICA B, V274, P473
   JUSTO JF, 2000, PHYS REV LETT, V84, P2172
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   KAPLAN T, 2000, PHYS REV B, V61, P1674
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NR 21
TC 4
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD MAY 1
PY 2002
VL 91
IS 9
BP 5892
EP 5895
PG 4
SC Physics, Applied
GA 542WR
UT ISI:000175069000053
ER

PT J
AU Pliego, JR
   Riveros, JM
TI A theoretical analysis of the free-energy profile of the different
   pathways in the alkaline hydrolysis of methyl formate in aqueous
   solution
SO CHEMISTRY-A EUROPEAN JOURNAL
LA English
DT Article
DE ab initio calculations; computer chemistry; ester hydrolysis;
   free-energy profile; nucleophilic addition
ID NUCLEOPHILIC DISPLACEMENT-REACTIONS; CARBOXYLIC-ACID ESTERS; GAS-PHASE
   REACTIONS; REACTION FIELD CALCULATIONS; DISCRETE-CONTINUUM MODELS;
   ANION CLUSTERS X-(H2O)N; X = OH; AB-INITIO; MOLECULAR-ENERGIES;
   GAUSSIAN-1 THEORY
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
CR ACHATZ U, 1998, J AM CHEM SOC, V120, P1876
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   BAKOWIES D, 1999, J AM CHEM SOC, V121, P5712
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   ZHAN CG, 2001, J PHYS CHEM A, V105, P1296
NR 71
TC 13
PU WILEY-V C H VERLAG GMBH
PI WEINHEIM
PA PO BOX 10 11 61, D-69451 WEINHEIM, GERMANY
SN 0947-6539
J9 CHEM-EUR J
JI Chem.-Eur. J.
PD APR 15
PY 2002
VL 8
IS 8
BP 1945
EP 1953
PG 9
SC Chemistry, Multidisciplinary
GA 543CQ
UT ISI:000175084000020
ER

PT J
AU de Andrade, J
   Boes, ES
   Stassen, H
TI A force field for liquid state simulations on room temperature molten
   salts: 1-ethyl-3-methylimidazolium tetrachloroaluminate
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Letter
ID IONIC LIQUIDS; SOLVENTS
AB A classical force field for the room temperature molten salt
   1-ethyl-3-methylimidazolium tetrachloroaluminate has been developed and
   successfully tested against experimental data (neutron diffraction,
   diffusion constants) by molecular dynamics computer simulation
   corresponding to a temperature of 298 K. The force field parameters for
   the cation have been derived from the AMBER description for the
   protonated amino acid histidine, whereas the AlCl4- parameters have
   been achieved by parametrization of intramolecular terms with van der
   Waals parameters taken from the Literature. All atomic partial charges
   have been obtained from ab initio calculations using the RESP
   methodology.
C1 Univ Fed Rio Grande Sul, Grp Quim Teor, Inst Quim, BR-91540000 Porto Alegre, RS, Brazil.
RP Stassen, H, Univ Fed Rio Grande Sul, Grp Quim Teor, Inst Quim,
   BR-91540000 Porto Alegre, RS, Brazil.
CR AKDENIZ Z, 1999, Z NATURFORSCH A, V54, P180
   ALLEN MP, 1987, COMPUTER SIMULATION
   CARPER WR, 1996, J PHYS CHEM-US, V100, P4724
   CASE DA, 1999, AMBER 6
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   DUDEK MJ, 1998, J COMPUT CHEM, V19, P548
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   FANNIN AA, 1984, J PHYS CHEM-US, V88, P2614
   FOX T, 1998, J PHYS CHEM B, V102, P8070
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   LARIVE CK, 1995, J PHYS CHEM-US, V99, P12400
   LYUBARTSEV AP, 2000, COMPUT PHYS COMMUN, V128, P565
   MAYO SL, 1990, J PHYS CHEM-US, V94, P8897
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   WELTON T, 1999, CHEM REV, V99, P2071
NR 24
TC 28
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1520-6106
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD APR 11
PY 2002
VL 106
IS 14
BP 3546
EP 3548
PG 3
SC Chemistry, Physical
GA 542AW
UT ISI:000175022100007
ER

PT J
AU Alves, CN
   da Silva, ABF
   Marti, S
   Moliner, V
   Oliva, M
   Andres, J
   Domingo, LR
TI An AMI theoretical study on the effect of Zn2+ Lewis acid catalysis on
   the mechanism of the cycloaddition between
   3-phenyl-1-(2-pyridyl)-2-propen-1-one and cyclopentadiene
SO TETRAHEDRON
LA English
DT Article
DE AM1 theoretical study; Diels-Alder reaction; Zn2+ Lewis acid catalyst
ID DIELS-ALDER REACTION; AQUEOUS-MEDIA; TRANSITION STRUCTURES; AB-INITIO;
   ACCELERATION; WATER; SELECTIVITY; ALGORITHM; STATES; STEP
AB The mechanism of the Diels-Alder reaction between
   3-phenyl-1-(2-pyridyl)-2-propen-1-one and cyclopentadiene has been
   investigated with the AM1 semiempirical method. Stationary points for
   two reactive channels, endo-cis and exo-cis, have been characterized.
   The role of the Lewis acid catalyst has been modeled taking into
   account the formation of a complex between Zn2+ and the carbonyl oxygen
   atom and the pyridyl nitrogen atom of the
   3-phenyl-1-(2-pyiidyl)-2-propen-1-one system with and without the
   presence of two molecules of water around the cation. The mechanism of
   the uncatalyzed reaction corresponds to a concerted process, but in the
   presence of Lewis acid catalyst the mechanism changes and the reaction
   takes place through a stepwise mechanism. A first step involves the
   nucleophilic attack of the cyclopentadiene in the double bond of the
   dienophile which produces an intermediate. A second step involves the
   closure of the intermediate yielding the corresponding final
   cycloadduct. The inclusion of the Zn2+ catalyst drastically decreases
   the energy barrier associated with the carbon-carbon bond formation of
   the first step in comparison to the concerted process. (C) 2002
   Elsevier Science Ltd. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Naturais, Dept Quim, BR-66075110 Belem, Para, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Valencia, Dept Quim Organ, Valencia, Spain.
RP da Silva, ABF, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis
   Mol, CP 780, BR-13560970 Sao Carlos, SP, Brazil.
EM alberico@iqsc.sc.usp.br
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   KAGAN HB, 1992, CHEM REV, V92, P1007
   KUMAR A, 2001, CHEM REV, V101, P1
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NR 38
TC 6
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0040-4020
J9 TETRAHEDRON
JI Tetrahedron
PD MAR 25
PY 2002
VL 58
IS 13
BP 2695
EP 2700
PG 6
SC Chemistry, Organic
GA 538MV
UT ISI:000174820500024
ER

PT J
AU Fontoura, LAM
   Rigotti, IJD
   Correia, CRD
TI Experimental and theoretical studies on the rotational barrier of
   1-acyl- and 1-alkoxycarbonyl-2-pyrrolines
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE dynamic NMR; computational methods; rotational barrier; enamides and
   enecarbamates
ID INTERNAL-ROTATION; AB-INITIO; BOND; AMIDES; N,N-DIMETHYLFORMAMIDE;
   ISOMERIZATION; RESONANCE; FORMAMIDE; EFFICIENT; ACIDS
AB The conformational equilibrium as a result of the N-carbonyl bond
   rotation of several N-acyl- and N-alkoxycarbonyl-2-pyrrolines have been
   studied. The equilibrium constants and the rotational barriers were
   determined by theoretical methods (AM1, PM3, HF/3-21G( * ) and
   HF/6-31G*) and, experimentally, by dynamic NMR (coalescence
   temperature). The measured rotational barriers for enecarbamates were
   found to be similar to 16 kcal mol(-1) in C6D6 or C6D5NO2, whereas
   slightly higher values were found for enamides in C6D5NO2,. Contrary to
   enamides, the rotational barriers for enecarbamates were not affected
   by changes in the polarity of the solvent employed. (C) 2002 Elsevier
   Science B.V. All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, Dept Quim, BR-13083970 Campinas, SP, Brazil.
   CIENTEC R, Fundacao Ciencia & Tecnol, Dept Quim, BR-90010460 Porto Alegre, Brazil.
RP Correia, CRD, Univ Estadual Campinas, Inst Quim, Dept Quim, Caixa
   Postal 6157, BR-13083970 Campinas, SP, Brazil.
CR *WAV, 1998, PC SPART PLUS 1 5
   ABRAHAM RJ, 1988, INTRO NMR SPECTROSCO
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   COSTENARO ER, 2001, TETRAHEDRON LETT, V42, P1599
   COX C, 1998, J ORG CHEM, V63, P2426
   DIETER RK, 1996, J ORG CHEM, V61, P4180
   DUFFY EM, 1992, J AM CHEM SOC, V114, P7535
   ELIEL E, 1994, STEREOCHEMISTRY ORGA
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   OLIVEIRA DF, 1999, J ORG CHEM, V64, P6646
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   VASSILEV NG, 1999, J MOL STRUCT, V484, P39
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NR 33
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD MAY 30
PY 2002
VL 609
IS 1-3
BP 73
EP 81
PG 9
SC Chemistry, Physical
GA 538ZV
UT ISI:000174845700010
ER

PT J
AU Terrazos, LA
   Petrilli, HM
   Marszalek, M
   Saitovitch, H
   Silva, PRJ
   Blaha, P
   Schwarz, K
TI Electric field gradients at Ta in Zr and Hf inter-metallic compounds
SO SOLID STATE COMMUNICATIONS
LA English
DT Article
DE metals; electronic band structure; NQR; electric field gradients
ID PERTURBED-ANGULAR-CORRELATION; TA-181
AB Here we calculate the electric field gradient (EFG) at the nucleus of
   the substitutional Ta impurity site in Zr2T and Hf2T (T = Cu, Ag, Au,
   and Pd) C11(b), inter-metallic compounds. We use the ab initio FP-LAPW
   method as embodied in the Wien97 code in a super-cell approach and
   include lattice relaxations around the impurity. Our results are
   compared with EFG values inferred from measurements of the quadrupole
   coupling constants at the Ta-111 probe in these compounds performed
   with the time differential perturbed angular correlation (TDPAC)
   technique. We also performed EFG calculations for the pure
   inter-metallic compounds. Through the comparison of theoretical and
   experimental EFGs in these cases, we elucidate the role played by the
   Ta probe in the TDPAC measurements of Hf and Zr compounds. Our results
   show that, although the EFGs at the Hf site are very similar to the
   EFGs at the Ta impurity, there is no direct correlation between the Zr
   and Ta EFGs. (C) 2002 Elsevier Science Ltd. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   H Niewodniczanski Inst Nucl Phys, PL-31342 Krakow, Poland.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Vienna Tech Univ, Inst Mat Chem, A-1060 Vienna, Austria.
RP Petrilli, HM, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR AKAI H, 1990, PROG THEOR PHYS SUPP, P11
   BLAHA P, 1990, COMPUT PHYS COMMUN, V59, P399
   BLAHA P, 1999, WIEN97 CODE
   BUTZ T, 1983, PHYS LETT A, V97, P217
   DAMONTE LC, 1989, PHYS REV B, V39, P12492
   DEMELLO LA, 1993, J PHYS-CONDENS MAT, V5, P8935
   FEIOCK FD, 1969, PHYS REV, V187, P39
   MARSZALEK M, 1994, II28 INP
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   PERDEW JP, 1992, PHYS REV B, V15, P13214
   PETRILLI HM, 1991, PHYS REV B, V44, P10493
   PETRILLI HM, 1998, PHYS REV B, V57, P11190
   VILLARS P, 1991, PEARSONS HDB CRYSTAL
   WODNIECKA B, 1995, J ALLOY COMPD, V219, P132
   WODNIECKI P, 1996, Z NATURFORSCH A, V51, S437
NR 15
TC 7
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0038-1098
J9 SOLID STATE COMMUN
JI Solid State Commun.
PY 2002
VL 121
IS 9-10
BP 525
EP 529
PG 5
SC Physics, Condensed Matter
GA 537HQ
UT ISI:000174753200016
ER

PT J
AU Capelle, K
   Vignale, G
TI Nonuniqueness and derivative discontinuities in density-functional
   theories for current-carrying and superconducting systems
SO PHYSICAL REVIEW B
LA English
DT Article
ID STRONG MAGNETIC-FIELDS
AB Current-carrying and superconducting systems can be treated within
   density-functional theory if suitable additional density variables (the
   current density and the superconducting order parameter, respectively!
   are included in the density-functional formalism. Here we show that the
   corresponding conjugate potentials (vector and pair potentials,
   respectively) are not uniquely determined by the densities. The
   Hohenberg-Kohn theorem of these generalized density-functional theories
   is thus weaker than the original one. We give explicit examples and
   explore some consequences.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA.
RP Capelle, K, Univ Sao Paulo, Inst Quim Sao Carlos, Caixa Postal 780,
   BR-13560970 Sao Carlos, SP, Brazil.
CR ARGAMAN N, 2000, AM J PHYS, V68, P69
   CAPELLE K, 2001, PHYS REV LETT, V86, P5546
   ESCHRIG H, 2001, SOLID STATE COMMUN, V118, P123
   HOHENBERG P, 1964, PHYS REV, V136, B864
   KOHN W, 1965, PHYS REV, V140, A1133
   KOHN W, 1989, J PHYS-PARIS, V50, P2601
   KOHN W, 1999, REV MOD PHYS, V71, P1253
   KURTH S, 1999, PHYS REV LETT, V83, P2628
   LEE AM, 1999, PHYS REV A, V59, P209
   OLIVEIRA LN, 1988, PHYS REV LETT, V60, P2430
   PERDEW JP, 1982, PHYS REV LETT, V49, P1691
   PERDEW JP, 1983, PHYS REV LETT, V51, P1884
   TEMMERMAN WM, 1996, PHYS REV LETT, V76, P307
   TINKHAMM, 1996, INTRO SUPERCONDUCTIV
   VIGNALE G, 1987, PHYS REV LETT, V59, P2360
   VIGNALE G, 1988, PHYS REV B, V37, P10685
   VONBARTH U, 1972, J PHYS C SOLID STATE, V5, P1629
NR 17
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD MAR 15
PY 2002
VL 65
IS 11
AR 113106
DI ARTN 113106
PG 4
SC Physics, Condensed Matter
GA 533UH
UT ISI:000174548400006
ER

PT J
AU Tormena, CF
   Amadeu, NS
   Ritter, R
   Abraham, RJ
TI Conformational analysis in N-methylfluoroamides. A theoretical, NMR and
   IR investigation
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID SOLVATION; ISOMERISM
AB Theoretical calculations plus the solvent dependence of the H-1, C-13
   NMR and IR spectra were used to determine the conformational
   equilibrium in N-methyl-2-fluoroacetamide (NMFA) and
   N-methyl-2-fluoropropionamide (NMFP). Ab initio calculations were used
   to identify the stable rotamers and obtain their geometries and the
   application of solvation theory on the (1)J(CF) coupling constant gave
   the conformer populations in the solvents studied. In NMFA ab initio
   calculations at the CBS-Q level yielded only two stable rotamers, the
   cis and trans, with DeltaE(cis-trans) = 19.7 kJ mol(-1). The presence
   of two conformers was confirmed by the FTIR spectra. Assuming these
   forms, the observed couplings when analysed by solvation theory gave
   DeltaE = 21.3 kJ mol(-1) in the vapour phase, decreasing to 8.9 kJ
   mol(-1) in CDCl3 and to 0.8 kJ mol(-1) in DMSO. For NMFP the B3LYP
   calculations at the 6-311++g(2df,2p) level gave only the trans rotamer
   as stable, while the gauche form was a plateau in the potential energy
   surface. However the FTIR spectra clearly showed the presence of two
   conformers. A minimum for the gauche rotamer was only found when the
   SCRF (self consistent reaction field) routine was included in the
   theoretical calculations. The equilibrium in NMFP was therefore
   analysed by solvation theory in terms of the trans and gauche rotamers
   to give DeltaE(gauche-trans) = 15.9 kJ mol(-1) in the vapour phase,
   decreasing to 10.8 kJ mol(-1) in CCl4 and to 0.5 kJ mol(-1) in DMSO.
C1 Univ Estadual Campinas, Inst Quim, Phys Organ Chem Lab, BR-13083970 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
RP Abraham, RJ, Univ Estadual Campinas, Inst Quim, Phys Organ Chem Lab, CP
   6154, BR-13083970 Campinas, SP, Brazil.
CR ABRAHAM RJ, 1974, INTERNAL ROTATION MO, CH13
   ABRAHAM RJ, 1996, J CHEM SOC PERK  APR, P533
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   FRISCH MJ, 1998, GAUSSIAN98 REVISION
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NR 16
TC 10
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1472-779X
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2002
IS 4
BP 773
EP 778
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 533UQ
UT ISI:000174549100012
ER

PT J
AU Esteves, PM
   Ramirez-Solis, A
   Mota, CJA
TI The nature of superacid electrophilic species in HF/SbF5: A density
   functional theory study
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID HYDROGEN-DEUTERIUM EXCHANGE; PROTOLYSIS DEUTEROLYSIS; SINGLE BONDS;
   SYSTEM; ALKANES
AB A density functional theory study at the B3LYP/6-31++G** + RECP(Sb)
   level of the HF/SbF5 superacid system was carried out. The geometries
   of possible electrophilic species, such as H2F+.Sb2F11- and
   H3F2+.Sb2F11-, were calculated and correspond with available
   experimental results. Calculations of different equilibrium reactions
   involving HF and SbF5 allowed the relative concentration of the most
   energetically favorable species present in 1:1 HF/SbF5 solutions to be
   estimated. These species are H+.Sb2F11-, H2F+.Sb2F11-, H3F2+.Sb2F11-,
   and H4F3+-Sb2F11-, which correspond to 36.9, 16.8, 36.9, and 9.4%,
   respectively. Calculations of the acid strength of the electrophilic
   species were also performed and indicated that, for the same anion, the
   acid strength increases with the solvation degree. The entropic term
   also plays a significant role in proton-transfer reactions in superacid
   systems.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Dept Fis, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
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   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
   GILLESPIE RJ, 1966, J CHEM SOC A, P1170
   HOOGEVEEN H, 1968, RECL TRAV CHIM PAY B, V87, P1295
   HYMAN HH, 1961, J PHYS CHEM-US, V65, P123
   JOST R, 1988, REV CHEM INTERMED, V9, P171
   KIM D, 2000, J PHYS CHEM B, V104, P10074
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   OLAH GA, 1971, J AM CHEM SOC, V93, P1251
   OLAH GA, 1973, J AM CHEM SOC, V95, P4960
   OLAH GA, 1985, SUPERACIDS
   TOUITI D, 1986, J CHEM SOC P2, P1793
NR 20
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AM CHEM SOC
JI J. Am. Chem. Soc.
PD MAR 20
PY 2002
VL 124
IS 11
BP 2672
EP 2677
PG 6
SC Chemistry, Multidisciplinary
GA 531UM
UT ISI:000174435700058
ER

PT J
AU Erben, MF
   Della Vedova, CO
   Romano, RM
   Boese, R
   Oberhammer, H
   Willner, H
   Sala, O
TI Anomeric and mesomeric effects in methoxycarbonylsulfenyl chloride,
   CH3OC(O)SCl: An experimental and theoretical study
SO INORGANIC CHEMISTRY
LA English
DT Article
ID GAS-PHASE STRUCTURE; METHYL THIOLFLUOROFORMATE; CONFORMATIONAL
   PROPERTIES; MONOTHIOFORMIC ACID; SPECTRUM
AB The molecular structure and conformational properties of
   methoxycarbonylsulfenyl chloride, CH3OC(O)SCl, were determinated in the
   gas and solid phases by gas electron diffraction, low-temperature X-ray
   diffraction, and vibrational spectroscopy. Furthermore, quantum
   chemical calculations were performed. Experimental and theoretical
   methods result in structures with a planar C-O-C(O)-S-Cl skeleton. The
   electron diffraction intensities are reproduced best with a mixture of
   72(8)% syn and 28(8)% anti conformers (S-Cl bond
   synperiplanar/antiperiplanar with respect to C=O bond) and the O-CH3
   bond synperiplanar with respect to the C=O bond. The syn form is the
   preferred form and becomes the exclusive form in the crystalline solid
   at low temperature. This experimental result is reproduced very well by
   Hartree-Fock approximation and by density functional theory at
   different levels of theory but not by the MP2/6-31 1G* method, which
   overestimates the value of AGO between the syn and anti conformers. The
   results are discussed in terms of anomeric effects and a natural bond
   orbital (NBO) calculation, Photolysis of matrix-isolated CH3OC(O)SCl
   with broad-band UV-visible irradiation produces an interconversion of
   the conformers, and the concomitant decomposition leads to formation of
   OCS and CO molecules.
C1 Natl Univ La Plata, Fac Ciencias Exactas, Dept Quim, CEQUINOR,CONICET, RA-1900 La Plata, Argentina.
   Natl Univ La Plata, Lab Serv Ind & Sistema Cientif, RA-1900 La Plata, Argentina.
   Univ Essen Gesamthsch, Inst Anorgan Chem, D-45117 Essen, Germany.
   Univ Tubingen, Inst Phys & Theoret Chem, D-7400 Tubingen, Germany.
   Univ Duisburg Gesamthsch, D-47048 Duisburg, Germany.
   Univ Sao Paulo, Inst Quim, Sao Paulo, Brazil.
RP Della Vedova, CO, CC 962, RA-1900 La Plata, Argentina.
CR *SIEM, 1991, SHELTX PLUS VERS SGI
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   CAMINATI W, 1981, J MOL SPECTROSC, V90, P15
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   CAMINATI W, 1981, J MOL SPECTROSC, V90, P315
   CROWDER GA, 1973, APPL SPECTROSC, V27, P440
   DELLAVEDOVA CO, 1989, J RAMAN SPECTROSC, V20, P483
   DELLAVEDOVA CO, 1991, J RAMAN SPECTROSC, V22, P291
   DELLAVEDOVA CO, 1993, INORG CHEM, V32, P948
   FRISCH MJ, 1998, GAUSSIAN 98
   GOBBATO KI, 1996, INORG CHEM, V35, P6152
   HAMILTON WC, 1965, ACTA CRYSTALLOGR, V18, P502
   HEDBERG L, 1993, J MOL SPECTROSC, V160, P117
   HOCKING WH, 1977, Z NATURFORSCH A, V32, P1108
   KIRBY AJ, 1983, ANOMERIC EFFECT RELA
   LARSON JR, 1978, J AM CHEM SOC, V100, P5713
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   MACK HG, 1992, J MOL STRUCT, V265, P347
   MACK HG, 1992, J PHYS CHEM-US, V96, P9215
   NOE EA, 1977, J AM CHEM SOC, V99, P2803
   OBERHAMMER H, 1976, MOL STRUCTURES DIFFR, V4, P24
   OBERHAMMER H, 1981, J MOL STRUCT, V70, P273
   ROMANO RM, UNPUB
   ROMANO RM, 2001, J AM CHEM SOC, V123, P12623
   ROMANO RM, 2001, J AM CHEM SOC, V123, P5794
   WILLNER H, 1984, Z NATURFORSCH B, V39, P314
NR 27
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0020-1669
J9 INORG CHEM
JI Inorg. Chem.
PD MAR 11
PY 2002
VL 41
IS 5
BP 1064
EP 1071
PG 8
SC Chemistry, Inorganic & Nuclear
GA 528TM
UT ISI:000174259300009
ER

PT J
AU Okulik, NB
   Sosa, LG
   Esteves, PM
   Mota, CJA
   Jubert, AH
   Peruchena, NM
TI Ab initio topological analysis of the electronic density in n-butonium
   cations and their van der Waals complexes
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID POTENTIAL-ENERGY SURFACE; ISOBUTONIUM CATIONS; CH5+
AB In this work, the topology of the ab initio electronic density charge,
   using the theory of atoms in molecules (AIM). developed by Bader, is
   studied for the n-C4H11 species, the protonated n-butane. The
   electronic delocalization that operates through the sigma bonds in
   saturated molecules and specifically in protonated alkanes is studied
   by means of analysis of the charge density and the bond critical
   points. This analysis is used in order to establish a relationship
   among the parameters that determine the stability order found for the
   different species and relate them with the carbonium ions structure.
   Comparing these results with the i-C4H11 allow us to study the nature
   of the 3c-2e bonds in alkanes in greater detail, permitting the
   description on the a basicity and reactivity scales in terms of
   structural parameters of the carbonium ions.
C1 UNNE, Fac Agroind, RA-3700 Peia R Saenz Pena, Chaco, Argentina.
   UNNE, Fac Ciencias Exactas Nat & Agrim, Dept Quim, Area Quim Fis, RA-3400 Corrientes, Argentina.
   Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   UNLP, Fac Ciencias Exactas, Ctr Quim Inorgan, CEQUINOR,CONICET, RA-1900 La Plata, Argentina.
RP Okulik, NB, UNNE, Fac Agroind, Cte Fernandez 755, RA-3700 Peia R Saenz
   Pena, Chaco, Argentina.
CR BADER RFW, 1990, ATOMS MOL QUANTUM TH
   CARNEIRO JWD, 1994, J AM CHEM SOC, V116, P3483
   ESTEVES PM, 1998, J AM CHEM SOC, V120, P3213
   ESTEVES PM, 1998, TOP CATAL, V6, P163
   ESTEVES PM, 1999, J AM CHEM SOC, V121, P7345
   ESTEVES PM, 2000, J PHYS CHEM A, V104, P6233
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   HIRAOKA K, 1993, CHEM PHYS LETT, V207, P178
   HOGEVEEN H, 1969, RECL TRAV CHIM PAY B, V88, P371
   KLIEGERKONIG W, 1982, J COMPUT CHEM, V3, P317
   KOCK W, 1989, J AM CHEM SOC, V11, P3479
   MARX D, 1995, NATURE, V375, P216
   MOTA CJA, 1997, J AM CHEM SOC, V119, P5193
   OKULIK N, 1999, J PHYS CHEM A, V103, P8491
   OKULIK N, 2000, J PHYS CHEM A, V104, P7586
   OLAH GA, 1968, J AM CHEM SOC, V90, P2726
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NR 26
TC 9
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD FEB 28
PY 2002
VL 106
IS 8
BP 1584
EP 1595
PG 12
SC Chemistry, Physical
GA 527ME
UT ISI:000174189200014
ER

PT J
AU Legoas, SB
   Galvao, DS
   Rodrigues, V
   Ugarte, D
TI Origin of anomalously long interatomic distances in suspended gold
   chains
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID TRANSMISSION ELECTRON-MICROSCOPY; QUANTIZED CONDUCTANCE; POINT-CONTACT;
   MECHANISMS; MOLECULES; NANOWIRES; SIGNATURE; CLUSTERS; SURFACES; ATOMS
AB The discovery of long bonds in gold atom chains has represented a
   challenge for physical interpretation. In fact, interatomic distances
   frequently attain 3.0-3.6 Angstrom values, and distances as large as
   5.0 Angstrom may be occasionally observed. Here we studied gold chains
   by transmission electron microscopy and performed theoretical
   calculations using cluster ab initio density functional formalism. We
   show that the insertion of two carbon atoms is required to account for
   the longest bonds, while distances above 3 Angstrom may be due to a
   mixture of clean and one C atom contaminated bonds.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Lab Nacl Luz Sincrotron, BR-13084971 Campinas, SP, Brazil.
RP Legoas, SB, Univ Estadual Campinas, Inst Fis Gleb Wataghin, CP 6165,
   BR-13083970 Campinas, SP, Brazil.
CR *WAV INC, TIT
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NR 39
TC 30
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD FEB 18
PY 2002
VL 88
IS 7
AR 076105
DI ARTN 076105
PG 4
SC Physics, Multidisciplinary
GA 524PB
UT ISI:000174021100051
ER

PT J
AU Biswas, PK
TI Effect of H- ion formation on positronium-hydrogen elastic scattering
SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
LA English
DT Article
ID CLOSE-COUPLING APPROXIMATION; STATIC-EXCHANGE MODEL; ATOM SCATTERING;
   ELECTRON-EXCHANGE; CHANNEL FRAMEWORK; HELIUM; MOLECULES; ANNIHILATION;
   COLLISIONS; HYDRIDE
AB Positronium-hydrogen scattering has been reinvestigated considering the
   charge-transfer rearrangement channel Ps + H--> e(+) + H- in the
   coupled-channel formalism. The virtual effects of this rearrangement
   channel on scattering length, PsH binding energy, and low-energy (0-10
   eV) elastic cross sections are evaluated and H- formation cross
   sections are reported for energies up to 100 eV. Results indicate that
   the inclusion of such a rearrangement channel could be of significant
   importance in obtaining a converged description of PsH scattering in
   any ab initio coupled-channel model.
C1 Inst Tecnol Aeronaut, CTA, Dept Fis, BR-12228900 Sao Jose Dos Campos, SP, Brazil.
RP Biswas, PK, Inst Tecnol Aeronaut, CTA, Dept Fis, BR-12228900 Sao Jose
   Dos Campos, SP, Brazil.
CR ADHIKARI SK, 1999, PHYS REV A, V59, P2058
   ADHIKARI SK, 1999, PHYS REV A, V59, P4829
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   BISWAS PK, 1998, J PHYS B-AT MOL OPT, V31, P5404
   BISWAS PK, 1998, J PHYS B-AT MOL OPT, V31, L315
   BISWAS PK, 1998, J PHYS B-AT MOL OPT, V31, L737
   BISWAS PK, 1999, PHYS REV A, V59, P363
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NR 57
TC 9
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-4075
J9 J PHYS-B-AT MOL OPT PHYS
JI J. Phys. B-At. Mol. Opt. Phys.
PD DEC 14
PY 2001
VL 34
IS 23
BP 4831
EP 4844
PG 14
SC Physics, Atomic, Molecular & Chemical; Optics
GA 522HQ
UT ISI:000173890700026
ER

PT J
AU Seidl, PR
   Carneiro, JWD
   Tostes, JGR
   Dias, JF
   Pinto, PSS
   Costa, VEU
   Taft, CA
TI Conformational effects on NMR chemical shifts of half-cage alcohols
   calculated by GIAO-DFT
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE NMR; chemical shifts; hyperconjugation; DFF-GIAO; half-cage alcohols;
   conformational effects
ID SHIELDING TENSORS; BETA-SUBSTITUENT; ABINITIO IGLO; AB-INITIO; C-C;
   C-13; HYPERCONJUGATION; METHYL; PENTACYCLODODECANE; DEPENDENCIES
AB Half-cage compounds have played an important role in the investigation
   of the way steric compression affects physical and chemical properties
   of organic molecules. Recent theoretical studies of half-cage alcohols
   have also shown that rotation around the carbon-oxygen bond of the
   hydroxyl group leads to low-energy conformers in which hyperconjugation
   affects bond lengths, bond angles, and charge distribution on carbon
   and hydrogen atoms in its vicinity while charge distribution is also
   affected by electrostatic effects. Chemical shifts are also sensitive
   to such variations, but we found that in smaller model systems steric
   effects may strongly attenuate those due to hyperconjugation so we
   optimized geometries for low energy rotamers of 'outside' and 'inside'
   half-cage alcohols, where these effects can be separated, and
   calculated their respective hydrogen and carbon-13 chemical shifts by
   gauge-independent atomic orbital (GIAO) methods at the 133LYP/6-31G(d)
   level. Results are compared to those obtained for the corresponding
   norbornyl alcohols as well as for the half-cage hydrocarbon. Carbon-13
   chemical shifts respond more strongly to effects owing to
   hyperconjugation while hydrogen chemical shifts are more sensitive to
   electrostatic effects due to the proximity of the hydroxyl group. (C)
   2002 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Escola Quim, BR-21949900 Rio De Janeiro, RJ, Brazil.
   Univ Fed Fluminense, Dept Quim Geral & Inorgan, BR-24020150 Niteroi, RJ, Brazil.
   Univ Estadual Norte Fluminense, Ctr Ciencias & Tecnol, Lab Ciencias Quim, BR-28015620 Sao Jose Dos Campos, RJ, Brazil.
   Inst Militar Engn, Dept Engn Quim, BR-22290270 Rio De Janeiro, RJ, Brazil.
   Univ Fed Rio Grande Sul, Inst Quim, BR-91509900 Porto Alegre, RS, Brazil.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, RJ, Brazil.
RP Seidl, PR, Univ Fed Rio de Janeiro, Escola Quim, Cidade Univ,
   BR-21949900 Rio De Janeiro, RJ, Brazil.
CR ABRAHAM RJ, 1997, J CHEM SOC P2, P1751
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NR 55
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAR 1
PY 2002
VL 579
BP 101
EP 107
PG 7
SC Chemistry, Physical
GA 523GT
UT ISI:000173946200012
ER

PT J
AU Klautau, AB
   Frota-Pessoa, S
TI Magnetism of Co clusters embedded in Cu(001) surfaces: an ab initio
   study
SO SURFACE SCIENCE
LA English
DT Article
DE cobalt; copper; surface defects; clusters; magnetic surfaces;
   metal-metal magnetic heterostructures
ID FE IMPURITIES; REAL-SPACE; ELECTRONIC-STRUCTURE; TRANSITION; CU(100);
   GROWTH; NANOSTRUCTURES; EXCHANGE; MOMENTS; METALS
AB We report calculations of electronic structure and magnetic properties
   of Co clusters (up to 50 atoms) embedded in Cu(0 0 1) surfaces,
   performed using the first-principles linear muffin tin orbital-atomic
   sphere approximation method, implemented directly in real space. Co
   agglomerates of different sizes and shapes are considered in order to
   investigate the influence of the local environment around the Co sites
   to the magnetism in this class of systems. We find that the magnitude
   of the Co moments is mainly governed by two factors: the position of
   the site relative to the Cu(0 0 1) surface layer and the number of Cu
   neighbors. The results show moment enhancement for sites located above
   the surface and/ or placed substitutionally in the surface layer, due
   to their reduced coordination numbers. For sites with the same
   coordination number, the moment tends to decrease as the number of Cu
   neighbors increases. As a consequence, in Co agglomerates, the magnetic
   moment decreases considerably as one goes from more central sites to
   those close to the grain boundary at the Co-Cu interface. (C) 2001
   Published by Elsevier Science B.V.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
RP Klautau, AB, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, SP, Brazil.
CR ALDEN M, 1992, PHYS REV B, V46, P6303
   ANDERSEN OK, 1975, PHYS REV B, V12, P3060
   ANDERSEN OK, 1984, PHYS REV LETT, V53, P2571
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   BEER N, 1984, ELECT STRUCTURE COMP
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   DEBOER FR, 1985, COHESION METALS, V1
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   FASSBENDER J, 1997, SURF SCI, V383, L742
   FERNANDO GW, 1988, PHYS REV B, V38, P3016
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   KIEF MT, 1993, PHYS REV B, V47, P10785
   KIM SK, 2000, SURF SCI, V453, P47
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NR 45
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD JAN 20
PY 2002
VL 497
IS 1-3
BP 385
EP 397
PG 13
SC Chemistry, Physical
GA 519QP
UT ISI:000173737200039
ER

PT J
AU Barbosa, KO
   Machado, WVM
   Assali, LVC
TI First-principles studies of Ti impurities in SiC
SO PHYSICA B-CONDENSED MATTER
LA English
DT Article
DE transition metals; silicon carbide; ab initio methods
AB In this work we perform a theoretical investigation on the atomic
   structure, atomic geometry, and formation energy of isolated
   substitutional and interstitial Ti impurities in cubic silicon carbide
   (3C-SiC). using the spill-polarized full-potential linearized augmented
   plane wave method. For each configuration, the atoms around the
   impurity site are allowed to relax without any constraints, following
   the damped Newton dynamics scheme. The overall structural stability is
   analyzed in the light of the electronic structure and the bonding
   features. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, Dept Fis Mat & Mecan, BR-05315970 Sao Paulo, Brazil.
RP Assali, LVC, Univ Sao Paulo, Inst Fis, Dept Fis Mat & Mecan, CP 66318,
   BR-05315970 Sao Paulo, Brazil.
CR BAUMHAUER H, 1912, Z KRISTALLOGR, V50, P33
   BEELER F, 1990, PHYS REV B, V41, P1603
   BLAHA P, 1999, WIEN97 FULL POTENTIA
   HOHENBERG P, 1964, PHYS REV B, V136, P864
   JEPPS NW, 1983, J CRYST GROWTH CHARA, V7, P259
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   LEBEDEV AA, 1999, SEMICONDUCTORS+, V33, P107
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   MULLER STG, 1995, SILICON CARBIDE RELA
   PASLOVSKY L, 1993, J LUMIN, V55, P167
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   SINGH DJ, 1994, PLANEWAVES PSEUDOPOT
   SON NT, 1994, APPL PHYS LETT, V65, P2687
   VERMA AP, 1966, POLYMORPHISM POLYTYP
NR 14
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0921-4526
J9 PHYSICA B
JI Physica B
PD DEC
PY 2001
VL 308
BP 726
EP 729
PG 4
SC Physics, Condensed Matter
GA 518GV
UT ISI:000173660100182
ER

PT J
AU Ahuja, R
   da Silva, AF
   Persson, C
   Osorio-Guillen, JM
   Pepe, I
   Jarrendahl, K
   Lindquist, OPA
   Edwards, NV
   Wahab, Q
   Johansson, B
TI Optical properties of 4H-SiC
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID SIC POLYTYPES; N-TYPE; POWER APPLICATIONS; BRILLOUIN-ZONE; SPECIAL
   POINTS; BAND; SYSTEMS; DEVICES
AB The optical band gap energy and the dielectric functions of n-type
   4H-SiC have been investigated experimentally by transmission
   spectroscopy and spectroscopic ellipsometry and theoretically by an ab
   initio full-potential linear muffin-tin-orbital method. We present the
   real and imaginary parts of the dielectric functions, resolved into the
   transverse and longitudinal photon moment a, and we show that the
   anisotropy is small in 4H-SiC. The measurements and the calculations
   fall closely together in a wide range of energies. (C) 2002 American
   Institute of Physics.
C1 Uppsala Univ, Dept Phys, Condensed Matter Theory Grp, SE-75121 Uppsala, Sweden.
   Univ Fed Bahia, Inst Fis, BR-40210340 Salvador, BA, Brazil.
   Linkoping Univ, Dept Phys & Measurement Technol, SE-58183 Linkoping, Sweden.
   Motorola Inc, Semicond Prod Sector, Mesa, AZ 85202 USA.
   Royal Inst Technol, Dept Mat Sci & Engn, SE-10044 Stockholm, Sweden.
RP Ahuja, R, Uppsala Univ, Dept Phys, Condensed Matter Theory Grp, POB
   530, SE-75121 Uppsala, Sweden.
CR ADOLPH B, 1997, PHYS REV B, V55, P1422
   AHUJA R, 1997, PHYS REV B, V55, P4999
   ANDERSEN OK, 1975, PHYS REV B, V12, P3060
   ARAUJO CM, 2000, PHYS REV B, V62, P12882
   CHADI DJ, 1973, PHYS REV B, V8, P5747
   COYKE WJ, 1969, MAT RES B, V4, P141
   EDMONDS AR, 1974, ANGULAR MOMENTUM QUA
   EDWARDS NV, IN PRESS SURF SCI LE
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   HARRIS GL, 1995, PROPERTIES SILICON C
   HEDIN L, 1971, J PHYS C SOLID STATE, V4, P2064
   JANSSON R, 2000, PHYS STATUS SOLIDI B, V218, R1
   JANZEN E, 1997, MAT SCI ENG B-SOLID, V46, P203
   LIMPIJUMNONG S, 1999, PHYS REV B, V59, P12890
   LINDQUIST OPA, 2000, MATER SCI FORUM, V338, P575
   LINDQUIST OPA, 2001, APPL PHYS LETT, V78, P2751
   MORKOC H, 1994, J APPL PHYS, V76, P1363
   OPPENEER PM, 1992, PHYS REV B, V45, P10924
   PALMOUR JW, 1993, PHYSICA B, V185, P461
   PERSSON C, 1998, J APPL PHYS, V83, P266
   PERSSON C, 1998, P 7 INT C SIL CARB 3, V264
   PERSSON C, 1999, J APPL PHYS, V86, P4419
   PERSSON C, 1999, PHYS REV B, V60, P16479
   PRICE DL, 1989, PHYS REV B, V39, P4945
   SKRIVER HL, 1984, LMTO METHOD
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   WILLS JM, UNPUB
   WILLS JM, 1987, PHYS REV B, V36, P3809
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   ZHUKOVA II, 1968, FIZ TVERD TELA, V10, P1097
   ZOLLNER S, 1999, J APPL PHYS, V85, P8353
NR 33
TC 7
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD FEB 15
PY 2002
VL 91
IS 4
BP 2099
EP 2103
PG 5
SC Physics, Applied
GA 516LB
UT ISI:000173553800052
ER

PT J
AU Tabata, A
   Teles, LK
   Scolfaro, LMR
   Leite, JR
   Kharchenko, A
   Frey, T
   As, DJ
   Schikora, D
   Lischka, K
   Furthmuller, J
   Bechstedt, F
TI Phase separation suppression in InGaN epitaxial layers due to biaxial
   strain
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID RESONANT RAMAN-SCATTERING; INXGA1-XN
AB Phase separation suppression due to external biaxial strain is observed
   in InxGa1-xN alloy layers by Raman scattering spectroscopy. The effect
   is taking place in thin epitaxial layers pseudomorphically grown by
   molecular-beam epitaxy on unstrained GaN(001) buffers. Ab initio
   calculations carried out for the alloy free energy predict and Raman
   measurements confirm that biaxial strain suppress the formation of
   phase-separated In-rich quantum dots in the InxGa1-xN layers. Since
   quantum dots are effective radiative recombination centers in InGaN, we
   conclude that strain quenches an important channel of light emission in
   optoelectronic devices based on pseudobinary group-III nitride
   semiconductors. (C) 2002 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Gesamthsch Paderborn, D-33095 Paderborn, Germany.
   Univ Jena, Inst Festkorpertheorie & Theoret Opt, D-07743 Jena, Germany.
   Univ Estadual Paulista, BR-17033360 Bauva, SP, Brazil.
RP Leite, JR, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR CHICHIBU S, 1996, APPL PHYS LETT, V69, P4188
   CHICHIBU S, 1997, APPL PHYS LETT, V70, P2822
   KARPOV SY, 1998, MRS INTERNET J N S R, V3
   LEMOS V, 2000, PHYS REV LETT, V84, P3666
   ODONNELL KP, 1999, PHYS REV LETT, V82, P237
   SILVEIRA E, 1999, APPL PHYS LETT, V75, P3602
   SINGH R, 1997, APPL PHYS LETT, V70, P1089
   TABATA A, 1996, J APPL PHYS 1, V79, P4137
   TELES LK, 2000, PHYS REV B, V62, P2475
   WANG T, 2001, APPL PHYS LETT, V78, P2617
   ZUNGER A, 1994, HDB CRYSTAL GROWTH, V3, P998
NR 11
TC 24
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 4
PY 2002
VL 80
IS 5
BP 769
EP 771
PG 3
SC Physics, Applied
GA 517NW
UT ISI:000173617700022
ER

PT J
AU Correa, RJ
   Mota, CJA
TI Theoretical study of protonation of butene isomers on acidic zeolite:
   the relative stability among primary, secondary and tertiary alkoxy
   intermediates
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID HARTREE-FOCK CALCULATIONS; SOLID ACIDS; SKELETAL ISOMERIZATION;
   AB-INITIO; ELECTROSTATIC POTENTIALS; HYDROCARBON CONVERSION; SN2-SN1
   SPECTRUM; DEUTERATED ZSM-5; MOLECULAR-MODELS; LINEAR BUTENES
AB A density functional theory (DFT) study of the protonation of
   but-1-ene, (E)-but-2-ene and isobutene over a cluster representing the
   zeolite acid site (HT3) was carried out. At the B3LYP=6-31+G** level of
   calculation all the reactions were exothermic, with respect to the
   isolated reactants, in forming an alkoxy species. Formation of a
   pi-complex involving the double bond and the acidic proton was the
   first step and shows a small dependence with the olefin structure. The
   proton transfer involves a transition state with carbenium ion like
   character, which is reflected in the calculated DeltaH(double dagger),
   being higher for the but-1-ene (to afford the 1-butoxy intermediate)
   and lower for the isobutene (to afford the tert-butoxy intermediate).
   However, the stability of the alkoxy formed shows a different trend.
   The tert-butoxy was computed to be only 1.5 kcal mol(-1) lower in
   energy than the pi-complex between isobutene and HT3 at the
   B3LYP/6-31+G** level of calculation, but the reaction becomes
   endothermic by 2.5 kcal mol(-1) when computed at B3LYP/6-311++G**. The
   calculated order of stability among the alkoxy species was 2-butoxy >
   1-butoxy > tert-butoxy. These results show that electronic effects
   dominate DeltaH(double dagger), which is associated with the kinetics
   of the protonation process, while steric effects play a major role in
   the stability of the alkoxy, which in turn is related to the
   thermodynamics of protonation.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, BR-21949900 Rio De Janeiro, Brazil.
RP Mota, CJA, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
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NR 42
TC 13
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI Phys. Chem. Chem. Phys.
PY 2002
VL 4
IS 2
BP 375
EP 380
PG 6
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 514MX
UT ISI:000173444900030
ER

PT J
AU Pliego, JR
   Riveros, JM
TI Theoretical study of the gas-phase reaction of fluoride and chloride
   ions with methyl formate
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID NUCLEOPHILIC DISPLACEMENT-REACTIONS; CYCLOTRON RESONANCE SPECTROSCOPY;
   INFRARED MULTIPLE-PHOTON; RELATIVE STABILITY; FLOWING AFTERGLOW;
   HYDROGEN-BONDS; NEGATIVE-IONS; ANIONS; COMPLEXES; PHOTODETACHMENT
AB The potential energy surface of the gas-phase reaction between halide
   ions (F- and Cl-) and methyl formate has been investigated by ab initio
   calculations. For F-, two pathways have been observed at thermal
   energies and identified in the calculations: (1) a-elimination of CO to
   yield a fluoride-methanol adduct, the so-called Riveros reaction that
   has found wide application in gas-phase ion chemistry, and (2) S(N)2
   displacement of HCOO-. The first reaction is shown to proceed by the
   initial formation of a loose complex followed by formal abstraction of
   a formyl hydrogen to yield a three-body complex that dissociates into
   the final products. The S(N)2 reaction initially involves formation of
   a loose complex with the fluoride attached to the methyl group of the
   ester. The first pathway is calculated to go through a lower energy
   local transition state than the corresponding S(N)2 reaction but the
   transition states are located below the energy of the reagents. Both
   ion-neutral complexes can interconvert via formation of a stable
   tetrahedral intermediate. The product distribution was estimated via a
   simple RRKM calculation that predicts 92% of alpha-elimination and 8%
   Of S(N)2 reaction. This prediction is in excellent agreement with
   measurements carried out by FT-ICR. This product distribution is
   predicted to remain essentially unchanged for the reaction with DCOOCH3
   in agreement with experimental observations. A similar analysis of the
   corresponding Cl- + HCOOCH3 reaction reveals that a-elimination has a
   substantial activation energy (well above the reagents) accounting for
   the failure to observe this reaction even though it is exothermic.
   These calculations also reveal that for the Cl- system, the tetrahedral
   intermediate is not a stable intermediate in agreement with previous
   experimental data on related systems.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
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NR 48
TC 5
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JAN 17
PY 2002
VL 106
IS 2
BP 371
EP 378
PG 8
SC Chemistry, Physical
GA 513AN
UT ISI:000173355900021
ER

PT J
AU Chaudhuri, P
   Canuto, S
TI An ab initio study of the peptide bond formation between alanine and
   glycine: electron correlation effects on the structure and binding
   energy
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE peptide bond; ab initio; electron correlation effects;
   density-functional theory; structure and properties
ID DENSITY-FUNCTIONAL APPROXIMATION; AQUEOUS-SOLUTION; CONFORMERS;
   DIPEPTIDES; GEOMETRIES; ABINITIO; H2O-HCN; MODELS; MP2; GAS
AB Ab initio methods are used to analyze the structure, energetics and
   binding energy of the four possible dipeptides that can be formed from
   alanine and glycine in gas phase. The structures of the peptides are
   optimized using Hartree-Fock, second-order Moller-Plesset perturbation
   theory and density functional methods (DFT). The effect of electron
   correlation is analyzed with special emphasis on the calculated binding
   energies. Single-point energy calculations are performed with CCSD(T)
   on MP2 geometries to get some additional information on the correlation
   effects. Electron correlation effects and zero-point vibrational energy
   corrections increase the binding energy. At the highest level, CCSD(T),
   we find that the binding energies for alanylalanine, alanylglycine,
   glycylalanine and glycylglycine are 4.86, 5.09, 5.61 and 5.89 kcal/mol,
   respectively. These numerical results suggest that glycine donates the
   OH group easier than alanine. A comparison between the Moller-Plesset
   and DFT in different basis sets is made and gives indication of the
   usefulness of these methods for bio-molecules and peptide formation.
   Two functionals, B3LYP and B3P86 with different basis sets differing by
   the systematic inclusion of diffuse and polarization functions, are
   used in the DFT method. The results obtained using both functionals
   with a basis that includes both diffuse and polarization functions are
   in reasonable agreement with the Moller-Plesset results. However,
   without including zero-point corrections, some DFT results lead to
   non-bonding of the peptide molecule. (C) 2002 Elsevier Science B.V. All
   rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BARTLETT RJ, 1989, J PHYS CHEM-US, V93, P1997
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NR 35
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD JAN 31
PY 2002
VL 577
IS 2-3
BP 267
EP 279
PG 13
SC Chemistry, Physical
GA 514FQ
UT ISI:000173428400018
ER

PT J
AU Avery, MA
   Alvim-Gaston, M
   Rodrigues, CR
   Barreiro, EJ
   Cohen, FE
   Sabnis, YA
   Woolfrey, JR
TI Structure-activity relationships of the antimalarial agent artemisinin.
   6. The development of predictive in vitro potency models using CoMFA
   and HQSAR methodologies
SO JOURNAL OF MEDICINAL CHEMISTRY
LA English
DT Article
ID MOLECULAR-FIELD ANALYSIS; SOLUBLE DIHYDROARTEMISININ DERIVATIVES;
   QINGHAOSU ARTEMISININ; TRICYCLIC ANALOGS; IN-VITRO; PEROXIDIC
   ANTIMALARIALS; HEPATIC-METABOLISM; AB-INITIO; DRUG; MECHANISM
AB Artemisinin (1) is a unique sesquiterpene peroxide occurring as a
   constituent of Artemisia annua L. Because of the effectiveness of
   Artemisinin in the treatment of drug-resistant Plasmodium falciparum
   and its rapid clearance of cerebral malaria, development of clinically
   useful semisynthetic drugs for severe and complicated malaria
   (artemether, artesunate) was prompt. However, recent reports of fatal
   neurotoxicity in animals with dihydroartemisinin derivatives such as
   artemether have spawned a renewed effort to develop nontoxic analogues
   of artemisinin. In our effort to develop more potent, less neurotoxic
   agents for the oral treatment of drug-resistant malaria, we utilized
   comparative molecular field analysis (CoMFA) and hologram QSAR (HQSAR),
   beginning with a series of 211 artemisinin analogues with known in
   vitro antimalarial activity. CoMFA models were based on two
   conformational hypotheses: (a) that the X-ray structure of artemisinin
   represents the bioactive shape of the molecule or (b) that the
   hemin-docked conformation is the bioactive form of the drug. In
   addition, we examined the effect of inclusion or exclusion of racemates
   in the partial least squares (pls) analysis. Databases derived from the
   original 211 were split into chiral (n = 157), achiral (n = 34), and
   mixed databases (n = 191) after leaving out a test set of 20 compounds.
   HQSAR and CoMFA models were compared in terms of their potential to
   generate robust QSAR models. The r(2) and q(2) (cross-validated r(2))
   were used to assess the statistical quality of our models. Another
   statistical parameter, the ratio of the standard error to the activity
   range (s/AR), was also generated. CoMFA and HQSAR models were developed
   having statistically excellent properties, which also possessed good
   predictive ability for test set compounds. The best model was obtained
   when racemates were excluded from QSAR analysis. Thus, CoMFA of the n =
   157 database gave excellent predictions with outstanding statistical
   properties. HQSAR did an outstanding job in statistical analysis and
   also handled predictions well.
C1 Univ Mississippi, Sch Pharm, Thad Cochran Natl Ctr Nat Prod Res, Dept Med Chem, University, MS 38677 USA.
   Univ Mississippi, Dept Chem, University, MS 38677 USA.
   UFRJ, Dept Farmacos, Fac Farm, LASSBio, BR-21944910 Rio De Janeiro, Brazil.
   Univ Calif San Francisco, Dept Cellular Mol Pharmacol, San Francisco, CA 94143 USA.
RP Avery, MA, Univ Mississippi, Sch Pharm, Thad Cochran Natl Ctr Nat Prod
   Res, Dept Med Chem, University, MS 38677 USA.
CR ACTON N, 1993, J MED CHEM, V36, P2552
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   MESHNICK SR, 1996, PARASITOL TODAY, V12, P79
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   PAITAYATAT S, 1997, J MED CHEM, V40, P633
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   POSNER GH, 1995, J AM CHEM SOC, V117, P5885
   POSNER GH, 1996, J AM CHEM SOC, V118, P3537
   POSNER GH, 1996, TETRAHEDRON LETT, V37, P815
   POSNER GH, 1998, TETRAHEDRON LETT, V39, P2273
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   TANG Y, 1996, INDIAN J CHEM B, V35, P325
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   WU J, 1991, PROG NAT SCI, V1, P72
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NR 79
TC 28
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-2623
J9 J MED CHEM
JI J. Med. Chem.
PD JAN 17
PY 2002
VL 45
IS 2
BP 292
EP 303
PG 12
SC Chemistry, Medicinal
GA 513YJ
UT ISI:000173408400007
ER

PT J
AU Borin, AC
TI The A(1)Pi-X-1 Sigma(+) transition in NiC
SO CHEMICAL PHYSICS
LA English
DT Article
DE nickel carbide; A(1)II excited electronic state and radiative
   lifetimes; A(1)II-X-1 Sigma(-) transition dipole moment; spectroscopic
   properties; multireference configuration interaction
ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS;
   ELECTRONIC-TRANSITIONS; RADIATIVE LIFETIMES; DIATOMIC-MOLECULES; METAL
   HYDRIDES; SCF METHOD; AB-INITIO; STATES; MOMENTS
AB The multireference configuration interaction (MRCI) method, based on
   complete-active-space self-consistent-field wave functions, has been
   employed to study the X(1)Sigma (+) and A(1)Pi states of NiC. Potential
   energy curves, dipole moments, and transition dipole moment functions
   (TDM) have been computed over a wide range of internuclear separations,
   Based on these results, the Franck-Condon factors and radiative
   lifetimes for several vibrational levels of the A(1)Pi state were
   computed. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Borin, AC, Univ Sao Paulo, Inst Quim, Av Prof Lineu Prestes 748,
   BR-05508900 Sao Paulo, Brazil.
CR ADAM AG, 1997, J MOL SPECTROSC, V181, P24
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NR 47
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD DEC 15
PY 2001
VL 274
IS 2-3
BP 99
EP 108
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 507FE
UT ISI:000173015700003
ER

PT J
AU Rivelino, R
   Canuto, S
TI Theoretical study of mixed hydrogen-bonded complexes: H2O center dot
   center dot center dot HCN center dot center dot center dot H2O and H2O
   center dot center dot center dot HCN center dot center dot center dot
   HCN center dot center dot center dot H2O
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID AB-INITIO CALCULATIONS; INTERMOLECULAR INTERACTIONS; QUANTUM-CHEMISTRY;
   CYANIDE POLYMERS; MATRIX-ISOLATION; CLUSTERS; WATER; SPECTRA;
   COOPERATIVITY; SPECTROSCOPY
AB Mixed hydrogen-bonded clusters H2O . . . HCN, HCN . . .H2O, H2O . . .
   HCN . . .H2O, and H2O . . . HCN . . . HCN . . .H2O are studied by using
   ab initio calculations. The optimized structures and harmonic
   vibrational frequencies are obtained at the DFT/B3LYP and MBPT/MP2
   levels with the 6-311++G(d,p) basis set. To investigate electron
   correlation effects on the binding energies, single-point calculations
   are also performed using the CCSD(T) method with the optimized MP2
   geometric,,. The complexation energies are obtained for these systems
   including correction for basis set superposition error. In addition,
   the cooperative effects in the properties of the complexes are
   investigated quantitatively. We found a cooperativity contribution of
   around 10% relative to the total interaction energy of the complex H2O
   . . . HCN . . .H2O. In the case of H2O . . . HCN . . . HCN . . .H2O,
   the binding energy of the HCN . . . HCN is ca. 8 kJ/mol stronger in the
   mixed tetramer than in the corresponding isolated dimer. The effects of
   higher-order electron correlation are found to be mild, with MP2 giving
   a well-balanced result. Cooperative effects are predicted either by MP2
   or by B3LYP in hydrogen bond distances and dipole moments of the
   clusters. In contrast, the B3LYP functional fails to account fur the
   out-of-plane bend angle in H2O . . . HCN, which is well-described by
   the MP2 method.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, POB 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BARTLETT RJ, 1989, J PHYS CHEM-US, V93, P1697
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NR 35
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD DEC 20
PY 2001
VL 105
IS 50
BP 11260
EP 11265
PG 6
SC Chemistry, Physical
GA 505ZN
UT ISI:000172945600014
ER

PT J
AU Silva, THA
   Oliveira, AB
   Dos Santos, HF
   De Almeida, WB
TI Conformational analysis of epiquinine and epiquinidine
SO STRUCTURAL CHEMISTRY
LA English
DT Article
DE conformational analysis; antimalarial; epiquinine; epiquinidine
ID POLARIZABLE CONTINUUM MODEL; CINCHONA ALKALOIDS; PLASMODIUM-FALCIPARUM;
   ANTIMALARIAL ACTIVITY; COMBINED NMR
AB The conformational potential energy surfaces for the epiquinine and
   epiquinidine molecules were analyzed in gas phase and water solution
   using semiempirical and ab initio levels of theory. The results
   obtained showed that the main conformation of the nonactive threo
   epimers is distinct from those observed for the active parent compounds
   quinine and quinidine. This result might be used, on a qualitative way,
   to understand the loss of activity of the threo epimers and allow
   selecting important conformations to be considered in molecular
   modeling quantitative studies addressing the drug-receptor interactions.
C1 UFMG, ICEx, Dept Quim, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Minas Gerais, Fac Farm, Dept Prod Farmaceut, Belo Horizonte, MG, Brazil.
   Univ Fed Juiz de Fora, ICE, Dept Quim, NEQC, BR-36036330 Juiz De Fora, MG, Brazil.
RP De Almeida, WB, UFMG, ICEx, Dept Quim, LQCMM, BR-31270901 Belo
   Horizonte, MG, Brazil.
CR ALLINGER NL, 1997, PCMODEL 1993 SERENA
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   FRISCH MJ, 1998, GAUSSIAN 98
   HOLTJE HD, 1996, MOL MODELING BASIC P
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   STEWART JP, 1990, MOPAC VERSION 6 0
NR 22
TC 4
PU KLUWER ACADEMIC/PLENUM PUBL
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013 USA
SN 1040-0400
J9 STRUCT CHEM
JI Struct. Chem.
PD DEC
PY 2001
VL 12
IS 6
BP 431
EP 437
PG 7
SC Chemistry, Multidisciplinary
GA 500QK
UT ISI:000172638100002
ER

PT J
AU de Koning, M
   Antonelli, A
   Yip, S
TI Single-simulation determination of phase boundaries: A dynamic
   Clausius-Clapeyron integration method
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID FREE-ENERGY CALCULATIONS; SOLID-FLUID COEXISTENCE; MOLECULAR-DYNAMICS;
   MELTING CURVE; NONEQUILIBRIUM MEASUREMENTS; STRUCTURAL-PROPERTIES;
   MODEL SYSTEMS; PURE THEORY; ARGON; EQUILIBRIUM
AB We present a dynamic implementation of the Clausius-Clapeyron
   integration (CCI) method for mapping out phase-coexistence boundaries
   through a single atomistic simulation run. In contrast to previous
   implementations, where the reversible path of coexistence conditions is
   generated from a series of independent equilibrium simulations, dynamic
   Clausius-Clapeyron integration (d-CCI) explores an entire coexistence
   boundary in a single nonequilibrium simulation. The method gives
   accurately the melting curve for a system of particles interacting
   through the Lennard-Jones potential. Furthermore, we apply d-CCI to
   compute the melting curve of an ab initio pair potential for argon and
   verify earlier studies on the effects of many-body interactions and
   quantum effects in the melting of argon. The d-CCI method shows to be
   effective in both applications, giving converged coexistence curves
   spanning a wide range of thermodynamic states from relatively short
   nonequilibrium simulations. (C) 2001 American Institute of Physics.
C1 Lawrence Livermore Natl Lab, Livermore, CA 94550 USA.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   MIT, Dept Nucl Engn, Cambridge, MA 02139 USA.
RP de Koning, M, Lawrence Livermore Natl Lab, L-371, Livermore, CA 94550
   USA.
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   KOFKE DA, 1999, MONTE CARLO METHODS, V105
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   YOUNG DA, 1984, J CHEM PHYS, V81, P2789
NR 35
TC 14
PU AMER INST PHYSICS
PI MELVILLE
PA CIRCULATION & FULFILLMENT DIV, 2 HUNTINGTON QUADRANGLE, STE 1 N O 1,
   MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD DEC 22
PY 2001
VL 115
IS 24
BP 11025
EP 11035
PG 11
SC Physics, Atomic, Molecular & Chemical
GA 501KE
UT ISI:000172683200003
ER

PT J
AU Nasar, RS
   Cerqueira, M
   Longo, E
   Varela, JA
   Beltran, A
TI Experimental and theoretical study of the ferroelectric and
   piezoelectric behavior of strontium-doped PZT
SO JOURNAL OF THE EUROPEAN CERAMIC SOCIETY
LA English
DT Article
DE calculations-aiPI; ferroelectrics; piezoelectrics; PZT
ID SOLID-SOLUTIONS; X-RAY; CERAMICS
AB Theoretical data using ab initio perturbed ion calculation were
   compared with ferroelectric and piezoelectric experimental data of
   strontium doped PZT. Various concentrations of SrO in PZT at constant
   temperature and sintering time were carried out. Experimental results,
   such as the remanent polarization, P-R of 6.9-8.9 muC/Cm-2, the
   coercive field, E-C of 6.6-7.8 kVcm, and the planar coupling factor, Kp
   of 0.45-0.53, were compared with the energy of Zr4+ and Ti4+ ion
   dislocation and the lattice interaction energy which show that
   strontium increment in PZT alter the energies and increase the values
   of piezoelectric and ferroelectric variables. Calculations of lattice
   energy of the rhombohedral phase show that a phase non-stability is
   coincident with increasing experimental values of the P-R, E-C and Kp.
   (C) 2001 Elsevier Science Ltd. All rights reserved.
C1 UFRN, Dept Quim, BR-59072970 Natal, RN, Brazil.
   UFSCar, Dept Quim, Lab Interdisciplinar Eletroqulmica & Ceram, BR-13565905 Sao Carlos, SP, Brazil.
   UNESP, Inst Quim, BR-14800900 Araraquara, SP, Brazil.
   Univ Jaume, Dept Ciencies Expt, Castello, Spain.
RP Nasar, RS, UFRN, Dept Quim, Caixa Postal 1662, BR-59072970 Natal, RN,
   Brazil.
CR ARIGUR P, 1974, SOLID STATE COMMUN, V15, P1077
   ATKINS PW, 1994, PHYSICAL CHEM, P446
   BENGUIGUI L, 1976, SOLID STATE COMMUN, V19, P979
   BERNARD J, 1971, PIEZOELECTRIC CERAMI
   CADY WG, 1971, PIEZOELECTRICITY
   CERQUEIRA M, 1997, J MATER SCI, V32, P2381
   CHANDLER D, 1987, INTRO STAT MECH
   GALASSO FS, 1969, STRUCTURE PROPERTIES
   HAERTLING GH, 1986, CERAMIC MAT ELECT
   HAERTLING GH, 1986, CERAMIC MAT ELECT, P168
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   ISOPOV VA, 1975, SOLID STATE COMMUN, V17, P1331
   ISOPOV VA, 1976, SOV PHYS-SOLID STATE, V18, P529
   JAFFE B, 1971, PIEZOELECTRIC CERAMI
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   NASAR RS, 1999, J MATER SCI, V34, P3659
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   YAMAMOTO T, 1992, AM CERAM SOC BULL, V71, P978
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NR 26
TC 6
PU ELSEVIER SCI LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND
SN 0955-2219
J9 J EUR CERAM SOC
JI J. European Ceram. Soc.
PD FEB
PY 2002
VL 22
IS 2
BP 209
EP 218
PG 10
SC Materials Science, Ceramics
GA 498RE
UT ISI:000172523600009
ER

PT J
AU Critchley, ADJ
   King, GC
   Kreynin, P
   Lopes, MCA
   McNab, IR
   Yencha, AJ
TI TPEsCO spectra of HCl2+ and DCl2+: experiment and theory
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID PHOTOELECTRONS COINCIDENCE SPECTROSCOPY; INITIO CI CALCULATIONS;
   DOUBLY-CHARGED IONS; AB-INITIO; INFRARED-SPECTRUM; MOLECULES; DYNAMICS;
   N-2(2+); PREDISSOCIATION; CHLORIDE
AB Vibrationally resolved threshold photoelectrons in coincidence (TPEsCO)
   spectra of the X(3)Sigma (-) and a(1)Delta states of HCl2+ and DCl2+
   are compared with ab initio simulations. The four resonances observed
   in the TPEsCO spectra of both the X(3)Sigma (-) and a(1)Delta states of
   HCl2+ are assigned as three quasi-bound vibrational levels and one
   continuum resonance with an energy greater than the potential barrier
   maximum. The four clearly identified resonances observed in Cl2+ the
   TPEsCO spectra of both the X(3)Sigma (-) and a(1)Delta states of DCl2+
   are assigned as quasi-bound vibrational levels. (C) 2001 Elsevier
   Science B.V. All rights reserved.
C1 Univ Newcastle Upon Tyne, Dept Phys, Newcastle Upon Tyne NE1 7RU, Tyne & Wear, England.
   Univ Manchester, Dept Phys & Astron, Manchester M13 9PL, Lancs, England.
   Univ Fed Juiz de Fora, ICE, Dept Fis, BR-36036330 Juiz De Fora, MG, Brazil.
   SUNY Albany, Dept Chem, Albany, NY 12222 USA.
RP McNab, IR, Univ Newcastle Upon Tyne, Dept Phys, Newcastle Upon Tyne NE1
   7RU, Tyne & Wear, England.
CR ABUSEN R, 1998, J CHEM PHYS, V108, P1761
   BENNETT FR, 1995, CHEM PHYS, V190, P53
   BENNETT FR, 1996, CHEM PHYS LETT, V250, P40
   BENNETT FR, 1996, CHEM PHYS LETT, V251, P405
   BENNETT FR, 1999, MOL PHYS, V97, P35
   CHANDRA N, 1999, EUR PHYS J D, V6, P457
   COX SG, 2001, UNPUB PCCP
   CRITCHLEY ADJ, 2001, THESIS U NEWCASTLE U
   EDVARDSSON D, 1996, CHEM PHYS LETT, V256, P341
   ELLINGSEN K, 2000, PHYS REV A, V6203, P2505
   FURUHASHI O, 2001, CHEM PHYS LETT, V337, P97
   HOCHLAF M, 1988, CHEM PHYS, V234, P249
   HRUSAK J, 2001, CHEM PHYS LETT, V338, P189
   LARSSON M, 1993, COMMENTS AT MOL PHYS, V29, P39
   LEROY RJ, 1989, COMPUT PHYS COMMUN, V52, P383
   LEROY RJ, 1993, CP329R U WAT CHEM PH
   LEROY RJ, 1996, CP555R U WAT CHEM PH
   LUNDQVIST M, 1996, J PHYS B-AT MOL OPT, V29, P499
   MARTIN PA, 1994, J CHEM PHYS, V100, P4766
   MCCONKEY AG, 1994, J PHYS B ATOM MOL PH, V27, P271
   MULLIN AS, 1992, J CHEM PHYS, V96, P3636
   PRICE SD, 1997, J CHEM SOC FARADAY T, V93, P2451
   SUNDSTROM G, 1994, CHEM PHYS LETT, V218, P17
   SVENSSON S, 1989, PHYS REV A, V40, P4369
   WERNER HJ, MOLPRO
   YENCHA AJ, 1999, CHEM PHYS LETT, V315, P37
NR 26
TC 11
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD NOV 23
PY 2001
VL 349
IS 1-2
BP 79
EP 83
PG 5
SC Physics, Atomic, Molecular & Chemical
GA 500AL
UT ISI:000172603600013
ER

PT J
AU Bezerra, EF
   Souza, AG
   Freire, VN
   Mendes, J
   Lemos, V
TI Strong interface localization of phonons in nonabrupt InN/GaN
   superlattices
SO PHYSICAL REVIEW B
LA English
DT Article
ID RESONANT RAMAN-SCATTERING; QUANTUM-WELL STRUCTURES; EPITAXIAL LAYERS;
   OPTICAL PHONONS; AB-INITIO; GAN; SPECTROSCOPY; INN; MICROSTRUCTURES;
   DYNAMICS
AB The Raman spectra of zinc-blende InN/GaN superlattices were calculated
   assuming the existence of an inter-face region with thickness delta
   varying from one to three monolayers. The acoustic branches are weakly
   affected by interfacing, but the optical branches can present frequency
   shifts up to 60 cm(-1). A downward shift is observed for the higher
   frequency and an upward shift for the lower frequency modes. As a
   consequence, the Raman peaks collapse together in the middle frequency
   range giving rise to a most prominent structure in the spectrum, for
   delta = 3. These effects are tracked to the localization of atomic
   displacements at the direct and inverse interface regions. The
   localization effects are strong in the InN/GaN superlattices because of
   the wide gap observed in the phonon density of states for both
   constituent materials.
C1 Univ Fed Ceara, Ctr Ciencias, Dept Fis, BR-60455760 Fortaleza, Ceara, Brazil.
RP Lemos, V, Univ Fed Ceara, Ctr Ciencias, Dept Fis, Caixa Postal
   6030,Campus Pici, BR-60455760 Fortaleza, Ceara, Brazil.
EM volia@fisica.ufc.br
CR BECHSTEDT F, 2000, PHYS REV B, V62, P8003
   BEHR D, 1997, APPL PHYS LETT, V70, P363
   BEZERRA EF, 2000, PHYS REV B, V61, P13060
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NR 24
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 15
PY 2001
VL 6420
IS 20
AR 201306
DI ARTN 201306
PG 4
SC Physics, Condensed Matter
GA 497PL
UT ISI:000172464600014
ER

PT J
AU Venezuela, P
   Dalpian, GM
   da Silva, AJR
   Fazzio, A
TI Ab initio determination of the atomistic structure of SixGe1-x alloy
SO PHYSICAL REVIEW B
LA English
DT Article
ID RANDOM SEMICONDUCTOR ALLOYS; LENGTH MISMATCH; BOND LENGTHS;
   CRYSTALLINE; SIGE; PSEUDOPOTENTIALS; SUPERLATTICES; SIMULATION;
   RELAXATION; PARAMETERS
AB We have performed systematical ab initio studies of the structural
   properties of SixGe1-x alloy. To simulate the disordered alloy we use
   supercells where the Si and Ge atoms are randomly placed with the
   constraint that the pair correlation functions agree with their values
   for a perfect random alloy within a given tolerance. We obtain that the
   Si-Si, Si-Ge, and Ge-Ge bond lengths dependence with composition varies
   only slightly for the different kinds of bonds, with topological
   rigidity parameters between 0.6 and 0.7.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Venezuela, P, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR 1999, SEMICOND SEMIMET, V56
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NR 28
TC 16
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 15
PY 2001
VL 64
IS 19
BP art. no.
EP 193202
AR 193202
PG 4
SC Physics, Condensed Matter
GA 494WB
UT ISI:000172307900005
ER

PT J
AU dos Santos, AS
   Masili, M
   De Groote, JJ
TI Binding energies of excitons trapped by ionized donors in semiconductors
SO PHYSICAL REVIEW B
LA English
DT Article
ID HYPERSPHERICAL ADIABATIC APPROACH; 3-ELECTRON ATOMIC SYSTEMS; HELIUM
   ATOM; POTENTIAL CURVES; BOUND EXCITONS; STATES; FORMALISM; IMPURITY;
   HYDROGEN
AB Using the hyperspherical adiabatic approach in a coupled-channel
   calculation, we present precise binding energies of excitons trapped by
   impurity donors in semiconductors within the effective-mass
   approximation. Energies for such three-body systems are presented as a
   function of the relative electron-hole mass sigma in the range 1 less
   than or equal to1/sigma less than or equal to6, where the
   Born-Oppenheimer approach is not efficiently applicable. The
   hyperspherical approach leads to precise energies using the intuitive
   picture of potential curves and nonadiabatic couplings in an ab initio
   procedure. We also present an estimation for a critical value of sigma
   (sigma (crit)) for which no bound state can be found. Comparisons are
   given with results of prior work by other authors.
C1 Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Assoc Escolas Reunidas, BR-13563470 Sao Carlos, SP, Brazil.
   Univ Estadual Paulista, Inst Quim Araraquara, BR-14801970 Araraquara, SP, Brazil.
RP dos Santos, AS, Univ Sao Paulo, Inst Fis Sao Carlos, Caixa Postal 369,
   BR-13560970 Sao Carlos, SP, Brazil.
CR ABRAMOWITIZ M, 1965, HDB MATH FUNCTIONS
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NR 49
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 15
PY 2001
VL 64
IS 19
BP art. no.
EP 195210
AR 195210
PG 9
SC Physics, Condensed Matter
GA 494WB
UT ISI:000172307900078
ER

PT J
AU Capelle, K
   Vignale, G
   Gyorffy, BL
TI Spin currents and spin dynamics in time-dependent density-functional
   theory
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID MAGNETISM; SYSTEMS
AB We derive and analyze the equation of motion for the spin degrees of
   freedom within time-dependent spin-density-functional theory (TD-SDFT).
   The results are (i) a prescription for obtaining many-body corrections
   to the single-particle spin currents from the Kohn-Sham equation of
   TD-SDFT, (ii) the existence of an exchange-correlation (xc) torque
   within TD-SDFr, (iii) a prescription for calculating, from TD-SDFT, the
   torque exerted by spin currents on the spin magnetization, (iv) a novel
   exact constraint on approximate. xc functionals, and (v) the discovery
   of serious deficiencies of popular approximations to TD-SDFT when
   applied to spin dynamics.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA.
   Univ Bristol, HH Wills Phys Lab, Bristol BS8 1TL, Avon, England.
RP Capelle, K, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol,
   Caixa Postal 780, BR-13560970 Sao Carlos, SP, Brazil.
CR ANTROPOV VP, 1995, PHYS REV LETT, V75, P729
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   DREIZLER RM, 1990, DENSITY FUNCTIONAL T
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   GEBAUER R, 2000, PHYS REV B, V61, P6459
   GROSS EKU, 1996, TOPICS CURRENT CHEM, V181
   HALILOV SV, 1998, PHYS REV B, V58, P293
   HESSLER P, 1999, PHYS REV LETT, V82, P378
   JOUBERT DP, 1998, LECT NOTES PHYSICS, V500
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   SANDRATSKII LM, 1998, ADV PHYS, V47, P91
   SLONCZEWSKI JC, 1996, J MAGN MAGN MATER, V159, L1
   STAUNTON JB, 1992, PHYS REV LETT, V69, P371
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   STOCKS GM, 1998, PHILOS MAG B, V78, P665
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NR 28
TC 12
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD NOV 12
PY 2001
VL 8720
IS 20
AR 206403
DI ARTN 206403
PG 4
SC Physics, Multidisciplinary
GA 492TD
UT ISI:000172182900035
ER

PT J
AU Gozzo, FC
   Eberlin, MN
TI Primary and secondary kinetic isotope effects in proton (H+/D+) and
   chloronium ion (35Cl(+)/37Cl(+)) affinities
SO JOURNAL OF MASS SPECTROMETRY
LA English
DT Article
ID COLLISION-INDUCED DISSOCIATION; QUADRUPOLE MASS SPECTROMETERS;
   GAS-PHASE ACIDITIES; ELECTRON-AFFINITIES; CLUSTER IONS; THERMOCHEMICAL
   DETERMINATIONS; BOUND HETERODIMERS; ATTACHMENT SITES; BOND-ENERGIES;
   AB-INITIO
AB The Cooks' kinetic method and tandem-in-space pentaquadrupole QqQqQ
   mass spectrometry were used to measure primary and secondary kinetic
   isotope effects (KIEs) in H+ and Cl+ (X+) affinity for a series of A/A'
   isotopomeric pairs. Gaseous, isotopomeric, and loosely bound dimers
   [A...chi (+)...A] were formed in combinations in which chi = H+, D+,
   Cl-35(+) or Cl-37(+) and A/A' = acetonitrile/acetonitrile-d(3),
   acetonitrile/acetonitrile-N-15, acetonitrile-d(3)/acetonitrile-N-15,
   acetone/acetone-d(6), acetone/acetone-O-18, acetone-d(6)/acetone-O-18,
   pyridine/pyridine-d(5), pyridine/pyridine-N-15,
   pyridine-d(5)/pyridine-N-15, or 3-(Cl-35)chloropyridine/3-(Cl-37)
   chloropyridine. Under nearly the same experimental conditions, the
   dimers were mass-selected and then dissociated by low-energy collisions
   with argon, yielding AX(+) and A'X+ as the fragment ions. KIEs were
   measured from the changes in ion affinities of the neutrals (AXI) as
   estimated by the AX(+)/A'X+ abundance ratios. Using [A...H+(D+)... ']
   and [A...Cl-35(+)(Cl-37(+))...A'] dimers and by comparing their extent
   of dissociation tinder nearly identical collision-induced dissociation
   conditions, the kinetic method was also applied, for the first time, to
   measure primary KIEs of the central ion as well as their influence on
   secondary KIEs. Becke3LYP/6311++G(2df,2p) calculations were found to
   provide Delta(Delta ZPE)s for the competitive dissociation reactions
   that accurately predict the nature (normal or inverse) of the measured
   KIEs. Copyright (C) 2001 John Wiley & Sons, Ltd.
C1 Univ Estadual Campinas, Inst Chem, UNICAMP, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, Univ Estadual Campinas, Inst Chem, UNICAMP, CP 6154,
   BR-13083970 Campinas, SP, Brazil.
CR BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BOAND G, 1983, J AM CHEM SOC, V105, P2203
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   CERDA BA, 1996, J AM CHEM SOC, V118, P11884
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   CHEN G, 1996, J AM SOC MASS SPECTR, V7, P619
   CHENG XH, 1993, J AM CHEM SOC, V115, P4844
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NR 44
TC 11
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND
SN 1076-5174
J9 J MASS SPECTROMETRY
JI J. Mass Spectrom.
PD OCT
PY 2001
VL 36
IS 10
BP 1140
EP 1148
PG 9
SC Chemistry, Organic; Biophysics; Spectroscopy
GA 488MV
UT ISI:000171941000008
ER

PT J
AU Hillebrand, S
   Segala, M
   Buckup, T
   Correia, RRB
   Horowitz, F
   Stefani, V
TI First hyperpolarizability in proton-transfer benzoxazoles:
   computer-aided design, synthesis and study of a new model compound
SO CHEMICAL PHYSICS
LA English
DT Article
DE nonlinear optics; QSPR; hyper-Rayleigh scattering; Stokes shift;
   excited state intramolecular proton transfer; fluorescence
ID NONLINEAR-OPTICAL-PROPERTIES; MOLECULES; CHROMOPHORES; DYES;
   DERIVATIVES; COPOLYMERS; DEPENDENCE; POLYMERS; ESIPT
AB With regard to second-order nonlinear optics (NLO) applications, a new
   class of 2-(2'-hydroxyphenyl)benzoxazoles (HBO) was designed for a
   combination of high first hyperpolarizability, fl, with good
   photothermal stability, in association with a fast excited state
   intramolecular proton transfer (ESIPT) mechanism. Semi-empirical
   optimization of molecular structures and ab initio calculations of
   dipole moments were performed. Clear evidence was found that conditions
   such as conjugation efficiency and electron donor/acceptor strength
   cannot be evaluated separately, due to structural changes in molecular
   spatial distribution. Experimentally, a new fluorescent molecule of the
   HBO family, 2(2'-hydroxy-4'-aminophenyl)-6-nitrobenzoxazole (BO6), was
   synthesized, purified and characterized, including solvent environments
   of distinct polarities. Hyper-Rayleigh scattering, UV-Vis absorption
   and emission spectroscopy, differential scanning calorimetry and
   thermogravimetric analysis of BO6 show a significant beta (213.4 +/-
   25.7 x 10(-30) esu in acetone, at 1064 nm) and thermal stability up to
   270 degreesC. Such results, in this first study of ESIPT dyes for
   second-order NLO to our best knowledge, indicate that the HBO family
   well deserves further attention towards promising application
   materials. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio Grande Sul, Inst Quim, Dept Quim Organ, Lab Novos Mat Organ, BR-91501970 Porto Alegre, RS, Brazil.
   Univ Fed Rio Grande Sul, Ctr Biotecnol Estado Rio Sul, BR-91501970 Porto Alegre, RS, Brazil.
   Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
RP Stefani, V, Univ Fed Rio Grande Sul, Inst Quim, Dept Quim Organ, Lab
   Novos Mat Organ, Av Bento Goncalves 9500,Caixa Postal 15003,
   BR-91501970 Porto Alegre, RS, Brazil.
CR BHAWALKAR JD, 1996, REP PROG PHYS, V59, P1041
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NR 30
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD NOV 1
PY 2001
VL 273
IS 1
BP 1
EP 10
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 486PW
UT ISI:000171827000001
ER

PT J
AU Furtado, EA
   Milas, I
   Lins, JOMDA
   Nascimento, MAC
TI The dehydrogenation reaction of light alkanes catalyzed by zeolites
SO PHYSICA STATUS SOLIDI A-APPLIED RESEARCH
LA English
DT Article
ID MOLECULAR-DYNAMICS; ELECTROPHILIC REACTIONS; ISOBUTANE CRACKING;
   HYDROXYL-GROUPS; ACIDIC ZEOLITE; AB-INITIO; SILICALITE; METHANE;
   SIMULATION; ACTIVATION
AB The several steps of the dehydrogenation reactions of ethane, propane
   and isobutane were studied by theoretical methods. Molecular dynamics
   simulation techniques have been used to study diffusion of the alkanes
   through the zeolite HZMS-5 framework. Adsorption energies were computed
   by the methods of molecular mechanics, molecular dynamics and
   Monte-Carlo. Molecular dynamics was also used to determine the
   preferred adsorption sites of the alkanes in silicalite and HZMS-5. The
   mechanism of the chemical reactions at the zeolite's acid site was
   investigated at the DFT(B3LYP) level of calculation using 6-31G** and
   6-311G** basis sets, and 3 and 5 T cluster models to represent the
   zeolite. GIAO/B3LYP calculations were performed on the 3 and 5 T
   alkyalkoxides and the results were compared with experimental C-13 NMR
   data.
C1 Univ Fed Rio de Janeiro, Dept Quim Fis, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Dept Quim Fis, Inst Quim,
   Cidade Univ,CT Bloco A,Sala 412, BR-21949900 Rio De Janeiro, Brazil.
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NR 54
TC 7
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA PO BOX 10 11 61, D-69451 BERLIN, GERMANY
SN 0031-8965
J9 PHYS STATUS SOLIDI A-APPL RES
JI Phys. Status Solidi A-Appl. Res.
PD SEP 16
PY 2001
VL 187
IS 1
BP 275
EP 288
PG 14
SC Physics, Condensed Matter
GA 480JJ
UT ISI:000171458000033
ER

PT J
AU Castellano, EE
   Piro, OE
   Caram, JA
   Mirifico, MV
   Aimone, SL
   Vasini, EJ
   Marquez-Lucero, A
   Glossman-Mitnik, D
TI Crystallographic study and molecular orbital calculations of
   thiadiazole derivatives. Part 3: 3,4-diphenyl-1,2,5-thiadiazoline
   1,1-dioxide, 3,4-diphenyl-1,2,5-thiadiazolidine 1,1-dioxide and
   4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE 1,2,5-thiadiazole 1,1-dioxide derivatives; ab initio MO calculations;
   single-crystal X-ray diffraction; DFT; sensitivity analysis
ID DENSITY-FUNCTIONAL THEORY; SOFT ACIDS; CHEMICAL-REACTIVITY;
   CRYSTAL-STRUCTURE; GAS-PHASE; HARDNESS; BASES; ELECTROREDUCTION;
   ELECTROCHEMISTRY; DESCRIPTORS
AB Single-crystal X-ray diffraction studies are reported for
   3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (I),
   3,4-diphenyl-1,2,5-thiadiazolidine 1,1-dioxide(II) and
   4-ethoxy-5-methyl-3,4-diphenyl-1,2,5-thiadiazoline 1,1-dioxide (III).
   Ab initio MO calculations on the electronic structure, conformation and
   reactivity of these compounds are also reported and compared with the
   X-ray results. A charge sensitivity analysis is performed on the
   results applying concepts derived from density functional theory,
   obtaining several sensitivity coefficients such as the molecular
   energy, net atomic charges, global and local hardness, global and local
   softness and Fukui functions. With these results and the analysis of
   the dipole moment and the total electron density and electrostatic
   potential maps, several conclusions have been inferred about the
   preferred sites of chemical reaction of the studied compounds. (C) 2001
   Elsevier Science B.V. All rights reserved.
C1 LAQUICOM, CIMAV, Chihuahua 31109, Chih, Mexico.
   Univ Sao Paulo, Dept Fis, Inst Fis & Quim Sao Carlos, BR-13560 Sao Carlos, SP, Brazil.
   Natl Univ La Plata, Fac Ciencias Exactas, Dept Fis, RA-1900 La Plata, Argentina.
   Consejo Nacl Invest Cient & Tecn, PROFIMO, RA-1900 La Plata, Argentina.
   Natl Univ La Plata, INIFTA, CONICET, RA-1900 La Plata, Argentina.
RP Glossman-Mitnik, D, LAQUICOM, CIMAV, Miguel de Cervantes 120,Complejo
   Ind Chihuahua, Chihuahua 31109, Chih, Mexico.
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NR 63
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD OCT 3
PY 2001
VL 597
IS 1-3
BP 163
EP 175
PG 13
SC Chemistry, Physical
GA 478GG
UT ISI:000171335000018
ER

PT J
AU Ellena, J
   Goeta, AE
   Howard, JAK
   Punte, G
TI Role of the hydrogen bonds in nitroanilines aggregation: Charge density
   study of 2-methyl-5-nitroaniline
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID X-RAY-DIFFRACTION; INTERMOLECULAR INTERACTIONS; ELECTRON-DENSITY;
   TOPOLOGICAL ANALYSIS; NEUTRON-DIFFRACTION; CRYSTAL-STRUCTURE;
   DIHYDROGEN BOND; 100 K; HYPERPOLARIZABILITIES; UREA
AB The electron charge distribution of 2-Methyl-5-nitroaniline has been
   studied from high-resolution singlecrystal X-ray data at 100 K, and ab
   initio calculations which include X-ray structure factors computed from
   a superposition of ab initio molecular electron densities. Using the
   Hansen and Coppens' rigid pseudoatom multipolar model refinements were
   performed on both the experimental and the theoretical X-ray data sets
   from which, molecular atomic charges and dipolar moments were obtained.
   To understand the nature and the magnitude of the intermolecular
   interactions. the Atoms in Molecules theory was used to investigate the
   topology of the electron density of the in-crystal, both experimental
   interacting as well as theoretical noninteracting, and in-vacuum
   molecules. A meticulous analysis of the topological properties of the
   experimental charge density and of its Laplacian indicates, contrary to
   expectations, a two center character of the N-(HO)-O-. . . synthons
   that induce the known polar chain formation in nitroanilines and the
   presence of a C-methyl-H-O interaction further strengthening the
   chains. It also shows the attractive nature of the rather strong
   C-(HO)-O-. . . interactions that help the head-to-tail arrangement of
   the chains. They build two intermolecular six membered hydrogen bonded
   rings, embracing a N-(HO)-O-. . . interaction, that originate
   centrosymmetric dimers which impair the macroscopic second harmonic
   generation of the title compound. The authenticity of a previously
   proposed closed shell C-aryl-H(. . .)pi interaction between adjacent
   chains has been confirmed. The latter has not been observed in
   m-nitroaniline, 2-methyl-4-aniline or other related compounds with
   chains built from similar N-(HO)-O-. . . synthons and assembled
   head-to-head. Crystallization causes a molecular electric dipolar
   moment higher than that of the free molecule, the latter being
   coincident with the experimental value in solution, and with the one
   calculated from the refinement of the theoretical X-ray data. It also
   induces changes in the charge density distribution and its topology,
   and an enhancement of the intramolecular conjugation that can be
   related to a molecular aggregation mechanism ruled by the N-(HO)-O-. .
   . synthon. These findings strongly point to the existence of
   cooperative effects.
C1 Univ Durham, Dept Chem, Durham DH1 3LE, England.
   Natl Univ La Plata, Fac Ciencias Exactas, Dept Fis, IFLP & LANADI, RA-1900 La Plata, Argentina.
   Univ Sao Paulo, Dept Fis & Informat, Inst Fis Sao Carlos, BR-13560 Sao Carlos, SP, Brazil.
RP Goeta, AE, Univ Durham, Dept Chem, South Rd, Durham DH1 3LE, England.
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NR 79
TC 12
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD SEP 27
PY 2001
VL 105
IS 38
BP 8696
EP 8708
PG 13
SC Chemistry, Physical
GA 476EW
UT ISI:000171214100014
ER

PT J
AU Ueno, LT
   Ornellas, FR
TI Theoretical investigation of the initial steps of the adsorption of N
   atoms on Si(100)-2x1
SO SURFACE SCIENCE
LA English
DT Letter
DE density functional calculations; surface chemical reaction; silicon;
   nitrogen atom; silicon nitride
ID SILICON-NITRIDE FORMATION; AB-INITIO; CERAMIC MATERIALS; MICROWAVE
   PLASMA; NH3; SURFACE; POWDER; FILMS; SPECTROSCOPY; DIFFRACTION
AB Structural, energetics, and mechanistics aspects of initial steps of
   the reaction of a N atom with Si(1 0 0)-2 x 1 modeled by the Si9H12 + N
   system are reported. Hybrid density functional B3LYP calculations
   predict a barrierless first step leading to an adsorbate where N is
   bound to one of the dimer Si. Two possible activated routes for
   internal rearrangements were found, with that leading to the
   incorporation of Si below the first layer predicted to be kinetically
   dominant (98%) under the experimental conditions. This structure and
   frequency calculations are consistent with the experimental finding of
   a planar NSi3 moeity and with the experimental SiN asymmetric
   stretching frequency of the NSi3 groups. (C) 2001 Elsevier Science B.V.
   All rights reserved.
C1 Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05513970 Sao Paulo, SP, Brazil.
RP Ornellas, FR, Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, CP
   26077, BR-05513970 Sao Paulo, SP, Brazil.
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NR 35
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD SEP 10
PY 2001
VL 490
IS 3
BP L637
EP L643
PG 7
SC Chemistry, Physical
GA 473XW
UT ISI:000171075300003
ER

PT J
AU Rocha, WR
   De Almeida, KJ
   Coutinho, K
   Canuto, S
TI The electronic spectrum of N-methylacetamide in aqueous solution: a
   sequential Monte Carlo/quantum mechanical study
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID CIRCULAR-DICHROISM CALCULATIONS; AMIDE-I MODE; FAR-ULTRAVIOLET;
   HYDROGEN-BOND; AB-INITIO; WATER; TRANSITION; LIQUID; SPECTROSCOPY;
   CHROMOPHORE
AB Sequential Monte Carlo/quantum mechanical (S-MC/QM) calculations are
   performed to study the solvent effects on the electronic transitions of
   N-methylacetamide (NMA) in aqueous solution. Full quantum mechanical
   INDO/CIS calculations are performed in the super-molecular clusters
   generated by Monte Carlo (MC) simulation. The largest calculation
   involves the ensemble average of 75 quantum mechanical results obtained
   with the NMA solute surrounded by 150 water solvent molecules. After
   extrapolation to the bulk limit we find that the n --> pi* transition
   suffers a blue shift of 1755 cm(-1) upon solvation and the pi --> pi*
   transition undergoes a red shift of 1180 cm(-1), in good agreement with
   the experimental findings. (C) 2001 Published by Elsevier Science B.V.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Fed Juiz Fora, ICE, Dept Quim, NEQC, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Minas Gerais, Dept Quim, ICEx, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Mogi Cruzes, CCET, BR-08701970 Mogi Das Cruzes, SP, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 20516, BR-05315970 Sao Paulo,
   Brazil.
CR AKIYAMA M, 1999, SPECTROCHIM ACTA A, V56, P137
   ALLEN MP, 1987, COMPUTER SIMULATION
   BERENDSEN HJC, 1981, INTERMOLECULAR FORCE, P331
   BESLEY NA, 1998, J PHYS CHEM A, V102, P10791
   BESLEY NA, 2000, J MOL STRUC-THEOCHEM, V506, P161
   CANUTO S, 2000, INT J QUANTUM CHEM, V77, P192
   CLARK LB, 1995, J AM CHEM SOC, V117, P7974
   COUTINHO K, 1997, ADV QUANTUM CHEM, V28, P89
   COUTINHO K, 1997, MONTE CARLO PROGRAM
   COUTINHO K, 2000, J CHEM PHYS, V112, P9874
   FILLAUX F, 1976, CHEM PHYS LETT, V39, P547
   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
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   ROCHA WR, 2001, CHEM PHYS LETT, V335, P127
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   SCHWEITZERSTENNER R, 1998, J PHYS CHEM A, V102, P118
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   ZERNER MC, ZINDO SEMIEMPIRICAL
NR 35
TC 11
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD SEP 7
PY 2001
VL 345
IS 1-2
BP 171
EP 178
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 473UK
UT ISI:000171066300027
ER

PT J
AU Carneiro, JWD
   Taft, CA
   Silva, CHTDE
   Tostes, JGR
   Seidl, PR
   Pinto, PSD
   Costa, VEU
   Alifantes, J
TI Ab initio and density functional study of the
   5-pentacyclo[6.2.1.1(3,6).0(2,7).0(4,10)]dodecyl cation. A symmetrical
   mu-hydride bridged carbocation
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID HALF-CAGE PENTACYCLODODECANE; 2-NORBORNYL CATION; FREQUENCIES;
   DERIVATIVES; EXCHANGE
AB MP2/6-31g(d,p) and B3LYP/6-31g(d,p) calculations for the
   pentacyclo[6.2.1.1(3,6).0(2,7).0(4,10)]dodecyl cation reveal two minima
   on the potential energy surface. The most stable minimum is the
   g-hydride bridged cation 2. The second minimum is the two-electron
   three-center bonded structure 3. At MP2/6-31g(d,p) 2 is only 0.2
   kcal/mol more stable than 3, but at B3LYP/6-31g(d,p) this energy
   difference increases to 3.3 kcal/mol. The energy difference between 2
   and 3 is only 3.8 kcal/mol. Solvent effect does not affect these
   numbers significantly. This low energy barrier may account for the
   product distribution observed on solvolysis of pentacyclic derivatives.
   (C) 2001 Elsevier Science B.V. All rights reserved.
C1 CBPF, Dept Mat Condensada, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Inst Quim, Dept Quim Geral & Inorgan, BR-24020150 Niteroi, RJ, Brazil.
   Univ Estadual Norte Fluminense, Lab Ciecias Quim, Ctr Ciencias & Tecnol, BR-28015620 Sao Jose Dos Campos, RJ, Brazil.
   Univ Fed Rio de Janeiro, Escola Quim, Dept Proc Organ, BR-21949900 Rio De Janeiro, Brazil.
   Inst Militar Engn, Dept Engn Quim, BR-22290270 Rio De Janeiro, Brazil.
   Univ Fed Rio Grande Sul, Inst Quim, Dept Quim Organ, BR-91509900 Porto Alegre, RS, Brazil.
RP Taft, CA, CBPF, Dept Mat Condensada, Rua Dr Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, Brazil.
CR BATTISTE MA, 1977, J CHEM SOC CHEM COMM, P941
   BECKE AD, 1988, PHYS REV A, V38, P3098
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   COSTA VEU, 2000, J MOL STRUCT, V519, P37
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NR 29
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD SEP 7
PY 2001
VL 345
IS 1-2
BP 189
EP 194
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 473UK
UT ISI:000171066300030
ER

PT J
AU Fonseca, TL
   Castro, MA
   Cunha, C
   Amaral, OAV
TI Ab initio polarizabilities calculations of singly charged polyacetylene
   oligomers
SO SYNTHETIC METALS
LA English
DT Article
DE polarizability; polyacetylene oligomers; charged soliton
ID VARIATIONAL PERTURBATIONAL TREATMENT; STATIC FIRST HYPERPOLARIZABILITY;
   NONLINEAR-OPTICAL PROPERTIES; CONJUGATED CHAINS;
   LINEAR-POLARIZABILITIES; ELECTRON CORRELATION; LOCAL VIEW; POLYENES;
   SOLITONS; ABINITIO
AB We present results for the static longitudinal linear polarizability
   and second-order hyperpolarizability of small polyacetylene chains
   bearing positively and negatively charged solitons, obtained through
   the second-order Moller-Plesset perturbation theory (MP2) method.
   Hartree-Fock (HF) calculations for these properties was performed only
   for negatively charged chains. The standard 6-31G basis set was used in
   all calculations. Our ab initio calculations showed that, regarding
   singly charged structures, only the second hyperpolarizability is
   affected by the ionization state. For both, positive and negative
   structures, it is shown that the electron correlation effect enhances
   the linear polarizability, and even more markedly the second
   hyperpolarizabilities. (C) 2001 Elsevier Science B.V. All rights
   reserved.
C1 Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
RP Fonseca, TL, Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
CR BOUDREAUX DS, 1983, PHYS REV B, V28, P6927
   CHAMPAGNE B, 1997, J CHEM PHYS, V107, P5433
   DEMELO CP, 1987, CHEM PHYS LETT, V140, P537
   DEMELO CP, 1988, J CHEM PHYS, V88, P2558
   DEMELO CP, 1988, J CHEM PHYS, V88, P2567
   DEMELO CP, 1996, CHEM PHYS LETT, V28, P261
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   GESKIN VM, 1998, J CHEM PHYS, V109, P6163
   GESKIN VM, 1999, SYNTHETIC MET, V101, P488
   HURST GJB, 1988, J CHEM PHYS, V89, P385
   JACQUEMIN D, 1998, CHEM PHYS LETT, V284, P24
   JACQUEMIN D, 1998, THEOCHEM-J MOL STRUC, V425, P69
   MADER SR, 1994, SCIENCE, V265, P632
   MCLEAN AD, 1967, J CHEM PHYS, V47, P1927
   MEYERS F, 1994, J AM CHEM SOC, V116, P10703
   PRASAD P, 1991, INTRO NONLINEAR OPTI
   ROBINS KA, 1995, SYNTHETIC MET, V71, P1671
   SILVA DA, 1999, SYNTHETIC MET, V102, P1584
   TOTO JL, 1995, CHEM PHYS LETT, V245, P660
   TOTO JL, 1995, J CHEM PHYS, V102, P8048
   TOTO TT, 1995, CHEM PHYS LETT, V244, P59
   VILLAR HO, 1988, J CHEM PHYS, V88, P2859
   VILLAR HO, 1988, PHYS REV B, V37, P2520
   VILLESUZANNE A, 1992, J CHEM PHYS, V96, P495
NR 24
TC 5
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD AUG 22
PY 2001
VL 123
IS 1
BP 11
EP 15
PG 5
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA 472EH
UT ISI:000170970200002
ER

PT J
AU Junqueira, GMA
   Rocha, WR
   De Almeida, WB
   Dos Santos, HF
TI Theoretical analysis of the oxocarbons: structure and spectroscopic
   properties of croconate ion and its coordination compound with lithium
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID DIFFERENTIAL-OVERLAP TECHNIQUE; INTERMEDIATE NEGLECT; MONTE-CARLO;
   TRANSITION; COMPLEXES; DIANIONS; FORMALDEHYDE; WATER
AB Ab initio methods were used in conjunction with Monte Carlo simulation
   to analyze the structure and spectroscopic properties of the croconate
   ion in the gas phase and in aqueous solution. The infrared and Raman
   spectra were calculated and band assignments were made showing a good
   agreement with experiment. The electronic spectrum of the croconate ion
   was calculated in the gas phase and in aqueous solution, using a
   sequential Monte Carlo/quantum mechanical approach, taking into account
   the solvent and counter ion effects. The electronic spectrum for the
   free croconate ion in aqueous solution showed two transitions at 479
   and 468 nm when the first solvation shell is considered. These
   transitions were not sensitive to additional solvent molecules beyond
   the first solvation shell. The experimental electronic spectrum was
   only reproduced when the combined effects of the solvent and counter
   ion were taken into account. The calculated spectrum for the
   cis-[Li-2(C5O5)(H2O)(21)] complex showed two transitions at 383 and 365
   nm, in agreement with the experimental observations of 372 and 351 nm.
   These results strongly suggest that in order to reproduce the
   experimental electronic spectrum of the oxocarbons in solution, we must
   take into account the combined effects of the solvent and the counter
   ions. A new proposal for the interaction of Li+ with the croconate
   anion in solution, based on the theoretical electronic spectra, is also
   discussed.
C1 Univ Fed Juiz de Fora, ICR, Dept Quim, NEQC, BR-36036330 Juiz de Fora, MG, Brazil.
   Univ Fed Minas Gerais, ICEx, Dept Quim, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
RP Dos Santos, HF, Univ Fed Juiz de Fora, ICR, Dept Quim, NEQC, Campus
   Martelos, BR-36036330 Juiz de Fora, MG, Brazil.
CR 1992, HDB CHEM PHYSICS
   AIHARA J, 1981, J AM CHEM SOC, V103, P1633
   ALLEN MP, 1987, COMPUTER SIMULATION
   BECKE AD, 1986, PHYS REV B, V33, P8822
   BERENDSEN HJC, 1981, INTERMOLECULAR FORCE, P331
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
   CANUTO S, 2000, INT J QUANTUM CHEM, V77, P192
   COUTINHO K, DICE MONTE CARLO PRO
   COUTINHO K, 1997, ADV QUANTUM CHEM, V28, P89
   COUTINHO K, 2000, J CHEM PHYS, V113, P9132
   DEALMEIDA KJ, 2001, PHYS CHEM CHEM PHYS, V3, P1583
   DORY M, 1994, J CHEM SOC FARADAY T, V90, P2319
   DOSSANTOS HF, UNPUB
   DUMESTRE F, 1998, J CHEM SOC DALT 1221, P4131
   EDWARDS WD, 1987, THEOR CHIM ACTA, V72, P347
   EGGERDING D, 1975, J AM CHEM SOC, V97, P207
   FABRE PL, 2000, ELECTROCHIM ACTA, V45, P2697
   FARNELL L, 1981, J MOL STRUCT, V76, P1
   FRISCH MJ, 1998, GAUSSIAN 98
   GLICK MD, 1964, INORG CHEM, V3, P1712
   GLICK MD, 1966, INORG CHEM, V5, P289
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   ITO M, 1963, J AM CHEM SOC, V85, P2580
   JORGENSEN WL, 1995, BOSS VERSION 3 5 BIO
   METROPOLIS N, 1953, J CHEM PHYS, V21, P1087
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   RIDLEY J, 1973, THEOR CHIM ACTA, V32, P111
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   SCHLEYER PV, 2000, J ORG CHEM, V65, P426
   SEITZ G, 1992, CHEM REV, V92, P1227
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   WEST R, 1963, J AM CHEM SOC, V85, P2577
   WEST R, 1963, J AM CHEM SOC, V85, P2586
   WEST R, 1981, J AM CHEM SOC, V103, P5073
   ZERNER MC, ZINDO SEMIEMPIRICAL
   ZERNER MC, 1980, J AM CHEM SOC, V102, P589
   ZHAO B, 1992, CAN J CHEM, V70, P135
NR 42
TC 8
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI Phys. Chem. Chem. Phys.
PY 2001
VL 3
IS 17
BP 3499
EP 3505
PG 7
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 471BW
UT ISI:000170907800004
ER

PT J
AU Almeida, AL
   Martins, JBL
   Longo, E
   Furtado, NC
   Taft, CA
   Sambrano, JR
   Lester, WA
TI Theoretical study of MgO(001) surfaces: Pure, doped with Fe, Ca, and
   Al, and with and without adsorbed water
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE MgO; ab initio; water adsorption; Fe; Ca; Al; theoretical study
ID TEMPERATURE-PROGRAMMED DESORPTION; LARGE CLUSTER-MODELS;
   MAGNESIUM-OXIDE; MGO SURFACES; AB-INITIO; MGO(100) SURFACE; ZNO
   SURFACES; DISSOCIATIVE ADSORPTION; HYDROGEN MOLECULE; PROPYLENE-OXIDE
AB Ab initio calculations of large cluster models have been performed in
   order to study water adsorption at the five-fold coordinated adsorption
   site on pure Mg(001) and MgO(001) surfaces doped with Fe, Ca, and Al.
   The geometric parameters of the adsorbed water molecule have been
   optimized preparatory to analysis of binding energies, charge transfer,
   preferential sites of interaction, and bonding distances. We have used
   Mulliken population analysis methods in order to analyze charge
   distributions and the direction of charge transfer. We have also
   investigated energy gaps, HOMO energies, and SCF orbital energies as
   well as the acid-base properties of our cluster model. Numerical
   results are compared, where possible, with experiment and interpreted
   in the framework of various analytical models. (C) 2001 John Wiley &
   Sons, Inc.
C1 Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estatist, BR-22290180 Rio De Janeiro, Brazil.
   Univ Estado Bahia, Dept Ciencias Exatas & Terra, BR-41195001 Salvador, BA, Brazil.
   Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-3565905 Sao Carlos, SP, Brazil.
   Univ Estadual Paulista, Dept Matemat, BR-17033360 Sao Paulo, Brazil.
   Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis
   Estatist, Rua Dr Xavier Sigaud 150, BR-22290180 Rio De Janeiro, Brazil.
CR AHDJOUDI J, 1999, CATAL TODAY, V50, P54
   ALMEIDA AL, 1998, J CHEM PHYS, V109, P367
   ALMEIDA AL, 1998, THEOCHEM-J MOL STRUC, V426, P199
   ALMEIDA AL, 1999, INT J QUANTUM CHEM, V71, P153
   ANCHELL JL, 1996, J PHYS CHEM-US, V100, P1831
   CHACONTAYLOR MR, 1996, J PHYS CHEM-US, V100, P7610
   COLBOURN EA, 1982, SURF SCI, V117, P571
   COLBOURN EA, 1983, SURF SCI, V126, P550
   COLUCCIA S, 1979, J CHEM SOC FARAD T 1, V75, P1769
   COLUCCIA S, 1987, SPECTROCHIM ACTA A, V43, P1573
   DELEEUW NH, 1995, J PHYS CHEM-US, V99, P17219
   DERCOLE A, 1999, J CHEM PHYS, V111, P9743
   DUNSKI H, 1994, J CATAL, V146, P166
   DURIEZ C, 1990, SURF SCI, V230, P123
   FRISCH MJ, 1995, GAUSSIAN 94
   GATES BC, 1992, CATALYTIC CHEM
   GERSON AR, 1999, PHYS CHEM CHEM PHYS, V1, P4889
   GONIAKOWSKI J, 1995, SURF SCI, V323, P129
   GONIAKOWSKI J, 1995, SURF SCI, V330, P337
   GONIAKOWSKI J, 1995, SURF SCI, V340, P191
   HENRICH E, 1984, SURFACE SCI METAL OX
   ILLAS F, 1999, CHEM PHYS LETT, V306, P202
   ITO T, 1991, J PHYS CHEM-US, V95, P4476
   JONES CF, 1984, J CHEM SOC FARAD T 1, V80, P2609
   KOBAYASHI H, 1990, J PHYS CHEM-US, V94, P7206
   KOBAYASHI H, 1994, J PHYS CHEM-US, V98, P5487
   KURODA Y, 1988, J CHEM SOC F1, V84, P2421
   LANGEL W, 1994, PHYS REV LETT, V73, P504
   LINTULUOTO M, 1999, SURF SCI, V429, P133
   LONGO E, 1985, ADV CERAM, V10, P592
   LONGO E, 1985, LANGMUIR, V1, P456
   LONGO E, 1987, HIGH TECH CERAMICS, P399
   MARTINS JBL, 1976, J MOL STRUCT THEOCHE, V363, P249
   MARTINS JBL, 1993, INT J QUANTUM CHEM, V27, P643
   MARTINS JBL, 1994, THEOCHEM-J MOL STRUC, V109, P19
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P301
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P347
   MARTINS JBL, 1995, THEOCHEM-J MOL STRUC, V335, P167
   MARTINS JBL, 1996, INT J QUANTUM CHEM, V57, P861
   MARTINS JBL, 1997, THEOCHEM-J MOL STRUC, V397, P147
   MARTINS JBL, 1997, THEOCHEM-J MOL STRUC, V398, P457
   MARTINS JBL, 1998, INT J QUANTUM CHEM, V70, P367
   MCCARTHY MI, 1996, J PHYS CHEM-US, V100, P16989
   MITAMURA T, 1998, NIPPON KAGAKU KA MAR, P174
   PAVAO AC, 1994, PHYS REV B, V50, P1868
   PAVAO AC, 1995, SURF SCI, V323, P340
   PICAUD S, 1993, CHEM PHYS LETT, V209, P340
   RODRIGUEZ JA, 1999, J CHEM PHYS, V111, P8077
   ROSSI PF, 1991, LANGMUIR, V7, P2677
   SCAMEHORN CA, 1993, J CHEM PHYS, V99, P2786
   SCAMEHORN CA, 1994, J CHEM PHYS, V101, P1547
   SHINOHARA Y, 1998, NIPPON KAGAKU KA OCT, P643
   VULLIERMET N, 1998, COLLECT CZECH CHEM C, V63, P1447
   WADT WR, 1985, J CHEM PHYS, V82, P284
NR 54
TC 4
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD SEP 20
PY 2001
VL 84
IS 6
BP 705
EP 713
PG 9
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 470RF
UT ISI:000170884400012
ER

PT J
AU Toma, HE
   Rocha, RC
TI Linkage isomerization reactions
SO CROATICA CHEMICA ACTA
LA English
DT Review
DE linkage isomerism; reaction mechanism; kinetics
ID OXIME-IMINE LIGANDS; NORMAL-COORDINATE ANALYSIS; AROMATIC NITROGEN
   HETEROCYCLES; DIMETHYL-SULFOXIDE COMPLEXES; INTERSTRAND CROSS-LINKING;
   DENSITY-FUNCTIONAL THEORY; BASE-CATALYZED NITRITO; RAY
   CRYSTAL-STRUCTURE; III AMMINE COMPLEXES; OXYGEN-ATOM TRANSFER
AB Linkage isomerization reactions have been reviewed from the aspect of
   the kinetics and mechanisms involved, focusing on selected cases of
   direct formation, as well as on electrochemical, photochemical, thermal
   and pH-induced generation of linkage isomers.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Toma, HE, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
CR ABRUNA HD, 1981, INORG CHEM, V20, P1481
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NR 348
TC 7
PU CROATIAN CHEMICAL SOC
PI ZAGREB
PA MARULICEV TRG 19/II, 41001 ZAGREB, CROATIA
SN 0011-1643
J9 CROAT CHEM ACTA
JI Croat. Chem. Acta
PD AUG
PY 2001
VL 74
IS 3
SI Sp. Iss. SI
BP 499
EP 528
PG 30
SC Chemistry, Multidisciplinary
GA 469JN
UT ISI:000170810900004
ER

PT J
AU Baierle, RJ
   Fagan, SB
   Mota, R
   da Silva, AJR
   Fazzio, A
TI Electronic and structural properties of silicon-doped carbon nanotubes
SO PHYSICAL REVIEW B
LA English
DT Article
ID AB-INITIO CALCULATIONS; LARGE SYSTEMS; BORON; CLUSTERS; MICROTUBULES;
   CONDUCTANCE; FULLERENES; NITROGEN; DEFECTS
AB Predictions of the electronic and structural properties of silicon
   substitutional doping in carbon nanotubes are presented using
   first-principles calculations based on the density-functional theory. A
   large outward displacement of the Si atom and its nearest-neighbor
   carbon atoms is observed. For the two tubes studied [metallic (6,6) and
   semiconducting ( 10,0)] the formation energies of the substitutional
   defects are obtained around 3.1 eV/atom. In the doped metallic nanotube
   case a resonant state appears about 0.7 eV above the Fermi level,
   whereas for the semiconductor tube, the silicon introduces an empty
   level at approximately 0.6 eV above the top of the valence band.
C1 Ctr Univ Franciscano, Dept Ciencias Exatas, BR-97010032 Santa Maria, RS, Brazil.
   Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Baierle, RJ, Ctr Univ Franciscano, Dept Ciencias Exatas, BR-97010032
   Santa Maria, RS, Brazil.
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NR 28
TC 24
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD AUG 15
PY 2001
VL 6408
IS 8
BP art. no.
EP 085413
AR 085413
PG 4
SC Physics, Condensed Matter
GA 466AW
UT ISI:000170623000096
ER

PT J
AU Dorfman, S
   Liubich, V
   Fuks, D
   Mundim, KC
TI Simulations of decohesion and slip of the Sigma(3) < 111 > grain
   boundary in tungsten with non-empirically derived interatomic
   potentials: the influence of boron interstitials
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID EMBEDDED-ATOM-METHOD; ELECTRONIC-STRUCTURE; INTERGRANULAR COHESION;
   MOLECULAR-DYNAMICS; TRANSITION-METALS; VACANCY-FORMATION; PAIR
   POTENTIALS; ALLOYS; IMPURITIES; IRON
AB Monte Carlo atomistic simulations of the properties Of Sigma (3) < 111
   > grain boundaries in W are carried out. We demonstrate the influence
   of boron additive on the resistance of the grain boundary with respect
   to different shifts. The interatomic potentials used in these
   simulations are obtained from ab initio total-energy calculations.
   These calculations are performed in the framework of density functional
   theory in the coherent potential approximation. A recursion procedure
   for extracting A-B-type interatomic potentials is suggested.
C1 Technion Israel Inst Technol, Dept Phys, IL-32000 Haifa, Israel.
   Ben Gurion Univ Negev, Dept Mat Engn, IL-84105 Beer Sheva, Israel.
   Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
RP Dorfman, S, Technion Israel Inst Technol, Dept Phys, IL-32000 Haifa,
   Israel.
CR ACKLAND GJ, 1990, PHYS REV B, V41, P10324
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NR 64
TC 8
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD AUG 6
PY 2001
VL 13
IS 31
BP 6719
EP 6740
PG 22
SC Physics, Condensed Matter
GA 466UD
UT ISI:000170663800015
ER

PT J
AU Okulik, NB
   Diez, RP
   Jubert, AH
   Esteves, PM
   Mota, CJA
TI A topological study of the transition states of the hydrogen exchange
   and dehydrogenation reactions of methane on a zeolite cluster
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID AB-INITIO; MECHANISM; ALKANES; PROTON; CD4
AB The transition states of the hydrogen exchange and dehydrogenation
   reactions of methane on a zeolite acid site are studied within the
   framework of the density functional theory and the atoms-in-molecules
   theory. The transition state for the hydrogen exchange reaction is
   found to be characterized by a slightly ionic interaction between a
   distorted CH5+ structure and the negatively charged zeolite. No free
   carbocation is found. The dehydrogenation reaction presents a
   transition state in which three different fragments can be well
   identified, namely, an almost planar CH3+ structure, a H-2
   pseudomolecule, and the negatively charged zeolite. The interaction
   between the fragments can be described as a closed-shell one, typical
   of rather ionic systems.
C1 Natl Univ La Plata, Fac Ciencias Exactas, Ctr Quim Inorgan, CEQUINOR,Dept Quim, RA-1900 La Plata, Argentina.
   UNNE, Fac Agroind, Dept Quim, RA-3700 Pena, Chaco, Argentina.
   Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
RP Diez, RP, Natl Univ La Plata, Fac Ciencias Exactas, Ctr Quim Inorgan,
   CEQUINOR,Dept Quim, CC 962, RA-1900 La Plata, Argentina.
CR BADER RFW, 1990, ATOMS MOL QUANTUM TH
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   LEE C, 1988, PHYS REV B, V37, P785
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   POPELIER PLA, 1999, ATOMS MOL INTRO
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   WANG LS, 1993, CATAL LETT, V21, P35
NR 27
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JUL 26
PY 2001
VL 105
IS 29
BP 7079
EP 7084
PG 6
SC Chemistry, Physical
GA 457TH
UT ISI:000170152600015
ER

PT J
AU Pliego, JR
   Riveros, JM
TI The cluster-continuum model for the calculation of the solvation free
   energy of ionic species
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID STATISTICAL PERTURBATION-THEORY; PERIODIC BOUNDARY-CONDITIONS;
   SELF-CONSISTENT-FIELD; AB-INITIO; MOLECULAR-DYNAMICS; HYDROXIDE ION;
   AQUEOUS SOLVATION; LIQUID WATER; THERMODYNAMIC INTEGRATION; POTENTIAL
   FUNCTIONS
AB A hybrid approach using a combination of explicit solvent molecules and
   the isodensity polarizable continuum model (IPCM) method is proposed
   for the calculation of the solvation thermodynamic properties of ions.
   This model, denominated cluster-continuum, has been applied to the
   calculation of the solvation free energy of 14 univalent ions, mainly
   organic species, and compared with the results obtained with the IPCM,
   polarizable continuum solvation model (PCM), and SM5.42R continuum
   methods. The average error in our calculated solvation free energies
   with respect to experimental data is 8.7 kcal mol(-1). However, the
   great merit of our model resides in the homogeneous treatment for
   different ions, resulting in a standard deviation of only 2.9 kcal
   mol(-1) for the average error. Our results suggest that the
   cluster-continuum model must be superior to the IPCM, PCM, and SM5.42R
   methods for studying chemical reactions in the liquid phase, because
   these continuum methods present a standard deviation of similar to8
   kcal mol(-1) for the average error for the species studied in this
   work. The model can also be used to calculate the solvation entropy of
   ions. Predicted solvation entropies for five ionic species are in good
   agreement with available experimental data.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Pliego, JR, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05508900
   Sao Paulo, Brazil.
CR ALEMAN C, 1999, CHEM PHYS LETT, V302, P461
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NR 59
TC 34
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 2
PY 2001
VL 105
IS 30
BP 7241
EP 7247
PG 7
SC Chemistry, Physical
GA 457TJ
UT ISI:000170152700015
ER

PT J
AU Persson, C
   da Silva, AF
   Ahuja, R
   Johansson, B
TI Effective electronic masses in wurtzite and zinc-blende GaN and AlN
SO JOURNAL OF CRYSTAL GROWTH
LA English
DT Article
DE computer simulation; crystal structure; nitrides; semiconducting III-V
   materials
ID GENERALIZED GRADIENT APPROXIMATION; LOCAL-DENSITY APPROXIMATION;
   OPTICAL BAND-GAP; GALLIUM NITRIDE; EPITAXIAL-GROWTH; HEXAGONAL GAN; 001
   SILICON; THIN-FILMS; ENERGY; AIN
AB The effective electron and hole masses are fundamental quantities of
   semiconductors, used in numerous analyses of experiments and
   theoretical investigations. We present calculations of the band
   structure near the band edges in intrinsic GaN and AIN, both for the
   wurtzite and the zinc-blende polytypes. We have utilized a
   full-potential linearized augmented plane wave method within the
   density functional theory and with two different exchange-correlation
   potentials. The lattice parameters have been determined by a
   minimization of the total energy, whereupon the crystal-field
   splitting, the spin-orbit splitting, and the effective electron and
   hole masses have been calculated. The calculated effective masses are
   in good agreement with available experimental values. We show the
   importance of performing a fully relativistic calculation. For
   instance, the hole mass in cubic AIN is a very large and negative
   quantity if the spin-orbit coupling is excluded, whereas the fully
   relativistic calculation gives a relatively small and positive value.
   (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Uppsala, Dept Phys, SE-75121 Uppsala, Sweden.
   Univ Fed Bahia, Inst Fis, BR-40210340 Salvador, BA, Brazil.
RP Persson, C, Univ Uppsala, Dept Phys, Box 530, SE-75121 Uppsala, Sweden.
CR BACHELET GB, 1985, PHYS REV B, V31, P879
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NR 38
TC 15
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-0248
J9 J CRYST GROWTH
JI J. Cryst. Growth
PD OCT
PY 2001
VL 231
IS 3
BP 397
EP 406
PG 10
SC Crystallography
GA 459GB
UT ISI:000170241700012
ER

PT J
AU Perottoni, CA
   da Jornada, JAH
TI The carbon analogues of type-I silicon clathrates
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; DIAMOND-LIKE MATERIALS; VALENCE BASIS-SETS;
   HIGH-PRESSURE; STRUCTURAL-PROPERTIES; AB-INITIO; THERMAL-CONDUCTIVITY;
   ELASTIC PROPERTIES; HARTREE-FOCK; SI
AB In this paper we present a survey on the structure and equation of
   state for some silicon clathrates and their carbon analogues, as
   obtained by means of ab initio calculations within the Hartree-Fock
   approximation. We restrict our consideration to type-I clathrates,
   namely M-x(Si, C)(46), With M = Na, Ba. The insertion of guest species
   into the carbon clathrate cages promotes a significant increase in the
   host volume, thus reducing the bulk modulus for these compounds. In
   spite of that, the estimated hardness for C-46, Of about 61 GPa,
   constitutes an exceptionally large value for a structure with such an
   open framework. The issue of electronic charge transference from the
   guest species to the host framework and the stability of carbon and
   silicon clathrates relative to the diamond phase are also discussed.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
   INMETRO, BR-25250020 Duque De Caxias, RJ, Brazil.
RP Perottoni, CA, Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto
   Alegre, RS, Brazil.
CR ADAMS GB, 1992, SCIENCE, V256, P1792
   ADAMS GB, 1994, PHYS REV B, V49, P8048
   ANDERSON OL, 1963, J PHYS CHEM SOLIDS, V24, P909
   BENEDEK G, 1995, CHEM PHYS LETT, V244, P339
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NR 55
TC 6
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD JUL 2
PY 2001
VL 13
IS 26
BP 5981
EP 5998
PG 18
SC Physics, Condensed Matter
GA 455EW
UT ISI:000170015400018
ER

PT J
AU da Silva, AJR
   Dalpian, GM
   Janotti, A
   Fazzio, A
TI Two-atom structures of Ge on Si(100): Dimers versus adatom pairs
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID SI AD-DIMERS; SCANNING-TUNNELING-MICROSCOPY; HOMOEPITAXIAL GROWTH;
   SI(001); DYNAMICS; SURFACE; ENERGETICS; DIFFUSION; SILICON; GE(001)
AB We present an ab initio study of the properties of structures composed
   of two and four Ge atoms adsorbed on the troughs of the Si(100)
   surface, and we conclude that these structures are all composed of
   dimers, with a chemical bonding between the adatoms. We compare our
   calculated local density of states with scanning tunneling microscope
   (STM) images, and we show that these Ge dimers adsorbed on the troughs
   between the substrate dimer rows can be identified with the adatom
   pairs observed experimentally. We also show that the local buckling of
   the substrate dimers can give rise to similar structures with very
   different STM images.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Janotti, A, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BEDROSSIAN PJ, 1995, PHYS REV LETT, V74, P3648
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BOROVSKY B, 1997, PHYS REV LETT, V78, P4229
   BROCKS G, 1996, PHYS REV LETT, V76, P2362
   DALPIAN GM, IN PRESS SURF SCI
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   DALPIAN GM, 2001, PHYS REV B, V63
   GALEA TM, 2000, PHYS REV B, V62, P7206
   KHARE SV, 1999, PHYS REV B, V60, P4458
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NR 22
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD JUL 16
PY 2001
VL 8703
IS 3
AR 036104
DI ARTN 036104
PG 4
SC Physics, Multidisciplinary
GA 454UF
UT ISI:000169989600034
ER

PT J
AU Resende, SM
   Ornellas, FR
TI Radiative and predissociative lifetimes of the A (2)Sigma(+) state
   (v(')=0,1) of SH and SD: A highly correlated theoretical investigation
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID CONFIGURATION-INTERACTION CALCULATIONS; GAUSSIAN-BASIS SETS; MOLECULAR
   CALCULATIONS; A2-SIGMA+ STATE; ELECTRONIC-STRUCTURE; ROW ATOMS;
   PHOTODISSOCIATION; SPECTROSCOPY; SPECTRUM; NM
AB Doublet and quartet states of the HS radical correlating with
   H(S-2)+S(P-3,D-1,S-1) were investigated by ab initio calculations, at
   the CASSCF-MRCI/aug-cc-pV5Z level of theory. Molecular parameters and
   spectroscopic constants obtained for both the ground (X (2)Pi) and the
   first excited (A (2)Sigma (+)) states represent the best overall
   theoretical description of this system to date. Transition moments,
   transition probabilities, and radiative and predissociative lifetimes
   were also determined for the X (2)Pi -A (2)Sigma (+) system. The values
   calculated for the radiative lifetimes of the A state show that
   previous results were too large. Theoretical predissociative lifetimes,
   although quite sensitive to the region of crossing of the potential
   energy curves, reproduce the experimental trends. (C) 2001 American
   Institute of Physics.
C1 Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05513970 Sao Paulo, Brazil.
RP Resende, SM, Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, Caixa
   Postal 26077, BR-05513970 Sao Paulo, Brazil.
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NR 54
TC 6
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD AUG 1
PY 2001
VL 115
IS 5
BP 2178
EP 2187
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 453QQ
UT ISI:000169927700025
ER

PT J
AU Miron, C
   Simon, M
   Morin, P
   Nanbu, S
   Kosugi, N
   Sorensen, SL
   de Brito, AN
   Piancastelli, MN
   Bjorneholm, O
   Feifel, R
   Bassler, M
   Svensson, S
TI Nuclear motion driven by the Renner-Teller effect as observed in the
   resonant Auger decay to the (X)over-tilde(2)Pi electronic ground state
   of N2O+
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID EXCITED-STATES; MOLECULES; DISSOCIATION; SCATTERING; SPECTRUM; CO2;
   SPECTROSCOPY; EDGE
AB High-resolution Auger spectroscopy applied under resonant Auger Raman
   conditions is shown to be a powerful tool for characterizing complex
   potential energy surfaces in core-excited systems. Using the example of
   N-t 1s(-1)pi*-->(X) over tilde (2)Pi resonant Auger transition in
   nitrous oxide we emphasize the interplay between the nuclear motion and
   the electronic decay. We show how the choice of excitation energy
   allows selection of core-excited species of different geometries. The
   nuclear dynamics of these species are mapped by measuring the resonant
   Auger decay spectra. In addition to the changes in vibrational
   structure observed for the resonant Auger decay spectra, a strong
   influence of nuclear motion on the electronic decay is revealed,
   inducing the so-called "dynamical Auger emission." The experimental
   results are supported by ab initio quantum chemical calculations
   restricted to a linear geometry of the core-excited state. (C) 2001
   American Institute of Physics.
C1 Univ Paris Sud, LURE, F-91898 Orsay, France.
   CENS, CEA, DRECAM, SPAM LFP, F-91191 Gif Sur Yvette, France.
   Inst Mol Sci, Okazaki, Aichi 4448585, Japan.
   Univ Lund, Dept Synchrotron Radiat Res, S-22100 Lund, Sweden.
   Lab Nacl Luz Sincrotron, BR-13083970 Campinas, SP, Brazil.
   Univ Roma Tor Vergata, Dept Chem Sci & Technol, I-00133 Rome, Italy.
   Univ Uppsala, Dept Phys, S-75121 Uppsala, Sweden.
RP Miron, C, Univ Paris Sud, LURE, Bat 209D,BP 34, F-91898 Orsay, France.
CR ADACHI J, 1997, J CHEM PHYS, V107, P4919
   ADACHI JI, 1995, J CHEM PHYS, V102, P7369
   BASSLER M, IN PRESS NUCL INST B
   BRAMLEY MJ, 1993, J CHEM PHYS, V99, P8519
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   DEMMEL JW, 1997, APPL NUMERICAL LINEA
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   GOLDFIELD EM, 1998, COMPUT PHYS COMMUN, V98, P1
   GRITLI H, 1993, CHEM PHYS, V178, P223
   HUZINAGA S, 1984, GAUSSIAN BASIS SETS
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   LILL JV, 1982, CHEM PHYS LETT, V89, P483
   MA Y, 1991, PHYS REV A, V44, P1848
   MIRON C, UNPUB
   MIRON C, 1998, J ELECTRON SPECTROSC, V93, P95
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   PIANCASTELLI MN, 2000, J ELECTRON SPECTROSC, V107, P1
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   SIMON M, 1997, PHYS REV LETT, V79, P3857
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   YANG CY, 1997, J CHEM PHYS, V107, P7773
NR 31
TC 9
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUL 8
PY 2001
VL 115
IS 2
BP 864
EP 869
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 448ZW
UT ISI:000169660700035
ER

PT J
AU Justo, JF
   Antonelli, A
   Fazzio, A
TI Dislocation core properties in semiconductors
SO SOLID STATE COMMUNICATIONS
LA English
DT Article
DE semiconductor; dislocations and disclinations; electronic band
   structure; electronic states (localized)
ID DENSITY-FUNCTIONAL THEORY; MOLECULAR-DYNAMICS; SILICON; MOBILITY;
   PSEUDOPOTENTIALS; VELOCITIES; CRYSTALS; GAAS; INAS
AB Using ab initio calculations, we computed the core reconstruction
   energies of {111} 30 degrees partial dislocations in zinc-blende
   semiconductors. Our results show a direct correlation between core
   reconstruction energies and the experimental activation energies for
   the velocity of 60 degrees dislocations. The electronic structure of
   unreconstructed dislocation cores comprises a half-filled band, which
   splits up in bonding and antibonding levels upon reconstruction. The
   levels in the electronic gap come from the core of beta dislocations,
   while the levels related to or dislocations lie on the valence band.
   (C) 2001 Elsevier Science Ltd. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
RP Justo, JF, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR ALEXANDER H, 1986, DISLOCATIONS SOLIDS, V7, P115
   ALEXANDER H, 1989, I PHYS C SER, V104, P281
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   CAI W, 2000, PHYS REV LETT, V84, P3346
   CAR R, 1985, PHYS REV LETT, V55, P2471
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   CHOI SK, 1978, JPN J APPL PHYS, V17, P329
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   IMAI M, 1983, PHILOS MAG A, V47, P599
   JUSTO JF, 1998, PHYS REV B, V58, P2539
   JUSTO JF, 1999, J APPL PHYS, V86, P4249
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   KLEINMAN L, 1982, PHYS REV LETT, V48, P1425
   MONKHORST HJ, 1976, PHYS REV B, V13, P5188
   OMRI M, 1990, PHILOS MAG A, V62, P203
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   TROULLIER N, 1991, PHYS REV B, V43, P1993
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   YONENAGA I, 1993, J APPL PHYS, V73, P1681
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   YONENAGA I, 1998, J APPL PHYS, V84, P4209
NR 24
TC 12
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0038-1098
J9 SOLID STATE COMMUN
JI Solid State Commun.
PY 2001
VL 118
IS 12
BP 651
EP 655
PG 5
SC Physics, Condensed Matter
GA 445NL
UT ISI:000169463900011
ER

PT J
AU Lopes, KC
   Pereira, FS
   Ramos, MN
   de Araujo, RCMU
TI An ab-initio study of the C3H6-HX, C2H4-HX and C2H2-HX hydrogen-bonded
   complexes with X=F or CI
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE ab-initio study; hydrogen bond; infrared spectrum; vibrational
   properties
ID QUADRUPOLE COUPLING-CONSTANTS; ROTATIONAL SPECTRUM;
   MOLECULAR-STRUCTURE; INFRARED-SPECTROSCOPY; FLUORIDE DIMER; HF COMPLEX;
   ACETYLENE; CYCLOPROPANE; GEOMETRY; ABINITIO
AB MP2/6-31G** ab-initio molecular orbital calculations have been
   performed to obtain geometries, H-bond energies and vibrational
   properties of the C3H6-HX, C2H4-HX and C2H2-HX H-bonded complexes with
   X=F or Cl. The more pronounced effects on the structural parameters of
   the isolated molecules due to complexation are verified to the CC and
   HX bond lengths, which are directly involved in the H-bond formation.
   They are increased after complexation. The calculated H-bond lengths
   for the hydrogen complexes for X=F are shorter than those for x-Cl by
   about 0.55 Angstrom whereas the corresponding experimental value is
   0.58 Angstrom. The H-bond energies are essentially determined by the
   nature of the proton donor molecule. For X-F, the AE mean value is 20
   kJ/mol, whereas it is approximately 14.5 kJ/mol for X=Cl. The H-bond
   energies including zero-point corrections show a good correlation with
   the H-bond lengths. The more pronounced effect on the normal modes of
   the isolated molecules after complexation occurs to the H-X stretching
   mode. The HX stretching frequency is shifted downward, whereas its IR
   intensity is much enhanced upon H-bond formation. The new vibrational
   modes arising from complexation show several interesting features. (C)
   2001 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50739901 Recife, PE, Brazil.
   Univ Fed Paraiba, Dept Quim, BR-58036300 Joao Pessoa, Paraiba, Brazil.
RP Ramos, MN, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50739901
   Recife, PE, Brazil.
CR ALDRICH PD, 1981, J CHEM PHYS, V75, P2126
   ARAUJO RCMU, 1995, SPECTROCHIM ACTA A, V51, P821
   ARAUJO RCMU, 1996, THEOCHEM-J MOL STRUC, V366, P233
   ARAUJO RCMU, 1998, J BRAZIL CHEM SOC, V9, P499
   BRYANT GW, 1988, J CHEM SOC F2, V84, P1443
   BUCKINGHAM AD, 1988, CHEM REV, V88, P963
   BUXTON LW, 1981, J CHEM PHYS, V75, P2681
   CHANDRA AK, 1995, CHEM PHYS LETT, V247, P95
   CRAW JS, 1991, J CHEM SOC FARADAY T, V87, P1293
   DASILVA JBP, 1997, SPECTROCHIM ACTA A, V53, P733
   FRISCH MJ, 1992, GAUSSIAN 92 REVISION
   GUSSONI M, 1987, CHEM PHYS LETT, V142, P515
   JUCKS KW, 1987, J CHEM PHYS, V86, P4341
   KUKOLICH SG, 1983, J CHEM PHYS, V78, P4832
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   TANG TH, 1990, J MOL STRUCT THEOCHE, V207, P319
NR 23
TC 6
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JUN
PY 2001
VL 57
IS 7
BP 1339
EP 1346
PG 8
SC Spectroscopy
GA 441EK
UT ISI:000169217900001
ER

PT J
AU Capelle, K
   Vignale, G
TI Nonuniqueness of the potentials of spin-density-functional theory
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID DERIVATIVE DISCONTINUITIES; ELECTRON-DENSITIES; ORBITAL ENERGIES; SHAM
AB It is shown that, contrary to widely held beliefs, the potentials of
   spin-density-functional theory (SDFT) are not unique functionals of the
   spin densities. Explicit tramples of distinct sets of potentials with
   the same ground-stale densities are constructed. These findings imply
   that the zero-temperature exchange-correlation energy is not always a
   differentiable functional of the spin density. As a consequence,
   various types of applications of SDFT must be critically reexamined.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Missouri, Dept Phys & Astron, Columbia, MO 65211 USA.
RP Capelle, K, Univ Sao Paulo, Inst Quim Sao Carlos, Caixa Postal 780,
   BR-13560970 Sao Carlos, SP, Brazil.
CR ARYASETIAWAN F, 1988, PHYS REV B, V38, P2974
   ESCHRIG H, 2001, SOLID STATE COMMUN, V118, P123
   GORLING A, 1992, PHYS REV A, V46, P3753
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   GRABO T, 1998, STRONG COULOMB CORRE
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NR 21
TC 23
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD JUN 11
PY 2001
VL 86
IS 24
BP 5546
EP 5549
PG 4
SC Physics, Multidisciplinary
GA 441PV
UT ISI:000169239500035
ER

PT J
AU Lopes, KC
   Pereira, FS
   de Araujo, RCMU
   Ramos, MN
TI An ab initio study of the structural and vibrational properties of the
   C3H6-HCN, C2H4-HCN and C2H2-HCN hydrogen-bonded complexes
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE hydrogen bond; infrared spectrum; ab initio study
ID QUADRUPOLE COUPLING-CONSTANTS; ROTATIONAL SPECTRUM;
   MOLECULAR-STRUCTURE; INFRARED-SPECTRA; CYCLOPROPANE-HCN; FLUORIDE
   DIMER; HF COMPLEX; ACETYLENE; GEOMETRY; SPECTROSCOPY
AB MP2/6-311+ +G(**) ab initio molecular orbital calculations have been
   performed to obtain the molecular properties of the C3H6-HCN, C2H4-HCN
   and C2H2-HCN H-bonded complexes. The more pronounced effects on the
   structural parameters of the isolated molecules due to complexation are
   verified by the CC and H-CN bond lengths which are directly involved in
   the H-bond formation. They are increased after complexation. The
   calculated H-bond lengths are in excellent agreement with the
   experimental ones. The H-bond energies after inclusion of the
   zero-point contributions are -8.7, -7.6 and -9.0 kJ mol(-1) for the
   C2H2-HCN, C2H2-HCN and C3H6-HCN complexes, respectively. These values
   are in very good agreement with the approximate experimental binding
   energies obtained from the well depth using a Lennard-Jones 6-12
   potential. The more pronounced effect on the normal modes of the
   isolated molecules after complexation occurs in the H-X stretching
   mode. The H-X stretching frequency is shifted downward whereas its IR
   intensity is much enhanced upon H-bond formation. (C) 2001 Elsevier
   Science B,V. All rights reserved.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50739901 Recife, PE, Brazil.
   Univ Fed Paraiba, Dept Quim, BR-58036300 Joao Pessoa, Paraiba, Brazil.
RP Ramos, MN, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50739901
   Recife, PE, Brazil.
CR ALDRICH PD, 1981, J CHEM PHYS, V75, P2126
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   ARAUJO RCMU, 1998, J BRAZIL CHEM SOC, V9, P499
   BUCKINGHAM AD, 1988, CHEM REV, V88, P963
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NR 22
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD MAY 30
PY 2001
VL 565
SI Sp. Iss. SI
BP 417
EP 420
PG 4
SC Chemistry, Physical
GA 441NC
UT ISI:000169235600070
ER

PT J
AU Dalpian, GM
   Fazzio, A
   da Silva, AJR
TI Adsorption of monomers on semiconductors and the importance of surface
   degrees of freedom
SO PHYSICAL REVIEW B
LA English
DT Article
ID SCANNING-TUNNELING-MICROSCOPY; SI(100) SURFACE; AB-INITIO;
   HOMOEPITAXIAL GROWTH; FILM GROWTH; SI ADATOM; DIFFUSION; SI(001); GE;
   BINDING
AB We study, through first-principles calculations based on the density
   functional theory, the adsorption of the Ge monomer on the Si(100)
   surface. We use this particular system to draw attention to the general
   fact that in semiconductors, one cannot talk about the adsorption sites
   and adsorption energies for a monomer without including in the
   description the local substrate configuration. As a consequence, for a
   given position of the monomer on the surface, there can be many local
   minima that differ basically in the substrate local configuration.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Dalpian, GM, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
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   DALPIAN GM, 1999, PHYSICA B, V273, P589
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   MILMAN V, 1994, PHYS REV B, V50, P2663
   MILMAN V, 1996, THIN SOLID FILMS, V272, P375
   MO YW, 1991, PHYS REV LETT, V66, P1998
   MO YW, 1991, SURF SCI, V248, P313
   MO YW, 1992, SURF SCI, V268, P275
   QIN XR, 1997, SCIENCE, V278, P1444
   QIN XR, 1998, PHYS REV LETT, V81, P2288
   RAMSTAD A, 1995, PHYS REV B, V51, P14504
   SAVAGE DE, 1999, SEMICONDUCT SEMIMET, V56, P49
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   SWARTZENTRUBER BS, 1997, PHYS REV B, V55, P1322
   TERAKURA K, 1997, SURF SCI, V386, P207
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   YAMASAKI T, 1996, PHYS REV LETT, V76, P2949
   ZANDVLIET HJW, 2000, PHYS REV LETT, V84, P1523
   ZHANG QM, 1995, PHYS REV LETT, V75, P101
   ZHANG ZY, 1997, ANNU REV MATER SCI, V27, P525
   ZHANG ZY, 1997, SCIENCE, V276, P377
NR 28
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 15
PY 2001
VL 6320
IS 20
AR 205303
DI ARTN 205303
PG 4
SC Physics, Condensed Matter
GA 436LK
UT ISI:000168937200050
ER

PT J
AU Freitas, MP
   Rittner, R
   Tormena, CF
   Abraham, RJ
TI Conformational analysis of 2-bromocyclohexanone. A combined NMR, IR,
   solvation and theoretical approach
SO JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
LA English
DT Article
DE 2-bromocyclohexanone; conformational analysis; NMR; IR; solvation;
   density functional theory
ID COUPLING-CONSTANTS; ORGANIC-MOLECULES; ISOMERISM
AB An improved method of conformational analysis using H-1 and C-13 NMR,
   IR, theoretical calculations and solvation theory is reported for
   2-bromocyclohexanone, used here as a model compound. The solvent
   dependence of the (3)J(HH), (1)J(CH) and (1)J(CD) NMR coupling
   constants and the associated changes in the IR first overtone carbonyl
   band intensities together with theoretical calculations allow the
   direct determination of the conformational equilibria without recourse
   to model compounds. Calculations with the Gaussian 98 program at the
   HF/6-31 g(d,p) and B3LYP/6-31 + g(d,p) levels together with solvation
   theory gave the conformer free energy difference (E-eq - E-ax) in
   different solvents. The observed couplings, when analyzed by solvation
   theory and utilizing DFT geometries, gave a value of E-eq - E-ax of
   1.15 kcal mol(-1) in the vapor phase, decreasing to 0.6 kcal mol(-1) in
   CCl4 and to -0.5 kcal mol(-1) in DMSO solution (1 kcal = 4.184 kJ). The
   axial percentage changes from 74% (in CCl4) to 30% (in DMSO), and these
   are in good agreement with infrared data (nu (C=O), first overtone),
   despite the uncertainties of the latter method. The results illustrate
   the advantages of the joint application of these techniques, which
   represents an improved approach to the study of the conformational
   equilibria of substituted cyclohexanones. Copyright (C) 2001 John Wiley
   & Sons, Ltd.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
RP Rittner, R, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083970 Campinas, SP, Brazil.
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NR 30
TC 10
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND
SN 0894-3230
J9 J PHYS ORG CHEM
JI J. Phys. Org. Chem.
PD JUN
PY 2001
VL 14
IS 6
BP 317
EP 322
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 437RZ
UT ISI:000169008500001
ER

PT J
AU Casanovas, J
   Namba, AM
   Leon, S
   Aquino, LB
   da Silva, GVJ
   Aleman, C
TI Calculated and experimental NMR chemical shifts of
   p-menthane-3,9-diols. A combination of molecular dynamics and quantum
   mechanics to determine the structure and the solvent effects
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID SPIN COUPLING-CONSTANTS; AB-INITIO METHODS; PERTURBATION-THEORY;
   SHIELDING TENSORS; BASIS-SETS; SIMULATIONS
AB NMR chemical shifts have been experimentally measured and theoretically
   estimated for all the carbon atoms of (LR,3S,4S,8S)-p-menthane-3,9-diol
   in chloroform solution. Theoretical estimations were performed using a
   combination of molecular dynamics simulations and quantum mechanical
   calculations. Molecular dynamics simulations were used to obtain the
   most populated conformations of the (1R,3S:4S,8S)-p-menthane-3,9-diol
   as well as the distribution of the solvent molecules around it. Quantum
   mechanical calculations of NMR chemical shifts were performed on the
   most relevant conformations employing the GIAO-DFT formalism. A special
   emphasis was put in evaluating the effects of the surrounding solvent
   molecules. For this purpose, supermolecule calculations were performed
   on complexes constituted by the solute and n chloroform molecules,
   where n ranges from 3 to 16. An excellent agreement with experimental
   data has been obtained following this computational strategy.
C1 Univ Lleida, Escola Univ Politecn, Dept Quim, Lleida 25001, Spain.
   Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Pret, Dept Quim, BR-14040901 Ribeirao Preto, Brazil.
   Univ Bologna, Dipartimento Chim G Ciamician, I-40126 Bologna, Italy.
   Univ Politecn Catalunya, ETS Enginyers Ind Barcelona, Dept Engn Quim, E-08028 Barcelona, Spain.
RP Casanovas, J, Univ Lleida, Escola Univ Politecn, Dept Quim, C Jaume II
   69, Lleida 25001, Spain.
CR ALEMAN C, 1999, CHEM PHYS LETT, V302, P461
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NR 36
TC 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD JUN 1
PY 2001
VL 66
IS 11
BP 3775
EP 3782
PG 8
SC Chemistry, Organic
GA 435ZD
UT ISI:000168911300017
ER

PT J
AU Ryde, U
   Olsson, MHM
   Roos, BO
   Borin, AC
TI A theoretical study of the copper-cysteine bond in blue copper proteins
SO THEORETICAL CHEMISTRY ACCOUNTS
LA English
DT Article
DE density functional theory; entatic state theory; protein strain;
   solvation effects; reorganisation energy
ID 2ND-ORDER PERTURBATION-THEORY; SIMPLE COMPUTATIONAL MODEL; MOLECULAR
   WAVE-FUNCTIONS; ANO BASIS-SETS; ELECTRONIC-STRUCTURE; SPECTROSCOPIC
   PROPERTIES; CONTINUUM APPROXIMATION; REDUCTION POTENTIALS; NITRITE
   REDUCTASE; SPECTRAL FEATURES
AB The accuracy of theoretical calculations on models of the blue copper
   proteins is investigated using density functional theory (DFT) Becke's
   three-parameter hybrid method with the Lee-Yang-Parr correlation
   functional (B3LYP) and medium-sized basis sets. Increasing the basis
   set to triple-zeta quality with f-type functions on all heavy atoms and
   enlarging the model [up to Cu(imidazole-CH3)(2)(SC2H5) (CH3SC2H5)(0/+)]
   has only a limited influence on geometries and relative energies.
   Comparative calculations with more accurate wave-function-based methods
   (second-order Moller-Plesset perturbation theory, complete-active-space
   second-order perturbation theory, coupled-cluster method, including
   single and double replacement amplitudes and in addition triple
   replacement perturbatively) and a variety of basis sets on smaller
   models indicate that the DFT/B3LYP approach gives reliable results with
   only a small basis set dependence, whereas the former methods strongly
   depend on the size of the basis sets. The effect of performing the
   geometry optimizations in a continuum solvent is quite small, except
   for the flexible Cu-S-Met bond. The results of this study confirm the
   earlier results that neither the oxidized nor the reduced copper site
   in the blue proteins is strained to any significant degree tin energy
   terms) by the protein surrounding.
C1 Univ Lund, Dept Theoret Chem, S-22100 Lund, Sweden.
   Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, SP, Brazil.
RP Ryde, U, Univ Lund, Dept Theoret Chem, POB 124, S-22100 Lund, Sweden.
CR ADMAN ET, 1991, ADV PROTEIN CHEM, V42, P145
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   ANDERSSON K, 1997, MOLCAS VERSION 4 0
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NR 63
TC 22
PU SPRINGER-VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1432-881X
J9 THEOR CHEM ACC
JI Theor. Chem. Acc.
PD MAY
PY 2001
VL 105
IS 6
BP 452
EP 462
PG 11
SC Chemistry, Physical
GA 433ZA
UT ISI:000168789600008
ER

PT J
AU Ruini, A
   Rossi, F
   Hohenester, U
   Molinari, E
   Capaz, RB
   Caldas, MJ
TI Ab-initio study of Coulomb-correlated optical properties in conjugated
   polymers
SO SYNTHETIC METALS
LA English
DT Article
DE density functional calculations; optical absorption;
   poly(phenylenevinylene)
ID QUANTUM-WIRE STRUCTURES; EXCITATIONS; POLYTHIOPHENE
AB The spatial extension and binding energy of excitons in semiconducting
   conjugated polymers are still the subject of a great debate. We address
   this problem through first-principles calculations (within DFT-LDA,
   plane-waves and ab-initio pseudopotentials), which allow to include
   electron-hole correlation effects in a fully three-dimensional approach
   through the density-matrix formalism. We show results for the
   correlated optical spectrum and the exciton wavefunctions of
   single-chain poly(para)phenylene-vinylene (PPV), that support the
   picture of a strongly bound anisotropic exciton localized over similar
   to 4-5 monomers.
C1 Univ Modena & Reggio Emilia, Dipartimento Fis, Modena, Italy.
   Politecn Torino, Dipartimento Fis, Turin, Italy.
   Univ Fed Rio de Janeiro, Inst Fis, Rio De Janeiro, Brazil.
   Univ Sao Paulo, Inst Fis, BR-01498 Sao Paulo, Brazil.
CR ALVARADO SF, 1998, PHYS REV LETT, V81, P1082
   AXT VM, 1998, REV MOD PHYS, V70, P145
   CONWELL EM, 1997, PHYS REV LETT, V78, P4301
   FRIEND RH, 1999, NATURE, V397, P121
   KOHLER A, 1998, NATURE, V392, P903
   MARTIN SJ, 1999, PHYS REV B, V59, P15133
   OSTERBACKA R, 1999, PHYS REV B, V60, P11253
   ROHLFING M, 1999, PHYS REV LETT, V82, P1959
   ROSSI F, 1996, PHYS REV B, V53, P16462
   ROSSI F, 1996, PHYS REV LETT, V76, P3642
   VANDERHORST JW, 1999, PHYS REV LETT, V83, P4413
   VANDERHORST JW, 2000, PHYS REV B, V61, P15817
   YAN M, 1995, PHYS REV LETT, V75, P1992
NR 13
TC 4
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD MAR 15
PY 2001
VL 119
IS 1-3
SI Sp. Iss. SI
BP 257
EP 258
PG 2
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA 433EC
UT ISI:000168741500112
ER

PT J
AU Del Nero, J
   de Melo, CP
TI Semiempirical and ab initio investigation of defects in PPV oligomers
SO SYNTHETIC METALS
LA English
DT Article
DE poly(phenylenevinylene); semiempirical methods; ab initio; absorption
   spectra
AB We report a theoretical study of the excited states and other
   electronic properties of para-phenylenevinylene oligomers and related
   compounds which present conformational defects. Our results reveal the
   existence of different electronic delocalization patterns for the
   lowest singlet and triplet structures of these molecules. A similar
   behavior is also observed for the corresponding bond lengths.
C1 Univ Fed Pernambuco, Dept Fis, BR-50670901 Recife, PE, Brazil.
RP de Melo, CP, Univ Fed Pernambuco, Dept Fis, BR-50670901 Recife, PE,
   Brazil.
CR *QCEP, 1993, MOPAC PROGR VERS 7 0, P455
   BELJONNE D, 1999, J CHEM PHYS, V111, P2829
   DEWAR MJS, 1977, J AM CHEM SOC, V99, P4899
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   EDWARDS WD, 1987, THEOR CHIM ACTA, V72, P347
   HEAD JD, 1985, CHEM PHYS LETT, V122, P264
   HEAD JD, 1986, CHEM PHYS LETT, V131, P59
   KOLLER A, 1998, NATURE, V392, P903
   SARICIFLCI NS, 1997, PRIMARY PHOTOEXCITAT
NR 9
TC 8
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD MAR 15
PY 2001
VL 121
IS 1-3
SI Sp. Iss. SI
BP 1741
EP 1742
PG 2
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA 434TD
UT ISI:000168831200303
ER

PT J
AU Esteves, PM
   Ramirez-Solis, A
   Mota, CJA
TI DFT calculations on the protonation of alkanes on HF/SbF5 superacids
   using cluster models
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID THEORETICAL AB-INITIO; ELECTROPHILIC REACTIONS; MOLECULAR-STRUCTURES;
   DEUTERIUM EXCHANGE; CH5+; DIFFRACTION; CATIONS; SYSTEM; STORY
AB Calculations at B3LYP/6-31++G** + RECP (Sb) level have been performed
   for the protonation of C-H and C-C bonds of methane, ethane, propane,
   and isobutane by models of the liquid superacid media HF/SbF5. The
   antimony atoms were dealt with by relativistic effective core
   potentials. The species H2F+. Sb2F11- was considered as the model
   electrophile. The transition states for the protonation of the C-H
   bonds (H/H exchange) are similar to an H-carbonium ion interacting with
   the anion moiety. The enthalpies of activation for WH exchange of
   alkanes were calculated in the range of 19 to 21 kcal/mol. For the
   protonation of the C-C bond, the enthalpy of activation strongly
   depends on the structure of the hydrocarbon being attacked, and was
   always higher than the enthalpy of activation for H/H exchange. This
   suggests the existence of steric demand for the C-C protonation.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
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   BRUNVOLL J, 1980, ACTA CHEM SCAND A, V34, P733
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   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
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   SOMMER J, 1994, J AM CHEM SOC, V116, P5491
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   WAN B, 1996, INT J MASS SPECTROM, V159, P209
   WHITE ET, 1999, SCIENCE, V284, P135
NR 38
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5647
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD MAY 17
PY 2001
VL 105
IS 19
BP 4331
EP 4336
PG 6
SC Chemistry, Physical
GA 434FE
UT ISI:000168803800042
ER

PT J
AU Miotto, R
   Srivastava, GP
   Miwa, RH
   Ferraz, AC
TI A comparative study of dissociative adsorption of NH3, PH3, and AsH3 on
   Si(001)-(2x1)
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID SCANNING-TUNNELING-MICROSCOPY; GENERALIZED-GRADIENT APPROXIMATION;
   DENSITY-FUNCTIONAL THEORY; MOLECULAR-BEAM EPITAXY; AB-INITIO; SI(100)
   SURFACE; PHOTOELECTRON DIFFRACTION; FIRST-PRINCIPLES; PHOTOEMISSION;
   PHOSPHINE
AB Using a first-principles pseudopotential method we have studied the
   adsorption and dissociation of NH3, PH3, and AsH3 on the Si(001)-(2x1)
   surface. Apart from the existence of a barrier for the adsorption of
   the precursor state for arsine, we observe that the global behavior for
   the chemisorption of the XH3 molecules considered in this work is as
   follows: the gas phase XH3 adsorbs molecularly to the electrophilic
   surface Si atom and then dissociates into XH2 and H, bonded to the
   electrophilic and nucleophilic surface silicon dimer atoms,
   respectively. The energy barrier, corresponding to a thermal
   activation, is much smaller than the usual growth temperature,
   indicating that all three molecules will be observed in their
   dissociated states at room temperature. All adsorbed systems are
   characterized by elongated Si-Si dimers that are (almost) symmetric in
   the dissociative case but asymmetric in the molecular case. According
   to our first-principles calculations, all XH3 and XH2 systems retain
   the pyramidal geometry observed for the gas molecules. Our calculated
   vibrational spectra further support the dissociative model for the XH3
   molecules considered here. (C) 2001 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Miotto, R, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR BATER C, 2000, SURF INTERFACE ANAL, V29, P208
   BISCHOFF JL, 1991, SURF SCI, V248, L240
   BOCKSTEDTE M, 1997, COMPUT PHYS COMMUN, V107, P187
   BOZSO F, 1986, PHYS REV LETT, V57, P1185
   BOZSO F, 1988, PHYS REV B, V38, P3937
   CAKMAK M, 1999, PHYS REV B, V60, P5497
   CAKMAK M, 2000, PHYS REV B, V61, P10216
   CAO PL, 1994, J PHYS-CONDENS MAT, V6, P6103
   CHO JH, 2000, PHYS REV B, V62, P1607
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   COPEL M, 1989, PHYS REV LETT, V63, P632
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   HAMERS RJ, 1996, APPL SURF SCI, V107, P25
   HARTMANN JM, 2000, SEMICOND SCI TECH, V15, P362
   HIROSE R, 1999, SURF SCI, V430, L540
   HLIL EK, 1987, PHYS REV B, V35, P5913
   IZUMI A, 1997, APPL PHYS LETT, V71, P1371
   JENKINS SJ, 1994, J PHYS-CONDENS MAT, V6, P8781
   JOHNSON AL, 1988, LANGMUIR, V4, P277
   KIPP L, 1994, PHYS REV B, V50, P5448
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   LIDE DR, 1995, HDB CHEM PHYSICS
   LIN DS, 1999, SURF SCI, V424, P7
   LIN DS, 2000, PHYS REV B, V61, P2799
   LOH ZH, 2000, J CHEM PHYS, V112, P2444
   MAITY N, 1995, APPL PHYS LETT, V66, P1909
   MIOTTO R, 1998, PHYS REV B, V58, P7944
   MIOTTO R, 1999, PHYS REV B, V59, P3008
   MORIARTY NW, 1992, SURF SCI, V265, P168
   NACTHIGAL P, 1996, J CHEM PHYS, V104, P148
   PENEV E, 1999, J CHEM PHYS, V110, P3986
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
   PILLING MJ, 1995, REACTION KINETICS
   QIU M, 1997, J PHYS-CONDENS MAT, V9, P6543
   SHAN J, 1996, J PHYS CHEM-US, V100, P4961
   SRIVASTAVA GP, 1990, PHYSICS PHONONS
   SRIVASTAVA GP, 1997, REP PROG PHYS, V60, P561
   TAKAOKA T, 1998, SURF SCI, V412, P30
   TROMP RM, 1992, PHYS REV LETT, V68, P954
   TROULLIER N, 1991, PHYS REV B, V43, P1993
   TSUKIDATE Y, 1999, APPL SURF SCI, V151, P148
   WANG YJ, 1994, J PHYS CHEM-US, V98, P5966
   WANG YJ, 1994, PHYS REV B, V50, P4534
   WIDJAJA Y, 2000, J PHYS CHEM B, V104, P2527
   WOODRUFF DP, 1994, REP PROG PHYS, V57, P1029
   XIE MH, 1998, SURF SCI, V397, P164
   YOO DS, 1995, J APPL PHYS, V78, P4988
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NR 58
TC 17
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUN 1
PY 2001
VL 114
IS 21
BP 9549
EP 9556
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 434BF
UT ISI:000168794700041
ER

PT J
AU Serra, RM
   Ramos, PB
   de Almeida, NG
   Jose, WD
   Moussa, HY
TI Engineering arbitrary motional ionic states through realistic
   intensity-fluctuating laser pulses
SO PHYSICAL REVIEW A
LA English
DT Article
ID TRAPPED ION; PROJECTION SYNTHESIS; QUANTUM STATES; RADIATION-FIELD;
   DECOHERENCE; GENERATION; CAVITY; ATOM; SUPERPOSITIONS; MANIPULATION
AB We present a reliable scheme for engineering arbitrary motional ionic
   states through an adaptation of the projection synthesis technique for
   trapped-ion phenomena. Starting from a prepared coherent motional
   state, the Wigner function of the desired state is thus sculpted from a
   Gaussian distribution. The engineering process has also been developed
   to take into account the errors arising from intensity fluctuations in
   the exciting-laser pulses required for manipulating the electronic and
   vibrational states of the trapped ion. To this end, a recently
   developed phenomenological-operator approach that allows for the
   influence of noise will be applied. This approach furnishes a
   straightforward technique to estimate the fidelity of the prepared
   state in the presence of errors, precluding the usual extensive ab
   initio calculations. The results obtained here by the phenomenological
   approach, to account for the effects of noise in our engineering
   scheme, can be directly applied to any other process involving
   trapped-ion phenomena.
C1 Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Estadual Santa Cruz, Dept Ciencias Exatas & Tecnol, BR-45650000 Bahia, Brazil.
RP Serra, RM, Univ Fed Sao Carlos, Dept Fis, POB 676, BR-13565905 Sao
   Carlos, SP, Brazil.
CR BARNETT SM, 1996, PHYS REV LETT, V76, P4148
   BASEIA B, 1997, PHYS LETT A, V231, P331
   BROBNY G, 1998, PHYS REV A, V58, P2481
   BRUNE M, 1992, PHYS REV A, V45, P5193
   BRUNE M, 1996, PHYS REV LETT, V77, P4887
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   DAKNA M, 1999, PHYS REV A, V59, P1658
   DALIBARD J, 1992, PHYS REV LETT, V68, P580
   DEALMEIDA NG, 2000, J OPT B-QUANTUM S O, V2, P792
   DEALMEIDA NG, 2000, PHYS REV A, V62
   DEMATOS RL, 1996, PHYS REV LETT, V76, P608
   DIFIDIO C, 2000, PHYS REV A, V62
   DUM R, 1992, PHYS REV A, V45, P4879
   FEYNMAN RP, 1957, J APPL PHYS, V28, P49
   FEYNMAN RP, 1996, FEYNMAN LECT COMPUTA
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   GARRAWAY BM, 1994, PHYS REV A, V49, P535
   ITANO WM, 1997, QUANTPH9702038
   JAMES DF, 1998, PHYS REV LETT, V81, P3417
   JOSE WD, 2000, J OPT B-QUANTUM S O, V2, P306
   KNEER B, 1996, PHYS REV A, V55, P2096
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   NIELSEN MA, 2000, QUANTUM COMPUTATION
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   PRESKILL J, UNPUB
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NR 48
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD MAY
PY 2001
VL 63
IS 5
AR 053813
DI ARTN 053813
PG 15
SC Physics, Atomic, Molecular & Chemical; Optics
GA 430RJ
UT ISI:000168589100115
ER

PT J
AU Carneiro, JWD
   de Oliveira, CDB
   Passos, FB
   Aranda, DAG
   de Souza, PRN
   Antunes, OAC
TI Host-guest interactions and their role in enantioselective
   hydrogenation of alpha-keto esters - An analysis of model systems
SO JOURNAL OF MOLECULAR CATALYSIS A-CHEMICAL
LA English
DT Article
DE heterogeneous; enantioselective; catalysis; mechanisms; calculations
ID CINCHONA-MODIFIED PLATINUM; ETHYL PYRUVATE; HETEROGENEOUS CATALYSIS;
   PI-STACKING; KETOESTERS; ADSORPTION; COMPLEXES; SOLVENTS; PT(111);
   DESIGN
AB The interaction between cinchonidine and methyl pyruvate has been
   proposed as the key step leading to enantiodifferentiation in the
   enantioselective hydrogenation of alpha -ketoesters, In the present
   work, we employ ab initio MP2/6-31G(d) and MP2/6-31G(d,p) methods to
   carry out an analysis of the most relevant kind of interactions
   operating in representative model systems. These interactions are
   discussed in terms of orbital superposition and dipolar interaction.
   When approaching H2CO to NH3 at distances lower than 3.4 Angstrom,
   orbital superposition is the predominant interaction, while at
   distances above 3.4 Angstrom, both orbital superposition and dipolar
   interactions may contribute to stabilization, with a small prevalence
   of dipolar interactions. The stabilization energy at large distances
   (above 4.5 Angstrom) is very small (about 0.5 kcal mol(-1)), probably
   not enough to be responsible for the enantiodifferentiation process.
   Semiempirical calculations on the parent systems were also unable to
   reveal any special interaction which could be attributed to the
   enantiodifferentiation process. (C) 2001 Elsevier Science B.V. All
   rights reserved.
C1 Univ Fed Fluminense, Inst Quim, Dept Quim Geral & Inorgan, BR-24021150 Niteroi, RJ, Brazil.
   Univ Fed Fluminense, Escola Engn, Dept Engn Quim, BR-24210230 Niteroi, RJ, Brazil.
   Fed Univ Rio De Janeiro, Ctr Technol, Escola Quim, Lab Termodinam & Cinet Aplicada, BR-21945970 Rio De Janeiro, Brazil.
   Fed Univ Rio De Janeiro, Ctr Tecnol, Inst Quim, BR-21945970 Rio De Janeiro, Brazil.
RP Carneiro, JWD, Univ Fed Fluminense, Inst Quim, Dept Quim Geral &
   Inorgan, Outeiro Sao Joao Batista S-N, BR-24021150 Niteroi, RJ, Brazil.
CR BAIKER A, 1997, J MOL CATAL A-CHEM, V115, P473
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   BURGI T, 2000, CATAL LETT, V66, P109
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   CIEPLAK AS, 1994, STRUCTURE CORRELATIO, V1
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   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
   HEHRE WJ, 1986, AB INITIO MOL ORBITA
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   MARGITFALVI JL, 2000, APPL CATAL A-GEN, V191, P177
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NR 26
TC 11
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 1381-1169
J9 J MOL CATAL A-CHEM
JI J. Mol. Catal. A-Chem.
PD MAY 14
PY 2001
VL 170
IS 1-2
BP 235
EP 243
PG 9
SC Chemistry, Physical
GA 431BY
UT ISI:000168613100026
ER

PT J
AU Beltran, A
   Andres, J
   Calatayud, M
   Martins, JBL
TI Theoretical study of ZnO (10(1)over-bar-0) and Cu/ZnO (10(1)over-bar-0)
   surfaces
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID AB-INITIO; ELECTRONIC-STRUCTURE; TOTAL ENERGIES; HARTREE-FOCK;
   ADSORPTION; CLUSTER; H-2; CO; ZNO(10(1)OVER-BAR0); DISSOCIATION
AB Periodic HF/6-31G and a hybrid density functional, B3LYP/6-31G.
   calculations have been carried out in order to determine the geometric
   and electronic structure of bulk ZnO. The lattice parameters, bulk
   modulus, charge distribution and band structure are reported. Surface
   energy and charge distribution of the ZnO (10(1) over bar 0) surface
   are obtained, while top site adsorption of Cu atoms on Zn or O atoms on
   the ZnO (10(1) over bar 0) surface are considered. Optimized distances,
   charge transfers. vibrational frequencies and binding energies
   associated with both types of adsorption processes are calculated. The
   theoretical results are compared with previous theoretical studies and
   available experimental data. (C) 2001 Elsevier Science B.V. All rights
   reserved.
C1 Univ Jaume 1, Dept Ciencies Expt, E-12071 Castello, Spain.
   Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
RP Beltran, A, Univ Jaume 1, Dept Ciencies Expt, Campus Riu Sec, E-12071
   Castello, Spain.
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NR 35
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD APR 27
PY 2001
VL 338
IS 4-6
BP 224
EP 230
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 430TN
UT ISI:000168591800002
ER

PT J
AU Ramos, LE
   Teles, LK
   Scolfaro, LMR
   Castineira, JLP
   Rosa, AL
   Leite, JR
TI Structural, electronic, and effective-mass properties of silicon and
   zinc-blende group-III nitride semiconductor compounds
SO PHYSICAL REVIEW B
LA English
DT Article
ID MOLECULAR-BEAM EPITAXY; GENERALIZED GRADIENT APPROXIMATION;
   VALENCE-BAND SPLITTINGS; DOPING QUANTUM-WELLS; GALLIUM NITRIDE;
   ZINCBLENDE GAN; V NITRIDES; CUBIC GAN; HIGH-PRESSURE; OPTICAL GAIN
AB The electronic band structures of silicon and the zinc-blende-type
   III-N semiconductor compounds BN, AlN, GaN, and InN are calculated by
   using the self-consistent full potential linear augmented plane wave
   method within the local-density functional approximation. Lattice
   constant, bulk modulus, and cohesive energy are obtained from full
   relativistic total-energy calculations for Si and for the nitrides.
   Band structures and total density of states (DOS) are presented. The
   role played by relativistic effects on the bulk band structures and DOS
   is discussed. In order to provide important band structure-derived
   properties, such as effective masses and Luttinger parameters, the ab
   initio band structure results are linked with effective-mass theory.
   Electron, heavy-, light-, and split-off-hole effective masses, as well
   as spin-orbit splitting energies an extracted from the band-structure
   calculations. By using the Luttinger-Kohn 6x6 effective-mass
   Hamiltonian we derive the corresponding Luttinger parameters for the
   materials. A comparison with other available theoretical results and
   experimental data is made.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Ramos, LE, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR AHN D, 1996, J APPL PHYS, V79, P7731
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NR 75
TC 23
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD APR 15
PY 2001
VL 63
IS 16
AR 165210
DI ARTN 165210
PG 10
SC Physics, Condensed Matter
GA 426HH
UT ISI:000168343400047
ER

PT J
AU Abraham, RJ
   Tormena, CF
   Rittner, R
TI Conformational analysis. Part 35. NMR, solvation and theoretical
   investigation of rotational isomerism in methyl fluoroacetate and
   methyl difluoroacetate
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID COUPLING-CONSTANTS
AB The solvent and temperature dependence of the C-13 NMR spectra of
   methyl fluoroacetate (MFA) and methyl difluoroacetate (MDFA) are
   reported and the (1)J(CF) coupling analysed in terms of the conformer
   couplings and energies. Density Functional Theory (DFT) calculations
   were used to obtain the conformer geometries and solvation theory gave
   the solvent dependence of the conformer energies. In MFA the DFT method
   at the B3LYP/6-311+G(d,p) level gave only two energy minima for the cis
   (F-C-C=O 0 degrees) and trans (F-C-C=O 180 degrees) conformers of ca.
   equal energy. The gauche conformer was not a minimum in the energy
   surface. The FTIR spectra of MFA support this result as two resolved
   carbonyl bands are observed whose relative intensity changes markedly
   with solvent polarity. Assuming only these forms, the observed coupling
   when analysed by solvation theory leads to the energy difference
   (E-cis-epsilonE(trans)) between the cis and trans conformers of 0.90
   kcal mol(-1) in the vapour phase, decreasing to 0.41 kcal mol(-1) in
   CCl4 and -0.71 kcal mol(-1) in DMSO. In MDFA the DFT calculations gave
   two minima for the cis (H-C-C=O 0 degrees) and gauche (H-C-C=O 141.9
   degrees) conformers with an energy difference (E-cis-E-gauche) of 0.2
   kcal mol(-1). The FTIR spectra of MDFA support this result as in the
   non-polar solvent (CCl4) two resolved bands are observed but in
   solvents of medium and high polarity the carbonyl absorption appears as
   a single band. Assuming only the two forms, the observed coupling when
   analysed by solvation theory leads to the energy difference
   (E-cis-E-gauche) between the cis and gauche conformers of 0.0 kcal
   mol(-1) in the vapour phase, increasing to 0.46 kcal mol(-1) in CCl4
   and 1.12 kcal mol(-1) in DMSO.
C1 Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
   Univ Estadual Campinas, Inst Quim, BR-13038970 Campinas, SP, Brazil.
RP Rittner, R, Univ Liverpool, Dept Chem, POB 147, Liverpool L69 3BX,
   Merseyside, England.
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NR 23
TC 12
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1472-779X
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2001
IS 5
BP 815
EP 820
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 428NZ
UT ISI:000168468900025
ER

PT J
AU Esteves, PM
   Alberto, GGP
   Ramirez-Solis, A
   Mota, CJA
TI Ab initio study of the adamantonium cations: the protonated adamantane
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID HYDROGEN-DEUTERIUM EXCHANGE; POTENTIAL-ENERGY SURFACE; PROTOLYSIS
   DEUTEROLYSIS; ELECTROPHILIC REACTIONS; SINGLE BONDS; SUPERACIDS;
   MECHANISM; ALKANES
AB The molecular structure and energetics of the adamantonium ions were
   computed at the MP2(full)/6-31G** level. Three structures were found to
   represent the adamantonium cations, respectively: the 1-H-adamantonium
   (1). 2-H-adamantonium (2), and C-adamantonium ions (3). This study
   revealed that, upon protonation, adamantane can also produce two van
   der Waals complexes: one formed by the weak interaction of the
   1-adamantyl cation and H-2 (4) and the other formed by the interaction
   of the 2-adamantyl cation and H-2 (5). The stability order is predicted
   to be 5 > 3 > 4 > 1 > 2, Given the size and complexity of this
   molecule, the quantum zero point energy (ZPE) and finite temperature
   (298 K) corrections were estimated from previously calculated values
   for the isobutonium (for protonation of tertiary C-H and C-C bonds) and
   the proponium cations (for protonation of the secondary C-H bond). The
   calculated proton affinity of adamantane was estimated as 175.7
   kcal/mol.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Organ, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR ESTEVES PM, 1998, J AM CHEM SOC, V120, P3213
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NR 19
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAY 3
PY 2001
VL 105
IS 17
BP 4308
EP 4311
PG 4
SC Chemistry, Physical
GA 428BT
UT ISI:000168441800019
ER

PT J
AU Sensato, FR
   Filho, OT
   Longo, E
   Sambrano, JR
   Andres, J
TI Theoretical analysis of the energy levels induced by oxygen vacancies
   and the doping process (Co, Cu and Zn) on SnO2 (110) surface models
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE tin oxide; clusters; surface electronic phenomena; surface defects;
   B3LYP hybrid functional
ID REDUCED SNO2(110) SURFACE; ZINC-OXIDE CERAMICS; DENSITY-FUNCTIONAL
   THEORY; ELECTRONIC-STRUCTURE; DIOXIDE CHEMISORPTION; CRYSTAL PHASES;
   TIN DIOXIDE; TIO2; ADSORPTION; VARISTORS
AB Density functional calculation at B3LYP level was employed to study the
   surface oxygen vacancies and the doping process of Co, Cu and Zn on
   SnO2 (110) surface models. Large clusters, based on (SnO2)(15) models,
   were selected to simulate the oxidized (Sn15O30), half-reduced
   (Sn15O29) and the reduced (Sn15O28) surfaces. The doping process was
   considered on the reduced surfaces: Sn13Co2O28, Sn13Cu2O28 and
   Sn13Zn2O28. The results are analyzed and discussed based on a
   calculation of the energy levels along the bulk band gap region,
   determined by a projection of the monoelectron level structure on to
   the atomic basis set and by the density of states. This procedure
   enables one to distinguish the states coming from the bulk, the oxygen
   vacancies and the doping process, On passing from an oxidized to a
   reduced surface, missing bridge oxygen atoms generate electronic levels
   along the band gap region, associated with 5s/5p of four-/five-fold Sn
   and 2p of in-plane O centers located on the exposed surface, which is
   in agreement with previous theoretical and experimental investigations.
   The formation energy of one and two oxygen vacancies is 3.0 and 3.9 eV,
   respectively. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Estadual Paulista, Dept Matemat, BR-17030360 Bauru, SP, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello 12080, Spain.
RP Sensato, FR, Univ Fed Sao Carlos, Dept Quim, CP 676, BR-13565905 Sao
   Carlos, SP, Brazil.
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   YANG SL, 1995, J MATER RES, V10, P345
   ZYUBINA TS, 1995, RUSS J ELECTROCHEM+, V31, P1280
NR 68
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAY 31
PY 2001
VL 541
BP 69
EP 79
PG 11
SC Chemistry, Physical
GA 427CJ
UT ISI:000168387000008
ER

PT J
AU Basso, EA
   Oliveira, PR
   Caetano, J
   Schuquel, ITA
TI Semiempirical and ab initio calculations versus dynamic NMR on
   conformational analysis of cyclohexyl-N,N-dimethylcarbamate
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE conformational analysis; theoretical calculations; cyclohexane
   derivative; dynamic NMR
AB Axial-equatorial conformational proportions for cyclohexyl-N,N-dimethyl
   carbamate have been measured, for the first time, by the Eliel method,
   H-1 and C-13 dynamic nuclear magnetic resonance (DNMR). The results
   were compared against those determined by theoretical calculations. By
   the Eliel method at least five experimentally independent measureables
   were used in CCl4, CDCl3 and CD3CN. The H-1 and C-13 low temperature
   experiments were performed in CF2Br2/CD2Cl2. Semiempirical methods
   MNDO, AM1 and PM3 and ab initio molecular orbital calculations at the
   HF/STO-3G and HF/6-31G(d,p) levels have been performed on the axial and
   equatorial conformers populations. All applied methods correctly
   predict the equatorial conformer preference over the axial one. The
   resulting equatorial preferences determined by NMR data and theoretical
   calculations are in good agreement.
C1 Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana, Brazil.
RP Basso, EA, Univ Estadual Maringa, Dept Quim, Av Colombo 5790,
   BR-87020900 Maringa, Parana, Brazil.
CR BASSO EA, 1993, J ORG CHEM, V58, P7865
   BOBRANSKII BR, 1941, J APPL CHEM-USSR, V14, P524
   CAREY FA, 1996, ORGANIC CHEM, P102
   COX C, 1998, J ORG CHEM, V63, P2426
   DODRELL DM, 1982, J MAGN RESON, V48, P323
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   ELIEL EL, 1965, CONFORMATIONAL ANAL
   ELIEL EL, 1968, J AM CHEM SOC, V90, P682
   ELIEL EL, 1994, STEREOCHEMISTRY ORGA
   FRISCH MJ, 1995, GAUSSIAN 94 DEV VERS
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   HIRSCH JA, 1967, TOP STEREOCHEM, V1, P199
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NR 20
TC 6
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PY 2001
VL 12
IS 2
BP 215
EP 222
PG 8
SC Chemistry, Multidisciplinary
GA 424ZF
UT ISI:000168263300015
ER

PT J
AU Rodrigues, SCP
   Sipahi, GM
   Scolfaro, LMR
   Leite, JR
TI Exchange-correlation effects on the hole miniband structure and
   confinement potential in zinc-blende AlxGa1-xN/GaN superlattices
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; DOPING QUANTUM-WELLS; ALGAN/GAN
   SUPERLATTICES; BAND-STRUCTURE; HETEROSTRUCTURES; SEMICONDUCTORS;
   TRANSPORT
AB We present valence band-structure calculations for undoped and p-doped
   cubic AlxGa1-xN/GaN superlattices (SLs), in which the coupling between
   the heavy hole, light-hole, and spin-orbit-split-hole bands and strain
   effects due to lattice mismatch are taken into account, The
   calculations are performed within a self-consistent approach to the k.p
   theory by means of a full six-band Luttinger- Kohn Hamiltonian.
   Exchange-correlation effects within the two-dimensional hole gas are
   included in the calculations in the local density approximation.
   Results for hole minibands and potential profiles are shown as
   functions of the SL period. It is shown that exchange and correlation
   play an important role in the correct description of the systems.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Rodrigues, SCP, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR AS DJ, 2000, APPL PHYS LETT, V76, P13
   EDGAR JH, 1994, PROPERTIES GROUP 3 N
   ENDERLEIN R, 1997, PHYS REV LETT, V79, P3712
   ENDERLEIN R, 1998, PHYS REV LETT, V80, P3160
   FAN WJ, 1996, J APPL PHYS, V80, P3471
   FREY T, 2001, IN PRESS J APPL PHYS
   GOEPFERT ID, 2000, J APPL PHYS, V88, P2030
   HSU L, 1999, APPL PHYS LETT, V74, P2405
   KOZODOY P, 1999, APPL PHYS LETT, V74, P3681
   KUMAKURA K, 1999, JPN J APPL PHYS 2, V38, L1012
   KUMAKURA K, 2000, JPN J APPL PHYS 1, V39, P2428
   MARQUES M, 2001, IN PRESS P 25 INT C
   ORTON JW, 1998, REP PROG PHYS, V61, P1
   PANKOVE JI, 1998, SEMICONDUCTORS SEMIM, V50
   PARKER CA, 1999, APPL PHYS LETT, V75, P2776
   RAMOS LE, 2001, IN PRESS PHYS REV B, V63
   RODRIGUES SCP, 2000, APPL PHYS LETT, V76, P1015
   RODRIGUES SCP, 2000, IPAP CONFERENCE SER, V1, P74
   ROSA AL, 1998, PHYS REV B, V58, P15675
   SAXLER A, 1999, APPL PHYS LETT, V74, P2023
   SIPAHI GM, 1996, PHYS REV B, V53, P9930
   VANDEWALLE CG, 1997, APPL PHYS LETT, V70, P2577
   WRIGHT AF, 1997, J APPL PHYS, V82, P2833
   WU J, 1999, J CRYST GROWTH, V197, P73
NR 24
TC 11
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD APR 9
PY 2001
VL 13
IS 14
BP 3381
EP 3387
PG 7
SC Physics, Condensed Matter
GA 425BV
UT ISI:000168269200012
ER

PT J
AU Dardenne, LE
   Werneck, AS
   Neto, MO
   Bisch, PM
TI Reassociation of fragments using multicentered multipolar expansions:
   Peptide junction treatments to investigate electrostatic properties of
   proteins
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE multicentered multipolar expansions; reassociation of fragments;
   electrostatic properties of proteins; peptide junction; ab initio
   calculations
ID MOLECULAR CHARGE-DISTRIBUTION; ACID SIDE-CHAINS; ATOMIC CHARGES; POINT
   CHARGES; SOLVENT; MODELS; PAPAIN; INHIBITORS; SURFACES; ENERGIES
AB We report an analysis of three schemes for fragment reassociation using
   multicentered multipolar expansions derived from ab initio quantum wave
   functions at the Hartree-Fock/6-31G* LCAO level, two of them involving
   single-bond partitioning in the peptide bond region, and the third one
   using a partially overlapping procedure based on a methodology proposed
   by Vigne-Maeder(21) (OME-overlap of multipolar expansions-reassociation
   method). The effects of different peptide junction treatments in the
   derivation of molecular electrostatic potentials and molecular electric
   fields of three peptide sequences are discussed. The results show that
   the OME reassociation method gives a better and a more homogeneous
   description of both the potential and the electric field than the other
   two treatments. We conclude that the OME method is the most indicated
   for studies involving electrostatic properties of proteins. Our results
   also indicate that the use of multicentered multipolar expansions
   coupled to the OME treatment is the best choice in protein studies
   including solvent effects using, for example, a continuum boundary
   method to solve the linearized Poisson-Boltzmann equation. (C) 2001
   John Wiley & Sons, Inc.
C1 UCB, Dept Fis, BR-72030170 Taguatinga, DF, Brazil.
   Univ Fed Rio de Janeiro, Inst Biofis Carlos Chagas Filho, BR-21949900 Rio De Janeiro, Brazil.
   Univ Brasilia, Inst Quim, BR-70910900 Brasilia, DF, Brazil.
RP Werneck, AS, UCB, Dept Fis, EPCT Q-57,Lote 01,Aguas Claras, BR-72030170
   Taguatinga, DF, Brazil.
CR ANGYAN JG, 1994, INT J QUANTUM CHEM, V52, P17
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   DAY PN, 1996, J CHEM PHYS, V105, P1968
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   FREITAG MA, 2000, J CHEM PHYS, V112, P7300
   GOLDBLUM A, 1979, INT J QUANTUM CHEM, V15, P121
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   GRESH N, 1997, BIOPOLYMERS, V41, P145
   HARIHARAN PC, 1973, THEOR CHIM ACTA, V28, P213
   HODGKIN EE, 1987, INT J QUANTUM CHEM, V14, P105
   JEZIORSKI B, 1994, CHEM REV, V94, P1887
   JUFFER AH, 1991, J COMPUT PHYS, V97, P144
   LANGLET J, 1988, J PHYS CHEM-US, V92, P1617
   LAVERY R, 1983, INT J QUANTUM CHEM, V24, P353
   LEWIS SD, 1981, BIOCHEMISTRY-US, V20, P48
   MERZ KM, 1992, J COMPUT CHEM, V13, P749
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NR 35
TC 4
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD MAY
PY 2001
VL 22
IS 7
BP 689
EP 701
PG 13
SC Chemistry, Multidisciplinary
GA 424WW
UT ISI:000168257800002
ER

PT J
AU de Souza, GGB
   Rocco, MLM
   Boechat-Roberty, HM
   Lucas, CA
   Borges, I
   Hollauer, E
TI Valence electronic excitation of the SiF4 molecule: generalized
   oscillator strength for the 5t(2)-> 6a(1) transition and ab initio
   calculation
SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
LA English
DT Article
ID SAC-CI THEORIES; CROSS-SECTIONS; EXCITED-STATES; PHOTOABSORPTION
   SPECTRA; SPECTROSCOPY; PHOTOELECTRON; IONIZATION; SCATTERING; ARGON;
   SICL4
AB The electronic excitation of the silicon tetrafluoride (SiF4) molecule
   has been studied using the angle-resolved electron energy-loss
   technique, at 1.0 keV incident electron energy, in the 0-50 eV energy
   range with an angular range of 1.5 degrees -20.0 degrees. The absolute
   generalized oscillator strength (GOS) for the 5t(2) --> 6a(1)
   electronic transition, located at 13.0 eV, has been determined. A
   minimum has been observed in the GOS for this transition at K-2 = 1.4
   au. We have also determined the absolute elastic and inelastic
   differential cross sections at I keV. In order to help in the
   interpretation of the experimental results, ab initio calculations have
   been performed for the vertical valence transitions and ionization
   energies for the SiF4 molecule. Configuration-interaction calculations,
   including single and double excitations (CI-SD) and the
   symmetry-adapted-cluster expansion (SAC) were used. The CI-SD approach
   was also employed to obtain the optical oscillator strength for the
   5t(2) --> 6a(1) transition.
C1 Fed Univ Rio De Janeiro, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Fed Univ Rio De Janeiro, Observ Valongo, BR-20080090 Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Inst Quim, BR-24020150 Niteroi, RJ, Brazil.
RP de Souza, GGB, Fed Univ Rio De Janeiro, Inst Quim, Cidade Univ,
   BR-21949900 Rio De Janeiro, Brazil.
CR BARTELL LS, 1984, J CHEM PHYS, V81, P3792
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   BOECHATROBERTY HM, 1997, J PHYS B-AT MOL OPT, V30, P3369
   BOZEK JD, 1990, CHEM PHYS, V145, P131
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   CHEN ZF, 1999, PHYS REV A, V60, P5115
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   DEMIRANDA MP, 1994, PHYS REV A, V49, P2399
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NR 38
TC 4
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-4075
J9 J PHYS-B-AT MOL OPT PHYS
JI J. Phys. B-At. Mol. Opt. Phys.
PD MAR 28
PY 2001
VL 34
IS 6
BP 1005
EP 1017
PG 13
SC Physics, Atomic, Molecular & Chemical; Optics
GA 422VP
UT ISI:000168140200010
ER

PT J
AU Castellano, EE
   Piro, OE
   Caram, JA
   Mirifico, MV
   Aimone, SL
   Vasini, EJ
   Lucero, AM
   Mitnik, DG
TI Crystallographic study and molecular orbital calculations of
   thiadiazole derivatives. 1. Phenanthro[9,10-c]-1,2,5-thiadiazole
   1,1-dioxide and acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE 1,2,5-thiadiazole 1,1-dioxide derivatives; ab initio MO calculations;
   single-crystal X-ray diffraction; density functional theory;
   sensitivity analysis
ID DENSITY-FUNCTIONAL THEORY; 3,4-DIPHENYL-1,2,5-THIADIAZOLE 1,1-DIOXIDE;
   CHEMICAL-REACTIVITY; SOFT ACIDS; CRYSTAL-STRUCTURE; GAS-PHASE;
   HARDNESS; BASES; ELECTROREDUCTION; DESCRIPTORS
AB Single-crystal X-ray diffraction studies are reported for
   phenanthro[9,10-c]-1,2,5-thiadiazole 1,1-dioxide (I) and
   acenaphtho[1,2-c]-1,2,5-thiadiazole 1,1-dioxide (II), Ab initio
   molecular orbital (MO) calculations on the electronic structure,
   conformation and reactivity of I and II an also reported and compared
   with the X-ray results. A charge sensitivity analysis of the studied
   molecules has been performed by resorting to density functional theory
   (DFT), obtaining several sensitivity coefficients such as the molecular
   energy, net atomic charges, global and local hardness, global and local
   softness and Fukui functions. With these results and the analysis of
   the dipole moments and the total electron density maps, several
   conclusions have been inferred about the preferred sites of chemical
   reaction of the studied compounds. (C) 2001 Elsevier Science B.V. All
   rights reserved.
C1 CIMAV, Chihuahua, Mexico.
   Univ Sao Paulo, Dept Fis, Inst Fis & Quim Sao Carlos, BR-13560 Sao Carlos, SP, Brazil.
   Natl Univ La Plata, Fac Ciencias Exactas, Dept Fis, RA-1900 La Plata, Argentina.
   CONICET, PROFIMO, RA-1900 La Plata, Argentina.
   Univ Nacl La Plata, INIFTA, CONICET, RA-1900 La Plata, Argentina.
RP Mitnik, DG, CIMAV, Miguel de Cervantes 120, Chihuahua, Mexico.
CR AIMONE SL, 2000, J PHYS ORG CHEM, V13, P272
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NR 55
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD MAY 2
PY 2001
VL 562
IS 1-3
BP 157
EP 166
PG 10
SC Chemistry, Physical
GA 421UA
UT ISI:000168080900017
ER

PT J
AU Milas, I
   Nascimento, MAC
TI A density-functional study of the dehydrogenation reaction of isobutane
   over zeolites
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID AB-INITIO; ELECTROPHILIC REACTIONS; ACIDIC ZEOLITE; CLUSTER-MODELS;
   LIGHT ALKANES; EXCHANGE; CRACKING; ACTIVATION; CARBOCATIONS; TEMPERATURE
AB The dehydrogenation reaction of isobutane over zeolites was
   investigated at the B3LYP/6-31G** and 6-311G** levels of calculation,
   and with T3 and T5 clusters representing the zeolite. The transition
   state (TS) exhibits a carbenium ion-like character, and the activation
   energy, at the best level of theory, is 53.4 kcal/mol. Contrary to what
   has been previously proposed, IRC calculations show that the mechanism
   does not involve the formation of alkoxide, but rather the carbocation
   collapses directly into isobutene while the eliminated proton, restores
   the zeolite's acid site. Increasing the size of the cluster and of the
   basis set does not change the mechanism. (C) 2001 Elsevier Science B.V.
   All rights reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim,
   Cidade Univ,CT Bloco A,Sala 412, BR-21949900 Rio De Janeiro, Brazil.
CR *SCHROD INC, 1998, JAGUAR 3 5
   BECKE AD, 1993, J CHEM PHYS, V98, P5648
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   CORMA A, 1994, J CATAL, V145, P171
   ESTEVES PM, 1999, J PHYS CHEM B, V103, P10417
   ESTEVES PM, 2000, THESIS U FEDERAL RIO
   EVELETH EM, 1996, J PHYS CHEM-US, V100, P11368
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NR 27
TC 14
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD APR 13
PY 2001
VL 338
IS 1
BP 67
EP 73
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 423QC
UT ISI:000168187400011
ER

PT J
AU De Almeida, MV
   Figueiredo, RM
   Dos Santos, HF
   Da Silva, AD
   De Almeida, WB
TI Synthesis and theoretical study of azido and amino inositol derivatives
   from L-quebrachitol
SO TETRAHEDRON LETTERS
LA English
DT Article
ID D-3-AZIDO-3-DEOXY-MYO-INOSITOL; ROUTES
AB Some azido and amino inositol derivatives were synthesised from
   L-quebrachitol. The reaction between the mesylated compound and sodium
   azide was studied experimentally. Ab initio quantum mechanical
   calculations were carried out for this process to better understand the
   reaction mechanism. (C) 2001 Elsevier Science Ltd. All rights reserved.
C1 Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Juiz de Fora, ICE, Dept Quim, Juiz De Fora, MG, Brazil.
RP De Almeida, WB, Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim
   Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR ACENA JL, 1996, TETRAHEDRON LETT, V37, P105
   ARJONA O, 1995, TETRAHEDRON LETT, V8, P6659
   BRUNN G, 1994, CANCER CHEMOTH PHARM, V35, P71
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NR 15
TC 5
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0040-4039
J9 TETRAHEDRON LETT
JI Tetrahedron Lett.
PD APR 9
PY 2001
VL 42
IS 15
BP 2767
EP 2769
PG 3
SC Chemistry, Organic
GA 421EF
UT ISI:000168048600004
ER

PT J
AU Verissimo-Alves, M
   Capaz, RB
   Koiller, B
   Artacho, E
   Chacham, H
TI Polarons in carbon nanotubes
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID FIRST-PRINCIPLES; LARGE SYSTEMS; EXCITATIONS; SOLITONS; C-60
AB We use ab initio total-energy calculations to predict the existence of
   polarons in semiconducting carbon nanotubes (CNTs). We find that the
   CNTs' band edge energies vary linearly and the elastic energy increases
   quadratically with both radial and with axial distortions, leading to
   the spontaneous formation of polarons. Using a continuum model
   parametrized by the nb initio calculations, we estimate electron and
   hole polaron lengths, energies, and effective masses and analyze their
   complex dependence on CNT geometry. Implications of polaron effects on
   recently observed electro- and optomechanical behavior of CNTs are
   discussed.
C1 Fed Univ Rio De Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil.
   Univ Autonoma Madrid, Inst Nicolas Cabrera, Madrid 28049, Spain.
   Univ Autonoma Madrid, Dipartiment Fis Mat Condensada, Madrid 28049, Spain.
   Univ Fed Minas Gerais, Dept Fis, ICEx, BR-30123970 Belo Horizonte, MG, Brazil.
RP Verissimo-Alves, M, Fed Univ Rio De Janeiro, Inst Fis, BR-21945970 Rio
   De Janeiro, Brazil.
CR APPEL J, 1968, SOLID STATE PHYS, V21, P193
   BAUGHMAN RH, 1999, SCIENCE, V284, P1340
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   CHAMON C, 2000, PHYS REV B, V62, P2806
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   PARK CJ, 1999, PHYS REV B, V60, P10656
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NR 25
TC 29
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD APR 9
PY 2001
VL 86
IS 15
BP 3372
EP 3375
PG 4
SC Physics, Multidisciplinary
GA 421CZ
UT ISI:000168045700039
ER

PT J
AU Barbatti, M
   Jalbert, G
   Nascimento, MAC
TI The structure and the thermochemical properties of the H-3(+)(H-2)(n)
   clusters (n=8-12)
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID PROTONATED HYDROGEN CLUSTERS; CONDENSED-PHASE; MONTE-CARLO; IONS;
   ABINITIO; ENERGIES; STABILITIES; ENERGETICS; N=1-9
AB Ab initio calculations were performed for the H-3(+)(H-2)(n) clusters
   (n=8-12), including complete optimization of several isomers of the
   n=10 cluster. Binding energies, enthalpies, and ionization potentials
   are calculated. Well defined patterns of chromism are predicted for the
   H-2 collective vibrations and for the H-3(+) breathing vibrations. The
   calculations for the n > 10 clusters allow us to understand their shell
   structure in terms of concentric spheres of H-2 molecules. The first
   and second shells have occupation numbers equal to 3 and 6,
   respectively, while for the third shell, this number is within the
   range 12-15. (C) 2001 American Institute of Physics.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21945970 Rio De Janeiro, Brazil.
RP Barbatti, M, Univ Fed Rio de Janeiro, Inst Fis, CP 68528, BR-21945970
   Rio De Janeiro, Brazil.
CR BARBATTI M, UNPUB J CHEM PHYS
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NR 33
TC 9
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD APR 22
PY 2001
VL 114
IS 16
BP 7066
EP 7072
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 420ZQ
UT ISI:000168036900013
ER

PT J
AU Rocha, AB
   Bielschowsky, CE
TI Intensity of the n -> pi* symmetry-forbidden electronic transition in
   acetone by direct vibronic coupling mechanism
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID METHYL INTERNAL-ROTATION; SUPERSONIC NOZZLE BEAM;
   CONFIGURATION-INTERACTION; AB-INITIO; SPECTRA
AB Absolute absorption intensities were calculated for the symmetry dipole
   forbidden n --> pi* transition in acetone. An analysis of the
   distribution per normal modes is performed and the results are compared
   with a recent calculation. Vibronic coupling mechanism is taken into
   account in a way that is different from the traditional Herzberg-Teller
   perturbation approach. In the present method the electronic transition
   moment is directly expanded in power series of the vibration normal
   coordinates. This approach was recently used for the equivalent n -->
   pi* transition in formaldehyde presenting an excellent agreement with
   the experimental results. (C) 2001 Elsevier Science B.V. All rights
   reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Fis Qim, BR-21949900 Rio De Janeiro, Brazil.
RP Bielschowsky, CE, Univ Fed Rio de Janeiro, Inst Quim, Dept Fis Qim,
   Cidade Univ,CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR BABA M, 1983, CHEM PHYS LETT, V103, P93
   BABA M, 1985, J CHEM PHYS, V82, P3938
   BAUSCHLICHER CW, 1980, J CHEM PHYS, V72, P880
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   HERZBERG G, 1991, ELECTRO SPECTRA ELEC
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   LEY H, 1931, Z PHYS CHEM B-CHEM E, V12, P132
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   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
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   WORDEN EF, 1966, SPECTROCHIM ACTA, V22, P21
   ZIEGLER L, 1974, J CHEM PHYS, V60, P3558
NR 22
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD APR 6
PY 2001
VL 337
IS 4-6
BP 331
EP 334
PG 4
SC Physics, Atomic, Molecular & Chemical
GA 420BP
UT ISI:000167984300016
ER

PT J
AU Gomez, JA
   Guenzburger, D
TI Influence of conduction electrons on the magnetism of cobalt grains in
   a copper matrix studied by density-functional theory
SO PHYSICAL REVIEW B
LA English
DT Article
ID CO GRANULAR ALLOYS; GIANT MAGNETORESISTANCE; PARTICLE-SIZE;
   GROUND-STATE; CU; IMPURITIES; SYSTEMS; CLUSTERS; SPIN; MOLECULES
AB Electronic structure calculations in the local spin-density
   approximation were performed for clusters of 79 atoms embedded in a Cu
   matrix. The discrete variational method was employed. Cobalt grains of
   up to 55 atoms surrounded by Cu were considered; the lattice parameter
   of Cu was used for the calculations. Local magnetic moments and
   hyperfine fields were obtained for all the clusters. The results show
   that the local magnetic moments at the Co atom sites have oscillatory
   behavior with a tendency to increase in the direction of the grain
   boundaries. The magnitude of the contact contribution to the hyperfine
   field at the Co atom sites also has oscillatory behavior but with a
   tendency to decrease from the center to the surface of the grains. This
   is due to a tendency of alignment of the 4s moment with the 3d moment.
   Dipolar contributions to the hyperfine field were also calculated for
   the cobalt atoms at the boundary of the grains. The highest magnitude
   of this contribution was 4.2 T, Found for the grain with 13 Co atoms.
   Charge oscillations on Co are observed from the center to the surface.
C1 Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
RP Guenzburger, D, Ctr Brasileiro Pesquisas Fis, Rua Dr Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, Brazil.
EM diana@cat.cbpf.br
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NR 49
TC 11
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD APR 1
PY 2001
VL 6313
IS 13
AR 134404
DI ARTN 134404
PG 10
SC Physics, Condensed Matter
GA 418MB
UT ISI:000167895000054
ER

PT J
AU Fagan, SB
   Mota, R
   Baierle, RJ
   Paiva, G
   da Silva, AJR
   Fazzio, A
TI Stability investigation and thermal behavior of a hypothetical silicon
   nanotube
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE nanotubes; electronic structure; silicon; ab initio; Monte Carlo
ID CARBON NANOTUBES; TUBULES; BORON
AB dEven though silicon nanotubes have never been observed, this paper
   attempts to establish the theoretical similarities and differences
   between Si and C structures. Through the use of two alternative
   theoretical approaches, the first principles calculations and empirical
   potential, the electronic and structural properties of this
   hypothetical material are examined. The first principles calculations
   are based on the density-functional theory and it is shown that
   depending on their chiralities and diameters, the silicon nanotubes may
   present metallic (armchair) or semiconductor (zigzag and mixed)
   behaviors, similar to carbon structures. It is shown that the gap
   decreases in inverse proportion to the diameter, thus approaching zero
   for planar graphite, as was expected. In the second alternative
   approach, the Monte Carlo simulations are used with the Tersoff's
   empirical potential to present a systematic study on the thermal
   behavior of these new structures, It is shown that similarities like
   band structures and density of states are observed between the C and Si
   nanotubes. Nevertheless, there are relevant discrepancies in the
   thermal stabilities and energy differences between the cohesive
   energies per atom for the two tubes, compared with the corresponding
   bulks, implying the very improbable structure of the silicon nanotubes.
   (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Ctr Univ Franciscano, Dept Ciencias Exatas, BR-97919032 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Mota, R, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BLASE X, 1994, PHYS REV LETT, V72, P1878
   BLOCKSTEDT M, 1997, COMPUT PHYS COMMUN, V107, P187
   CAR R, 1985, PHYS REV LETT, V55, P2471
   CHOPRA NG, 1995, SCIENCE, V269, P966
   DAI HJ, 1998, APPL PHYS LETT, V73, P1508
   ESTEFARJANI K, 1999, APPL PHYS LETT, V74, P79
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   HAMADA N, 1992, PHYS REV LETT, V68, P1579
   HAMMERSLEY JM, 1979, MONTE CARLO METHODS
   HOHENBERG P, 1964, PHYS REV B, V136, P864
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   KLEYNMAN L, 1982, PHYS REV LETT, V48, P1425
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   PERDEW JP, 1981, PHYS REV B, V23, P5048
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   TANS SJ, 1997, NATURE, V386, P474
   TERSOFF J, 1986, PHYS REV LETT, V56, P632
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   YAKOBSON BI, 1997, AM SCI, V85, P324
NR 27
TC 16
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 20
PY 2001
VL 539
SI Sp. Iss. SI
BP 101
EP 106
PG 6
SC Chemistry, Physical
GA 417LB
UT ISI:000167835500013
ER

PT J
AU Oliveira, KMT
   Trsic, M
TI Comparative theoretical study of the electronic structures and
   electronic spectra of Fe2+-, Fe+3-porphyrin and free base porphyrin
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE porphyrin; Iron II; Iron III; ZINDO; electronic spectra; electronic
   structure
ID DENSITY-FUNCTIONAL CALCULATIONS; DIFFERENTIAL-OVERLAP TECHNIQUE;
   TRANSITION-METAL COMPLEXES; VAPOR ABSORPTION SPECTRA; SPIN FERROUS
   PORPHYRIN; AB-INITIO CALCULATIONS; INTERMEDIATE NEGLECT; IRON(II)
   PORPHINE; GROUND-STATE; PERTURBATION-THEORY
AB The Intermediate Neglect of Differential Overlap quantum chemical
   procedure, with configuration interaction, as implemented in the ZINDO
   program, was employed for a theoretical calculation of Fe2+-porphyrin,
   Fe3+-porphyrin and free base porphyrin. The ground states for the first
   two species were found to be, at the HF level, a triplet and a
   quadruplet, respectively. The geometries, electronic charge
   distribution and energy levels, as well as theoretical UV/Vis spectra,
   for the three species are shown. The calculated wavelengths were good
   agreement with the experimental values of the electronic spectra of
   Fe2+-porphyrin, Fe3+-porphyrin and free base porphyrin. (C) 2001
   Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, BR-13560250 Sao Carlos, SP, Brazil.
RP Trsic, M, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol,
   POB 780, BR-13560250 Sao Carlos, SP, Brazil.
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NR 88
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 20
PY 2001
VL 539
SI Sp. Iss. SI
BP 107
EP 117
PG 11
SC Chemistry, Physical
GA 417LB
UT ISI:000167835500014
ER

PT J
AU Seidl, PR
   Tostes, JGR
   Carneiro, JWD
   Taft, CA
   Dias, JF
TI Stereo-electronic effects on carbon-13 and hydrogen chemical shifts of
   bicyclic alcohols
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE DFT/GIAO calculations; chemical shifts; hyperconjugation;
   exo-2-norborneol; endo-2-norborneol; electronic effects
ID NMR; EXCHANGE
AB Since the 1990s ab initio calculations have become affordable and
   accurate enough to be useful in the problem of correct assignment in
   high field, multipulse NMR spectroscopy as well as in the understanding
   the relationships between chemical shifts and molecular structure.
   Density functional theory (DFT) methods enable accurate calculations to
   be made on systems that cannot easily be treated by standard methods
   beyond Hartree-Fock, such as large organic molecules. In order to probe
   the effects of rotation about the C-O bond using the DFT/GIAO method,
   we calculated chemical shifts for the three minima obtained by a
   complete rotation of the C-O bond of exo- and endo-2-norborneol. Our
   results show that conformational effects leading to chemical shift
   differences of almost 4 ppm for carbon-13 and 1 ppm for hydrogen may be
   observed. These are interpreted in terms of steric and electronic
   effects. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 UFRJ, Escola Quim, Dept Proc Organ, BR-21949900 Rio De Janeiro, Brazil.
   ENF, Lab Ciencias Quim, BR-28015620 Campos, RJ, Brazil.
   IME, Dept Engn Quim, BR-22290180 Rio De Janeiro, Brazil.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   UFF, Dept Quim Geral & Inorgan, BR-24020150 Niteroi, RJ, Brazil.
RP Seidl, PR, UFRJ, Escola Quim, Dept Proc Organ, BR-21949900 Rio De
   Janeiro, Brazil.
CR ABRAHAM RJ, 1989, MAGN RESON CHEM, V27, P1074
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NR 15
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 20
PY 2001
VL 539
SI Sp. Iss. SI
BP 163
EP 169
PG 7
SC Chemistry, Physical
GA 417LB
UT ISI:000167835500021
ER

PT J
AU Mundim, KC
   Malbouisson, LAC
   Dorfman, S
   Fuks, D
   Van Humbeeck, J
   Liubich, V
TI Diffusion properties of tungsten from atomistic simulations with ab
   initio potentials
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE diffusion; tungsten; vacancy; interatomic potentials; non-empirical
   calculations
ID VACANCY SOLID-SOLUTION; BCC TRANSITION-METALS; SELF-DIFFUSION;
   ARRHENIUS PLOT; FORCES
AB The results of atomistic simulations of migration and formation
   energies of mono- and di-vacancies in bulk tungsten are presented in
   our paper. The interatomic potential for tungsten was extracted with
   the recursive procedure from ah initio calculations of the cohesive
   energy. A stochastic molecular dynamics using a generalized simulated
   annealing procedure was employed in the simulations. Calculated values
   of mono- and di-vacancies energy parameters are in a good agreement
   with experimental data and with the results of other calculations. (C)
   2001 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
   Technion Israel Inst Technol, Fac Phys, IL-32000 Haifa, Israel.
   Katholieke Univ Leuven, Dept Mat Engn, Louvain, Belgium.
   Ben Gurion Univ Negev, Dept Mat Engn, IL-84105 Beer Sheva, Israel.
RP Mundim, KC, Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
CR ANDERSEN OK, 1975, PHYS REV B, V12, P3060
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NR 39
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 20
PY 2001
VL 539
SI Sp. Iss. SI
BP 191
EP 197
PG 7
SC Chemistry, Physical
GA 417LB
UT ISI:000167835500024
ER

PT J
AU Bauerfeldt, GF
   Arbilla, G
   da Silva, EC
TI Theoretical study and rate constants for the unimolecular isomerization
   of YONO (Y = F, Cl and Br)
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE halogen nitrites; trans-cis isomerization;
   Rice-Ramsperger-Kassel-Marcus rate constants
ID AB-INITIO CHARACTERIZATION; NITROSYL HYPOFLUORITE; ATMOSPHERIC
   CHEMISTRY; VIBRATIONAL-SPECTRA; MATRIX REACTIONS; NO2 MOLECULES;
   ISOMERS; ROTATION; ATOMS
AB This work introduces the theoretical study of cis-trans isomerization
   reactions of the halogenated nitrites FONO, CIONO and BrONO. The direct
   dynamics methodology has been employed. Geometries have been optimized
   and a saddle point located for each process. Critical energies have
   been determined as 10.93, 10.17 and 9.92 kcal/mol for the trans-cis
   isomerization reactions of FONO, CIONO and BrONO. respectively.
   Thermodynamics of the equilibrium trans-YONO = cis-YONO has been
   investigated and high-pressure unimolecular rate constants calculated
   for a range of temperature of 223-323 K. A trend has been observed in
   geometric parameters and thermodynamic data when comparing FONO, CIONO
   and BrONO conformers. (C) 2001 Elsevier Science B.V. All rights
   reserved.
C1 Univ Fed Rio de Janeiro, Ctr Tecnol, Inst Quim, Dept Quim Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Arbilla, G, Univ Fed Rio de Janeiro, Ctr Tecnol, Inst Quim, Dept Quim
   Fis, Bloco A,Cidade Univ, BR-21949900 Rio De Janeiro, Brazil.
CR BAUERFELDT GF, UNPUB
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   FINLAYSONPITTS BJ, 1986, ATMOSPHERIC CHEM FIN
   FORST W, 1973, THEORY UNIMOLECULAR
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   GUHA S, 1998, J PHYS CHEM A, V102, P2072
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NR 36
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD APR 20
PY 2001
VL 539
SI Sp. Iss. SI
BP 223
EP 232
PG 10
SC Chemistry, Physical
GA 417LB
UT ISI:000167835500027
ER

PT J
AU Longo, RL
   Nunes, RL
   Bieber, LW
TI On the origin of the regioselective hydrolysis of a naphthoquinone
   diacetate: A molecular orbital study
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE regioselectivity; MO calculations; solvent effects
ID BASIS-SETS; 1ST-ROW ELEMENTS; ABINITIO
AB The regioselectivity found in the mild basic hydrolysis of the
   2,5-dimethyl-1,4-naphthohydroquinone diacetate (Nunes, R. L.; Bieber,
   L. W.; Longo, R. L. J. Nat. Prod. 1999, 62, 1600) has been studied with
   ab initio and semiempirical molecular orbital methods. In the gas phase
   (isolated systems), these methods were not able to provide results that
   could explain the observed selectivity. However, when the solvent
   effects were included in the AM1 method using the discrete solvation
   model it was possible to establish that this selectivity is due to the
   relative stability of the tetrahedral intermediates and their
   transitions states. The origin of this relative stability and thus of
   the observed selectivity is due to the repulsive interactions between
   the 2-methyl substituent in the naphthalene ring and the methyl group
   in the 4-acetate substituent, as well as their hindrance towards the
   hydration of the ionic group in the tetrahedral intermediates.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540 Recife, PE, Brazil.
RP Longo, RL, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540
   Recife, PE, Brazil.
CR BAKER BR, 1942, J AM CHEM SOC, V64, P1100
   BENDER ML, 1960, CHEM REV, V60, P53
   BENDER ML, 1967, J AM CHEM SOC, V89, P1211
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   BLAKE JF, 1987, J AM CHEM SOC, V109, P3856
   CAREY FA, 1987, ORGANIC CHEM, P798
   CLARK T, 1983, J COMPUT CHEM, V4, P294
   CLARK T, 1985, HDB COMPUTATIONAL CH
   DEWAR MJS, 1977, J AM CHEM SOC, V99, P4899
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   FREITAS LCG, 1992, J CHEM SOC FARADAY T, V88, P189
   GRANT HN, 1963, HELV CHIM ACTA, V46, P415
   HEHRE WJ, 1986, AB INITIO MOL ORBITA
   INGOLD C, 1969, STRUCTURE MECH ORGAN
   MADURA JD, 1986, J AM CHEM SOC, V108, P2517
   MARCH J, 1992, ADV ORGANIC CHEM
   NUNES RL, 1999, J NAT PRODUCTS, V62, P1600
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
   STEVENS WJ, 1984, J CHEM PHYS, V81, P6026
   STEWART JJP, 1989, J COMPUT CHEM, V10, P210
   STEWART JJP, 1993, MOPAC 9300 MANUAL
   WILBUR JL, 1994, J AM CHEM SOC, V116, P5839
NR 22
TC 4
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PY 2001
VL 12
IS 1
BP 52
EP 56
PG 5
SC Chemistry, Multidisciplinary
GA 401HV
UT ISI:000166922900006
ER

PT J
AU Orellana, W
   Ferraz, AC
TI Ab initio study of substitutional nitrogen in GaAs
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID ALLOYS; PSEUDOPOTENTIALS; IMPURITIES; ENERGETICS; DEFECT; GROWTH
AB We investigate the atomic geometry, formation energies, and electronic
   structure of nitrogen occupying both arsenic and gallium sites in GaAs
   (N-As and N-Ga) using first-principles total-energy calculations. We
   find that both neutral defects induce impurity-like empty levels in the
   band gap acting as acceptors. While N-As shows a s-like a(1) level in
   the middle of the band gap, N-Ga shows a p-like t(2) level close to the
   bottom of the conduction band. The gap level of N-As gives theoretical
   support for the experimentally observed band-edge redshift on the GaAsN
   alloy for a N concentration similar to3%. Strong inward relaxations
   preserving the T-d symmetry characterize the N-As equilibrium geometry
   in all the charge states investigated. In contrast, N-Ga exhibits a
   structural metastability in neutral charge state and Jahn-Teller
   off-center distortions in negative charge states forming a negative-U
   center. Formation energies of competing N-As and N-Ga defects are also
   discussed. (C) 2001 American Institute of Physics.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Orellana, W, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BELLAICHE L, 1996, PHYS REV B, V54, P17568
   CALDAS MJ, 1990, PHYS REV LETT, V65, P2046
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NR 22
TC 8
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 26
PY 2001
VL 78
IS 9
BP 1231
EP 1233
PG 3
SC Physics, Applied
GA 405GK
UT ISI:000167151000021
ER

PT J
AU Miwa, RH
   Srivastava, GP
TI Atomic geometry, electronic structure and image state for the
   Si(111)-In(4 x 1) nanowire
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; many body and quasi-particle theories;
   surface electronic phenomena (work function; surface potential, surface
   states etc.); indium; self-assembly; single crystal surfaces
ID INVERSE-PHOTOEMISSION; POTENTIAL STATES; SURFACE-BARRIER;
   METAL-SURFACES; MODEL; RECONSTRUCTION; SPECTROSCOPY; DIFFRACTION;
   DISPERSION; CHAINS
AB We have performed a detailed theoretical study of the atomic geometry,
   electronic structure, and dispersion of the most tightly bound (n = 1)
   image state for the Si(111)-In(4 x 1) nanowire system. The calculations
   were performed using ab initio pseudopotentials, based on the local
   density approximation and a first-order energy correction for its
   asymptotic classical-image behaviour. The calculated atomic geometry,
   within the structural model proposed by Bunk et ai. [Phys. Rev. B 59
   (1999) 12228], agrees well with their X-ray diffraction studies, and
   the electronic band structure calculations confirm the
   quasi-one-dimensional semimetallic behaviour, in agreement with
   previous photoemission studies. The anisotropic dispersion of the image
   state measured in a recent inverse photoemission study by Hill and
   McLean [Phys. Rev. Lett. 82 (1999) 2155] is verified, and an
   explanation based on the calculated surface corrugation potential is
   presented. (C) 2001 Elsevier Science B.V. All rights reserved.
C1 Univ Exeter, Sch Phys, Dept Phys, Exeter EX4 4QL, Devon, England.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Srivastava, GP, Univ Exeter, Sch Phys, Dept Phys, Stocker Rd, Exeter
   EX4 4QL, Devon, England.
CR ABUKAWA T, 1995, SURF SCI, V325, P33
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   HEDIN L, 1969, SOLID STATE PHYS, V23, P1
   HILL IG, 1997, PHYS REV B, V56, P15725
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   HIMPSEL FJ, 1992, APPL SURF SCI, V56, P160
   JENNINGS PJ, 1988, PHYS REV B, V37, P6113
   JONES RO, 1984, PHYS REV B, V29, P6474
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NR 31
TC 18
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD FEB 10
PY 2001
VL 473
IS 1-2
BP 123
EP 132
PG 10
SC Chemistry, Physical
GA 404EA
UT ISI:000167083400013
ER

PT J
AU Leitao, AA
   Neto, JAC
   Pinhal, NM
   Bielschowsky, CE
   Vugman, NV
TI Pulsed EPR and ab initio calculation on [Ni(CN)(4)](3-) in NaCl and KCl
   host lattices
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID ELECTRON-SPIN-RESONANCE; F-CENTERS; CRYSTALS; IMPURITY; CLUSTER; DEFECTS
AB Paramagnetic 3d(9) [Ni(CN)(4)](3-) complexes, with the unpaired
   electron in a d(x2-y2) orbital, have been generated from diamagnetic
   Ni(II) 3d(8) cyanide complexes in KCl or NaCl host lattices. The
   magnetic and quadrupolar hyperfine interactions with the four N-14,
   hidden in the CW-EPR (continuous wave electron paramagnetic ressonance)
   line width, are revealed by pulsed EPR and ENDOR (electron nuclear
   double resonance) angular variation studies. Ab initio embedded UMP2
   cluster calculations, which take into account short- and long-range
   crystal interactions, confirm the unpaired electron orbital assignment
   and are in agreement with the measured hyperfine values. The trend of
   N-14 A(iso) values (7.7 MHz for NaCl and 6.8 MHz for KCI) is given by
   the Ni-CN distance, modified in each host lattice. Small asymmetry
   factors (about 0.04) for the N-14 quadrupolar tensor are obtained both
   in experiment and in theory. The experimental lines and the
   calculations indicate spin density at the cations of both lattices.
   Experimental and theoretical data indicate that lattice chlorine ions
   near the Ni atom, in axial positions, are not chemically coordinated to
   Ni. Spin density on these ions arises only from spin polarization of
   their valence orbitals and of the valence orbitals of the complex.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21910240 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21910240 Rio De Janeiro, Brazil.
RP Vugman, NV, Univ Fed Rio de Janeiro, Inst Fis, BR-21910240 Rio De
   Janeiro, Brazil.
CR AACHI JI, 1993, B CHEM SOC JPN, V66, P3314
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   EVJEN HM, 1932, PHYS REV, V39, P675
   FRISCH JM, 1995, GAUSSIAN 94 REVISION
   GAULD JW, 1997, J PHYS CHEM A, V101, P1352
   HARRISON WA, 1989, ELECT STRUCTURE PROP, CH8
   HAY PJ, 1985, J CHEM PHYS, V82, P299
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NR 27
TC 6
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JAN 25
PY 2001
VL 105
IS 3
BP 614
EP 619
PG 6
SC Chemistry, Physical
GA 402RE
UT ISI:000167001300014
ER

PT J
AU Laali, KK
   Okazaki, T
   Kumar, S
   Galembeck, SE
TI Substituent effects and charge delocalization mode in chrysenium,
   benzo[c]phenanthrenium, and benzo[g]chrysenium cations: A stable ion
   and electrophilic substitution study
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID POLYCYCLIC AROMATIC-HYDROCARBONS; DIOL EPOXIDE METABOLITES; AM1
   CALCULATIONS; CARCINOGEN BENZO<G>CHRYSENE; ANTI-DIOL; REGION;
   4H-CYCLOPENTA<DEF>CHRYSENE; DERIVATIVES
AB The first series of persistent carbocations derived from mono- and
   disubstituted chrysenes Ch (5-methyl- 3, 2-methoxy- 19,
   2-methoxy-11-methyl- 20, 2-methoxy-5-methyl- 21, and
   9-methyl-4H-cyclopenta[def] chrysene 22), monosubstituted benzo[c]
   phenanthrenes BcPh (3-methoxy- 23, 3-hydroxy- 24), and monosubstituted
   benzo[g]chrysenes BgCh (12-methoxy- 25; 12-hydroxy- 26) were generated
   in FSO3H/SO2CIF or FSO3H-SbF5 (4:1)/SO2CIF and studied by
   low-temperature NMR at 500 MHz. The methoxy and methyl substituents
   direct the protonation to their respective ortho positions. Whereas
   parent Ch 1 is protonated at C-6/C-12, 3 is protonated at C-6 (3aH(+))
   and at C-12 (3bH(+)) with the latter being the thermodynamic cation.
   The 2-methoxy-Ch 19 is protonated at C-1 to give two conformationally
   distinct carboxonium ions (19aH(+)/19bH(+)). In the disubstituted Ch
   derivatives 20 and 21, the 2-methoxy overrides the 5-methyl and the
   predominant carbocations formed are via attack ortho to methoxy. For
   the methano derivative 22 (Me at C-9), a 3:1 mixture of 22aH(+)/22bH(+)
   is formed. For parent BcPh 13, nitration and benzoylation are directed
   to C-5. With 3-methoxy-BcPh 23, the site of attack moves to C-4 thus
   producing two conformationally distinct carboxonium ions
   (23aH(+)/23bH(+)), whereas conventional nitration gave a 2:1 mixture of
   23aNO(2) and 23bNO(2). In 3-hydroxy-BcPh 24, the carboxonium ion 24H(+)
   is exclusively formed. For parent BgCh 16, protonation, nitration, and
   benzoylation are all directed to C-10 (16H(+), 16NO(2), 16COPh), but
   presence of OMe or OH substituent at C-12 changes the site of attack to
   C-11. Charge delocalization mode is probed based on magnitude of Delta
   delta Cs-13 and conformational aspects via NOED experiments. Complete
   NMR data are also reported for several benzoylation/nitration products.
   Using ab initio/GIAO (and NICS), the NMR chemical shifts (and
   aromaticity) in model carbocations A-D were evaluated. This work
   represents the first direct study of the carbocations derived from the
   methyl-, methoxy-/hydroxy-derivatives of three important classes of
   bay-region and fjord-region PAHs whose diol-epoxides extensively bind
   to DNA. It also extends the available data on electrophilic chemistry
   of BcPh and BgCh.
C1 Kent State Univ, Dept Chem, Kent, OH 44242 USA.
   SUNY Coll Buffalo, Great Lakes Ctr Environm Res & Educ, Buffalo, NY 14222 USA.
   USP, FFCLRP, Dept Quim, LAMMOL, Sao Paulo, Brazil.
RP Laali, KK, Kent State Univ, Dept Chem, Kent, OH 44242 USA.
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   FRISCH MJ, 1998, GAUSSIAN 98 REVISION
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   HARVEY RG, 1991, POLYCYCLIC AROMATIC, CH3
   HARVEY RG, 1997, POLYCYCLIC AROMATIC, CH2
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NR 38
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD FEB 9
PY 2001
VL 66
IS 3
BP 780
EP 788
PG 9
SC Chemistry, Organic
GA 401TF
UT ISI:000166943800020
ER

PT J
AU Barba, D
   Jandl, S
   Nekvasil, V
   Marysko, M
   Divis, M
   Martin, AA
   Lin, CT
   Cardona, M
   Wolf, T
TI Infrared transmission study of crystal-field excitations in
   Sm1+xBa2-xCu3O6+y
SO PHYSICAL REVIEW B
LA English
DT Article
ID SINGLE-CRYSTALS; INTERMETALLIC COMPOUNDS; NDBA2CU3O7-DELTA;
   SUPERCONDUCTORS; TRANSITIONS; YBA2CU3O7-X; GRADIENT; SYSTEMS; ND2CUO4;
   SM
AB Absorption bands, corresponding to the crystal-field (CF) excitations
   of the Sm3+ ions in SmBa2Cu3O6, have been observed by infrared
   transmission spectroscopy and assigned to transitions from the lowest
   energy levels of the H-6(5/2) multiplet to the excited multiplets
   H-6(7/2), H-6(9/2), H-6(11/2), H-6(13/2), F-6(7/2), and F-6(9/2) Of
   Sm3+ ions on the regular D-4h-symmetry sites and the C-4v-symmetry Pa
   sites. A set of the CF parameters that fits the levels in the regular
   sites and reproduces the magnetic susceptibility anisotropy has been
   derived. The CF interaction parameters in the Sm/Ba sites have been
   modeled by combining the superposition model and an ab initio method
   based on the density-functional calculations.
C1 Univ Sherbrooke, Dept Phys, Ctr Rech Proprietes Elect Mat Avances, Sherbrooke, PQ J1K 2R1, Canada.
   Acad Sci Czech Republ, Inst Phys, Prague 16253 6, Czech Republic.
   Charles Univ, Dept Electron Syst, Prague 12116 2, Czech Republic.
   Max Planck Inst Festkorperforsch, D-70569 Stuttgart, Germany.
   Inst Festkorperphys, D-76021 Karlsruhe, Germany.
   IP&D Univap Sao Jose dos Campos, Inst Pesquisa & Desenvolvimento, BR-12244000 Sao Jose Dos Campos, Brazil.
RP Barba, D, Univ Sherbrooke, Dept Phys, Ctr Rech Proprietes Elect Mat
   Avances, Sherbrooke, PQ J1K 2R1, Canada.
CR BARBA D, UNPUB
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NR 34
TC 11
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD FEB 1
PY 2001
VL 6305
IS 5
AR 054528
DI ARTN 054528
PG 10
SC Physics, Condensed Matter
GA 399PB
UT ISI:000166820600123
ER

PT J
AU Moraes, LAB
   Eberlin, MN
TI Ketalization of gaseous acylium ions
SO JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
LA English
DT Article
ID DISTONIC RADICAL CATIONS; GAS-PHASE REACTIONS; MOLECULE REACTIONS;
   MASS-SPECTROMETRY; DIMETHYLCHLORINIUM ION; CHARGED ELECTROPHILES;
   METHOXYMETHYL CATION; CYCLIC ACETALS; SUBSTITUTION; ALCOHOLS
AB A novel reaction of gaseous acylium ions: ketalization with diols and
   analogs, has been systematically studied via pentaquadrupole MS2 and
   MS3 experiments and ab initio calculations. A variety of alpha,beta
   -diols and their amino, thiol, ether, and thioether analogs have been
   tested for reactivity, mechanism evaluation, site selectivity, and for
   the effects of alpha- and beta -interfunctional separation. As for
   condensed-phase ketalization of neutral carbonyl compounds followed by
   hydrolysis, gaseous acylium ions are chemically deactivated in the form
   of cyclic ionic ketals by ketalization, and are efficiently released
   via on-line collision-induced dissociation. Ketalization of acylium
   ions is shown to identify and structurally characterize alpha,beta
   -diols and their analogs, and to distinguish regioisomers.
   Diastereomers can also be distinguished, as illustrated for cis and
   trans 1,2-diaminocyclohexane. The MS2 and MS3 data together with
   O-18-labeling and ab initio calculations establish for acylium ion
   ketalization a mechanism of anchimeric assistance with participation of
   the neighboring acyl group. (C) 2001 American Society for Mass
   Spectrometry.
C1 Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Moraes, LAB, Univ Estadual Campinas, Inst Chem, CP 6154, BR-13083970
   Campinas, SP, Brazil.
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NR 60
TC 11
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA
SN 1044-0305
J9 J AMER SOC MASS SPECTROM
JI J. Am. Soc. Mass Spectrom.
PD FEB
PY 2001
VL 12
IS 2
BP 150
EP 162
PG 13
SC Chemistry, Analytical; Chemistry, Physical; Spectroscopy
GA 399NF
UT ISI:000166818700003
ER

PT J
AU Schmidt, TM
   Justo, JF
   Fazzio, A
TI Stacking fault effects in pure and n-type doped GaAs
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID ELECTRONIC-STRUCTURE; DX CENTERS; AB-INITIO; SEMICONDUCTORS;
   PSEUDOPOTENTIALS; DEFECTS
AB Using ab initio total-energy calculations, we investigate the effects
   of stacking faults on the properties of dopants in pure and n-type
   doped GaAs. We find that the Si impurity segregates towards a GaAs
   stacking fault. A Si atom at a Ga site in the stacking fault, in either
   a neutral or a negative charge state, is energetically favorable as
   compared to a Si atom at a Ga site in a crystalline environment by as
   much as 0.2 eV. We also find that a Si impurity in the stacking fault
   cannot occupy metastable positions, as occurs in the formation of DX
   centers. Thus, stacking faults can prevent the formation of DX-like
   centers in GaAs. (C) 2001 American Institute of Physics.
C1 Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Schmidt, TM, Univ Fed Uberlandia, Dept Ciencias Fis, CP 593,
   BR-38400902 Uberlandia, MG, Brazil.
CR ALEXANDER H, 1986, DISLOCATIONS SOLIDS, V7, P115
   ANTONELLI A, 1999, PHYS REV B, V60, P4711
   BACHELET GB, 1982, PHYS REV B, V26, P4199
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   CHADI DJ, 1988, PHYS REV LETT, V61, P873
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   JONES R, 1993, PHYS STATUS SOLIDI A, V137, P389
   JUSTO JF, 1999, PHYSICA B, V273, P473
   JUSTO JF, 2000, PHYS REV LETT, V84, P2172
   KACKELL P, 1998, PHYS REV B, V58, P1326
   KAPLAN T, 2000, PHYS REV B, V61, P1674
   KLEINMAN L, 1982, PHYS REV LETT, V48, P1425
   MAITI A, 1996, PHYS REV LETT, V77, P1306
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   MIWA RH, 1999, APPL PHYS LETT, V74, P1999
   SCHMIDT TM, 1996, PHYS REV B, V53, P1315
   STAMPFL C, 1998, PHYS REV B, V57, P15052
NR 18
TC 6
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD FEB 12
PY 2001
VL 78
IS 7
BP 907
EP 909
PG 3
SC Physics, Applied
GA 398TN
UT ISI:000166772600019
ER

PT J
AU Alves, CN
   Romero, OAS
   da Silva, ABF
TI A theoretical study of the intramolecular hetero Dials-Alder
   cycloaddition reactions of azoalkenes
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE Hartree-Fock; density functional theory; Diels-Alder cycloaddition;
   transition structures; azoalkenes
ID TRANSITION STRUCTURES; REACTIVITY; CATALYSIS
AB Ab initio Hartree-Fock and density functional theory calculations were
   performed to study transition geometries in intramolecular Diels-Alder
   cycloaddition reactions of azoalkene compounds. The Hartree-Fock (HF)
   calculations were formed at the RHF/3-21G level and the density
   functional theory (DFT) calculations were performed with the B3LYP
   functional and 6-31G* basis set. The order of the reactivity of
   azoalkenes with different substituents in intramolecular hetero
   Diels-Alder reactions was predicted from the frontier orbital energies,
   and calculations of the reaction barriers were performed. The HF and
   DFT calculations generated transition geometries with a very small
   degree of asynchronicity, The DFT results are in full agreement with
   experimental evidence and show the capability of this level of DFT
   calculation to predict the reactivity of intramolecular hetero
   Diels-Alder cycloaddition correctly. (C) 2001 Elsevier Science B.V. All
   rights reserved.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, BR-13560970 Sao Carlos, SP, Brazil.
   Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, BR-66075110 Belem, Para, Brazil.
RP da Silva, ABF, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis
   Mol, CP 780, BR-13560970 Sao Carlos, SP, Brazil.
CR BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BOGER DL, 1987, HETERO DIELSALDER ME
   BROWN FK, 1985, TETRAHEDRON LETT, V26, P2297
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   JURSIC BS, 1995, J CHEM SOC PERK T, V2, P1223
   JURSIC BS, 1995, J MOL STRUCT THEOCHE, V331, P215
   LEE C, 1988, PHYS REV B, V37, P785
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   POPLE JA, 1998, GAUSSIAN 98
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NR 18
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD JAN 15
PY 2001
VL 535
BP 165
EP 169
PG 5
SC Chemistry, Physical
GA 396JR
UT ISI:000166633100018
ER

PT J
AU Barbatti, M
   Jalbert, G
   Nascimento, MAC
TI The effects of the presence of an alkaline atomic cation in a molecular
   hydrogen environment
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID BINDING-ENERGIES; CLUSTERS; GEOMETRIES; LI
AB Ab initio calculations were performed for X+(H-2)(n) clusters [X=Li, Na
   (n=1-7) and K (n=1-3)]. For n=1-6, the equilibrium geometries
   correspond to spherically symmetrical distributions of H-2 units around
   the X+. The binding energies and the geometric parameters indicate that
   the seventh H-2 unit opens a new shell of ligands for the cluster with
   X=Li but not for X=Na. (C) 2001 American Institute of Physics.
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21945970 Rio De Janeiro, Brazil.
RP Barbatti, M, Univ Fed Rio de Janeiro, Inst Fis, CP 68528, BR-21945970
   Rio De Janeiro, Brazil.
CR BARBATTI M, 2000, J CHEM PHYS, V113, P4230
   BAUSCHLICHER CW, 1992, J PHYS CHEM-US, V96, P2475
   BLAUDEAU JP, 1997, J CHEM PHYS, V107, P5016
   BOYS SF, 1970, MOL PHYS, V19, P553
   BUSHNELL JE, 1994, J PHYS CHEM-US, V98, P2044
   CURTISS LA, 1988, J PHYS CHEM-US, V92, P894
   DAVY R, 1999, MOL PHYS, V97, P1263
   FALCETTA MF, 1993, J PHYS CHEM-US, V97, P1011
   FARIZON B, 1999, PHYS REV B, V60, P3821
   GOBET F, UNPUB
   GORA RW, 1999, J PHYS CHEM A, V103, P9138
   HERZBERG G, 1950, MOL SPECTRA MOL STRU, V1
   IGNACIO EW, 1998, CHEM PHYS LETT, V287, P563
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   PANG T, 1994, CHEM PHYS LETT, V228, P555
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   STICH I, 1997, PHYS REV LETT, V78, P3669
   SWITALSKI JD, 1974, J CHEM PHYS, V60, P2252
   WU CH, 1979, J CHEM PHYS, V71, P783
NR 21
TC 8
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD FEB 1
PY 2001
VL 114
IS 5
BP 2213
EP 2218
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 397CQ
UT ISI:000166676100034
ER

PT J
AU Olivato, PR
   Ruiz, R
   Zukerman-Schpector, J
   Dal Colle, M
   Distefano, G
TI Comparative spectroscopic and theoretical studies on the conformation
   of some alpha-diethoxyphosphoryl carbonyl compounds and their
   alpha-ethylsulfonyl analogues
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID ELECTRONIC INTERACTION; INTRAMOLECULAR INTERACTIONS;
   PHOTOELECTRON-SPECTROSCOPY; IR SPECTROSCOPY; AB-INITIO; DERIVATIVES;
   SULFONES; ACETOPHENONES; SPECTRA; ORBITALS
AB Comparative nu (CO) IR analysis of beta -carbonylphosphonates
   [XC(O)CH2P(O)(OR)(2): X = Me 1, Ph 2, OEt 3, NEt2 4 and SEt 5; R = Et]
   (series I) and beta -carbonylsulfones [XC(O)CH2SO2R: X = Me 6, Ph 7,
   OEt 8, NEt2 9 and SEt 10; R = Et] (series II) along with ab initio
   6-31G** calculations on 1a and 6a (R = Me) suggest the existence of
   only a single gauche conformer for series I. The negative carbonyl
   frequency shifts for both series follow approximately the
   electron-affinities of the pi*(CO) orbital of the parent compounds
   MeC(O)X 11-15. The less positive asymmetric sulfonyl frequency shifts
   (Delta nu (SO2)) for II in relation to the phosphoryl frequency shifts
   (Delta nu (PO)) for I and the larger negative carbonyl frequency shifts
   for II with respect to the corresponding values for I are in line with
   the upfield C-13 NMR chemical shifts of the carbonyl carbon for II
   compared to I. These trends agree with the shorter O-(SO2)...C-(CO)
   contact in comparison with the O-(PO)...C-(CO) one and are discussed in
   terms of O-1p--> pi*(CO) charge transfer and electrostatic
   interactions, which are stronger for series II than for I, indicating
   that the sulfonyl oxygen atom is a better electron donor than the
   phosphoryl oxygen atom. Intrinsic geometrical parameters of O=S CH2 and
   O=P-CH2 moieties seem to be responsible for this behaviour as indicated
   by X-ray study and ab initio calculations of dialkyl
   (methylsulfonyl)methylphosphonate MeSO2CH2P(O)(OR)(2) (R = Et 18, Me
   18a).
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13560 Sao Carlos, SP, Brazil.
   Univ Ferrara, Dipartmento Chim, I-44100 Ferrara, Italy.
RP Olivato, PR, Univ Sao Paulo, Inst Quim, CP 26077, BR-05513970 Sao
   Paulo, Brazil.
CR 1998, 18 INT S ORG CHEM SU
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   DALCOLLE M, 1995, J PHYS CHEM-US, V99, P15011
   DISTEFANO G, UNPUB
   DISTEFANO G, 1991, J CHEM SOC P2, P1195
   DISTEFANO G, 1996, J CHEM SOC PERK  AUG, P1661
   FARRUGIA LJ, 2000, WINGX WINDOWS PROGRA
   FRISCH MJ, 1998, GAUSSIAN 98
   GIORDAN JC, 1985, J AM CHEM SOC, V107, P5600
   HANSH C, 1995, EXPLORING QSAR HYDRO
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   OLIVATO PR, 1985, PHOSPHORUS SULFUR, V24, P225
   OLIVATO PR, 1987, PHOSPHORUS SULFUR, V33, P135
   OLIVATO PR, 1989, PHOSPHORUS SULFUR, V44, P9
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   OLIVATO PR, 1991, PHOSPHORUS SULFUR, V59, P219
   OLIVATO PR, 1992, MAGN RESON CHEM, V30, P81
   OLIVATO PR, 1996, REV HETEROATOM CHEM, V15, P115
   OLIVATO PR, 1997, PHOSPHORUS SULFUR, V130, P155
   OLIVATO PR, 1998, 18 INT S ORG CHEM SU, P214
   OLIVATO PR, 1998, J CHEM SOC PERK  JAN, P109
   OLIVATO PR, 1999, PHOSPHORUS SULFUR, V153, P353
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   OLIVATO PR, 2000, PHOSPHORUS SULFUR, V156, P255
   OLIVEIRA JE, 1980, THESIS U SAO PAULO B
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NR 42
TC 7
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1472-779X
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD JAN
PY 2001
IS 1
BP 97
EP 102
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 395VF
UT ISI:000166601400015
ER

PT J
AU Pliego, JR
   Riveros, JM
TI The gas-phase reaction between hydroxide ion and methyl formate: A
   theoretical analysis of the energy surface and product distribution
SO CHEMISTRY-A EUROPEAN JOURNAL
LA English
DT Article
DE ab initio calculations; gas-phase reactions; hydrolysis
ID S(N)2 NUCLEOPHILIC-SUBSTITUTION; BASE-CATALYZED-HYDROLYSIS;
   DISPLACEMENT-REACTIONS; ESTER HYDROLYSIS; AB-INITIO; MECHANISM;
   KINETICS; RESONANCE; ABINITIO; CLUSTERS
AB The potential energy surface for the prototype solvent-free ester
   hydrolysis reaction: OH-+HCOOCH3-> products has been characterized by
   high level ab initio calculations of MP4/6311 + G(2df,2p)//MP2/6-31 +
   G(d) quality. These calculations reveal that the approach of an OH- ion
   leads to the formation of two distinct ion-molecule complexes: 1) the
   MS1 species with the hydroxide ion hydrogen bonded to the methyl group
   of the ester, and 2) the MS4 moiety resulting from proton abstraction
   of the formyl hydrogen by the hydroxide ion and formation of a
   three-body complex of water, methoxide ion and carbon monoxide. The
   first complex reacts to generate formate anion and methanol products
   through the well known B(AC)2 and S(N)2 mechanisms. RRKM calculations
   predict that these pathways will occur with a relative contribution of
   85% and 15% at 298.15 K, in excellent agreement with experimentally
   measured Values of 87 % and 13 %, respectively. The second complex
   reacts by loss of carbon monoxide to yield the water-methoxide complex
   through a single minimum potential surface and is the preferred pathway
   in the gas-phase. This water-methoxide adduct can further dissociate if
   the reactants have excess energy. These results provide clear evidence
   that the preferred pathways for ester hydrolysis in solution are
   dictated by solvation of the hydroxide ion.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, Brazil.
RP Pliego, JR, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
CR *GAUSS INC, 1995, GAUSS 94 REV D 2
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NR 43
TC 11
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA PO BOX 10 11 61, D-69451 BERLIN, GERMANY
SN 0947-6539
J9 CHEM-EUR J
JI Chem.-Eur. J.
PD JAN 5
PY 2001
VL 7
IS 1
BP 169
EP 175
PG 7
SC Chemistry, Multidisciplinary
GA 392PH
UT ISI:000166419500017
ER

PT J
AU de Almeida, NG
   Ramos, PB
   Serra, RM
   Moussa, MY
TI Phenomenological-operator approach to introduce damping effects on
   radiation field states
SO JOURNAL OF OPTICS B-QUANTUM AND SEMICLASSICAL OPTICS
LA English
DT Article
DE radiation field states; damping effects; cavity field
ID ARBITRARY QUANTUM STATES; PODOLSKY-ROSEN CHANNELS; EXPERIMENTAL
   REALIZATION; PROJECTION SYNTHESIS; TELEPORTATION; ENTANGLEMENT;
   GENERATION; ATOM; SUPERPOSITIONS; PHOTONS
AB In this paper we propose an approach to deal with radiation field
   states which incorporates damping effects at zero temperature. By using
   some well known results on dissipation of a cavity-field state,
   obtained by standard ab initio methods, it was possible to infer,
   through a phenomenological way, the explicit form for the evolution of
   the state vector for the whole system: the cavity field plus reservoir.
   This proposal turns out to be extremely convenient for accounting for
   the influence of the reservoir over the cavity field. To illustrate the
   universal applicability of our approach we consider the attenuation
   effects on cavity-field states engineering. The main concern of the
   present phenomenological approach consists in furnishing a
   straightforward technique to estimate the fidelity resulting from
   processes in cavity QED phenomena. A proposal to maximize the fidelity
   of the process is presented.
C1 Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Carlos, SP, Brazil.
RP de Almeida, NG, Univ Fed Sao Carlos, Dept Fis, CP 676, BR-13565905 Sao
   Carlos, SP, Brazil.
CR BELL JS, 1964, PHYSICS, V1, P195
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   NUSSENZVEIG P, COMMUNICATION
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NR 35
TC 7
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 1464-4266
J9 J OPT B-QUANTUM SEMICL OPT
JI J. Opt. B-Quantum Semicl. Opt.
PD DEC
PY 2000
VL 2
IS 6
BP 792
EP 798
PG 7
SC Physics, Applied; Optics
GA 389LL
UT ISI:000166239300015
ER

PT J
AU Pliego, JR
   Riveros, JM
TI New values for the absolute solvation free energy of univalent ions in
   aqueous solution
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID GIBBS FREE-ENERGY; AB-INITIO; PROTON AFFINITIES; CONTINUUM MODEL;
   GAS-PHASE; THERMODYNAMICS; PHOTOIONIZATION; MOLECULES; HYDRATION;
   SOLVENTS
AB The absolute solvation free energy of 30 univalent ions, mainly organic
   species, has been calculated from experimental and theoretical data on
   proton affinities, aqueous acidity constants, solvation free energy of
   neutral species, and the new value for the absolute solvation free
   energy of the proton determined by Tissandier et al. [J. Phys. Chem. A
   102 (1998) 7787]. Our new values reveal considerable differences with
   previous compilations, and should be taken into consideration for
   comparison with liquid simulation results and in the development of
   implicit solvation models. (C) 2000 Elsevier Science B.V. All rights
   reserved.
C1 Univ Sao Paulo, Inst Quim, BR-05513970 Sao Paulo, SP, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Caixa Postal 26077, BR-05513970
   Sao Paulo, SP, Brazil.
CR ALBERT A, 1984, DETERMINATION IONIZA
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NR 30
TC 23
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD DEC 29
PY 2000
VL 332
IS 5-6
BP 597
EP 602
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 389JY
UT ISI:000166235900027
ER

PT J
AU Nunes, RW
   Vanderbilt, D
TI Models of core reconstruction for the 90 degrees partial dislocation in
   semiconductors
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID ELECTRONIC-STRUCTURE; SILICON; KINKS; MOTION
AB We compare the models that have been proposed in the literature for the
   atomic structure of the 90 degrees partial dislocation in the homopolar
   semiconductors, silicon, diamond, and germanium. In particular, we
   examine the traditional single-period and our recently proposed
   double-period core structures. Ab initio and tight-binding results on
   the core energies are discussed, and the geometries are compared in the
   light of the available experimental information about dislocations in
   these systems. The double-period geometry is found to be the
   ground-state structure for all three materials. We address
   boundary-condition issues that have been recently raised concerning
   these results. The structures of point excitations (kinks, solitons,
   and kink-soliton complexes) in the two geometries are also reviewed.
C1 Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte, MG, Brazil.
   Rutgers State Univ, Dept Phys & Astron, Piscataway, NJ 08854 USA.
RP Nunes, RW, Univ Fed Minas Gerais, Dept Fis, BR-30123970 Belo Horizonte,
   MG, Brazil.
CR ALEXANDER H, 1991, MATERIALS SCI TECHNO, V4, P249
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   OBERG S, 1995, PHYS REV B, V51, P13138
NR 28
TC 4
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD DEC 11
PY 2000
VL 12
IS 49
BP 10021
EP 10027
PG 7
SC Physics, Condensed Matter
GA 386BC
UT ISI:000166039400002
ER

PT J
AU Justo, JF
   Fazzio, A
   Antonelli, A
TI Dislocation core reconstruction in zinc-blende semiconductors
SO JOURNAL OF PHYSICS-CONDENSED MATTER
LA English
DT Article
ID 90-DEGREES PARTIAL DISLOCATION; DENSITY-FUNCTIONAL THEORY;
   MOLECULAR-DYNAMICS; SILICON; MOBILITY; GAAS; PSEUDOPOTENTIALS;
   VELOCITIES; CRYSTALS; INAS
AB Using ab initio total-energy calculations, we computed core
   reconstruction energies of partial dislocations in zinc-blende
   semiconductors. The reconstruction energy of 30 degrees partials was
   found to scale almost linearly with the experimental activation energy
   of 60 degrees dislocations. The electronic structure of a dislocation
   shows that in an unreconstructed core, the gap states comprise a
   half-filled one-dimensional band, which splits up into bonding and
   antibonding states upon reconstruction. The energy states which lie in
   the electronic gap come from the core of beta -partials, while those
   related to alpha -partials remain resonant in the valence band.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
RP Justo, JF, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   SP, Brazil.
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NR 26
TC 9
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-8984
J9 J PHYS-CONDENS MATTER
JI J. Phys.-Condes. Matter
PD DEC 11
PY 2000
VL 12
IS 49
BP 10039
EP 10044
PG 6
SC Physics, Condensed Matter
GA 386BC
UT ISI:000166039400004
ER

PT J
AU Prudente, FV
   Costa, LS
   Acioli, PH
TI Correlation function quantum Monte Carlo studies of rovibrational
   excited states in molecules
SO JOURNAL OF PHYSICS B-ATOMIC MOLECULAR AND OPTICAL PHYSICS
LA English
DT Review
ID POTENTIAL-ENERGY SURFACES; CONSISTENT-FIELD APPROACH; QUASI-ADIABATIC
   CHANNELS; ELECTRONIC GROUND-STATE; AB-INITIO CALCULATIONS;
   VIBRATIONAL-STATES; VARIATIONAL CALCULATIONS; WAVE-FUNCTIONS;
   TRIATOMIC-MOLECULES; HYDROGEN-PEROXIDE
AB In this paper we review the correlation function quantum Monte Carlo
   (CFQMC) method. We describe the functional forms and the optimization
   of trial basis functions used to treat the vibrational and rotational
   motions. We discuss selected applications to di-, tri- and tetra-atomic
   molecules. Our main goal is to discuss the potentiality of the CFQMC
   method in the study of rovibrational excited states of polyatomic
   molecules. In particular, we focus our discussion on the generation of
   the trial basis functions for ground and excited states, and the
   guiding function used to perform the multidimensional integral sampling
   required by the method.
C1 Univ Coimbra, Dept Quim, P-3049 Coimbra, Portugal.
   Univ Brasilia, Inst Fis, BR-70919970 Brasilia, DF, Brazil.
RP Prudente, FV, Univ Coimbra, Dept Quim, P-3049 Coimbra, Portugal.
CR ACIOLI PH, 1999, J CHEM PHYS, V111, P6311
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   PAPOUSEK D, 2000, MOL VIBRATIONAL ROTA
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   SEVERSON MW, 1999, J CHEM PHYS, V111, P10866
   SILVA WB, UNPUB
   SILVA WB, 2000, THESIS U BRASILIA
   SUHM MA, 1991, PHYS REP, V204, P293
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   ZARE RN, ANGULAR MOMENTUM
NR 109
TC 8
PU IOP PUBLISHING LTD
PI BRISTOL
PA DIRAC HOUSE, TEMPLE BACK, BRISTOL BS1 6BE, ENGLAND
SN 0953-4075
J9 J PHYS-B-AT MOL OPT PHYS
JI J. Phys. B-At. Mol. Opt. Phys.
PD NOV 28
PY 2000
VL 33
IS 22
BP R285
EP R313
PG 29
SC Physics, Atomic, Molecular & Chemical; Optics
GA 387CE
UT ISI:000166101900003
ER

PT J
AU Amalvy, JI
   Asua, JM
   Leite, CAP
   Galembeck, F
TI Elemental mapping by ESI-TEM, during styrene emulsion polymerization
SO POLYMER
LA English
DT Article
DE latex particles; seeded emulsion polymerization; styrene
ID PARTICLE MORPHOLOGY; LATEX-PARTICLES; CLUSTER DYNAMICS; SYSTEMS
AB The elemental distribution in latex particles during the ab-initio and
   seeded emulsion polymerization of styrene was studied by electron
   spectroscopy imaging, in an analytical transmission electron
   microscope. Surface anchoring effect, chain migration and the extent of
   burying of the sulfate groups from the initiator were investigated by
   comparing the distributions of the different elements. (C) 2000
   Elsevier Science Ltd. All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, Dept Chem, BR-13083970 Campinas, SP, Brazil.
   Ctr Invest & Desarrollo Tecnol Pinturas, CIDEPINT, Buenos Aires, DF, Argentina.
   Univ Pais Vasco, Fac Ciencias Quim, Dept Quim Aplicada, Grp Ingn Quim, E-20080 San Sebastian, Spain.
   Univ Pais Vasco, Inst Polymer Mat, POLYMAT, E-20080 San Sebastian, Spain.
RP Galembeck, F, Univ Estadual Campinas, Inst Quim, Dept Chem, Caixa
   Postal 6154, BR-13083970 Campinas, SP, Brazil.
CR AHMED SM, 1980, ORG COAT PLAST CHEM, V43, P120
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   GONZALEZORTIZ LJ, 1995, MACROMOLECULES, V28, P3135
   GONZALEZORTIZ LJ, 1996, MACROMOLECULES, V29, P383
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NR 20
TC 6
PU ELSEVIER SCI LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, OXON, ENGLAND
SN 0032-3861
J9 POLYMER
JI Polymer
PD MAR
PY 2001
VL 42
IS 6
BP 2479
EP 2489
PG 11
SC Polymer Science
GA 384GJ
UT ISI:000165934200022
ER

PT J
AU Gonzalez, L
   Hoki, K
   Kroner, D
   Leal, AS
   Manz, J
   Ohtsuki, Y
TI Selective preparation of enantiomers by laser pulses: From optimal
   control to specific pump and dump transitions
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID VIBRATIONAL-EXCITATION; MOLECULES; SUPERPOSITIONS; DYNAMICS; STATES;
   FIELDS
AB Starting from optimal control, various series of infrared, ultrashort
   laser pulses with analytical shapes are designed in order to drive a
   preoriented molecule from its ground torsional state, which represents
   the coherent superposition of left and right atropisomers, towards a
   single enantiomer. Close analysis of the population dynamics, together
   with the underlying symmetry selection rules for the laser induced
   transitions, yields the mechanism. Namely, the molecule is driven from
   its ground vibrational state towards the coherent superposition of the
   lowest doublet of states via a doublet of excited torsional states with
   opposite symmetries. This pump-and-dump mechanism can be achieved by
   simpler series of analytical laser pulses. This decomposition of the
   optimal pulse into analytical subpulses allows us to design different
   scenarios for the selective preparation of left or right enantiomers.
   Exemplary this is demonstrated by quantum simulations of representative
   wave packets for the torsional motions of the model system, H2POSH, in
   the electronic ground state, based on the ab initio potential energy
   surface, and with ab initio dipole couplings. (C) 2000 American
   Institute of Physics. [S0021-9606(00)00940-5].
C1 Free Univ Berlin, Inst Chem Phys & Theoret Chem, D-14195 Berlin, Germany.
   Tohoku Univ, Grad Sch Sci, Dept Chem, Sendai, Miyagi 9808578, Japan.
   UFMG, ICEX, Dept Quim, BR-31270901 Belo Horizonte, MG, Brazil.
RP Gonzalez, L, Free Univ Berlin, Inst Chem Phys & Theoret Chem, Takustr
   3, D-14195 Berlin, Germany.
CR BRUMER P, 1992, ANNU REV PHYS CHEM, V43, P257
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NR 29
TC 14
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD DEC 22
PY 2000
VL 113
IS 24
BP 11134
EP 11142
PG 9
SC Physics, Atomic, Molecular & Chemical
GA 382TZ
UT ISI:000165841300032
ER

PT J
AU Denault, JW
   Wang, F
   Cooks, RG
   Gozzo, FC
   Eberlin, MN
TI Structural characterization of clusters formed from alkyl nitriles and
   the methyl cation
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID NUCLEOPHILIC DISPLACEMENT-REACTIONS; ION-MOLECULE REACTIONS; GAS-PHASE;
   KINETIC METHOD; THERMOCHEMICAL DETERMINATIONS; MASS-SPECTROMETRY;
   PROTON AFFINITIES; SN2 REACTIONS; TRANSITION; ETHYLATION
AB Cluster ions composed of the alkyl nitriles, acetonitrile (CH3CN) and
   butyronitrile (C3H7CN), and the methyl cation (CH3+) have been examined
   in an effort to study methyl cation affinities and the intrinsic
   nucleophilicity of these bases. Structural characterization of the
   sas-phase dimeric adduct ions was achieved via multiple stage mass
   spectrometry (MSn) experiments and by quantum mechanical calculations.
   The kinetic method was used as a diagnostic tool in determining the
   structure of the dimeric adduct: the results of tandem mass
   spectrometry (MS2) experiments' are found to provide ratios which
   exclude loosely bonded dimers based on the thermochemistry of the
   constituent monomers, and which are consistent with a mixture of
   noninterconverting covalently bonded structures predicted by ab initio
   calculations. These clusters are bound such that one nitrile is
   N-methylated and the second nitrile is bound covalently to the carbon
   of the methylated cyano group. Collision-induced dissociation of this
   cluster ion results in the loss of a single neutral nitrile whereas
   both N-methylated nitriles should be formed upon dissociation of a
   loosely bound dimer with the greater fragment ion abundance
   corresponding to the nitrile having the higher CH3+ affinity. Ab initio
   calculations show a large barrier between the two isomeric forms of the
   dimeric cluster and this precludes intramolecular methyl cation
   transfer between the nitriles. The effects of fluorine substitution at
   the methyl cation, i.e., CH2F+ and CF3+, on the adducts of the nitriles
   greatly affects the stability order of the methylated nitrile monomers
   and dimeric adducts, and thus the abundance ratios of the MS/MS
   fragments. As the number of fluorine atoms in the cation is increased,
   the methylated nitrile becomes less stable relative to the dimeric
   cluster ion.
C1 Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
   Triangle Pharmaceut, Durham, NC 27707 USA.
   State Univ Campinas, Inst Chem, Campinas, SP, Brazil.
RP Cooks, RG, Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
CR ALVEREZ J, IN PRESS J MASS SPEC
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NR 57
TC 6
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD DEC 7
PY 2000
VL 104
IS 48
BP 11290
EP 11296
PG 7
SC Chemistry, Physical
GA 380WB
UT ISI:000165725500007
ER

PT J
AU Borin, AC
   Serrano-Andres, L
TI A theoretical study of the absorption spectra of indole and its
   analogs: indene, benzimidazole, and 7-azaindole
SO CHEMICAL PHYSICS
LA English
DT Article
DE indole; indene; benzimidazole; 7-azaindole; absorption spectra; CASPT2
ID EXCITED-STATE PROPERTIES; MOLECULAR WAVE-FUNCTIONS; BAND CONTOUR
   ANALYSIS; ANO BASIS-SETS; ELECTRONIC-SPECTRA; AB-INITIO;
   MICROWAVE-SPECTRUM; PROTEIN-STRUCTURE; SPECTROSCOPY; FLUORESCENCE
AB The complete active space (CAS) SCF method and multiconfigurational
   second-order perturbation theory (CASPT2) have been used to study the
   electronic spectra of indole, indene, benzimidazole, and 7-azaindole.
   Singlet and triplet excited states and transition properties in the
   absorption spectra, such as oscillator strengths and transition moment
   directions, have been computed and the experimental data interpreted in
   order to gain insight into the rich spectroscopy of these compounds,
   which are alternative candidates to indole as biochemical probes in the
   characterization of protein properties. (C) 2000 Elsevier Science B.V.
   All rights reserved.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
   Univ Valencia, Dept Quim Fis, E-46100 Valencia, Spain.
RP Borin, AC, Univ Sao Paulo, Inst Quim, Av Prof Lineu Prestes 748,
   BR-05508900 Sao Paulo, Brazil.
CR ALBINSSON B, 1992, J PHYS CHEM-US, V96, P6204
   ANDERSON BE, 1986, CHEM PHYS LETT, V125, P106
   ANDERSSON K, 1997, MOLCAS VERSION 4 0
   BERDEN G, 1995, J CHEM PHYS, V103, P9596
   BORIN AC, 1999, J MOL STRUC-THEOCHEM, V464, P121
   BORIN AC, 1999, J PHYS CHEM A, V103, P1838
   BULSKA H, 1984, J LUMIN, V29, P65
   CAMINATI W, 1990, J MOL STRUCT, V223, P415
   CANE E, 1991, J MOL SPECTROSC, V148, P123
   CHANG CT, 1974, PHOTOCHEM PHOTOBIOL, V19, P347
   CHEN Y, 1994, J PHYS CHEM-US, V98, P2203
   DEMCHENKO AP, 1986, ULTRAVIOLET SPECTROS
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NR 51
TC 15
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD DEC 15
PY 2000
VL 262
IS 2-3
BP 253
EP 265
PG 13
SC Physics, Atomic, Molecular & Chemical
GA 380UN
UT ISI:000165722000005
ER

PT J
AU Serrano-Andres, L
   Borin, AC
TI A theoretical study of the emission spectra of indole and its analogs:
   indene, benzimidazole, and 7-azaindole
SO CHEMICAL PHYSICS
LA English
DT Article
DE indole; indene; benzimidazole; 7-azaindole; emission spectra; CASPT2
ID MOLECULAR WAVE-FUNCTIONS; DOUBLE-PROTON-TRANSFER; ANO BASIS-SETS;
   EXCITED-STATE; AB-INITIO; ELECTRONIC-SPECTRA; TRIPLET-STATES;
   GAS-PHASE; SPECTROSCOPY; PHOTOPHYSICS
AB The complete active space (CAS) SCF method and multiconfigurational
   second-order perturbation theory (CASPT2) have been used to study the
   electronic spectra of indole, indene, benzimidazole, and 7-azaindole.
   The paper is focused on the study of the low-lying valence triplet and
   singlet electronic states at the optimized geometries of the excited
   states. The geometries have been optimized by using analytic CASSCF
   derivatives. CASPT2 point calculations have been performed in order to
   obtain band origins and relaxed emission energies. The results are
   analyzed in the context of the complex emission processes, both
   fluorescence and phosphorescence, displayed by the title compounds,
   which can be used as biochemical probes in the characterization of
   protein properties and activity. (C) 2000 Elsevier Science B.V. All
   rights reserved.
C1 Univ Valencia, Dept Quim Fis, E-46100 Valencia, Spain.
   Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Serrano-Andres, L, Univ Valencia, Dept Quim Fis, Av Dr Moliner 50,
   E-46100 Valencia, Spain.
CR ANDERSON BE, 1986, CHEM PHYS LETT, V125, P106
   ANDERSSON K, 1997, MOLCAS VERSION 4 0
   AVOURIS P, 1976, PHOTOCHEM PHOTOBIOL, V24, P211
   BEARPARK MJ, 1997, J PHYS CHEM A, V101, P8395
   BERDEN G, 1995, J CHEM PHYS, V103, P9596
   BICKEL GA, 1989, J CHEM PHYS, V91, P6013
   BORIN AC, 1999, J MOL STRUC-THEOCHEM, V464, P121
   BROCKLEHURST B, 1974, SPECTROCHIM ACTA A, V30, P1807
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   BULSKA H, 1984, J LUMIN, V29, P65
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   DEMCHENKO AP, 1986, ULTRAVIOLET SPECTROS
   EFTINK MR, 1991, FLUORESCENCE TECHNIQ
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   FENDER BJ, 1999, INT J QUANTUM CHEM, V72, P347
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   FUKE K, 1989, J PHYS CHEM-US, V93, P614
   FULSCHER MP, 1997, J AM CHEM SOC, V119, P6168
   HAHN DK, 1997, J PHYS CHEM A, V101, P2686
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   NI T, 1989, J AM CHEM SOC, V111, P457
   NODA M, 1984, B CHEM SOC JPN, V57, P2376
   PERKAMPUS HH, 1992, UV VIS ATLAS ORGANIC
   PIERLOOT K, 1995, THEOR CHIM ACTA, V90, P87
   RICE JE, 1994, MULLIKEN VERSION 1 1
   ROBEY MJ, 1975, PHOTOCHEM PHOTOBIOL, V21, P363
   ROOS BO, 1995, QUANTUM MECH ELECT S, V357
   ROOS BO, 1996, ADV CHEM PHYS, V93, P219
   ROOS BO, 1996, J MOL STRUC-THEOCHEM, V388, P257
   RUBIO M, 1999, MOL PHYS, V96, P603
   SERRANOANDRES L, 1993, J PHYS CHEM-US, V97, P9360
   SERRANOANDRES L, 1996, J AM CHEM SOC, V118, P185
   SERRANOANDRES L, 1996, J PHYS CHEM-US, V100, P6484
   SERRANOANDRES L, 1998, J CHEM PHYS, V108, P7202
   SHUKLA MK, 1998, CHEM PHYS, V230, P187
   SOBOLEWSKI AL, 1999, CHEM PHYS LETT, V315, P293
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   VELINO B, 1992, J MOL SPECTROSC, V152, P434
   WERNER HJ, 1998, MOLPRO
   WIDMARK PO, 1990, THEOR CHIM ACTA, V77, P291
   WILKINSON F, 1977, J CHEM SOC FARAD T 2, V73, P222
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NR 68
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD DEC 15
PY 2000
VL 262
IS 2-3
BP 267
EP 283
PG 17
SC Physics, Atomic, Molecular & Chemical
GA 380UN
UT ISI:000165722000006
ER

PT J
AU Takahata, Y
   Chong, DP
TI Accurate density-functional calculation of core-electron binding
   energies of some substituted benzenes
SO BULLETIN OF THE CHEMICAL SOCIETY OF JAPAN
LA English
DT Article
ID ZETA BASIS-SET; RAY PHOTOELECTRON-SPECTROSCOPY; GAS; APPROXIMATION;
   DERIVATIVES; PARAMETERS; SPECTRA; BORON
AB The core electron binding energies (CEBE's) of benzene, seven
   monosubstituted benzenes (Ph-X) and one disubstituted benzene
   (p-NH2-C6H4-NO2) were calculated using density-functional theory (DFT).
   The unrestricted generalized transition-state (uGTS) model was
   employed. The DeMon DFT program with a combined functional of Becke's
   exchange (B88) with Perdew's correlation (P86) was used. The average
   absolute deviation of the calculated CEBE's of the title compounds was
   0.3 eV when the cc-pVDZ basis set was used. The "CEBE shift" of the
   ring carbon in Ph-X was calculated while taking the CEBE on the ring
   carbon in Ph-H as a reference. The thus-calculated CEBE shifts agree
   with experiment within the value of the average absolute deviation, 0.1
   eV. The signs and quantitative numerical values of the CEBE shifts are
   very close to the corresponding Hammett sigma constants.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ British Columbia, Dept Chem, Vancouver, BC V6T 1Z1, Canada.
RP Takahata, Y, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083970 Campinas, SP, Brazil.
CR BECKE AD, 1988, PHYS REV A, V38, P3098
   BROWN RS, 1980, CAN J CHEM, V58, P694
   CAVIGLIASSO G, 1999, CAN J CHEM, V77, P24
   CHAERTON M, 1987, PROG PHYS ORG CHEM, V16, P287
   CHEN PC, 1995, J PHYS CHEM-US, V99, P15023
   CHONG DP, 1995, CHEM PHYS LETT, V232, P486
   CHONG DP, 1995, J CHEM PHYS, V103, P1842
   CHONG DP, 1996, CHEM PHYS LETT, V249, P491
   CLEMENTI E, 1963, J CHEM PHYS, V38, P2686
   DUNNING TH, 1989, J CHEM PHYS, V90, P1007
   HAMMETT LP, 1937, J AM CHEM SOC, V59, P96
   JANAK JF, 1978, PHYS REV B, V18, P7165
   JOLLY WL, 1984, ATOMIC DATA NUCL DAT, V31, P434
   KENDALL RA, 1992, J CHEM PHYS, V96, P6796
   LINDBERG B, 1975, UUIP910
   LINDBERG B, 1976, CHEM PHYS LETT, V40, P175
   LISTER DG, 1974, J MOL STRUCT, V23, P253
   MADELUNG O, 1987, LANDOLTBORNSTEIN NUM, V15
   OHTA T, 1975, B CHEM SOC JPN, V48, P2017
   PERDEW JP, 1986, PHYS REV B, V33, P8822
   PULFER M, 1997, CHEM PHYS, V216, P91
   SADOVA NI, 1976, RUSS J STRUCT CHEM, V17, P954
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   SHISHKOV IF, 1984, RUSS J STRUCT CHEM, V25, P260
   SIEGBAHN K, 1969, ESCA APPL FREE MOL, P104
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   SPIESECKE H, 1961, J CHEM PHYS, V35, P731
   STAMANT A, 1990, CHEM PHYS LETT, V169, P387
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   WILLIAMS AR, 1975, J CHEM PHYS, V63, P628
NR 32
TC 5
PU CHEMICAL SOC JAPAN
PI TOKYO
PA 1-5 KANDA-SURUGADAI CHIYODA-KU, TOKYO, 101, JAPAN
SN 0009-2673
J9 BULL CHEM SOC JPN
JI Bull. Chem. Soc. Jpn.
PD NOV
PY 2000
VL 73
IS 11
BP 2453
EP 2460
PG 8
SC Chemistry, Multidisciplinary
GA 380KR
UT ISI:000165701500004
ER

PT J
AU da Silva, RS
   Gorelsky, SI
   Dodsworth, ES
   Tfouni, E
   Lever, ABP
TI Synthesis, spectral and redox properties of tetraammine dioxolene
   ruthenium complexes
SO JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
LA English
DT Review
ID TRANSITION-METAL COMPLEXES; QUINONE-RELATED LIGANDS; COMPACT EFFECTIVE
   POTENTIALS; INDUCED VALENCE TAUTOMERISM; EFFECTIVE CORE POTENTIALS;
   CHARGE-TRANSFER SPECTRA; EXPONENT BASIS-SETS; ELECTRON-TRANSFER;
   DINUCLEAR COMPLEXES; CRYSTAL-STRUCTURES
AB A series of species [Ru-III(NH3)(4)(Cat-R)](n+) have been synthesized
   where Cat-R is a catecholate dianion having the substituent R=CO2-,
   CO2H, OMe or H. These so-called parent species were characterized by
   their electronic spectra, FTIR, mass spectrum, cyclic voltammetry and
   EPR. Controlled potential reduction yields
   [Ru-II(NH3)(4)(Cat-R)]((n-1)+) while controlled potential oxidation
   yields [Ru-II(NH3)(4)(Q-R)]((n+1)+) (Q-R=substituted quinone). Density
   Functional Theory (DFT) was primarily used to explore the electronic
   structures of these complexes. Application of the INDO semi-empirical
   model proved less useful. Time dependent density functional response
   theory was used to calculate the electronic spectra of the species with
   R=H. The electronic spectra of the closed shell species are well
   reproduced by the calculations. The physical properties of these
   complexes indicate a charge delocalized system reminiscent of a
   delocalized organic molecule. The simple valence descriptions noted
   above are convenient to use but do not reflect the actual electronic
   structure. The electronic spectra of the parent species are temperature
   dependent. The visible region charge transfer band shifts by about 1500
   cm(-1) to higher energy in acidic media at liquid nitrogen temperature.
   This is interpreted in terms of solvent effects rather than valence
   tautomerism. The electrochemical properties of [Ru-III(NH3)(4)(Cat-R)],
   in aqueous solution, reveal the first example of a reversible and
   stable Ru-quinone species in that medium. The pK(a) values for several
   dioxolene species, with R=CO2-, are derived from a Pourbaix diagram.
C1 York Univ, Dept Chem, N York, ON M3J 1P3, Canada.
   Univ Sao Paulo, Fac Ciencias Farmaceut Ribeirao Preto, BR-14040901 Ribeirao Preto, SP, Brazil.
   Univ Sao Paulo, Dept Quim, Fac Filosofia Ciencias & Letras Ribeirao Pret, BR-14040901 Ribeirao Preto, SP, Brazil.
RP Lever, ABP, York Univ, Dept Chem, 4700 Keele St, N York, ON M3J 1P3,
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NR 159
TC 12
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1470-479X
J9 J CHEM SOC DALTON TRANS
JI J. Chem. Soc.-Dalton Trans.
PY 2000
IS 22
BP 4078
EP 4088
PG 11
SC Chemistry, Inorganic & Nuclear
GA 374EC
UT ISI:000165330600019
ER

PT J
AU Levin, Y
TI Crystallization of hard spheres under gravity
SO PHYSICA A
LA English
DT Article
ID DENSITY FUNCTIONAL THEORY
AB We present a simple argument to account for crystallization of hard
   spheres under the action of a gravitational field. The paper attempts
   to bridge the gap between two communities of scientists, one working on
   granular materials and the other on inhomogeneous liquid state theory.
   (C) 2000 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
RP Levin, Y, Univ Fed Rio Grande Sul, Inst Fis, Caixa Postal 15051,
   BR-91501970 Porto Alegre, RS, Brazil.
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NR 17
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0378-4371
J9 PHYSICA A
JI Physica A
PD NOV 15
PY 2000
VL 287
IS 1-2
BP 100
EP 104
PG 5
SC Physics, Multidisciplinary
GA 372HE
UT ISI:000165227600007
ER

PT J
AU Dos Santos, HF
   De Oliveira, LFC
   Dantas, SO
   Santos, PS
   De Almeida, WB
TI Quantum mechanical investigation of the tautomerism in the azo dye
   Sudan III
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE tautomerism; Sudan III bis-azo; ab initio (HF and MP2)
ID RAMAN EXCITATION PROFILES; MOLECULAR-ORBITAL METHODS;
   DIFFERENTIAL-OVERLAP TECHNIQUE; GAUSSIAN-TYPE BASIS; TRANS-AZOBENZENE;
   BASIS-SETS; AB-INITIO; CONFORMATIONAL-ANALYSIS; INTERMEDIATE NEGLECT;
   ELECTRON CORRELATION
AB The tautomerism in Sudan ill bis-azo dye has been analyzed using ab
   initio Hartee-Fock [HF] and second-order Moller-Plesset perturbatim
   theory [MP2] and density functional (B3LYP) methods. Gas-phase and
   solution calculations were performed to investigate the solvent effect
   on the azo (OH) --> hydrazone (NH) tautomeric equilibrium. The azo (OH)
   tautomer was found to be preferred in gas phase at the HF level of
   theory. The inclusion of the electronic correlation (MP2) shifted the
   equilibrium toward the hydrazone (NH) form. The NH isomer was also
   found to be more favorable in the gas phase according to the B3LYP
   results. In solution the equilibrium is shifted toward the NH tautomer
   as the dielectric constant of the medium increases. The energy barrier
   for the intramolecular proton transference was calculated and the value
   found suggested a strong hydrogen bond. The B3LYP and MP2 activation
   Gibbs free energies were very close and much lower than the HF value.
   The ultraviolet/visible electronic spectra for the minima and
   transition state (TS) structures were calculated and compared with the
   experimental data. The theoretical band positions obtained considering
   the TS geometry were found to best agree with the experimental data.
   (C) 2000 John Wiley & Sons, Inc.
C1 Univ Fed Juiz de Fora, NEQC, Dept Quim, Inst Ciencias Exatas, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Juiz de Fora, NEEM, Dept Quim, Inst Ciencias Exatas, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Juiz de Fora, Inst Ciencias Exatas, Dept Fis, Juiz De Fora, MG, Brazil.
   Univ Sao Paulo, Inst Quim, Lab Expectroscopia Mol, BR-05508 Sao Paulo, Brazil.
   Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Quim, Belo Horizonte, MG, Brazil.
RP Dos Santos, HF, Univ Fed Juiz de Fora, NEQC, Dept Quim, Inst Ciencias
   Exatas, BR-36036330 Juiz De Fora, MG, Brazil.
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NR 63
TC 7
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD NOV-DEC
PY 2000
VL 80
IS 4-5
BP 1076
EP 1086
PG 11
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 370DP
UT ISI:000165108300056
ER

PT J
AU de Moraes, PRP
   Linnert, HV
   Aschi, M
   Riveros, JM
TI Experimental and theoretical characterization of long-lived triplet
   state CH3CH2S+ cations
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID ION-MOLECULE REACTIONS; POTENTIAL-ENERGY SURFACES; GAS-PHASE REACTIONS;
   G2 AB-INITIO; NEUTRALIZATION-REIONIZATION; METHOXYMETHYL CATION;
   FRAGMENTATION PROCESSES; IONIZATION ENERGIES; UNIMOLECULAR DECAY;
   PROTON AFFINITIES
AB Gas-phase [C2H5S](+) ions obtained by electron impact ionization from
   CH3SC2H5 at 13 eV undergo three distinct low-pressure ion/molecule
   reactions with the parent neutral: proton transfer, charge transfer,
   and hydride abstraction. The kinetics of these reactions studied by
   FT-ICR techniques clearly suggests the [C2H5S](+) species to be a
   mixture of isomeric ions. While proton transfer and hydride abstraction
   are consistent with CH3CHSH+ and CH3SCH2+ reagent ions, the observed
   charge transfer strongly argues for the presence of thioethoxy cation,
   CH3CH2S+, predicted to be stable only in the triplet state. Charge
   transfer reactions only occur with substrates having an IE below 8.8 eV
   and thus yield an upper limit for he recombination energy of the
   CH3CH2S+ ions. Studies using CD3SC2H5 show that charge-transfer
   reactions are promoted by cations originating from a sulfur-methyl
   carbon bond cleavage. Ab initio calculations at several levels of
   theory predict that CH3CH2S+ ions are only stable in the triplet state.
   Calculations along the fragmentation pathway of the molecular ion
   reveal the tendency to generate triplet CH3CH2S+ ions upon cleavage of
   the sulfur-methyl carbon bond. Calculations were also carried out to
   determine the lifetime of triplet CH3CH2S+ using nonadiabatic RRKM
   theory. The exothermic or near thermoneutral spin-forbidden
   unimolecular isomerizations and dissociations were first characterized
   at different levels of theory, and the minimum energy crossing points
   (MECPs) for all the channels were identified at the CCSD(T) level. The
   probability for surface hopping was then estimated from the spin-orbit
   matrix elements. The calculated unimolecular dissociation rate
   constants predict that triplet CH3CH2S+ ions with less than 10 kcal
   mol(-1) of internal energy and at any level of rotational excitation
   should be long-lived, and strongly support the experimental
   observations.
C1 Univ Sao Paulo, Inst Chem, BR-05513970 Sao Paulo, Brazil.
   Univ Rome La Sapienza, Dipartimento Chim, I-00185 Rome, Italy.
RP Riveros, JM, Univ Sao Paulo, Inst Chem, Caisa Postal 26077, BR-05513970
   Sao Paulo, Brazil.
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NR 76
TC 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AM CHEM SOC
JI J. Am. Chem. Soc.
PD OCT 18
PY 2000
VL 122
IS 41
BP 10133
EP 10142
PG 10
SC Chemistry, Multidisciplinary
GA 368FT
UT ISI:000090107600031
ER

PT J
AU De Oliveira, MA
   Duarte, HA
   Pernaut, JM
   De Almeida, WB
TI Energy gaps of alpha,alpha '-substituted oligothiophenes from
   semiempirical, ab initio, and density functional methods
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID MOLECULAR-ORBITAL THEORY; EXTENDED BASIS-SETS; ORGANOMETALLIC
   COMPOUNDS; ELECTRONIC-STRUCTURE; THIOPHENE OLIGOMERS;
   VIBRATIONAL-SPECTRA; BIPOLARONIC DEFECT; TRANSITION-METALS;
   2,2'-BITHIOPHENE; POLYTHIOPHENE
AB Energy gaps have been estimated for -OMe and -NO2
   alpha,alpha'-substituted oligothiophenes up to six monomers using
   semiempirical, Hartree-Fock and density functional methods. Scaled
   values calculated using noncorrelated methods are in good agreement
   with the experimental values, and so were nonscaled estimates predicted
   by density functional methods. Error bars are ca. 0.2 eV for all II
   oligothiophenes studied. The influence of the quality of the basis set
   on the energy estimates is discussed. The discrepancy observed for the
   -OMe- and -NO2-substituted sexithiophene result with respect to the
   experimental value is discussed and has been attributed to a charge
   transfer in the molecule. The Delta SCF approach has been found to be
   an alternative way to estimate energy gaps for molecular systems where
   Koopmans' theorem may not provide good results. Implications for
   predictions of HOMO-LUMO gaps of pi-conjugated systems are discussed
   and analyzed in terms of designing new materials with controlled
   properties.
C1 Univ Fed Minas Gerais, Lab Quim Computac & Modelagem Mol, BR-31270 Belo Horizonte, MG, Brazil.
   Univ Fed Minas Gerais, ICEx, Lab Novos Mat, Dept Quim, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, UFJF, ICE, Dept Quim, Campus Univ, Juiz de Fora, MG,
   Brazil.
CR BECKE AD, 1993, J CHEM PHYS, V98, P1372
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NR 48
TC 26
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD SEP 7
PY 2000
VL 104
IS 35
BP 8256
EP 8262
PG 7
SC Chemistry, Physical
GA 359HC
UT ISI:000089604600013
ER

PT J
AU Tormena, CF
   Rittner, R
   Abraham, RJ
   Basso, EA
   Pontes, RM
TI Conformational analysis. Part 33. An NMR, solvation and theoretical
   investigation of conformational isomerism in
   N,N-dimethylfluoroacetamide and N,N-dimethyl-alpha-fluoropropionamide
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID INTERNAL-ROTATION; VIBRATIONAL ASSIGNMENT; ABINITIO CALCULATIONS;
   BARRIERS; STABILITY; CHLORIDE; FLUOROACETONE; SPECTRA; RAMAN
AB The solvent and temperature dependence of the H-1 and C-13 NMR spectra
   of N,N-dimethylfluoroacetamide (DMFA) and
   N,N-dimethyl-alpha-fluoropropionamide (DMFP) are reported and the
   (5)J(CF), (1)J(CF) and (4)J(CF) couplings analysed by solvation theory.
   Density function theory (DFT) at the B3LYP/6-311+G(d,p) level with ZPE
   (zero point energy) corrections was used to obtain the conformer
   geometries. In DMFA, the DFT method gave only two minima for the cis
   (F-C-C=O, 0 degrees) and gauche (F-C-C=O, 140.6 degrees) rotamers. The
   trans rotamer was not a minimum in the energy surface. Assuming only
   the cis and gauche forms, the observed couplings when analysed by
   solvation theory gave the energy difference (E-cis - E-g) of 2.5 kcal
   mol(-1) in the vapour phase, (cf. the ab initio value of 2.3 kcal
   mol(-1)) decreasing to 0.87 kcal mol(-1) in CCl4 and to -1.29 kcal
   mol(-1) in DMSO. In DMFP the ab initio calculations gave three minima;
   the cis (F-C-C=O, 30.4 degrees), gauche-1 (F-C-C=O, 144.7 degrees) and
   gauche-2 (F-C-C=O, -124.1 degrees) rotamers with (E-cis - E-g2) equal
   to 2.5 kcal mol(-1) and (E-g1 - E-g2) equal to 0.3 kcal mol(-1). The
   observed couplings were analysed by solvation theory assuming one
   "average" gauche conformer to give (E-cis - E-g(AV)) equal to 2.1 kcal
   mol(-1) in the vapour phase, decreasing to 0.83 kcal mol(-1) in CCl4
   and to -1.11 kcal mol(-1) in DMSO.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
   Univ Estadual Maringa, Dept Quim, BR-87020900 Maringa, Parana, Brazil.
RP Rittner, R, Univ Estadual Campinas, Inst Quim, Caixa Postal 6154,
   BR-13083970 Campinas, SP, Brazil.
CR ABRAHAM RJ, 1974, INTERNAL ROTATION MO, CH13
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NR 25
TC 18
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1470-1820
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2000
IS 10
BP 2054
EP 2059
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA 358HU
UT ISI:000089553200009
ER

PT J
AU Cuccovia, IM
   da Silva, MA
   Ferraz, HMC
   Pliego, JR
   Riveros, JM
   Chaimovich, H
TI Revisiting the reactions of nucleophiles with arenediazonium ions:
   dediazoniation of arenediazonium salts in aqueous and micellar
   solutions containing alkyl sulfates and alkanesulfonates and an ab
   initio analysis of the reaction pathway
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID COUNTERION SELECTIVITY; ARYL CATIONS; TETRAFLUOROBORATE;
   2-METHYLBENZENEDIAZONIUM; 3-METHYLBENZENEDIAZONIUM; DECOMPOSITION;
   MECHANISM; RATES; WATER; MODEL
AB Dediazoniation of 2,4,6-trimethylbenzenediazonium tetrafluoroborate,
   1-ArN2BF4 (for the z-Ar compounds described in this paper, z refers to
   the length of the carbon chain of the substituent at C4 of the benzene
   ring), in aqueous solutions containing sodium methyl sulfate, NaMeSO4,
   or sodium methanesulfonate, NaMeSO3, yields 2,4,6-trimethylphenol,
   1-ArOH, 2,4,6-trimethylphenyl methyl sulfate, 1-ArOSO3Me and
   2,4,6-trimethylphenyl methanesulfonate, 1-ArO3SMe, respectively. The
   relative yields of 1-ArO3SMe or 1-ArOSO3Me and 1-ArOH depend on the
   NaMeSO4 or NaMeSO3 concentrations.
   4-n-Hexadecyl-2,6-dimethylbenzenediazonium tetrafluoroborate,
   16-ArN2BF4, was used to determine the local head group concentration in
   sodium dodecyl sulfate and sodium dodecanesulfonate micelles by
   chemical trapping comparing the relative product yields with those
   obtained in water using the short chain analogs.
   Ab initio calculations of the spontaneous dediazoniation of
   phenyldiazonium ion in the gas phase, as well as in aqueous solution
   with, or without, added MeSO3-, yield potential energy surfaces for the
   reaction. For this model the calculated and experimental values of the
   spontaneous dediazoniation rate constants in aqueous solution, as well
   as the product composition, were similar to those obtained with
   1-ArN2+. These results suggest that in aqueous solution nucleophiles
   can only compete with water if a diazonium ion . nucleophile complex is
   formed prior to N-2 loss. Calculations show that the addition of
   nucleophiles to the arenediazonium ion occurs without a saddle point in
   the potential energy surface, suggesting that the free phenyl cation is
   not an obligatory intermediate in aqueous solutions.
C1 Univ Sao Paulo, Inst Quim, Dept Bioquim, BR-05508900 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Quim, Dept Quim Fundamental, BR-05508900 Sao Paulo, Brazil.
RP Cuccovia, IM, Univ Sao Paulo, Inst Quim, Dept Bioquim, Av Prof Lineu
   Prestes 748, BR-05508900 Sao Paulo, Brazil.
CR AMBROZ HB, 1979, CHEM SOC REV, V8, P353
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NR 40
TC 13
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1470-1820
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2000
IS 9
BP 1896
EP 1907
PG 12
SC Chemistry, Organic; Chemistry, Physical
GA 356CM
UT ISI:000089426800021
ER

PT J
AU Martins, JBL
   Taft, CA
   Lie, SK
   Longo, E
TI Lateral interaction of CO and H-2 molecules on ZnO surfaces: an AM1
   study
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE ZnO surface; (ZnO)(60) clusters; CO and H-2 adsorption; AM1
   semi-empirical model
ID LARGE CLUSTER-MODELS; ROOM-TEMPERATURE; ZINC-OXIDE; AB-INITIO;
   POTENTIAL DEPENDENCE; METHANOL SYNTHESIS; BASIS-SET; ADSORPTION;
   HYDROGEN; PHOTOELECTRON
AB We have studied the effects of lateral interactions for CO and H-2
   adsorbed on large (ZnO)(60) cluster models. The calculations were
   performed with the AM1 semi-empirical method. The geometric parameters
   of the adsorbed molecules were fully optimized. CO interacts with the
   zinc cation located at the site having the lowest coordination at the
   edge sites between the (0001) and (10 (1) over bar 0) surfaces, The
   binding energy is increased as we increase the number of adsorbed CO
   molecules on the ZnO surface. For H-2 molecular interaction, the
   calculated energy gaps and ionization potentials are modified relative
   to the bare cluster. We have analyzed the optimized geometric
   parameters, charge transfer as well as the density of states and
   compared our results with available experimental data such as density
   of states, vibrational frequencies, adsorption energies and surface
   charge. (C) 2000 Elsevier Science B.V. All rights reserved.
C1 Univ Brasilia, Inst Quim, BR-70919970 Brasilia, DF, Brazil.
   Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estatist, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Inst Fis, BR-24020 Niteroi, RJ, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13560905 Sao Carlos, SP, Brazil.
RP Martins, JBL, Univ Brasilia, Inst Quim, Caixa Postal 04478, BR-70919970
   Brasilia, DF, Brazil.
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NR 42
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD AUG 25
PY 2000
VL 528
BP 161
EP 170
PG 10
SC Chemistry, Physical
GA 355DN
UT ISI:000089370600017
ER

PT J
AU de Almeida, NG
   Napolitano, R
   Moussa, MHY
TI Phenomenological-operator approach to dissipation in cavity quantum
   electrodynamics
SO PHYSICAL REVIEW A
LA English
DT Article
ID PODOLSKY-ROSEN CHANNELS; EXPERIMENTAL REALIZATION; TELEPORTATION;
   STATE; DECOHERENCE; METER
AB We present a phenomenological-operator approach to describe energy
   dissipation in cavity QED phenomena. This approach, developed for an
   absolute-zero and a thermal environment, considerably simplifies the
   introduction of the inevitable errors due to the environmental degrees
   of freedom when describing processes involving dispersive atom-field
   interactions. The main result in the present work consists in
   furnishing a straightforward technique to estimate the fidelity
   resulting from dispersive atom-field interactions, precluding the
   necessity of performing the usually extensive ab initio calculations.
   Furthermore, we expect that the present work can help us account for
   dissipation in resonant atom-field interactions and even help us
   achieve a general phenomenological approach to estimate the effects of
   dissipation in whichever system. To illustrate the universal
   applicability of the present technique, we calculate the fidelity of a
   mesoscopic quantum superposition state engineered in a lossy cavity,
   considering also the excited-state spontaneous decay of the required
   atom. For the case of a stable atomic excited state, the fidelity
   computed here is in agreement with a recently announced exact
   calculation.
C1 Univ Fed Sao Carlos, Dept Fis, BR-13565905 Sao Paulo, Brazil.
   Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560970 Sao Paulo, Brazil.
RP de Almeida, NG, Univ Fed Sao Carlos, Dept Fis, Via Washington Luis,Km
   235, BR-13565905 Sao Paulo, Brazil.
CR ALMEIDA NG, UNPUB
   BENNETT CH, 1993, PHYS REV LETT, V70, P1895
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   BRIEGEL HJ, QUANTPH9712027
   BRIEGEL HJ, 1998, PHYS REV LETT, V81, P5932
   BRUNE M, 1992, PHYS REV A, V45, P5193
   BRUNE M, 1996, PHYS REV LETT, V76, P1800
   BRUNE M, 1996, PHYS REV LETT, V77, P4887
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   CALDEIRA AO, 1983, PHYSICA A, V121, P587
   CHUANG IL, 1998, NATURE, V393, P143
   CIRAC JI, 1997, PHYS REV LETT, V78, P3221
   DEALMEIDA NG, IN PRESS PHYS REV A
   DEOLIBEIRA MC, IN PRESS PHYS REV A
   FURUSAWA A, 1998, SCIENCE, V282, P706
   HOLLAND MJ, 1991, PHYS REV LETT, V67, P1716
   MAITRE X, 1997, PHYS REV LETT, V79, P769
   MOLLOW BR, 1967, PHYS REV, V160, P1076
   MOLLOW BR, 1967, PHYS REV, V160, P1097
   MOUSSA MHY, 1996, PHYS REV A, V54, P4661
   MOUSSA MHY, 1997, PHYS REV A, V55, P3287
   PELLIZZARI T, 1997, PHYS REV LETT, V79, P5242
   SCULLY MO, 1997, QUANTUM OPTICS
   SHOR PW, 1994, P 35 ANN S FDN COMP, P124
   VANENK SJ, 1997, PHYS REV LETT, V79, P5178
   VITALI D, 1997, PHYS REV LETT, V79, P2442
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   VONNEUMANN J, 1995, MATH FDN QUANTUM MEC
NR 29
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD SEP
PY 2000
VL 62
IS 3
AR 033815
DI ARTN 033815
PG 9
SC Physics, Atomic, Molecular & Chemical; Optics
GA 353CD
UT ISI:000089255400094
ER

PT J
AU Miotto, R
   Srivastava, GP
   Ferraz, AC
TI Effects of gradient and non-linear core corrections on structural and
   electronic properties of GaN bulk and (001) surfaces
SO PHYSICA B-CONDENSED MATTER
LA English
DT Article
DE density functional calculations; pseudopotential; surface relaxation;
   surface states
ID MOLECULAR-BEAM EPITAXY; DENSITY-FUNCTIONAL CALCULATIONS; GROUP-III
   NITRIDES; GALLIUM NITRIDE; VALENCE-BAND; 3D STATES; AB-INITIO;
   BETA-GAN; GAAS; SEMICONDUCTORS
AB We have investigated the effects of density gradient and non-linear
   core corrections, within the first-principles pseudopotential method,
   on structural and electronic properties of GaN bulk and (0 0 1)
   surfaces. We find that the combined use of the generalized gradient
   approximation and non-linear core correction for exchange and
   correlation (NGGA) produces important changes in structural properties.
   The calculated bulk valence band electronic structure shows much better
   agreement with experiment when the NGGA scheme is used than when the Ga
   3d electrons are considered explicitly as a part of the valence shell.
   We have discussed the atomic structure and chemical bonding on the
   gallium terminated (1 x 1), (2 x 2), c(2 x 2) and (1 x 4) cubic-GaN(0 0
   1) surface reconstructions, and find that the most stable of these,
   viz. the (1 x 4) structure, is characterised by a linear Ga tetramer
   with an energy gain of 0.29 eV per (1 x 1) cell over the
   unreconstructed (1 x 1) structure in agreement with previous results by
   Neugebauer and coworkers. (C) 2000 Elsevier Science B.V. All rights
   reserved.
C1 Univ Exeter, Sch Phys, Exeter EX4 4QL, Devon, England.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Miotto, R, Univ Exeter, Sch Phys, Stocker Rd, Exeter EX4 4QL, Devon,
   England.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
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   EDGAR JH, 1994, EMIS DATAREVIEW SERI
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NR 44
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0921-4526
J9 PHYSICA B
JI Physica B
PD OCT
PY 2000
VL 292
IS 1-2
BP 97
EP 108
PG 12
SC Physics, Condensed Matter
GA 353YX
UT ISI:000089304000012
ER

PT J
AU Esteves, PM
   Ramirez-Solis, A
   Mota, CJA
TI A theoretical study of alkane protonation in HF/SbF5 superacid system
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE superacid; carbonium ions; alkane; DFT
ID AB-INITIO; ELECTROSTATIC POTENTIALS; ELECTROPHILIC REACTIONS; DEUTERIUM
   EXCHANGE; CARBONIUM-IONS; CH5+; CARBOCATIONS; CHEMISTRY; DENSITY; ENERGY
AB Ab initio calculations for the protonation of the C-H and C-C bonds of
   methane, ethane, propane and isobutane by a superacid moiety was
   carried out. For the C-H protonation (H/H exchange) the transition
   state resembles an H-carbonium ion coordinated with the superacid. The
   activation energy for the H/H exchange was about 16 kcal.mol(-1), at
   B3LYP/6-31++G"* + RECP (Sb) level, regardless the type of C-H bond
   being protonated. For the C-C protonation the activation energy depends
   on the structure of the hydrocarbon and was always higher than the
   activation energy for C-H protonation, indicating a higher steric
   demand.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Esteves, PM, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim,
   Cidade Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
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   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
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   KIM SJ, 1993, J PHYS CHEM-US, V97, P12232
   KOHLER HJ, 1978, CHEM PHYS LETT, V58, P175
   KOLBUSZEWSKI M, 1996, J CHEM PHYS, V105, P3649
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   MOTA CJA, 1992, J AM CHEM SOC, V114, P1121
   MOTA CJA, 1997, J AM CHEM SOC, V119, P5193
   MULLER H, 1997, J CHEM PHYS, V106, P1863
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NR 37
TC 8
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PD JUL-AUG
PY 2000
VL 11
IS 4
BP 345
EP 348
PG 4
SC Chemistry, Multidisciplinary
GA 354NY
UT ISI:000089337600003
ER

PT J
AU Duarte, HA
   Dos Santos, HF
   Rocha, WR
   De Almeida, WB
TI Improved quantum mechanical study of the potential energy surface for
   the bithiophene molecule
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID GAUSSIAN-BASIS SETS; AB-INITIO; ORBITAL METHODS; CONDUCTING POLYMERS;
   ORGANIC-MOLECULES; EXCHANGE-ENERGY; POLYTHIOPHENE; ATOMS;
   2,2'-BITHIOPHENE; APPROXIMATION
AB The potential energy surface (PES) for the 2,2'-bithiophene molecule
   was investigated using Hartree-Fock, correlated MP2, MP4(SDQ), CCSD,
   and density functional theory levels. Distinct basis sets ranging from
   double-zeta to triple-zeta quality, with polarization functions added
   on all atoms, were employed as well as the Dunning correlated
   consistent polarized valence double-zeta (cc-pVDZ) basis set. Single
   point configuration interaction CISD calculations were also performed
   using the cc-pVDZ basis set. Harmonic frequency calculations were
   performed for the unambiguous characterization of the stationary points
   located on the PES and also to calculate thermal Gibbs free energy
   corrections. Regarding the structural predictions we found that the
   B3LYP/6-311G** and MP2/cc-pVDZ fully optimized geometries exhibit the
   best agreement with the gas phase electron diffraction data. The
   calculated B3LYP/6-311G**, MP2/cc-pVDZ and experimental torsional angle
   for the syn-gauche structure are, respectively, 37.4 degrees (B3LYP),
   39.9 degrees (MP2), and 36 degrees +/- 5 degrees (expt.) with the
   corresponding values for the anti-gauche form being, respectively,
   150.3 degrees (B3LYP), 146.0 degrees (MP2), and 148 degrees +/- 3
   degrees (expt.). The relative energy between the two minima and
   torsional barriers are sensitive both to the size of the basis set and
   the level of the quantum mechanical method used. Therefore, larger
   basis sets are needed to assess the ability of the DFT approach for
   describing torsional barriers. The MP4(SDQ) and CCSD relative energy
   results, reported in this work, can be considered as the most reliable
   torsional potential data available for the 2,2'-bithiophene molecule.
   Our results indicate that the experimentally estimated relative energy
   value for the two equilibrium structures present on the PES for the
   bithiophene molecule, and consequently the relative abundance of the
   anti-gauche species, is somewhat underestimated. By comparison with
   MP4(SDQ) and CCSD results we have shown that single point DFT/6-311G**
   calculations using HF/6-31G* geometries is the most computationally
   efficient procedure to study bithiophene like systems, with energy
   barriers agreeing within 2 kJ/mol. (C) 2000 American Institute of
   Physics. [S0021-9606(00)31634-8].
C1 Univ Fed Minas Gerais, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Minas Gerais, Dept Quim, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Juiz de Fora, Lab Quim Coumputac & Modelagem Mol, BR-36036330 Juiz De Fora, MG, Brazil.
   Univ Fed Juiz de Fora, Dept Quim, ICE, BR-36036330 Juiz De Fora, MG, Brazil.
RP Duarte, HA, Univ Fed Minas Gerais, Lab Quim Computac & Modelagem Mol,
   BR-31270901 Belo Horizonte, MG, Brazil.
CR ALMLOF J, 1987, J CHEM PHYS, V86, P4070
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NR 47
TC 23
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD SEP 8
PY 2000
VL 113
IS 10
BP 4206
EP 4215
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 349GC
UT ISI:000089034900034
ER

PT J
AU Barbatti, M
   Jalbert, G
   Nascimento, MAC
TI Isomeric structures and energies of H-n(+) clusters (n=13, 15, and 17)
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID HYDROGEN CLUSTERS; VIBRATIONAL FREQUENCIES; ENERGETICS; ABINITIO; IONS;
   STABILITIES
AB Ab initio calculations have been performed for the H-n(+) clusters
   (n=3-17; odd) at Moller-Plesset second order (MP2)/6-311G(mp),
   Moller-Plesset complete fourth order (MP4)/6-311G(mp), and
   coupled-cluster single-double-triple [CCSD(T)/6-311G(1p)] levels of
   calculations. Such hydrogen clusters are constituted by an H-3(+) core
   in which H-2 units are bound. In order to understand the features of
   these bindings, enthalpy and entropy variations upon cluster formation,
   binding energies, and charge distributions have been computed, and a
   molecular orbital analysis, based on localized orbital, was performed.
   Our results show that the way the first three H-2 units bind to the
   H-3(+) core is fundamentally different from the others, providing an
   explanation for the binding energies observed for these molecules. For
   the H-13(+), H-15(+), and H-17(+) clusters, the way in which the
   external H-2 units are distributed around the H-3(+) plane leads to the
   formation of different isomers with very close energies, but with a
   rotational barrier large enough to inhibit the interconversions. (C)
   2000 American Institute of Physics. [S0021-9606(00)31434-9].
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21945970 Rio De Janeiro, Brazil.
RP Barbatti, M, Univ Fed Rio de Janeiro, Inst Fis, CP 68528, BR-21945970
   Rio De Janeiro, Brazil.
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NR 23
TC 21
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD SEP 8
PY 2000
VL 113
IS 10
BP 4230
EP 4237
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 349GC
UT ISI:000089034900036
ER

PT J
AU Ribeiro, MCC
   Almeida, LCJ
TI Validating a polarizable model for the glass-forming liquid
   Ca0.4K0.6(NO3)(1.4) by ab initio calculations
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID ORBITAL ELECTRONEGATIVITY METHOD; MOLECULAR-DYNAMICS SIMULATIONS;
   MODIFIED PARTIAL EQUALIZATION; DENSITY-FUNCTIONAL THEORY; IONIC
   SYSTEMS; FLUCTUATING CHARGE; ATOMIC CHARGES; NEUTRON-DIFFRACTION;
   QUANTUM-CHEMISTRY; FORCE-FIELDS
AB Ab initio calculations have been performed in order to investigate a
   recently proposed polarizable model [M. C. C. Ribeiro, Phys. Rev. B 61,
   3297 (2000)] for molecular dynamics (MD) simulation of the molten salt
   Ca0.4K0.6(NO3)(1.4). On the basis of the electronegativity equalization
   method, polarization effects in the MD simulations have been introduced
   by a fluctuating charge (FC) model for the nitrate ion. Partial charges
   in the nitrate ion are obtained by ab initio calculations at several
   levels of theory, and compared with previously proposed models for MD
   simulations of nitrate melts. Charge fluctuation is achieved in the ab
   initio calculations by using positive probe charges placed around a
   nitrate ion. The parameters of the FC model are corroborated by
   comparison of the ab initio partial charges with the ones obtained
   directly by the electronegativity equalization method. Simulated
   annealing of a cluster including two double-charged cations and two
   nitrate ions shows that very different structures are obtained
   depending on whether the FC model or its nonpolarizable counterpart is
   considered. Ab initio calculations show that the structure of this
   cluster is strongly dependent on polarization effects in the nitrate
   ions. (C) 2000 American Institute of Physics. [S0021- 9606(00)52235-1].
C1 Univ Sao Paulo, Inst Quim, Lab Espectroscopia Mol, BR-05513970 Sao Paulo, Brazil.
RP Ribeiro, MCC, Univ Sao Paulo, Inst Quim, Lab Espectroscopia Mol, CP
   26077, BR-05513970 Sao Paulo, Brazil.
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NR 67
TC 11
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD SEP 15
PY 2000
VL 113
IS 11
BP 4722
EP 4731
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 351DC
UT ISI:000089139900028
ER

PT J
AU Batista, H
   Carpenter, GB
   Srivastava, RM
TI Synthesis and molecular structure of
   N-[3-(p-bromophenyl)-1,2,4-oxadiazol-5-yl]methylphthalimide. III.
SO JOURNAL OF CHEMICAL CRYSTALLOGRAPHY
LA English
DT Article
DE 1,2,4-oxadiazole; crystal structure; phthalimide derivative; AM1
   method; STO-3G basis set
AB The synthesis, spectroscopic studies and crystal structure of the title
   compound is described. The crystallographic studies showed that the
   p-bromophenyl group is very nearly coplanar with the 1,2,4-oxadiazole
   ring. The nearly planar phthalimide group makes an angle of about 98
   degrees with the bromophenyloxadiazole plane. Semi-empirical (AM1) and
   ab initio (STO-3G, 6-31G) molecular orbital calculations have been
   carried out for this compound and a comparison of bond angles, bond
   lengths and torsion angles has been made with the experimental values,
   which are remarkably close to each other. This compound crystallizes in
   the monoclinic space group P2(1)/c with a = 13.6299(2), b = 13.9836(2),
   c = 8.4817(2) Angstrom, beta = 101.9070(10)degrees, V = 1581.79(5)
   Angstrom(3), and Z = 4.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540 Recife, PE, Brazil.
   Brown Univ, Dept Chem, Providence, RI 02912 USA.
RP Srivastava, RM, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540
   Recife, PE, Brazil.
CR ANTUNES R, 1996, HETEROCYCL COMMUN, V2, P247
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   MORI K, 1994, ACTA CRYSTALLOGR C, V50, P807
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   STEWART JJP, 1990, MOPAC MANUAL
NR 6
TC 5
PU KLUWER ACADEMIC/PLENUM PUBL
PI NEW YORK
PA 233 SPRING ST, NEW YORK, NY 10013 USA
SN 1074-1542
J9 J CHEM CRYSTALLOGRAPHY
JI J. Chem. Crystallogr.
PD FEB
PY 2000
VL 30
IS 2
BP 131
EP 134
PG 4
SC Crystallography; Spectroscopy
GA 351PW
UT ISI:000089168200010
ER

PT J
AU Iglesias, RS
   Goncalves, PFB
   Livotto, PR
TI Semi-empirical study of a set of 2-(2 '-hydroxyphenyl)benzazoles using
   the polarizable continuum model
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID INTRAMOLECULAR PROTON-TRANSFER; EXCITED-STATE PROTON; TRIPLET-STATES;
   AB-INITIO; 2-(2-HYDROXYPHENYL)BENZOTHIAZOLE; BENZOTHIAZOLE;
   SPECTROSCOPY; FEMTOSECOND; ROTAMERISM; SOLVENT
AB A set of molecules (2-(2'-hydroxyphenyl)benzoxazol (HBO),
   2-(2'-hydroxyphenyl benzothiazole (HBT) and
   2-(2'-hydroxyphenyl)benzimidazole (HBI)) exhibiting excited-state
   intramolecular proton transfer was studied using the polarizable
   continuum model in low-polar, non-protic solvents (chloroform and
   carbon tetrachloride), combined with the AM1 semi-empirical molecular
   orbital method in both gaseous and condensed phase. The heats of
   formations (Delta H-f) are lowered by the solvent effect, especially in
   chloroform. The increase in the solvent polarity causes an enlargement
   of the Stokes shift between absorption and emission. (C) 2000 Published
   by Elsevier Science B.V.
C1 Univ Fed Rio Grande Sul, Inst Quim, Grp Quim, BR-91509900 Porto Alegre, RS, Brazil.
RP Livotto, PR, Univ Fed Rio Grande Sul, Inst Quim, Grp Quim, Av Bento
   Goncalves 9500, BR-91509900 Porto Alegre, RS, Brazil.
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NR 30
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD SEP 1
PY 2000
VL 327
IS 1-2
BP 23
EP 28
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 349QC
UT ISI:000089056300005
ER

PT J
AU Olivato, PR
   Guerrero, SA
   Rittner, R
TI Conformational and electronic interaction studies of alpha-substituted
   carbonyl compounds. XV. alpha-(arylsulfinyl)-p-substituted acetophenones
SO PHOSPHORUS SULFUR AND SILICON AND THE RELATED ELEMENTS
LA English
DT Article
DE conformational studies; electronic interactions; IR and C-13 NMR
   spectroscopies; alpha-(p-phenylsulfinyl)-p-substituted acetophenones
ID ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY; KETONES
AB The V-CO IR analysis of alpha-(p-phenylsulfinyl)-p-substituted
   acetophenones X-phi C(O)CH2S(O) phi-Y 1-8, being X and Y = NO2, H and
   OMe substituents, supported by ab initio calculations of the
   alpha-methylsulfinyl/acetophenone (model compound) along with the X-ray
   geometrical data for 1, 7 and 8, indicates the existence of the cis(2)
   and gauche rotamers for compounds 1-4 and 6. Compounds 5, 7 and 8
   present another less stable and more polar cis(1) rotamer. The cis(2)
   rotamer concentration for 4 (ca. 97% in CCl4) is reduced to ca. 50% for
   2, 3, 5-7 and to ca. 20% for 1 and 8. This behavior is discussed in
   terms of O-(CO)(delta-)-S-(SO)(delta+) charge transfer and Coulombic
   interactions, which stabilize the cis(1) rotamer, and the
   pi(CO)/sigma*(C-S), pi*(CO)/n(s) and pi*(CO)/sigma(C-S) orbital
   interactions, which stabilize the gauche rotamers. The progressive more
   negative carbonyl cis(2) shifts (Delta v(c)), when X varies from NO2 to
   H and to OMe for the same Y, along with the unexpected NAE values of
   the alpha-methylene carbon chemical shifts for compounds 1-8 give
   further support for the existence of a strong intramolecular complex
   between C=O and S=O dipoles which stabilizes the cis(2) rotamer. The
   progressive more negative carbonyl gauche shifts (Delta v(g)), when X
   varies from NO2 to H and to OMe for the same Y, is in line with the
   higher contribution of the interaction pi(CO)/sigma*(C-S), which
   stabilizes the gauche rotamer of the title compounds.
C1 Univ Sao Paulo, Inst Quim, BR-05599970 Sao Paulo, Brazil.
   Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP Olivato, PR, Univ Sao Paulo, Inst Quim, Caixa Postal 26-077,
   BR-05599970 Sao Paulo, Brazil.
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   1996, 17 INT S ORG CHEM SU
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NR 30
TC 4
PU GORDON BREACH SCI PUBL LTD
PI READING
PA C/O STBS LTD, PO BOX 90, READING RG1 8JL, BERKS, ENGLAND
SN 1042-6507
J9 PHOSPHOR SULFUR SILICON
JI Phosphorus Sulfur Silicon Relat. Elem.
PY 2000
VL 156
BP 255
EP 277
PG 23
SC Chemistry, Inorganic & Nuclear
GA 344YL
UT ISI:000088788600020
ER

PT J
AU Okulik, N
   Peruchena, N
   Esteves, PM
   Mota, C
   Jubert, AH
TI Ab initio topological analysis of the electronic density in proponium
   cations
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID MOLECULAR CHARGE-DISTRIBUTIONS; QUANTUM TOPOLOGY; CARBONIUM-IONS; CH5+;
   CARBOCATIONS; CHEMISTRY; ENERGIES; TERMS
AB Studies performed on proponium cations at the ab initio level show that
   six different stable structures can be characterized: four proponium
   cations and two van der Waals complexes. Among the proponium cations,
   the most stable structure corresponds to the C-proponium ion. Between
   the van der Waals complexes, the most stable one corresponds to the
   structure that results from the interaction between the isopropyl ion
   and the hydrogen molecule. The topology of the electronic density
   charge of the different structures is studied, at ab initio level,
   using the theory of atoms in molecules (AIM) developed by Bader.
C1 UNNE, Fac Agroind, RA-3700 Pcia R Saenz Pena, Chaco, Argentina.
   UNNE, Fac Ciencias Exactas & Nat & Agrimensura, Dept Quim, RA-3400 Corrientes, Argentina.
   Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Natl Univ La Plata, Fac Ciencias Exactas, Dept Quim, RA-1900 La Plata, Argentina.
RP Jubert, AH, UNNE, Fac Agroind, Cte Fernandez 755, RA-3700 Pcia R Saenz
   Pena, Chaco, Argentina.
CR BADER RFW, 1979, J AM CHEM SOC, V101, P1389
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   BADER RFW, 1990, ATOMS MOL
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   GILLESPIE RJ, 1972, MOL GEOMETRY
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   OLAH GA, 1973, CARBOCATIONS ELECTRO
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NR 33
TC 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 17
PY 2000
VL 104
IS 32
BP 7586
EP 7592
PG 7
SC Chemistry, Physical
GA 345RK
UT ISI:000088828800022
ER

PT J
AU Bettega, MHF
TI Low-energy electron scattering by boron trihalides
SO PHYSICAL REVIEW A
LA English
DT Article
ID SCHWINGER MULTICHANNEL; PLASMA CHEMISTRIES; CROSS-SECTIONS; AB-INITIO;
   BCL3; COLLISIONS; PSEUDOPOTENTIALS; SPECTROSCOPY; EXCITATION; SPECTRA
AB We report the integral elastic cross section for low-energy electron
   scattering by the boron trihalides BCl3, BBr3, and BI3. To perform our
   calculations, we employed the Schwinger multichannel method with
   pseudopotentials. We have focused our attention only in the B-2
   irreducible representation, where we found shape resonances for the
   three molecules in a previous static-exchange calculation, at energies
   below 5 eV. We included polarization effects to improve the description
   of the resonances and found that only the resonance for BCl3 remains.
   For BBr3 and BI3, the resonances become bound states.
C1 Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil.
RP Bettega, MHF, Univ Fed Parana, Dept Fis, Caixa Postal 19081,
   BR-81531990 Curitiba, Parana, Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BAECK KK, 1997, J CHEM PHYS, V106, P4604
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   BETTEGA MHF, 2000, J CHEM PHYS, V112, P8806
   BETTEGA MHF, 2000, PHYS REV A, V61
   BIEHL H, 1996, MOL PHYS, V87, P1199
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NR 38
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD AUG
PY 2000
VL 6202
IS 2
AR 024701
DI ARTN 024701
PG 3
SC Physics, Atomic, Molecular & Chemical; Optics
GA 343CD
UT ISI:000088683400118
ER

PT J
AU De Oliveira, MA
   Dos Santos, HF
   De Almeida, WB
TI Structure and torsional potential of p-phenylthiophene: a theoretical
   comparative study
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; VALENCE BASIS-SETS; GAUSSIAN-TYPE BASIS;
   AB-INITIO; ELECTRONIC-PROPERTIES; CONJUGATED SYSTEMS;
   ORGANIC-MOLECULES; 2ND-ROW ELEMENTS; 2,2'-BITHIOPHENE; POLYTHIOPHENE
AB Quantum chemical calculations employing Hartree-Fock, MP2 and density
   functional (using distinct functionals) approaches were carried out for
   the p-phenylthiophene dimer. The fully optimized stationary points
   located on the potential energy surface were characterized as minima or
   transition state (TS) structures according to harmonic frequency
   analysis. A mixture of syn-gauche and anti-gauche conformers was
   predicted with a relative percentage of ca. 60% and 40%, respectively.
   A TS structure connecting the syn-gauche and anti-gauche minima was
   also determined, with the MP2 energy barrier being ca. 10 kJ mol(-1). A
   six-term truncated Fourier series representation of the potential
   energy for internal rotation was obtained using a fitting procedure to
   the calculated HF/6-31G* and B3LYP/6-31G* partially optimized points.
   Additional fittings were performed with the MP2/6-31G*//HF/6-31G*,
   MP2/6-31G*//B3LYP/6-31G*, B3LYP/6-31G*//HF/6-31G*,
   BLYP/6-31G*//HF/6-31G*, B3P86/6-31G*//HF/6-31G* and
   SVWN/6-31G*//HF/6-31G* single energy points. The energy barriers
   obtained from the fitted curve were compared to the ones calculated
   from the energy differences between fully optimized minima and TS
   structures. The fitted Fourier potential is found to be adequate for
   the description of the internal rotation in the p-phenylthiophene
   dimer. The B3LYP/6-31G*//HF/6-31G* level of calculation seems
   sufficient for studying this class of compounds. The inclusion of the
   phenyl substituent group in the bithiophene, which makes it more easily
   processable, does not alter significantly the energy gap. Therefore,
   the p-phenylthiophene would be expected to exhibit similar conductivity
   to the parent non-substituted bithiophene compound.
C1 Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Juiz de Fora, ICE, Dept Quim, BR-36036330 Juiz De Fora, MG, Brazil.
RP De Oliveira, MA, Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim
   Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR 1998, GAUSSIAN DFT SUPPLEM
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NR 52
TC 5
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI PCCP Phys. Chem. Chem. Phys.
PY 2000
VL 2
IS 15
BP 3373
EP 3380
PG 8
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 338FP
UT ISI:000088407700003
ER

PT J
AU Esteves, PM
   Alberto, GGP
   Ramirez-Solis, A
   Mota, CJA
TI The n-butonium cation (n-C4H11+): The potential energy surface of
   protonated n-butane
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID THEORETICAL AB-INITIO; CARBONIUM-IONS; ELECTRONIC-STRUCTURE;
   ELECTROPHILIC REACTIONS; INFRARED-SPECTROSCOPY; MOLECULAR-HYDROGEN;
   SINGLE BONDS; CH5+; C2H7+; REARRANGEMENT
AB The structure and energetics of the n-butonium ion, the protonated form
   of n-butane, were computed at the
   MP4SDTQ(fc)/6-311++G**//MP2(full)/6-31G** level. Eleven stable
   structures were found for the n-butonium ion, following the stability
   order 2-C-n-butonium > 1-C-n-butonium > 2-H-n-butonium >
   1-H-n-butonium. The transition states for intramolecular bond-to-bond
   rearrangement and for decomposition of the carbonium ions into the van
   der Waals complexes were also calculated. The H-n-butonium and the
   1-C-n-butonium ions are higher in energy than the van der Waals
   complexes 13, 14, and 15. The van der Waals complexes between the
   isopropyl cation plus CH4 and the tert-butyl cation plus H-2 are the
   most stable C4H11+ species. It was concluded that the 1-H-n-butonium
   ion prefers to undergo intramolecular rearrangement to the
   1-C-n-butonium ion, whereas the 2-H-n-butonium ion prefers to decompose
   into the van der Waals complex of the sec-butyl cation plus H-2. The
   calculated proton affinity of n-butane (156.7 kcal/mol) agrees well
   with the experimental value of 153.7 kcal/mol. The C4H11+ (b) species,
   formed upon the gas-phase reaction between C2H5+ and ethane, was
   confirmed to be the 2-C-n-butonium cation, and the C4H11+ (a) species
   was confirmed to be the 2-H-n-butonium cation, as proposed by Hiraoka
   and Kebarle (Can. J. Chem. 1980, 58, 2262-2270). The experimental
   activation energy of 9.6 kcal/mol was compared with the value of 12.8
   kcal/mol, computed for the reaction 11 --> 5 through the transition
   state 21.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, Cidade
   Univ CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
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NR 39
TC 12
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JUL 6
PY 2000
VL 104
IS 26
BP 6233
EP 6240
PG 8
SC Chemistry, Physical
GA 332CY
UT ISI:000088057000016
ER

PT J
AU Capelle, K
   Oliveira, LN
TI Density-functional theory for spin-density waves and antiferromagnetic
   systems
SO PHYSICAL REVIEW B
LA English
DT Article
ID GENERALIZED-GRADIENT-APPROXIMATION; HIGH-TEMPERATURE SUPERCONDUCTORS;
   BAND-STRUCTURE CALCULATIONS; STRONG MAGNETIC-FIELDS;
   ELECTRONIC-STRUCTURE; GROUND-STATE; GAMMA-FE; EXCHANGE; MOLECULES;
   CHROMIUM
AB An extension of density-functional theory, designed to treat
   spin-density waves and antiferromagnetic systems, is presented. The
   nonlocal nature of the antiferromagnetic correlations and possible
   noncollinearity in spin space are incorporated via an additional
   fundamental variable, the staggered density, which supplements the spin
   densities of conventional density-functional theory. Inclusion of this
   variable is justified by both physical and methodological
   considerations. We prove the corresponding Hohenberg-Kohn theorem,
   derive the pertinent Kohn-Sham equations, and present several
   approximate functionals depending explicitly on the staggered density.
   As a first test the formalism is applied to two simple model systems, a
   one-dimensional electron gas with a short-range interaction, and the
   three-dimensional electron gas with Coulomb interactions. These
   calculations serve to test the developed formalism, bur also already
   allow us to draw a number of conclusions regarding the stability and
   nature of possible spin-density wave states in homogeneous electron
   systems.
C1 Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Sao Paulo, Inst Fis Sao Carlos, Dept Fis & Informat, BR-13560970 Sao Carlos, SP, Brazil.
RP Capelle, K, Univ Sao Paulo, Inst Quim Sao Carlos, Dept Quim & Fis Mol,
   Caixa Postal 780, BR-13560970 Sao Carlos, SP, Brazil.
CR BONEV SA, 1999, B AM PHYS SOC, V44, P105
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NR 66
TC 9
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD JUN 1
PY 2000
VL 61
IS 22
BP 15228
EP 15240
PG 13
SC Physics, Condensed Matter
GA 325AL
UT ISI:000087654100049
ER

PT J
AU Pliego, JR
   Riveros, JM
TI On the calculation of the absolute solvation free energy of ionic
   species: Application of the extrapolation method to the hydroxide ion
   in aqueous solution
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID MONTE-CARLO SIMULATION; PERIODIC BOUNDARY-CONDITIONS; AB-INITIO;
   CONTINUUM ELECTROSTATICS; POTENTIAL FUNCTIONS; LIQUID WATER; GAS-PHASE;
   HYDRATION; CLUSTERS; MODEL
AB The absolute solvation free energy of the hydroxide ion in aqueous
   solution was calculated by Monte Carlo simulation and free energy
   perturbation. We have used the TIP3P model for water and the
   solute-solvent interaction was modeled as an effective two-body
   potential of charge-charge plus Lennard-Jones terms fitted to reproduce
   the interaction energy in the OH-(H2O)(3) and OH-(H2O)(4) ionic
   clusters. The electrostatic contribution to the solvation free energy
   was determined by using solvent boxes having 120, 160, 216, 350, and
   512 water molecules, and the limit for N approaching infinity was
   obtained by an extrapolation procedure. The final solvation free energy
   obtained by considering the Lennard-Jones potential contribution,
   correcting for the cutoff surface potential, and including the surface
   potential of water cluster amounts to -108.0 kcal mol(-1): in very good
   agreement with the experimental value of -105.0 kcal mol(-1). This
   result shows that the extrapolation method coupled with the use of an
   effective two-body potential is a viable and accurate procedure for
   calculating the absolute solvation free energy of ionic species.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, SP, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, SP,
   Brazil.
CR ALLEN MP, 1989, COMPUTER SIMULATION
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NR 42
TC 12
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5647
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD JUN 1
PY 2000
VL 104
IS 21
BP 5155
EP 5160
PG 6
SC Chemistry, Physical
GA 320WU
UT ISI:000087424500019
ER

PT J
AU Gorelsky, SI
   da Silva, SC
   Lever, ABP
   Franco, DW
TI Electronic spectra of trans-[Ru(NH3)(4)(L)NO](3+/2+) complexes
SO INORGANICA CHIMICA ACTA
LA English
DT Article
DE electronic spectra; ruthenium complexes; nitrosyl-metal complexes; DFT;
   TD-DFT
ID DENSITY-FUNCTIONAL THEORY; MOLECULAR-ORBITAL THEORY; EXTENDED
   BASIS-SETS; COMPACT EFFECTIVE POTENTIALS; EFFECTIVE CORE POTENTIALS;
   EXPONENT BASIS-SETS; ORGANOMETALLIC COMPOUNDS; TRANSITION-METALS;
   EXCITATION-ENERGIES; 1ST-ROW ELEMENTS
AB Density functional theory (DFT) with local, non-local and hybrid
   functionals has been used to obtain the geometry of a series of
   nitrosyl-metal complexes [Ru(NH3)(4)(L)NO](n+), where L = NH3, H2O,
   pyrazine and pyridine (n = 3), Cl- and OH- (n = 2). Based on the
   molecular orbital analysis and the time dependent DFT (TD-DFT)
   calculations, we discuss the electronic structure and the assignment of
   the bands in the electronic spectra of these complexes. (C) 2000
   Elsevier Science S.A. All rights reserved.
C1 York Univ, Dept Chem, Toronto, ON M3J 1P3, Canada.
   Univ Sao Paulo, Inst Quim, BR-13560970 Sao Carlos, SP, Brazil.
RP Lever, ABP, York Univ, Dept Chem, Toronto, ON M3J 1P3, Canada.
CR *HYP INC, 1997, HYPERCHEM WIND REL 5
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   ZERNER MC, ZINDO PROGRAM VERSIO
NR 68
TC 41
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0020-1693
J9 INORG CHIM ACTA
JI Inorg. Chim. Acta
PD APR 30
PY 2000
VL 300
BP 698
EP 708
PG 11
SC Chemistry, Inorganic & Nuclear
GA 320WA
UT ISI:000087422800083
ER

PT J
AU de Oliveira, AE
   Haiduke, RLA
   Bruns, RE
TI The infrared fundamental intensities and polar tensor of CF4
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE infrared intensities; atomic polar tensors; electronegativity; G sum
   rule; simple potential model
ID DIPOLE-MOMENT DERIVATIVES; PRINCIPAL COMPONENT ANALYSIS; CORIOLIS
   INTERACTIONS; METHANE; CHLOROFLUOROCARBONS; ENERGIES; FLUORIDE;
   CHARGES; SIGNS
AB Atomic polar tensors of carbon tetrafluoride are calculated from
   experimental fundamental infrared intensities measured by several
   research groups. Quantum chemical calculations using a 6-311 + + G(3d,
   3p) basis set at the Hartree-Fock, Moller-Plesset 2 and Density
   Functional Theory (B3LYP) levels are used to resolve the sign
   ambiguities of the dipole moment derivatives. The resulting carbon mean
   dipole moment derivative, (p) over bar(C) = 2.051 e, is in excellent
   agreement with values estimated by a MP2/6-311 + + G(3d, 3p)
   theoretical calculation, 2.040 e, and by an empirical electronegativity
   model. 2.016 e. The (p) over bar(C) value determined here is also in
   excellent agreement with the one obtained from the CF4 Is carbon
   ionization energy using a simple potential model, 2.059 e. Crawford's G
   intensity sum rule applied to the fundamental intensities of CH4, CH3F,
   CH2F2 and CHF3 results in a prediction of a 1249 km mol(-1) intensity
   sum for CF4 in good agreement with the experimental values of 1328 +/-
   37.9, 1208.0 +/- 54.4 and 1194.8 +/- 7.4 km mol(-1) reported in the
   literature. (C) 2000 Elsevier Science B.V. All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP de Oliveira, AE, Univ Estadual Campinas, Inst Quim, CP 6154,
   BR-13083970 Campinas, SP, Brazil.
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NR 36
TC 8
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JUN
PY 2000
VL 56
IS 7
BP 1329
EP 1335
PG 7
SC Spectroscopy
GA 319YW
UT ISI:000087374900011
ER

PT J
AU Rivelino, R
   Canuto, S
TI An ab initio study of the hydrogen-bonded H2O : HCN and HCN : H2O
   isomers
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID QUANTUM-CHEMISTRY; CYANIDE; WATER; COMPLEXES; SPECTROSCOPY; MOLECULES;
   SPECTRA
AB Ab initio calculations an performed on the hydrogen bond interaction
   between HCN and water to analyze the structure, binding energy and
   change in vibrational frequencies of the HCN:H2O isomer. After geometry
   optimization, single-point calculations are made with many-body
   perturbation/coupled-cluster theories with different basis sets. At the
   highest level, CCSD(T), we find that the binding energy between HCN and
   water is 3.4 kcal/mol, after correcting for the basis-set-super
   position error. Changes in intra-molecular vibrational frequencies are
   analyzed. (C) 2000 Elsevier Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Canuto, S, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 30
TC 17
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 19
PY 2000
VL 322
IS 3-4
BP 207
EP 212
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 318EX
UT ISI:000087271900009
ER

PT J
AU Bezerra, EF
   Freire, VN
   Teixeira, AMR
   Silva, MAA
   Freire, PTC
   Mendes, J
   Lemos, V
TI Smooth interface effects on the Raman scattering in zinc-blende AlN/GaN
   superlattices
SO PHYSICAL REVIEW B
LA English
DT Article
ID III NITRIDE SEMICONDUCTORS; QUANTUM-WELLS; CUBIC GAN; LATTICE-DYNAMICS;
   EPITAXIAL LAYERS; OPTICAL PHONONS; AB-INITIO; MODES; SPECTROSCOPY;
   SPECTRA
AB Raman spectra of
   (AlN)(8-delta)/(AlxGa1-xN)(delta)/(GaN)(8-delta)/(AlxGa1-xN)(delta)
   superlattices with interface thickness varying between delta = 0 and
   delta = 3 are calculated. The influence of the nonabrupt interface
   related broadening is described in the complete range of scattering,
   with special attention to the modes giving stronger contribution to the
   Raman intensity. It is shown that the dispersion of folded acoustic
   phonons does not change appreciably with the interface smoothing. For
   delta = 0 the Raman spectra display new peaks due to the enhancement of
   some confined optic modes.
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, UNICAMP, BR-13083970 Campinas, SP, Brazil.
RP Lemos, V, Univ Fed Ceara, Dept Fis, Ctr Ciencias, Caixa Postal
   6030,Campus do Pici, BR-60455760 Fortaleza, Ceara, Brazil.
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   KARCH K, 1998, PHYS REV B, V57, P7043
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   LEMOS V, 1999, J RAMAN SPECTROSC, V30, P379
   LIU XH, 1996, PHYS REV B, V53, P4699
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   NAKAMURA S, 1997, BLUE LASER DIODE
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NR 33
TC 11
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 15
PY 2000
VL 61
IS 19
BP 13060
EP 13063
PG 4
SC Physics, Condensed Matter
GA 316GK
UT ISI:000087159100092
ER

PT J
AU Bettega, MHF
   Winstead, C
   McKoy, V
TI Elastic scattering of low-energy electrons by benzene
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID TEMPORARY NEGATIVE-IONS; SELECTION-RULES; VIBRATIONAL-EXCITATION;
   MOLECULE COLLISIONS; RESONANCES; IMPACT
AB We present elastic cross sections obtained from ab initio calculations
   for low-energy electron scattering by benzene, C6H6. The calculations
   employed the Schwinger multichannel method as implemented for parallel
   computers within both the static-exchange and
   static-exchange-polarization approximations. We compare our results
   with other theoretical calculations and with available experimental
   data. In general, agreement is good. (C) 2000 American Institute of
   Physics. [S0021-9606(00)01120-X].
C1 CALTECH, Arthur Amos Noyes Lab Chem Phys, Pasadena, CA 91125 USA.
   Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil.
RP Bettega, MHF, CALTECH, Arthur Amos Noyes Lab Chem Phys, Pasadena, CA
   91125 USA.
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NR 37
TC 17
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD MAY 22
PY 2000
VL 112
IS 20
BP 8806
EP 8812
PG 7
SC Physics, Atomic, Molecular & Chemical
GA 310WC
UT ISI:000086851200010
ER

PT J
AU Rocha, WR
   De Almeida, WB
TI Carbonyl insertion reaction into the Pt-C bond in heterobimetallic
   Pt(SnCl3)(PH3)(2)(CO)(CH3) compound: Theoretical study
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE Pt(SnCl3)(PH3)(2)(CO)(CH3); heterobimetallic; catalytic species;
   carbonyl insertion reaction; quantum mechanical
ID OLEFIN HYDROFORMYLATION; ABINITIO MO; ASYMMETRIC HYDROFORMYLATION;
   ALKYL MIGRATION; REACTION-PATH; BASIS-SETS; AB-INITIO; COMPLEXES; PD;
   MECHANISM
AB Quantum-mechanical calculations were carried out at the MP4(SDQ)//MP2
   level of theory to determine the energies and reaction mechanism for
   the carbonyl insertion reaction (second step in the olefin
   hydroformylation catalytic cycle), using a heterobimetallic
   Pt(SnCl3)(PH3)(2)(CO)(CH3) compound as a model catalytic species. The
   results show that this reaction proceeds through a three-center
   transition state, with an activation energy of 26.4 kcal/mol, followed
   by an intramolecular rearrangement to the square-planar
   cis-Pt(SnC4)(PH3)(2)(MeCO) metal-acyl product. Analysis of the nature
   of the bonds shows that there is a negligible participation of Be tin
   d-orbitals in the formation of the Pt-Sn bond. (C) 2000 John Wiley &
   Sons, Inc.
C1 UFMG, ICEX, Dept Quim, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, UFMG, ICEX, Dept Quim, LQCMM, BR-31270901 Belo
   Horizonte, MG, Brazil.
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   BOTTEGHI C, 1997, QUIM NOVA, V20, P30
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   DIAS AD, 1997, TETRAHEDRON LETT, V38, P41
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   FUKUI K, 1981, ACCOUNTS CHEM RES, V14, P363
   GATES BC, 1992, CATALYTIC CHEM
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NR 36
TC 4
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD JUN
PY 2000
VL 21
IS 8
BP 668
EP 674
PG 7
SC Chemistry, Multidisciplinary
GA 310MC
UT ISI:000086831100005
ER

PT J
AU Fagan, SB
   Baierle, RJ
   Mota, R
   da Silva, AJR
   Fazzio, A
TI Ab initio calculations for a hypothetical material: Silicon nanotubes
SO PHYSICAL REVIEW B
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; CARBON NANOTUBES; ELECTRONIC-STRUCTURE;
   MOLECULAR-DYNAMICS; SYSTEMS; TUBULES; BORON
AB Electronic and structural properties of a hypothetical material,
   silicon nanotubes, are examined through first-principles calculations
   based on density functional theory. Even considering that Si nanotubes
   have never been observed, this paper attempts to establish the
   theoretical similarities between Si and C, like band structures and
   density of states, as well as the main differences, especially
   associated with cohesive energies. The band-structure calculations for
   silicon nanotubes show that, similar to carbon structures, depending on
   their chiralities, they may present metallic (armchair) or
   semiconductor (zigzag and mixed) behaviors.
C1 Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Fagan, SB, Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS,
   Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BETHUNE DS, 1993, NATURE, V363, P605
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NR 23
TC 43
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD APR 15
PY 2000
VL 61
IS 15
BP 9994
EP 9996
PG 3
SC Physics, Condensed Matter
GA 306PZ
UT ISI:000086606200039
ER

PT J
AU Pinheiro, JC
   Jorge, FE
   De Castro, EVR
TI An improved generator coordinate Hartree-Fock method applied to the
   choice of contracted Gaussian basis sets for first-row diatomic
   molecules
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE improved generator coordinate Hartree-Fock method; contracted Gaussian
   basis sets; first-row diatomic molecules
ID UNIVERSAL BASIS-SET; CORRELATION-ENERGY; 2ND-ROW ATOMS; MP2 ENERGY;
   EXCHANGE; HYDROGEN
AB Accurate Gaussian basis sets (18s for Li and Be and 20s11p for the
   atoms from B to Ne) for the first-row atoms, generated with an improved
   generator coordinate Hartree-Fock method, were contracted and enriched
   with polarization functions. These basis sets were tested for B-2, C-2,
   BeO, CN-, LiF, N-2, CO, BF, NO+, O-2, and F-2. At the Hartree-Fock
   (HP), second-order Moller-Plesset (MP2), fourth-order Moller-Plesset
   (MP4), and density functional theory (DFT) levels, the dipole moments,
   bond lengths, and harmonic vibrational frequencies were studied, and at
   the MP2, MP4, and DFT levels, the dissociation energies were evaluated
   and compared with the corresponding experimental values and with values
   obtained using other contracted Gaussian basis sets and numerical HF
   calculations. For all diatomic molecules studied, the differences
   between our total energies, obtained with the largest contracted basis
   set [6s5p3d1f], and those calculated with the numerical HF methods were
   always less than 3.2 mhartree. (C) 2000 John Wiley & Sons, Inc.
C1 Univ Fed Espirito Santo, Dept Fis, BR-29060900 Vitoria, ES, Brazil.
   Univ Fed Espirito Santo, Dept Quim, BR-29060900 Vitoria, ES, Brazil.
   Fed Univ Para, Fac Ciencias Exactas & Nat, Dept Quim, BR-66075110 Belem, Para, Brazil.
   Ctr Estudos Panamazonico, BR-66060000 Belem, Para, Brazil.
RP Jorge, FE, Univ Fed Espirito Santo, Dept Fis, BR-29060900 Vitoria, ES,
   Brazil.
CR BECKE AD, 1982, J CHEM PHYS, V76, P6037
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NR 34
TC 12
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD MAY 15
PY 2000
VL 78
IS 1
BP 15
EP 23
PG 9
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 306TW
UT ISI:000086613600003
ER

PT J
AU Rocha, WR
   De Almeida, WB
TI Insertion reaction of propane into Rh-H bond in HRh(CO)(PH3)(2)(C3H6)
   compound: A density functional study
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE propene; insertion reaction; hydroformylation; regioselectivity;
   density functional
ID RHODIUM-CATALYZED HYDROFORMYLATION; TRANSITION-METAL ATOMS; AB-INITIO;
   PROPENE HYDROFORMYLATION; REACTION-PATH; COMPLEXES; LIGANDS;
   TRIPHENYLPHOSPHINE; APPROXIMATION; CHEMISTRY
AB Quantum mechanical calculations at the MP4 (SDQ) level using the
   BP86-optimized geometries were carried out to investigate the energies
   and reaction mechanism for the propene (CH3-(CH)-H-1=CH22) insertion
   reaction into the Rh-H bond, using the cis-HRh(CO)(PH3)(2) compound as
   a model catalytic species. Since the reaction may occur on the branched
   carbon 1 or in the normal carbon 2, which leads to branched and normal
   Rh(alkyl) compounds, respectively, we investigated these two
   mechanisms. The results show that the insertion in the branched carbon
   has an activation energy of 16.2 kcal/mol, and the activation energy
   for the reaction to take place at the normal carbon is 14.3 kcal/mol.
   These activation energies, together with the calculated relative energy
   of the metal-alkyl compounds formed after the insertion considering
   these two pathways, were used to access the regioselectivity on this
   reaction. We found a ratio of normal- and iso-products, n:iso, of
   (96:4), which is in excellent agreement with the experimental
   regioselectity of (95:5). (C) 2000 John Wiley & Sons, Inc.
C1 UFMG, ICEX, Dept Quim, LQCMM, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, UFMG, ICEX, Dept Quim, LQCMM, BR-31270901 Belo
   Horizonte, MG, Brazil.
CR BECKE AD, 1988, PHYS REV A, V38, P3098
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NR 38
TC 13
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD MAY 15
PY 2000
VL 78
IS 1
BP 42
EP 51
PG 10
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 306TW
UT ISI:000086613600006
ER

PT J
AU Leitao, AA
   Vugman, NV
   Bielschowsky, CE
TI On the origin of C-13 and N-14 hyperfine interactions in
   [Co(CN)(6)](4-) and [Rh(CN)(6)](4-) complexes in KC1 host lattice
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID EFFECTIVE CORE POTENTIALS; MOLECULAR CALCULATIONS; COUPLING-CONSTANTS;
   BASIS-SETS; AB-INITIO; ABINITIO; MODEL
AB Ab-initio ROHF, PUHF and PUHF-MP2 calculations of C-13 and N-14
   hyperfine interactions for the [Co(CN)(6)](4-) and [Rh(CN)(6)](4-)
   complexes in the KCl host lattice were performed and compared to
   experimental results. The host lattice was represented by a set of 80
   potentials located at the ion positions, leading to a consistent
   picture of the complex electronic structure. A detailed analysis of
   each molecular orbital contribution shows that collective effects are
   very important and must be considered to achieve a realistic
   description of this property. (C) 2000 Elsevier Science B.V. All rights
   reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Fed Rio de Janeiro, Inst Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Bielschowsky, CE, Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim,
   Cidade Univ,CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR BERRONDO M, 1996, INT J QUANTUM CHEM, V57, P1115
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   WINTER NW, 1987, J CHEM PHYS, V87, P2945
NR 21
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD APR 28
PY 2000
VL 321
IS 3-4
BP 269
EP 274
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 308FW
UT ISI:000086700700012
ER

PT J
AU Eustatiu, IG
   Tyliszczak, T
   Hitchcock, AP
   Turci, CC
   Rocha, AB
   Bielschowsky, CE
TI Experimental and theoretical study of generalized oscillator strengths
   for C 1s and O 1s excitations in CO2
SO PHYSICAL REVIEW A
LA English
DT Article
ID ELECTRON-ENERGY-LOSS; INTRAMOLECULAR BOND LENGTHS; ABSORPTION
   FINE-STRUCTURE; IMPACT CORE EXCITATION; SHELL SHAPE RESONANCES; FAST
   CHARGED-PARTICLES; INELASTIC-COLLISIONS; MOMENTUM-TRANSFER; LEVEL
   EXCITATION; LOSS SPECTRA
AB Electron-energy-loss spectra of CO2 in the region of C 1 s and O 1 s
   excitations have been recorded over a wide range of momentum transfer
   (K), (2 a.u.(-2)<K-2<70a.u.(-2)). The dipole-forbidden transition to
   the (C 1 s sigma(g)(-1),sigma(g)(*)) (1)Sigma (+)(g) state in CO2 is
   detected for the first time, to our knowledge. A detailed analysis,
   with careful consideration of minimization of systematic experimental
   errors, has been used to convert the measured relative cross sections
   to absolute, momentum-transfer-dependent, generalized oscillator
   strength (GOS) profiles for all resolved C 1 s and O 1 s transitions of
   CO2. Theoretical results for the GOS, computed within the first Born
   approximation, were obtained with ab initio configuration interaction
   wave functions for the C 1 s transitions and with ab initio generalized
   multistructural wave functions for the O 1 s transitions. These wave
   functions include relaxation, correlation, and hole localization
   effects. Theory predicts large quadrupole contributions to the GOS for
   O 1 s excitations. In addition the computed GOS for O 1 s-->ns sigma
   and np sigma Rydberg states clearly show oscillations arising from
   interference between localized core excitations. Overall there is good
   agreement between the experimental and theoretical results, indicating
   that the first Born approximation holds to a surprisingly large
   momentum transfer for the core excitations studied.
C1 McMaster Univ, Dept Chem, Hamilton, ON L8S 4M1, Canada.
   Univ Fed Rio de Janeiro, Inst Quim, BR-21910 Rio De Janeiro, Brazil.
RP Eustatiu, IG, McMaster Univ, Dept Chem, 1280 Main St W, Hamilton, ON
   L8S 4M1, Canada.
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NR 71
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD APR
PY 2000
VL 6104
IS 4
AR 042505
DI ARTN 042505
PG 14
SC Physics, Atomic, Molecular & Chemical; Optics
GA 301ME
UT ISI:000086313300041
ER

PT J
AU Bettega, MHF
TI Elastic scattering of low-energy electrons by boron trihalides
SO PHYSICAL REVIEW A
LA English
DT Article
ID AB-INITIO; PLASMA; EXCITATION; BCL3; PSEUDOPOTENTIALS; SPECTROSCOPY;
   GENERATION; IMPACT; BBR3
AB We used the Schwinger multichannel method with pseudopotentials
   [Bettega et nl., Phys. Rev. A 47, 1111 (1993)] to study elastic
   scattering of low-energy electrons by the boron trihalides BCl3, BBr3,
   and BI3, at the static-exchange approximation. We calculated elastic
   integral, differential, and momentum transfer cross section from 5 to
   50 eV. In particular, our integral cross section fur BCl3 agrees in
   shape with results of previous calculations by Isaacs et al. [Phys.
   Rev. A 58, 2881 (1998)]. The symmetry decomposition of the integral
   cross section in the C-2v group is also presented. We discuss the
   existence of shape resonances for energies above 5 eV at the A(1), B-1,
   B-2, and A(2) symmetries. We also investigated the low-energy cross
   section for the B-2 symmetry for these three molecules. For BCl3 our
   B-2 cross section shows good agreement with the results of Isaacs et al.
C1 Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil.
RP Bettega, MHF, Univ Fed Parana, Dept Fis, Caixa Postal 19081,
   BR-81531990 Curitiba, Parana, Brazil.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BAECK KK, 1997, J CHEM PHYS, V106, P4604
   BETTEGA MHF, 1993, PHYS REV A, V47, P1111
   BETTEGA MHF, 1996, INT J QUANTUM CHEM, V60, P821
   BETTEGA MHF, 1998, J PHYS B-AT MOL OPT, V31, P2091
   BETTEGA MHF, 1998, J PHYS B-AT MOL OPT, V31, P4419
   BETTEGA MHF, 1998, PHYS REV A, V57, P4987
   BIEHL H, 1996, MOL PHYS, V87, P1199
   CHO H, 1998, MRS INTERNET J N S R, V3
   DACOSTA SMS, 1998, EUR PHYS J D, V3, P67
   GULLEY RJ, 1998, J PHYS B-AT MOL OPT, V31, P2735
   HONG J, 1998, J VAC SCI TECHNOL B, V16, P2690
   HONG J, 1998, J VAC SCI TECHNOL B, V16, P3349
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NR 26
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD APR
PY 2000
VL 6104
IS 4
AR 042703
DI ARTN 042703
PG 6
SC Physics, Atomic, Molecular & Chemical; Optics
GA 301ME
UT ISI:000086313300044
ER

PT J
AU Fuks, D
   Mundim, K
   Liubich, V
   Dorfman, S
TI Nonempirical simulations of Sigma(3)< 111 > tungsten grain boundary
   with boron atoms
SO SURFACE REVIEW AND LETTERS
LA English
DT Article
ID ELECTRONIC-STRUCTURE; MAGNETIC-PROPERTIES; ALLOYS; APPROXIMATION;
   OPTIMIZATION; IMPURITIES; ALUMINUM; FEAL
AB We perform the atomistic simulations of the properties of the
   Sigma(3)[111] grain boundary in W and demonstrate the influence of
   boron additive on the resistance of the grain boundary with respect to
   different shifts. The interatomic potentials used in these simulations
   are obtained from ab initio total energy calculations. These
   calculations are carried out in the framework of density functional
   theory in the coherent potential approximation. The recursion procedure
   to extract A-B type interatomic potentials is suggested.
C1 Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
   Ben Gurion Univ Negev, Dept Mat Engn, IL-84105 Beer Sheva, Israel.
   Technion Israel Inst Technol, Fac Phys, IL-32000 Haifa, Israel.
RP Fuks, D, Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
CR ABRIKOSOV IA, 1998, PHYS REV B, V57, P14164
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NR 37
TC 5
PU WORLD SCIENTIFIC PUBL CO PTE LTD
PI SINGAPORE
PA JOURNAL DEPT PO BOX 128 FARRER ROAD, SINGAPORE 912805, SINGAPORE
SN 0218-625X
J9 SURF REV LETTERS
JI Surf. Rev. Lett.
PD OCT
PY 1999
VL 6
IS 5
BP 705
EP 718
PG 14
SC Materials Science, Multidisciplinary; Physics, Atomic, Molecular &
   Chemical; Physics, Condensed Matter
GA 300LQ
UT ISI:000086254800019
ER

PT J
AU Fink, RF
   Sorensen, SL
   de Brito, AN
   Ausmees, A
   Svensson, S
TI The resonant Auger electron spectrum of C 1s(-1)pi(*) excited ethene: A
   combined theoretical and experimental investigation
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID TIME-DEPENDENT FORMULATION; VIBRATIONAL FINE-STRUCTURE; CORE-LEVEL
   PHOTOEMISSION; AB-INITIO CALCULATION; NUCLEAR-DYNAMICS;
   SYMMETRY-BREAKING; HOLE LOCALIZATION; TRANSITION RATES; X-RAY; ETHYLENE
AB The resonant Auger electron spectrum for ethene has been calculated
   with an ab initio approach using configuration-interaction energies and
   wave functions for the intermediate core-excited and final states. The
   transition rates were determined by the "one-center approximation." The
   role of vibrational relaxation on the line shapes was described by a
   moment method which considers the case of symmetric core holes and
   their localization due to the vibrational relaxation of the
   core-excited state. The core hole localization is investigated in some
   detail and is found to be extremely efficient in the C 1s(-1)pi*
   excited state of ethene. Another property of the core-excited state is
   found to be the polarization of the valence electron density toward the
   core hole. We demonstrate this by using three different symmetric
   configuration interaction representations and one nonsymmetric
   Hartree-Fock representation for this state. A modified improved virtual
   orbitals method is described and employed to obtain virtual orbitals
   which give a compact description of this effect. The theoretical
   spectra obtained in this way are compared with a measured spectrum and
   assignment of the structures in the spectrum to electronic
   configurations is made. We find strong configuration mixing in the
   higher excited final states which is evidence for the breakdown of the
   one-particle picture. (C) 2000 American Institute of Physics.
   [S0021-9606(00)31213-2].
C1 Univ Lund, Inst Phys, Dept Synchrotron Radiat Res, S-22100 Lund, Sweden.
   Ruhr Univ Bochum, Chair Theoret Chem, D-44780 Bochum, Germany.
   Univ Brasilia, Dept Phys, BR-70910900 Brasilia, DF, Brazil.
   Univ Uppsala, Dept Phys, S-75121 Uppsala, Sweden.
   Lab Nacl Luz Sincrotron, BR-13083360 Campinas, SP, Brazil.
   Univ Tartu, Inst Phys, EE-51014 Tartu, Estonia.
RP Sorensen, SL, Univ Lund, Inst Phys, Dept Synchrotron Radiat Res, Box
   118, S-22100 Lund, Sweden.
CR AGREN H, 1981, J CHEM PHYS, V75, P1267
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   ZAHRINGER K, 1992, PHYS REV A, V46, P5643
NR 56
TC 10
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD APR 15
PY 2000
VL 112
IS 15
BP 6666
EP 6677
PG 12
SC Physics, Atomic, Molecular & Chemical
GA 301EV
UT ISI:000086297000020
ER

PT J
AU Goncalves, CP
   Mohallem, JR
TI Ab initio isotope simulated dynamics in the adiabatic approximation
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; EXCESS PROTON; WATER; D2O
AB We present, for the first time, ab initio simulated molecular dynamics
   within the adiabatic approximation. The tests are made for H-2(+) and
   its isotopomers. We show that the farces on the nuclei can be
   calculated with sufficient accuracy to distinguish among the
   isotopomers. We also show that there are two regions where these forces
   are non-negligible, compared to those of Born-Oppenheimer: at large
   nuclear distances and near the equilibrium positions. (C) 2000 Elsevier
   Science B.V. All rights reserved.
C1 Univ Fed Minas Gerais, ICEX, Dept Fis, Lab Atomos & Mol Especiais, BR-31270123 Belo Horizonte, MG, Brazil.
RP Mohallem, JR, Univ Fed Minas Gerais, ICEX, Dept Fis, Lab Atomos & Mol
   Especiais, POB 702, BR-31270123 Belo Horizonte, MG, Brazil.
CR BORN M, 1927, ANN PHYS-BERLIN, V84, P457
   CAR R, 1985, PHYS REV LETT, V55, P2471
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NR 14
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAR 31
PY 2000
VL 320
IS 1-2
BP 118
EP 122
PG 5
SC Physics, Atomic, Molecular & Chemical
GA 299RG
UT ISI:000086211200020
ER

PT J
AU Miwa, RH
   Ferraz, AC
TI Adsorption process, atomic geometry, electronic structure and stability
   of Si(001)/Te surface
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; growth; silicon; surface relaxation
   and reconstruction
ID DENSITY-FUNCTIONAL THEORY; SI(100) SURFACE; GROUND-STATE; GROWTH; TE;
   TELLURIUM; RESTORATION; INTERFACE; CDTE; GE
AB The adsorption process, atomic geometry, electronic structure and
   energetics of a Si(001) surface covered by Te atoms have been studied
   using first-principles total-energy calculations. Our findings indicate
   that the Te atoms adsorb in the 'bridge' site on the surface Si dimer
   bond, in agreement with recent experimental results. We have also
   verified that the Si dimers (underneath adsorbed Te atoms) do not
   dissociate, The subsequent atomic exchange between the adsorbed Te atom
   and the surface Si atom, giving rise to an interdiffusion process of Te
   atoms towards Si substrate, is not an exothermic process. We have
   considered a number of possible coverages of Te atoms on Si(001)
   surface and our results indicate that for a coverage of one monolayer
   (1 ML). the Si(001)/Te-(1 x 1) surface represents the energetically
   more stable configuration. For a coverage of 2/3 hit, we have verified
   the formation of Te-Si-Te mixed trimers, in a (3 x 1) reconstructed
   surface. At 1/3 ML coverage, we have obtained the formation of Si
   dimers with a single Te atom at the surface, in a (3 x 1)
   reconstruction. Finally, for a coverage of 1/2 ML, we have obtained the
   formation of Si-Te mixed dimers, in a (2 x 1) reconstructed surface,
   but the calculated formation energy indicates that this atomic
   configuration is not energetically favourable. (C) 2000 Elsevier
   Science B.V. All rights reserved.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, SP, Brazil.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Ferraz, AC, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   SP, Brazil.
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NR 28
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD MAR 20
PY 2000
VL 449
IS 1-3
BP 180
EP 190
PG 11
SC Chemistry, Physical
GA 296ZN
UT ISI:000086056800023
ER

PT J
AU Silva, CO
   da Silva, EC
   Nascimento, MAC
TI Ab initio calculations of absolute pK(a) values in aqueous solution II.
   Aliphatic alcohols, thiols, and halogenated carboxylic acids
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID POLARIZABLE CONTINUUM MODEL; DENSITY-FUNCTIONAL THEORY; MOLLER-PLESSET;
   FREE-ENERGIES; SOLVATION; IMPLEMENTATION; ACIDITIES
AB A thermodynamical cycle is proposed to calculate absolute pK(a) values
   for Bronsted acids in aqueous solution. The polarizable continuum model
   (PCM) was used to describe the solvent, and absolute pK(a) values were
   computed for different classes of organic compounds: aliphatic
   alcohols, thiols, and halogenated derivatives of carboxylic aliphatic
   acids. The model furnishes pK(a) values in good agreement with the
   experimental results for some classes of compounds. For the cases where
   appreciable deviations are, observed, we have tried to establish a
   correlation among the neglected components of Delta G(solv) resulting
   from the model adopted, the level of calculation employed, and the
   pK(a) deviations relative to the experimental results.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis,
   CT,Bloco A,Sala 412,Cidade Univ Ilha Fundao, BR-21949900 Rio De
   Janeiro, Brazil.
CR ADAMO C, 1997, J COMPUT CHEM, V18, P1993
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   SILVA CO, IN PRESS J PHYS CH A
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NR 32
TC 48
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAR 23
PY 2000
VL 104
IS 11
BP 2402
EP 2409
PG 8
SC Chemistry, Physical
GA 296LF
UT ISI:000086025300033
ER

PT J
AU Olivato, PR
   Guerrero, SA
   Zukerman-Schpector, J
TI Preferred conformation in the solid state of some
   alpha-(p-phenylsulfinyl)-p-substituted acetophenones
SO ACTA CRYSTALLOGRAPHICA SECTION B-STRUCTURAL SCIENCE
LA English
DT Article
ID SUBSTITUTED CARBONYL-COMPOUNDS; ELECTRONIC INTERACTION
AB Information on the geometrical structures of
   alpha-(p-phenylsulfinyl)-p-substituted acetophenones
   X-PhC(O)CH2S(O)Ph-Y [X = OMe, Y = H (1); X = NO2, Y = OMe (2); X = OMe,
   Y = NO2 (3); IUPAC names: (1) 4-methoxyphenyl phenylsulfinylmethyl
   ketone; (2) 4 - nitrophenyl 4-methoxyphenylsulfinyl-methyl ketone; (3)
   4-methoxyphenyl 4-nitrophenyl-sulfinylmethyl ketone] have been obtained
   from X-ray diffraction analyses. A comparison of these results with
   those previously obtained from X-ray diffraction and ab initio
   computations of alpha-methylsulfinylacetophenone, PhC(O)CH2S(O)Me,
   indicated that (1) and (2) adopt in the crystal a cis(1) conformation
   and (3) assumes a quasi-gauche geometry. The stabilization of these
   conformations in the crystal is discussed in terms of the dipole moment
   coupling Coulombic and intramolecular charge transfer interactions
   between the oppositely charged atoms of the C=O and S=O dipoles. The
   p-substituted benzene ring is quasi-coplanar with the sulfinyl group
   for (1) and (3), but is quasi-perpendicular for (2), Conjugation and
   repulsion between the sulfinyl sulfur lone pair and the pi-benzene ring
   seem to be responsible for the observed geometries.
C1 Univ Sao Paulo, Inst Quim, BR-05599970 Sao Paulo, Brazil.
   UFSCar, DQ, Lab Cristalog Estereodinam & Modelagem Mol, BR-13565905 Sao Carlos, SP, Brazil.
RP Olivato, PR, Univ Sao Paulo, Inst Quim, CP 26077, BR-05599970 Sao
   Paulo, Brazil.
CR 1989, CAD 4 SOFTWARE VERSI
   BELLAMY LJ, 1978, ADV INFRARED GROUP F
   DISTEFANO G, 1996, J CHEM SOC PERK  AUG, P1661
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   OLIVATO PR, 1997, PHOSPHORUS SULFUR, V130, P155
   SHELDRICK GM, 1990, ACTA CRYSTALLOGR A, V46, P467
   SHELDRICK GM, 1997, SHELXL 97 PROGRAM RE
   ZSOLNAI L, 1995, ZORTOP
NR 13
TC 7
PU MUNKSGAARD INT PUBL LTD
PI COPENHAGEN
PA 35 NORRE SOGADE, PO BOX 2148, DK-1016 COPENHAGEN, DENMARK
SN 0108-7681
J9 ACTA CRYSTALLOGR B-STRUCT SCI
JI Acta Crystallogr. Sect. B-Struct. Sci.
PD FEB
PY 2000
VL 56
PN Part 1
BP 112
EP 117
PG 6
SC Crystallography
GA 295CV
UT ISI:000085949900012
ER

PT J
AU Moraes, LAB
   Eberlin, MN
TI The gas-phase Meerwein reaction
SO CHEMISTRY-A EUROPEAN JOURNAL
LA English
DT Article
DE epoxides; thioepoxides; acylium ions; thioacylium ions; ion-molecule
   reactions; mass spectroscopy
ID ION-MOLECULE REACTIONS; ACYLIUM IONS; MASS-SPECTROMETRY; CYCLIC
   ACETALS; CATIONS; TRANSACETALIZATION; SUBSTITUTION; KETALS; 3D
AB A systematic investigation of a novel epoxide and thioepoxide ring
   expansion reaction promoted by gaseous acylium and thioacylium ions is
   reported. As ab initio calculations predict, and O-18-labeling and MS3
   pentaquadrupole experiments demonstrate, the reaction proceeds by
   initial O(S)-acylation of the (thio)epoxides followed by rapid
   intramolecular nucleophilic attack that results in
   three-to-five-membered ring expansion, and forms cyclic
   1,3-dioxolanylium, 1,3-oxathiolanylium, or 1,3-dithiolanylium ions.
   This gas-phase reaction is analogous to a condensed-phase reaction long
   since described by H. Meerwein (Chem. Ber. 1955, 67, 374), and is
   termed as "the gas-phase Meerwein reaction"; it occurs often to great
   extents or even exclusively, but in some cases, particularly for the
   most basic (thio)epoxides and the most acidic (thio)acylium ions,
   proton transfer (eventually hydride abstraction) competes efficiently,
   or even dominates. When (thio)epoxides react with (thio)acylium ions,
   the reaction promotes O(S)-scrambling; when epoxides react with
   thioacylium ions and the adducts are dissociated, it promotes S/O
   replacement. An analogous four-to-six-membered ring expansion also
   occurs predominantly in reactions of trimethylene oxide with acylium
   and thioacylium ions.
C1 UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, UNICAMP, Inst Chem, CP6154, BR-13083970 Campinas, SP,
   Brazil.
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NR 44
TC 12
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY
SN 0947-6539
J9 CHEM-EUR J
JI Chem.-Eur. J.
PD MAR 3
PY 2000
VL 6
IS 5
BP 897
EP 905
PG 9
SC Chemistry, Multidisciplinary
GA 292VF
UT ISI:000085815200017
ER

PT J
AU Pliego, JR
   Riveros, JM
TI Ab initio study of the hydroxide ion-water clusters: An accurate
   determination of the thermodynamic properties for the processes
   nH(2)O+OH--> HO-(H2O)(n) (n=1-4)
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID GAS-PHASE; VIBRATIONAL SPECTROSCOPY; MOLECULAR-ENERGIES; GAUSSIAN-2
   THEORY; OH; SOLVATION; ABINITIO; ADDITIVITY; HYDRATION; COMPLEXES
AB Clusters of hydroxide ion, HO-(H2O)(n=1-4), have been studied by high
   level ab initio calculations in order to better understand the first
   coordination shell of OH- ions. Geometry optimizations were performed
   at Hartree-Fock, density functional theory and second order
   Moller-Plesset perturbation theory levels using the 6-31+G(d,p) basis
   set. Single point energy calculations were carried out on the optimized
   geometries using the more extended 6-311+G(2df,2p) basis set and a
   higher level of electron correlation, namely fourth-order
   Moller-Plesset perturbation theory. For the n=1-3 clusters, only
   structures with the hydroxide ion hydrogen bonded to all waters
   molecules were considered. For the n=4 cluster, three minima were
   found; the most stable species has all four waters directly bound to
   the hydroxide ion, while the other two clusters have only three waters
   in the first coordination shell. In addition, the transition state
   connecting the cluster containing four waters in the first coordination
   shell to the species having three waters in the coordination shell was
   characterized. The barrier for this rearrangement is very low (1.82
   kcal/mol), and we predict this process to occur on the picosecond time
   scale. The thermodynamic properties (enthalpy, entropy and Gibbs free
   energy) for the formation of the clusters have been calculated for all
   the species (including the fully deuterated clusters). Comparison of
   our calculations with experimental data reveals good agreement in the
   free energy. Nevertheless, our ab initio results suggest that for the n
   > 1 clusters, both -Delta H-0 and -Delta S-0 are larger than those
   reported from experiment and new experiments may be necessary to obtain
   accurate experimental values. (C) 2000 American Institute of Physics.
   [S0021-9606(00)30909-6].
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
RP Pliego, JR, Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
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NR 32
TC 28
PU AMER INST PHYSICS
PI MELVILLE
PA 2 HUNTINGTON QUADRANGLE, STE 1NO1, MELVILLE, NY 11747-4501 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD MAR 1
PY 2000
VL 112
IS 9
BP 4045
EP 4052
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 286QA
UT ISI:000085455600017
ER

PT J
AU Gomez, JA
   Guenzburger, D
TI Density functional study of electronic, magnetic and hyperfine
   properties of [M(CN)(5)NO](2-) (M = Fe, Ru) and reduction products
SO CHEMICAL PHYSICS
LA English
DT Article
ID METAL-NITROSYL COMPLEXES; SODIUM-NITROPRUSSIDE; SPECTROSCOPIC
   PROPERTIES; NEUTRON-DIFFRACTION; MOLECULAR-STRUCTURE; SINGLE-CRYSTALS;
   SPECTRA; REACTIVITY; DIHYDRATE; ENERGY
AB The discrete variational method (DVM) in density functional theory
   (DFT) was employed to investigate the electronic structure of the
   complexes: [Fe(CN)(5)NO](2-) (nitroprusside), [Fe(CN)(5)NO](3-),
   [Fe(CN)(4)NO](2-), [Ru(CN)(5)NO](2-) and [Ru(CN)(5)NO](3-). Total
   energy calculations revealed that in pentacyanonitrosylferrate(I) and
   pentacyanonitrosylruthenate(I), which are paramagnetic ions containing
   one unpaired electron, the M-N-O bond angle is bent. From
   self-consistent spin-polarized calculations, the distribution of the
   unpaired electron in the paramagnetic complexes [Fe(CN)(5)NO](3-),
   [Fe(CN)(4)NO](2-) and [Ru(CN)(5)NO](3-) was obtained, as well as
   spin-density maps. A long-standing controversy regarding the
   configuration of [Fe(CN)(5)NO](3-) was elucidated, and it was found
   that the unpaired electron in this complex is in an orbital primarily
   localized on pi* (NO). Mossbauer quadrupole splittings on Fe and Ru
   were derived from calculations of the electric-field gradients.
   Magnetic hyperfine coupling constants on N of the NO ligand were also
   obtained for the paramagnetic complexes. (C) 2000 Elsevier Science B.V.
   All rights reserved.
C1 Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
RP Guenzburger, D, Ctr Brasileiro Pesquisas Fis, Rua Xavier Sigaud 150,
   BR-22290180 Rio De Janeiro, Brazil.
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NR 63
TC 17
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD FEB 15
PY 2000
VL 253
IS 1
BP 73
EP 89
PG 17
SC Physics, Atomic, Molecular & Chemical
GA 286KM
UT ISI:000085445200008
ER

PT J
AU Fazzio, A
   Janotti, A
   da Silva, AJR
   Mota, R
TI Microscopic picture of the single vacancy in germanium
SO PHYSICAL REVIEW B
LA English
DT Article
ID ELECTRONIC-STRUCTURE; POINT-DEFECTS; AB-INITIO; SILICON;
   PSEUDOPOTENTIALS; SEMICONDUCTORS; DENSITY; MODEL
AB A complete microscopic picture of the germanium vacancy is presented,
   and our results are compared with recent measurements. We analyze,
   through first principles calculations, the structural relaxations,
   Jahn-Teller distortions, and orbitals for the charge states (+ +, +, 0,
   -, - -). The formation energies for the different charge states are
   presented, as well as the positions of the (+ +/+), (+/0), (0/-), and
   (-/- -) levels, and we obtain that the vacancy in Ge is not an Anderson
   negative-U system, as opposed to the silicon vacancy. We propose as an
   explanation a much smaller electron-lattice coupling for the E mode in
   germanium than in silicon.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Fed Santa Maria, Dept Fis, BR-97105900 Santa Maria, RS, Brazil.
RP Fazzio, A, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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   REMEDIAKIS IN, 1999, PHYS REV B, V59, P5536
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NR 23
TC 14
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD JAN 15
PY 2000
VL 61
IS 4
BP R2401
EP R2404
PG 4
SC Physics, Condensed Matter
GA 284TJ
UT ISI:000085348300004
ER

PT J
AU Laali, KK
   Hollenstein, S
   Galembeck, SE
   Coombs, MM
TI Stable ion study of protonated cyclopenta[a]phenanthrenes.
   Structure-reactivity relationships and charge delocalization in the
   carbocations
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-TYPE BASIS; AM1 CALCULATIONS;
   ORGANIC-MOLECULES; CARCINOGEN; CATIONS; SUBSTITUENT; METABOLITES;
   OXIDATION; ARENES
AB Protonation studies are reported for a series of
   cyclopenta[a]phenanthrenes C-p[a]P in superacid media. Hydrocarbons 1,
   4, 7, are ring protonated in FSO3H-SO2ClF to form monoarenium ions. The
   Delta(16,17) compounds 3, 6 are protonated at the D-ring double-bond to
   form stable alpha-phenanthrene-substituted carbocations.
   The 17-keto derivatives 2, 5, 8, 9, 19, 20 are CO-protonated in
   FSO3H-SO2ClF to form carboxonium ions. Carboxonium ions derived from 8
   and 20 undergo ring fluorosulfonation in the biologically important
   A-ring under thermodynamic control (higher temperatures and prolonged
   reaction times). Low temperature protonation of 8 and 9 with FSO3H .
   SbF5 (4 : 1)-SO2ClF gives their corresponding carboxonium-arenium
   dications (protonation of 2 with FSO3H . SbF5 (1 : 1)-SO2ClF gave a
   mixture of mono- and dications), where ring protonation sites are
   controlled by the position of the methyl group and occur in the A-ring
   for the A-ring methylated derivatives (8, 9).
   Whereas the 11-methoxy derivative (16) forms a carboxonium ion in
   FSO3H-SO2ClF analogous to the 11-Me derivative (5), the 11-phenol
   derivative (15), the ethoxy (17) and propoxy (18) derivatives are more
   reactive, forming a mixture of mono- and dication (with 15 and 17) or
   give mostly a carboxonium-arenium dication (with 18).
   Substituent effects observed under stable ion conditions emphasize
   relative carbocation stability and relief of peri-strain. Under
   thermodynamic control, carboxonium ions undergo fluorosulfonation in
   the biologically important A-ring. Charge delocalizations in the
   resulting mono- and dications (deduced primarily based on magnitude of
   Delta delta(13)C) are discussed and compared. In an effort to further
   enhance the NMR assignments and for comparison, mono-arenium ions
   1H(+), 4H(+), 6H(+), 7H(+) and their neutral precursors were calculated
   at the B3LYP/6-31G(d,p) level of ab initio theory; their H-1 and C-13
   NMR chemical shifts were computed by the GIAO method and their overall
   charge delocalization paths were deduced via differences in the NPA
   charges (cation minus neutral). The results are compared and discussed.
   Stable ion studies of C-P[a]P provide useful insights into the
   contrasting regioselectivities observed in chemical and biological
   activiation.
C1 Kent State Univ, Dept Chem, Kent, OH 44242 USA.
   USP, FFCLRP, Dept Quim, LAMMOL, Ribeirao Preto, SP, Brazil.
   Univ Surrey, Dept Chem, Guildford GU2 5XH, Surrey, England.
RP Laali, KK, Kent State Univ, Dept Chem, Kent, OH 44242 USA.
CR BECKE AD, 1996, J CHEM PHYS, V104, P1040
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   COOMBS MM, 1996, COMMUNICATION
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   GLEDINING ED, NBO VERSION 3 1
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   LAALI KK, 1997, J ORG CHEM, V62, P7752
   LAALI KK, 1998, J CHEM SOC PERK  APR, P897
   LAALI KK, 1998, J ORG CHEM, V63, P7280
   REDDY VP, 1992, J FLUORINE CHEM, V56, P195
   REED AE, 1983, J CHEM PHYS, V78, P4066
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NR 35
TC 6
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PY 2000
IS 2
BP 211
EP 220
PG 10
SC Chemistry, Organic; Chemistry, Physical
GA 279PN
UT ISI:000085054500008
ER

PT J
AU Sparrapan, R
   Mendes, MA
   Carvalho, M
   Eberlin, MN
TI Formal fusion of a pyrrole ring onto 2-pyridyl and 2-pyrimidyl cations:
   One-step gas-phase synthesis of indolizine and its derivatives
SO CHEMISTRY-A EUROPEAN JOURNAL
LA English
DT Article
DE cycloadditions; heterocycles; ion-molecules reactions; mass spectroscopy
ID DIELS-ALDER CYCLOADDITION; EVEN-ELECTRON RULE; MASS-SPECTROMETRY;
   ACYLIUM IONS; IMMONIUM IONS; TRANSACETALIZATION; 3D
AB Two ortho-hetarynium ions, the 2-pyridyl and 2-pyrimidyl cations, react
   promptly with 1,3-dienes in the gas phase by annulation, formally by
   fusion, onto the ions of a pyrrole ring. This novel reaction proceeds
   through an initial polar [4 + 2(+)] cycloaddition across the C=N+ bond,
   followed by fast ring opening, a [1,4-H] shift, and finally a
   recyclization that results in a contraction of a six- to a
   five-membered ring and dissociation by the loss of a methyl radical.
   For the 2-pyridyl cation. this reaction yields ionized indolizines
   (pyrrolo[1,2-a]pyridines), while for the 2-pyrimidyl cation, it gives
   ionized pyrrolo[1,2-a]pyrimidines. The annulation reaction, performed
   in the rf-only collision quadrupole of a pentaquadrupole (QqQqQ) mass
   spectrometer, occurs readily with both 1,3-butadiene and isoprene, and
   is thermodynamically and kinetically favored as predicted by ab initio
   calculations. Ortho-hetarynium ions and 1,3-dienes provide, therefore,
   the two building blocks for the efficient one-step gas-phase synthesis
   of ionized bicyclic pyrrolo[1,2-a]pyridine (indolizine) and
   pyrrolo[1,2-a] pyrimidine, as well as their analogues and derivatives.
C1 Univ Estadual Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, Univ Estadual Campinas, Inst Chem, CP 6154, BR-13083970
   Campinas, SP, Brazil.
CR BORDEN WT, 1982, DIRADICALS
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NR 35
TC 12
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY
SN 0947-6539
J9 CHEM-EUR J
JI Chem.-Eur. J.
PD JAN
PY 2000
VL 6
IS 2
BP 321
EP 326
PG 6
SC Chemistry, Multidisciplinary
GA 277JV
UT ISI:000084931200013
ER

PT J
AU Morgon, NH
   Xavier, LA
   Riveros, JM
TI Gas-phase nucleophilic reactions of Ge(OCH3)(4): experimental and
   computational characterization of pentacoordinated Ge anions
SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
LA English
DT Article
DE germanium methoxide; gas-phase nucleophilic reactions; pentacoordinated
   Ge anions; fluoride affinity; germyl anions; computational Ge chemistry
ID ION-MOLECULE REACTIONS; TRAP MASS-SPECTROMETRY; CYCLOTRON RESONANCE;
   THEORETICAL CHARACTERIZATION; GLASS POWDERS; NEGATIVE-IONS; SILICON;
   AFFINITIES; CHEMISTRY; FLUORIDE
AB The gas-phase ion/molecule reactions of F- and CH3O- with Ge(OCH3)(4)
   have been investigated by Fourier transform ion cyclotron mass
   spectrometry. Both nucleophiles react preferentially by an addition
   mechanism to yield XGe(OCH3)(4)(-) (X = F, OCH3) complexes that are
   identified as typical pentacoordinated Ge species, Pentacoordinated Ge
   adducts formed with excess internal energy can undergo elimination of
   formaldehyde to yield HGe(OCH3)(4)(-) or further elimination processes
   that result in the formation of germyl anions like Ge(OCH3)(3)(-).
   Other minor product ions are also observed which can be attributed to
   the intermediacy of a pentacoordinated adduct. Dissociation of the
   XGe(OCH3)(4)(-) anions induced by infrared multiphoton excitation leads
   to sequential losses of formaldehyde and gives rise to different germyl
   anions like Ge(OCH3)(3)(-) HGe(OCH3)(2)(-), and H2GeOCH3-. The
   XGe(OCH3)(4)(-) and germyl anions react readily with BF3 through
   successive methoxide-fluoride exchange and this reaction provides a
   gas-phase synthetic pathway for multiply fluorinated Ge anions. Ab
   initio calculations performed on model pentacoordinated species
   Fn+1Ge(OH)(4-n)(-) (n = 0-4) reveal that addition of a fluoride ion on
   hydroxygermanes occurs preferentially in the apical position of a
   trigonal bipyramid. The fluoride affinity of the prototype molecule
   Ge(OH)(4) is calculated to be 60.9 kcal mol(-1), and fluoride affinity
   increases monotonically with increasing fluorine substitution, The
   fluoride affinity of GeF4 is calculated to be 79 kcal mol(-1). Similar
   calculations also predict an unusually high hydride affinity (60 kcal
   mol(-1)) for Ge(OH)(4) with the hydride occupying an equatorial
   position. (C) 2000 Elsevier Science B.V.
C1 Univ Sao Paulo, Inst Quim, BR-05508900 Sao Paulo, Brazil.
   Univ Estadual Campinas, UNICAMP, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP Riveros, JM, Univ Sao Paulo, Inst Quim, Av Lineu Prestes 748,Cidade
   Univ, BR-05508900 Sao Paulo, Brazil.
EM jmrnigra@quim.iq.usp.br
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NR 59
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 1387-3806
J9 INT J MASS SPECTROM
JI Int. J. Mass Spectrom.
PD JAN 21
PY 2000
VL 196
SI Sp. Iss. SI
BP 363
EP 375
PG 13
SC Physics, Atomic, Molecular & Chemical; Spectroscopy
GA 277HR
UT ISI:000084927100032
ER

PT J
AU Coelho, LAF
   Marchut, A
   de Oliveira, JV
   Balbuena, PB
TI Theoretical studies of energetics and diffusion of aromatic compounds
   in supercritical carbon dioxide
SO INDUSTRIAL & ENGINEERING CHEMISTRY RESEARCH
LA English
DT Article
ID MOLECULAR-DYNAMICS; LENNARD-JONES; AB-INITIO; BENZENE DIMER;
   FORCE-FIELD; HARD-SPHERE; CO2 DIMER; COEFFICIENTS; MODEL; PHASE
AB Atomic and molecular interactions of aromatic compounds in carbon
   dioxide are studied with ab initio and molecular dynamics techniques.
   Ab initio calculations are used to determine the nature of the CO2-CO2,
   CO2-benzene, and benzene-benzene interactions. We select an explicit
   all-atom force field without partial atomic charges to describe the
   intermolecular and intramolecular pair interactions of CO2 with benzene
   and toluene. Molecular dynamics simulations are used to calculate
   diffusion coefficients for benzene and toluene at infinite dilution in
   CO2 along isotherms at 313.15, 323.15, and 333.15 K, in the density
   range from 1.35 rho(c) to 2.10 rho(c) (rho(c) = critical CO2 density).
   Diffusion coefficients are also calculated with a model based on
   perturbation theory of simple liquids. The calculated diffusion
   coefficients agree fairly well with the experimental results of Suarez
   et al. (Chem. Eng. Sci. 1993, 48, 2419).
C1 Univ S Carolina, Dept Chem Engn, Columbia, SC 29208 USA.
   Univ Fed Rio de Janeiro, Chem Engn Program, Rio De Janeiro, Brazil.
RP Balbuena, PB, Univ S Carolina, Dept Chem Engn, Columbia, SC 29208 USA.
CR ALLEN MP, COMPUTER SIMULATION
   BALBUENA PB, 1999, MOL DYNAMICS CLASSIC, V7, P431
   BELBUENA PB, 1999, MOL DYNAMICS CLASSIC, V7
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   DARIVA C, 1999, BRAZ J CHEM ENG
   DARIVA C, 1999, IN PRESS FLUID PHASE
   EGGENBERGER R, 1991, MOL PHYS, V72, P433
   EINSTEIN A, 1926, INVESTIGATIONS THEOR
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NR 46
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0888-5885
J9 IND ENG CHEM RES
JI Ind. Eng. Chem. Res.
PD JAN
PY 2000
VL 39
IS 1
BP 227
EP 235
PG 9
SC Engineering, Chemical
GA 272JD
UT ISI:000084646000029
ER

PT J
AU Diehl, A
   Tamashiro, MN
   Barbosa, MC
   Levin, Y
TI Density-functional theory for attraction between like-charged plates
SO PHYSICA A
LA English
DT Article
ID ELECTRICAL DOUBLE-LAYER; ELECTROSTATIC CORRELATION; LIQUIDS; FORCES;
   SURFACES; FLUIDS
AB We study the interactions between two negatively charged macroscopic
   surfaces confining positive counterions. A density-functional approach
   is introduced which, besides the usual mean-field interactions, takes
   into account the correlations in the positions of counterions. The
   excess free energy is derived in the framework of the Debye-Huckel
   theory of the one-component plasma, with the homogeneous density
   replaced by a weighted density. The minimization of the total free
   energy yields the density profile of the microions. The pressure is
   calculated and compared with the simulations and the results derived
   from integral equations theories. We find that the interaction between
   the two plates becomes attractive when their separation distance is
   sufficiently small and the surface charge density is larger than a
   threshold value. (C) 1999 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto Alegre, RS, Brazil.
   Univ Fed Ceara, Dept Fis, BR-60455760 Fortaleza, Ceara, Brazil.
   Univ Calif Santa Barbara, Mat Res Lab, Santa Barbara, CA 93106 USA.
RP Barbosa, MC, Univ Fed Rio Grande Sul, Inst Fis, Caixa Postal 15051,
   BR-91501970 Porto Alegre, RS, Brazil.
CR ARENZON JJ, 1999, EUR PHYS J B, V12, P79
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   LEVIN Y, 1999, PHYSICA A, V265, P432
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   ROBBINS MO, COMMUNICATION
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   SAFRAN SA, 1994, STAT THERMODYNAMICS
   SHKLOVSKII BI, 1999, PHYS REV LETT, V82, P3268
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NR 34
TC 19
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0378-4371
J9 PHYSICA A
JI Physica A
PD DEC 15
PY 1999
VL 274
IS 3-4
BP 433
EP 445
PG 13
SC Physics, Multidisciplinary
GA 268BG
UT ISI:000084394000005
ER

PT J
AU da Silva, CO
   da Silva, EC
   Nascimento, MAC
TI Ab initio calculations of absolute pK(a) values in aqueous solution I.
   Carboxylic acids
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID POLARIZABLE CONTINUUM MODEL; DENSITY-FUNCTIONAL THEORY; SOLVATION
   MODEL; FREE-ENERGIES; ACIDITIES; SOLVENT; ABINITIO; DERIVATIVES;
   POTENTIALS; CHARGES
AB A thermodynamical cycle is proposed to calculate absolute pK(a) values
   for a Bronsted acid in aqueous solution. The solvent (water) was
   represented by a dielectric using the polarizable continuum model
   (PCM), and the absolute pK(a) values of some aliphatic carboxylic acids
   were computed. The results indicate that the proposed methodology seems
   to be capable of predicting reasonably good absolute pK(a) values,
   although in some cases appreciable deviations are observed, which can
   be related to neglecting the molecular motion contributions (Delta
   G(Mm)) to the solvation energy (Delta G(solv)).
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Nascimento, MAC, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis,
   Bloco A,Sala 412,Cidade Univ, BR-21949900 Rio De Janeiro, Brazil.
CR *GEOM CTR SOFTW DE, MOL CAV FIG 3 WER OB
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   MENNUCCI B, COMMUNICATION
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   NETTO JDM, 1996, J PHYS CHEM-US, V100, P15105
   NEWTON MD, 1971, J AM CHEM SOC, V93, P4971
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   TOMASI J, 1994, CHEM REV, V94, P2027
NR 41
TC 40
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD DEC 16
PY 1999
VL 103
IS 50
BP 11194
EP 11199
PG 6
SC Chemistry, Physical
GA 268PP
UT ISI:000084425000069
ER

PT J
AU Costa, MF
   Fonseca, TL
   Amaral, OAV
   Castro, MA
TI Calculations of the polarizability and hyperpolarizability of the NaH
   molecule including vibrational corrections
SO PHYSICS LETTERS A
LA English
DT Article
DE polarizability; vibrational correction; NaH
ID QUADRATIC CONFIGURATION-INTERACTION; ELECTRON CORRELATION THEORIES;
   BODY-PERTURBATION-THEORY; AB-INITIO; TRIPLE EXCITATIONS; NUCLEAR;
   MODEL; HF
AB In this work we present results for the dipole moment, polarizability
   and first hyperpolarizability of the NaH molecule obtained through the
   many-body perturbation-theory, coupled cluster and quadratic
   configuration interaction methods, including vibrational corrections.
   It is shown that the nuclear relaxation contribution is of fundamental
   importance for both polarizability and first hyperpolarizability of
   this system. Besides, inclusion of electron correlation effects changes
   appreciably the size of this contribution. In addition, our results
   show that the curvature contribution does not alter significantly the
   values obtained for the polarizability. (C) 1999 Published by Elsevier
   Science B.V. All rights reserved.
C1 Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
RP Costa, MF, Univ Fed Goias, Inst Fis, BR-74001970 Goiania, Go, Brazil.
CR ARCHIBONG EF, 1991, PHYS REV A, V44, P5478
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   BISHOP DM, 1998, ADV CHEM PHYS, V104, P1
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   CASTRO MA, 1996, PHYS REV A, V53, P3664
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   FRISCH MJ, 1995, GAUSSIAN 94
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   MARTI J, 1993, MOL PHYS, V80, P625
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NR 33
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0375-9601
J9 PHYS LETT A
JI Phys. Lett. A
PD NOV 29
PY 1999
VL 263
IS 3
BP 186
EP 192
PG 7
SC Physics, Multidisciplinary
GA 265RX
UT ISI:000084258100007
ER

PT J
AU Teles, LK
   Scolfaro, LMR
   Leite, JR
   Ramos, LE
   Tabata, A
   Castineira, JLP
   As, DJ
TI Relaxation effects on the negatively charged Mg impurity in zincblende
   GaN
SO PHYSICA STATUS SOLIDI B-BASIC RESEARCH
LA English
DT Article
ID NITRIDE
AB The electronic structure of Mg impurity in zincblende (c-)GaN is
   investigated by using the ab initio full potential linear-augmented
   plane-wave method and the local density-functional approximation. Fun
   geometry optimization calculations, including nearest and next-nearest
   neighbor displacements, are performed far the impurity in the neutral
   and negatively charged states. A value of 190 +/- 10 meV was obtained
   for the Franck-Condon shift to the thermal energy, which is in good
   agreement with that observed in recent low temperature
   photoluminescence and Hall-effect measurements. We conclude that the
   nearest and next-nearest neighbors of the Mg impurity replacing Ga in
   c-GaN undergo outward relaxations which play an important role in the
   determination of the center acceptor energies.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Estadual Paulista, Fac Ciencias Bauru, BR-17033360 Bauru, SP, Brazil.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Gesamthsch Paderborn, FB Phys 6, D-33098 Paderborn, Germany.
RP Scolfaro, LMR, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
CR AS DJ, 1998, PHYS STATUS SOLIDI B, V210, P445
   AS DJ, 1999, J NITRIDE SEMICON S1, V4
   BLAHA P, 1990, COMPUT PHYS COMMUN, V59, P399
   CASTINEIRA JLP, 1998, MAT SCI ENG B-SOLID, V51, P53
   FIORENTINI V, 1996, P 23 ICPS, V4, P28777
   GOTZ W, 1996, APPL PHYS LETT, V68, P667
   ORTON JW, 1998, REP PROG PHYS, V61, P1
   PANKOVE JI, 1998, SEMICONDUCTORS SEMIM, V50
   PERDEW JP, 1996, PHYS REV LETT, V77, P3865
   SCHWARZ K, 1996, LECT NOTES CHEM, V67, P139
NR 10
TC 6
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY
SN 0370-1972
J9 PHYS STATUS SOLIDI B-BASIC RE
JI Phys. Status Solidi B-Basic Res.
PD NOV
PY 1999
VL 216
IS 1
BP 541
EP 545
PG 5
SC Physics, Condensed Matter
GA 264QX
UT ISI:000084193900104
ER

PT J
AU Takahata, Y
   Chong, DP
TI Density-functional calculations of molecular electron affinities
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE molecular electron affinities; density functional theory
ID BASIS-SETS; THERMOCHEMISTRY; APPROXIMATION; EXCHANGE; ENERGY; ATOMS;
   SF4; GAS
AB Electron affinities of twelve small molecules were calculated by
   density functional theory using two different functionals(B88-P86 and
   B3LYP) combined with three different basis sets 6-31++G**:; 6-311++G**;
   aug-cc-pVTZ. Outer valence Green's function method is also employed for
   calculation of electron affinities of the molecules. The two most
   efficient approaches were found to be the combination of (1)B88-P86
   with 6-31++G**;: basis set and (2)B3LYP with 6-31++G**:;: The two
   approaches were employed to calculate electron affinities of some
   medium size molecules.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
   Univ British Columbia, Dept Chem, Vancouver, BC V6T 1Z1, Canada.
RP Takahata, Y, Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas,
   SP, Brazil.
CR BABCOCK LM, 1981, J CHEM PHYS, V75, P3864
   BECKE AD, 1988, PHYS REV A, V38, P3098
   BECKE AD, 1993, J CHEM PHYS, V98, P5648
   BOESCH SE, 1996, J PHYS CHEM-US, V100, P10083
   CHONG DP, 1995, CAN J CHEM, V73, P79
   CHOWDHURY S, 1986, J AM CHEM SOC, V108, P5453
   FARRAGHER AL, 1967, T FARADAY SOC, V63, P2369
   FRISH MJ, 1995, GAUSSIAN 94
   HEHRE WJ, 1986, AB INITIO MOL ORBITA
   HELLWEGE KL, 1976, LANDOLTBORNSTEIN NUM, V7
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   KLOBUKOWSKI M, 1997, ADV QUANTUM CHEM, V28, P189
   LEE C, 1988, PHYS REV B, V37, P785
   LIDE DR, 1995, CRC HDB CHEM PHYSICS
   MADELUNG O, 1992, LANDOLTBORNSTEIN NUM, V21
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   ZIEGLER T, 1992, J CHEM PHYS, V96, P7623
   ZIEGLER T, 1992, J COMPUT CHEM, V13, P70
NR 25
TC 4
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PD SEP-OCT
PY 1999
VL 10
IS 5
BP 354
EP 358
PG 5
SC Chemistry, Multidisciplinary
GA 261MC
UT ISI:000084012100003
ER

PT J
AU Esteves, PM
   Nascimento, MAC
   Mota, CJA
TI Reactivity of alkanes on zeolites: A theoretical ab initio study of the
   H/H exchange
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID H-D EXCHANGE; PENTACOORDINATED CARBONIUM-IONS; HYDROGEN-DEUTERIUM
   EXCHANGE; HARTREE-FOCK CALCULATIONS; DIMETHYL ETHER FORMATION; C-C
   BONDS; SOLID ACIDS; ELECTROSTATIC POTENTIALS; ELECTROPHILIC REACTIONS;
   SURFACE METHOXY
AB Ab initio calculations were performed to study the H/H exchange between
   light alkanes (methane, ethane, propane, and isobutane) in protonated
   zeolites. The Bronsted acid site of the zeolite was represented by a T3
   cluster (T = Si, Al). The results of the calculations, at the
   B3LYP/6-31G** and MP2/6-31G**//HF/6-31G** levels, indicated that the
   transition state resembles a pentacoordinated carbonium ion. The
   enthalpy of activation was similar, regardless of the alkane and the
   type of hydrogen being exchanged. The Delta H-double dagger values, at
   room temperature, ranged from 32.2 kcal/mol for methane to 36.2
   kcal/mol for the exchange of the tertiary hydrogen of isobutane, both
   at the B3LYP/6-31G** level. These results are not in complete agreement
   with experiments, as it has been shown that for isobutane only the
   primary hydrogens exchange at temperatures near ambient. This
   disagreement may be attributed to the fact that the cluster model
   employed in the calculations neither includes the electrostatic effects
   of the zeolite cavity nor takes into account steric repulsion
   associated with the framework.
C1 Univ Fed Rio de Janeiro, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
RP Mota, CJA, Univ Fed Rio de Janeiro, Inst Quim, Cidade Univ,CT Bloco A,
   BR-21949900 Rio De Janeiro, Brazil.
CR BECK LW, 1995, J AM CHEM SOC, V117, P11594
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   ESTEVES PM, 1999, J AM CHEM SOC, V121, P7345
   EVLETH EM, 1994, J PHYS CHEM-US, V98, P1421
   EVLETH EM, 1996, J PHYS CHEM-US, V100, P11368
   FRASH MV, 1997, J PHYS CHEM B, V101, P5346
   FRASH MV, 1998, J PHYS CHEM B, V102, P2232
   FRISCH MJ, 1995, GAUSSIAN 94
   HOGEVEEN H, 1969, RECL TRAV CHIM PAY B, V88, P703
   JOBIC H, 1996, J PHYS CHEM-US, V100, P19545
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   KAZANSKY VB, 1992, J MOL CATAL, V74, P257
   KAZANSKY VB, 1994, CATAL LETT, V28, P211
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   LINS JOMDL, 1996, THEOCHEM-J MOL STRUC, V371, P237
   MOTA CJA, UNPUB
   MOTA CJA, 1991, J CHEM SOC CHEM COMM, P171
   MOTA CJA, 1992, J AM CHEM SOC, V114, P1121
   MOTA CJA, 1993, STUD SURF SCI CATAL, V75, P463
   MOTA CJA, 1994, J CHEM SOC FARADAY T, V90, P2297
   MOTA CJA, 1996, APPL CATAL A-GEN, V146, P181
   MOTA CJA, 1996, J PHYS CHEM-US, V100, P12418
   MOTA CJA, 1997, J AM CHEM SOC, V119, P5193
   MOTA CJA, 1997, J CATAL, V172, P194
   NASCIMENTO MAC, 1999, J MOL STRUC-THEOCHEM, V464, P239
   OLAH GA, 1968, J AM CHEM SOC, V90, P2726
   OLAH GA, 1973, ANGEW CHEM INT EDIT, V12, P173
   OLAH GA, 1973, J AM CHEM SOC, V95, P4960
   ORTIZ W, 1999, ORG LETT, V1, P531
   RIGBY AM, 1997, J CATAL, V170, P1
   SINCLAIR PE, 1997, J PHYS CHEM B, V101, P295
   SOMMER J, 1992, J AM CHEM SOC, V114, P5884
   SOMMER J, 1994, J AM CHEM SOC, V116, P5491
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   STEVENSON DP, 1952, J AM CHEM SOC, V74, P3269
   VIRUELAMARTIN P, 1993, J PHYS CHEM-US, V97, P13713
   ZICOVICHWILSON C, COMMUNICATION
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   ZYGMUNT SA, 1994, J MOL STRUCT THEOCHE, V314, P113
   ZYGMUNT SA, 1996, J PHYS CHEM-US, V100, P6663
NR 53
TC 25
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5647
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD NOV 25
PY 1999
VL 103
IS 47
BP 10417
EP 10420
PG 4
SC Chemistry, Physical
GA 261LF
UT ISI:000084010100015
ER

PT J
AU Goeppert, A
   Sassi, A
   Sommer, J
   Esteves, PM
   Mota, CJA
   Karlsson, A
   Ahlberg, P
TI Protonation of small alkanes in liquid superacids: Absence of
   intramolecular C-13 and H-2 scrambling in propane and isobutane
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID THEORETICAL AB-INITIO; ACTIVATION; DEUTERIUM; CRACKING; ZEOLITE; CATIONS
C1 Univ Strasbourg 1, Inst Chim, F-67070 Strasbourg, France.
   Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Gothenburg, Dept Organ Chem, S-41296 Gothenburg, Sweden.
RP Sommer, J, Univ Strasbourg 1, Inst Chim, 4 Rue Blaise Pascal, F-67070
   Strasbourg, France.
CR BROUWER DM, 1968, RECL TRAV CHIM PAY B, V87, P1435
   CORMA A, 1985, J CATAL, V93, P30
   CORMA A, 1994, J CATAL, V145, P171
   ESTEVES PM, 1998, J AM CHEM SOC, V120, P3213
   ESTEVES PM, 1998, TOP CATAL, V6, P163
   HAAG WO, 1984, 8TH P INT C CAT BERL, V2, P305
   IVANOVA II, 1998, TOP CATAL, V6, P49
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   OLAH G, 1985, SUPERACIDS
   OLAH GA, 1972, J AM CHEM SOC, V94, P808
   OLAH GA, 1973, ANGEW CHEM INT EDIT, V12, P173
   OLAH GA, 1995, HYDROCARBON CHEM
   PINES H, 1981, CHEM CATALYTIC HYDRO
   SAUNDERS M, 1992, CROAT CHEM ACTA, V65, P673
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   SOMMER J, 1993, ACCOUNTS CHEM RES, V26, P370
   SOMMER J, 1997, J AM CHEM SOC, V119, P3274
NR 17
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD NOV 17
PY 1999
VL 121
IS 45
BP 10628
EP 10629
PG 2
SC Chemistry, Multidisciplinary
GA 258UP
UT ISI:000083857800022
ER

PT J
AU Okulik, N
   Peruchena, NM
   Esteves, PM
   Mota, CJA
   Jubert, A
TI Ab initio topological analysis of the electronic density in isobutonium
   cations
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID MOLECULAR CHARGE-DISTRIBUTIONS; ELECTROPHILIC REACTIONS; QUANTUM
   TOPOLOGY; TERMS
AB Studies performed on isobutonium cations at the ab initio level show
   that five different stable structures can be characterized. The two
   structures most energetically favored correspond to van der Waals
   complexes, one of them between CH4 and i-C3H7+ and one of smaller
   energy between H-2 and the C4H9+ cation. Among the isobutonium cations,
   the most stable structure corresponds to the C-isobutonium cation where
   a three-center two-electron bond is formed. The isobutonium cations on
   the H are significantly higher in energy. The topology of the
   electronic density charge of the isobutonium cations is studied, at ab
   initio level, using the theory of atoms in molecules (AIM) developed by
   Bader. The electronic delocalization that operates through the sigma
   bonds in saturated molecules and specifically in protonated alkanes can
   be studied by means of the analysis of the charge density and of the
   Laplacian of the electronic charge density at the bond critical points.
C1 Natl Univ La Plata, Fac Ciencias Exactas, Dept Quim, CONICET,Ctr Quim Inorgan,CEQUINOR,UNLP, RA-1900 La Plata, Argentina.
   UNNE, Fac Ciencias Exactas & Nat & Agrimensura, Dept Quim, RA-3400 Corrientes, Argentina.
   Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Fac Agroind, RA-3700 Pcia R Saenz Pena, Chaco, Argentina.
RP Okulik, N, Natl Univ La Plata, Fac Ciencias Exactas, Dept Quim,
   CONICET,Ctr Quim Inorgan,CEQUINOR,UNLP, CC 962, RA-1900 La Plata,
   Argentina.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
   BADER RFW, 1979, J AM CHEM SOC, V101, P1389
   BADER RFW, 1979, J CHEM PHYS, V70, P6316
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   BADER RFW, 1981, REP PROG PHYS, V44, P893
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   BADER RFW, 1990, ATOMS MOL QUANTUM TH
   CREMER D, 1983, J AM CHEM SOC, V105, P5069
   ESTEVES PM, 1998, TOP CATAL, V6, P163
   FRISCH MJ, 1995, GAUSSIAN 94
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   MULLIKEN RS, 1955, J CHEM PHYS, V23, P1833
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   OLAH GA, 1973, J AM CHEM SOC, V95, P4960
NR 16
TC 6
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD OCT 21
PY 1999
VL 103
IS 42
BP 8491
EP 8495
PG 5
SC Chemistry, Physical
GA 251DT
UT ISI:000083429900019
ER

PT J
AU de Oliveira, AE
   Bruns, RE
TI CCl4: mean dipole moment derivatives and core electron binding energies
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE atomic polar tensor; density functional theory; CCl4
ID POLAR TENSORS; VIBRATIONAL INTENSITIES; INFRARED INTENSITIES;
   SUBSTITUTED METHANES
AB Atomic polar tensors for the carbon tetrachloride molecule are
   calculated from experimental fundamental infrared intensities, a normal
   coordinate transformation determined from observed fundamental
   frequency values and experimentally determined CCl bond lengths. Dipole
   moment derivative sign ambiguities were eliminated by comparing the
   alternative mathematical solutions obtained from the experimental data
   with results of Hartree-Fock, Moller-Plesset 2 and Density Functional
   Theory calculations using a 6 -31 + + G(d,p) basis set. Carbon and
   chlorine mean dipole moment derivatives of 1.043 +/- 0.022e and - 0.261
   +/- 0.006e, respectively, are determined from the preferred atomic
   polar tensors. These values are in excellent agreement with those
   obtained from the CCl4 Is carbon atom ionization energy using a simple
   potential model (1.081e and - 0.270e), from an electronegativity model
   proposed earlier (1.008e and - 0.252e) and from an electronegativity
   equalization model (1.066e and - 0.266e). (C) 1999 Elsevier Science
   B.V. AU rights reserved.
C1 Univ Estadual Campinas, Inst Quim, BR-13081970 Campinas, SP, Brazil.
RP Bruns, RE, Univ Estadual Campinas, Inst Quim, CP 6154, BR-13081970
   Campinas, SP, Brazil.
CR BAGUS PS, 1965, PHYS REV           A, V139, P619
   BASSI ABM, 1975, THESIS U ESTADUAL CA
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   FRISCH MJ, 1995, GAUSSIAN 94
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   TANABE K, 1970, SPECTROCHIM ACTA A, V26, P1469
NR 17
TC 5
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD SEP 20
PY 1999
VL 55
IS 11
BP 2215
EP 2219
PG 5
SC Spectroscopy
GA 240GD
UT ISI:000082816800007
ER

PT J
AU Ramos, JCS
   Hollauer, E
   Cardoso, SP
TI The vibration frequencies predicted by the AM1 model.
SO QUIMICA NOVA
LA Portuguese
DT Review
DE AM1; frequencies; CH; NH; OW; CO; CC frequencies
ID DENSITY-FUNCTIONAL THEORY; GROUND-STATES; MOLECULES; SPECTRA; MNDO
AB We analyse vibrational frequencies of 168 compounds with the AMI model
   concerning its experimentally observed gaseous frequencies. Stretching
   of CH, NH, OH and CO bonds, its related bending frequencies, and the CC
   frame movements ape the studied vibrations. The results show problems
   with the AMI vibrational splittings, Often symmetric stretching
   frequencies, like in CH3, CH2 and NN3, appear switched with the
   corresponding antisymmetrical ones. among the studied vibrations many
   stretchings are overestimated, while bendings oscillate around
   experimental values. Fluorine stretchings, NN, OO, CH, double and
   triples CG bonds and cyclic hydrocarbon breathing modes are always
   overestimated while torsions, umbrella modes and OH/SH stretching are,
   in average, underestimated. Graphical analysis shaw that compounds with
   the lowest molecular masses are the ones with the largest difference to
   the experimental values. From our results it is not possible to fit
   confortably the calculated frequencies by a simple linear relationship
   of the type, v(obs)=a*v(AM1). Better aggreement is obtained when
   different curves are adjusted for the stretching and bending modes, and
   when a complete linear function is used. Among our studies the best
   obtained statistical results are for CH, NN and OH. The conclusions
   obtained in this work will improve the AMI calculated frequencies
   leading to accurate results for these properties.
C1 Univ Fed Fluminense, Inst Quim, Dept Quim Fis, BR-24210150 Niteroi, RJ, Brazil.
   UnED, Escola Tecn Fed Quim, Secao Quim, BR-26530060 Nilopolis, RJ, Brazil.
RP Ramos, JCS, Univ Fed Fluminense, Inst Quim, Dept Quim Fis, Morro do
   Valonguinho S-N, BR-24210150 Niteroi, RJ, Brazil.
CR BRAND JCD, 1970, MATH COMPUT, V24, P647
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NR 32
TC 4
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0100-4042
J9 QUIM NOVA
JI Quim. Nova
PD SEP-OCT
PY 1999
VL 22
IS 5
BP 684
EP 692
PG 9
SC Chemistry, Multidisciplinary
GA 237BB
UT ISI:000082632800012
ER

PT J
AU Pliego, JR
   De Almeida, WB
   Celebi, S
   Zhu, ZD
   Platz, MS
TI Singlet-triplet gap, and the electronic and vibrational spectra of
   chlorophenylcarbene: A combined theoretical and experimental study
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID LASER FLASH-PHOTOLYSIS; O-H BOND; AB-INITIO; YLIDE FORMATION;
   PERTURBATION-THEORY; CARBENE FORMATION; EXCITED-STATES; SPIN STATES;
   KINETICS; CCL2
AB Minimum energy structures of singlet and triplet chlorophenylcarbene, a
   prototypical carbene, were computed. The singlet-triplet energy
   separation was predicted to be 7.84 and 7.70 kcal/mol at the
   UCCSD(T)/6-31+G* and QCISD(T)/6-31+G** levels of theory, respectively,
   after zero-point correction. This is slightly larger than that
   predicted by the CAS(6,6) (4.5 kcal/mol), local spin density
   approximation (5.6 kcal/mol), and the BLYP (7.3 kcal/mol) methods with
   the 6-31G* basis set reported by Trindle et al. The UV-vis and IR
   spectra of chlorophenylcarbene were analyzed with the aid of the
   CASPT2/CASSCF(10,10) and the B3LYP/6-31G* levels of theory,
   respectively. The UV-vis and IR spectra of chlorophenylcarbene were
   assigned on the basis of these calculations. The ab initio calculations
   predicted the existence of strong absorption bands in the UV and a weak
   band in the visible in good agreement with published spectra. The long
   (750 nm) wavelength band corresponds to electron promotion from the
   lone pair sigma (HOMO) to the pi* (LUMO). On the basis of the
   calculated harmonic frequencies, we cannot assign the 1244 and 1600
   cm(-1) IR bands observed in an argon matrix to chlorophenyl carbene.
   The most intense IR band (1225 cm(-1)) corresponds to the symmetric C-C
   stretch of the carbene and aromatic carbon. The asymmetric and
   symmetric C-C-Cl stretches are assigned to the bands observed at 847
   and 739 cm(-1), respectively.
C1 Univ Fed Minas Gerais, Dept Quim, Lab Quim Computac & Modelagem Mol, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
   Ohio State Univ, Newman & Wolfrom Lab Chem, Columbus, OH 43210 USA.
RP Platz, MS, Univ Fed Minas Gerais, Dept Quim, Lab Quim Computac &
   Modelagem Mol, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
CR ADMASU A, 1997, J PHYS CHEM A, V101, P3832
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NR 60
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD SEP 16
PY 1999
VL 103
IS 37
BP 7481
EP 7486
PG 6
SC Chemistry, Physical
GA 238JH
UT ISI:000082706800014
ER

PT J
AU Taft, CA
   Guimaraes, TC
   Pavao, AC
   Lester, WA
TI Adsorption and dissociation of diatomic molecules on transition-metal
   surfaces
SO INTERNATIONAL REVIEWS IN PHYSICAL CHEMISTRY
LA English
DT Review
ID ANGLE-RESOLVED PHOTOEMISSION; ELECTRON-ENERGY LOSS; TEMPERATURE
   PROGRAMMED DESORPTION; RAY PHOTOELECTRON DIFFRACTION;
   DENSITY-FUNCTIONAL THEORY; MORSE-POTENTIAL ANALYSIS; SULFUR MODIFIED
   FE(100); SINGLE-CRYSTAL SURFACE; SMALL NICKEL CLUSTERS; QUANTUM
   MONTE-CARLO
AB The interaction between transition-metal surfaces and simple diatomic
   molecules (CO, NO, H-2, N, and O-2) may lead to the breaking and making
   of chemical bonds and trigger important surface-catalysed reactions. We
   discuss the most common surface interaction and orientation models and
   consider the electronic structure of the transition metal, and the
   influence of structure, bonding and coordination of the diatomic
   molecule. We emphasize the importance of the tilted precursor in the
   dissociation of diatomic molecules on transition-metal surfaces.
C1 Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Pernambuco, Dept Quim Fundamental, BR-50960450 Recife, PE, Brazil.
   Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Rua Dr Xavier Sigaud 150,Urca,
   BR-22290180 Rio De Janeiro, Brazil.
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NR 449
TC 8
PU TAYLOR & FRANCIS LTD
PI LONDON
PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND
SN 0144-235X
J9 INT REV PHYS CHEM
JI Int. Rev. Phys. Chem.
PD APR-JUN
PY 1999
VL 18
IS 2
BP 163
EP 233
PG 71
SC Chemistry, Physical
GA 232ER
UT ISI:000082357600001
ER

PT J
AU Antonelli, A
   Justo, JF
   Fazzio, A
TI Point defect interactions with extended defects in semiconductors
SO PHYSICAL REVIEW B
LA English
DT Article
ID STACKING-FAULTS; PARTIAL DISLOCATIONS; MOLECULAR-DYNAMICS; AB-INITIO;
   SILICON; DIFFUSION; PSEUDOPOTENTIALS; MOBILITY; STATES; MODEL
AB We performed a theoretical investigation of the interaction of point
   defects (vacancy and self-interstitials) with an intrinsic stacking
   fault in silicon using ab initio total-energy calculations. Defects at
   the fault and in the crystalline environment display a different
   behavior, which is evidenced by changes in formation energy and
   electronic structure. The formation energies for the vacancy and the
   [110]-split interstitial are lower at the intrinsic stacking fault than
   those in the crystal, indicating that in nonequilibrium conditions,
   intrinsic stacking faults can act, together with other extended
   defects, as a sink for point defects, and also that in equilibrium
   conditions, there can be a higher concentration of such defects at the
   fault than that in bulk silicon. [S0163-1829(99)03631-0].
C1 Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
RP Antonelli, A, Univ Estadual Campinas, Inst Fis Gleb Wataghin,
   BR-13083970 Campinas, SP, Brazil.
CR ALEXANDER H, 1986, DISLOCATIONS SOLIDS, V7, P115
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   BOURGOIN J, 1983, POINT DEFECTS SEMI 2, V35
   BULATOV VV, 1995, PHILOS MAG A, V72, P453
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NR 28
TC 14
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD AUG 15
PY 1999
VL 60
IS 7
BP 4711
EP 4714
PG 4
SC Physics, Condensed Matter
GA 230FQ
UT ISI:000082241500061
ER

PT J
AU Esteves, PM
   Alberto, GGP
   Ramirez-Solis, A
   Mota, CJA
TI The alkane sigma-bond basicity scale revisited
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID THEORETICAL AB-INITIO; ELECTROSTATIC POTENTIALS; VIBRATIONAL
   FREQUENCIES; REVERSIBLE PROTONATION; ACTIVATION; SUPERACIDS; ISOBUTANE;
   DENSITY; CATIONS
AB The energy of the n-butonium and isobutonium cations was calculated. At
   the MP4/6-311++G**//MP2(fu)/6-31G** level, the C-carbonium ions were
   more stable than the H-carbonium ions. The results are in agreement
   with gas-phase data of n-butane and isobutane protonation but disagree
   with results in liquid superacid, where protonation of the tertiary C-H
   of isobutane is preferred over C-C protonation. Additional
   calculations, including the superacid moiety, revealed that the
   activation energy for C-C protonation is higher than the energy for
   attack at the tertiary C-H. This suggests that the sigma bond
   reactivity in the liquid superacid system is controlled by the
   activation energy for proton transfer, rather than by the intrinsic
   basisity of the bond. The higher stability of the C-carbonium relative
   to the H-carbonium ions was ascribed to a better charge distribution
   among the atoms and groups of the three center bond.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-2194990 Rio De Janeiro, Brazil.
   Univ Autonoma Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, Cidade
   Univ CT Bloco A, BR-2194990 Rio De Janeiro, Brazil.
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NR 30
TC 19
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD AUG 18
PY 1999
VL 121
IS 32
BP 7345
EP 7348
PG 4
SC Chemistry, Multidisciplinary
GA 230KH
UT ISI:000082250000010
ER

PT J
AU Duarte, HA
   Salahub, DR
   Haslett, T
   Moskovits, M
TI Fe(N-2)(n) (n=1-5): Structure, bonding, and vibrations from density
   functional theory
SO INORGANIC CHEMISTRY
LA English
DT Article
ID GENERALIZED GRADIENT APPROXIMATION; TRANSITION-METAL ATOMS;
   EXCHANGE-ENERGY; OPTIMIZATION; MOLECULES; FE(CO)5; BINDING; STATES
AB The Fe(N-2)(n) (n = 1-5) complexes have been studied with the
   LCGTO-KS-DF method. The structures containing end-on and side-on N2
   ligands have been fully optimized and the dissociation energies
   estimated. The ground states are predicted to be end-on complexes with
   the exception of n = 2. The vibrational analysis of all predicted
   ground states is reported. The effect of N-15 isotopic substitution on
   the vibrational frequencies has been estimated. Comparisons are made
   with the isoelectronic species Fe(CO)(n). The Fe-N-2 bonding has been
   discussed in terms of sigma donation and pi back-donation and the
   Mulliken population analysis. The predicted harmonic frequencies show
   that the infrared spectra of Fe(N-2)(4) and Fe(N-2)(5) are similar, and
   the two complexes could not be distinguished in nitrogen matrix
   experiments using infrared spectroscopy.
C1 Univ Montreal, Dept Chim, Montreal, PQ H3C 3J7, Canada.
   Univ Toronto, Dept Chem, Toronto, ON M5S 1A1, Canada.
   Univ Fed Minas Gerais, Dept Quim, BR-31270901 Belo Horizonte, MG, Brazil.
RP Duarte, HA, Natl Res Council Canada, Steacie Inst Mol Sci, 100 Sussex
   Dr, Ottawa, ON K1A 0R6, Canada.
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NR 41
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0020-1669
J9 INORG CHEM
JI Inorg. Chem.
PD AUG 23
PY 1999
VL 38
IS 17
BP 3895
EP 3903
PG 9
SC Chemistry, Inorganic & Nuclear
GA 230FF
UT ISI:000082240600022
ER

PT J
AU Klautau, AB
   Legoas, SB
   Muniz, RB
   Frota-Pessoa, S
TI Magnetic behavior of thin Cr layers sandwiched by Fe
SO PHYSICAL REVIEW B
LA English
DT Article
ID DENSITY-WAVE CHROMIUM; REAL-SPACE; FE/CR(001) SUPERLATTICES; FE/PD(001)
   SUPERLATTICES; AB-INITIO; MULTILAYERS; IMPURITIES; MAGNETORESISTANCE;
   POLARIZATION; INTERFACES
AB The magnetic behavior of thin layers of Cr in Fe/Cr/Fe(001) trilayers
   and superlattices is studied using the first principles self-consistent
   RS-LMTO-ASA (real space - linear muffin-tin orbital - atomic sphere
   approximation) method. The effects of lattice compression and interface
   mixing are investigated, and it is shown that they can cause large
   reductions of the Cr magnetic moments. [S0163-1829(99)12625-0].
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Fed Fluminense, Dept Fis, BR-24210340 Niteroi, RJ, Brazil.
RP Klautau, AB, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
CR ANDERSEN OK, 1975, PHYS REV B, V12, P3060
   ANDERSEN OK, 1984, PHYS REV LETT, V53, P2571
   ANDERSEN OK, 1985, HIGHLIGHTS CONDENSED
   BAIBICH MN, 1988, PHYS REV LETT, V61, P2472
   BEER N, 1984, ELECT STRUCTURE COMP
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   FERREIRA S, 1990, PHYS REV B, V41, P5627
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NR 45
TC 13
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD AUG 1
PY 1999
VL 60
IS 5
BP 3421
EP 3427
PG 7
SC Physics, Condensed Matter
GA 225VH
UT ISI:000081986300075
ER

PT J
AU Abraham, RJ
   Tormena, CF
   Rittner, R
TI Conformational analysis, Part 32. NMR, solvation and theoretical
   investigation of conformational isomerism in 3-fluorobutan-2-one and
   3,3-difluorobutan-2-one
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID VIBRATIONAL ASSIGNMENT; INTERNAL-ROTATION; ABINITIO CALCULATIONS;
   BARRIERS; STABILITY; CHLORIDE; SPECTRA; RAMAN
AB The solvent and temperature dependence of the H-1 and C-13 NMR spectra
   of 3-fluorobutan-2-one (FB) and 3,3-difluorobutan-2-one (DFB) are
   reported and the (4)J(HF), (1)J(CF) and (2)J(CF) couplings analysed
   using ab initio calculations and solvation theory. The solvent
   dependence of the IR spectra (carbonyl band) was also measured. In FB,
   ab initio theory at the 6-31G**/MP2 level gives only two energy minima
   for the cis (F-C-C=O 22 degrees) and trans (F-C-C=O 178 degrees)
   rotamers. The gauche rotamer was not a minimum in the energy surface.
   Assuming only the cis and trans forms, the observed couplings when
   analysed by solvation theory lead to the energy difference (E-cis -
   E-trans) between the cis and trans rotamers of 3.7 kcal mol(-1) in the
   vapour phase, decreasing to 2.5 kcal mol(-1) in CCl4 and to 0.1 kcal
   mol(-1) in DMSO. In all solvents used the trans rotamer is more stable
   than the cis. The vapour state energy difference compares very well
   with that calculated [3.67 kcal mol(-1) including a zero-point energy
   correction (ZPE)]. In DFB ab initio calculations at this level and also
   at (6-311G**/MP2 and ZPE) gave only one minimum in the potential energy
   surface corresponding to the cis rotamer (C-C-C=O 0 degrees). The H-1
   and C-13 NMR data, (4)J(HF), (1)J(CF) and (2)J(CF) couplings do not
   change with solvent confirming that there is only one rotamer in
   solution for DFB, in agreement with the ab initio calculations.
C1 Univ Liverpool, Dept Chem, Liverpool L69 3BX, Merseyside, England.
   Univ Estadual Campinas, Inst Quim, BR-13083970 Sao Paulo, Brazil.
RP Abraham, RJ, Univ Liverpool, Dept Chem, POB 147, Liverpool L69 3BX,
   Merseyside, England.
CR ABRAHAM RJ, 1974, INTERNAL ROTATION MO, CH13
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NR 21
TC 15
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD AUG
PY 1999
IS 8
BP 1663
EP 1667
PG 5
SC Chemistry, Organic; Chemistry, Physical
GA 224UR
UT ISI:000081918800016
ER

PT J
AU Nasar, RS
   Cerqueira, M
   Longo, E
   Leite, ER
   Varela, AJ
   Beltran, A
   Andres, J
TI Experimental and theoretical study on the piezoelectric behavior of
   barium doped PZT
SO JOURNAL OF MATERIALS SCIENCE
LA English
DT Article
ID MORPHOTROPIC PHASE-BOUNDARY; PERTURBED-ION; CRYSTALS; SEPARABILITY;
   SIMULATION; CERAMICS; MODEL; FILMS
AB An experimental and theoretical study of the ferroelectric and
   piezoelectric behavior of PZT doped with barium is presented. Ab initio
   perturbed ion calculations was carried out. The properties, such as
   remnant polarization, coercive field and the coupling factor of the PZT
   at constant sintering temperature was compared with the Zr4+/Ti4+ ions
   dislocation energy and the lattice interaction energy. An agreement
   between the experimental and theoretical results, with a decrease of
   the interaction energy and an inversion of the energy stability from
   tetragonal to rhombohedral phase was observed. (C) 1999 Kluwer Academic
   Publishers.
C1 Univ Fed Rio Grande Norte, Dept Quim, BR-59072970 Natal, RN, Brazil.
   UFSCar, Dept Quim, Lab Interdisciplinar Electroquim & Ceram, BR-13565 Sao Carlos, SP, Brazil.
   UNESP, Inst Quim, BR-14800900 Araraquara, SP, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello 12080, Spain.
RP Nasar, RS, Univ Fed Rio Grande Norte, Dept Quim, Caixa Postal 1662,
   BR-59072970 Natal, RN, Brazil.
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   JAFFE B, 1971, PIEZOELECTRIC CERAMI
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NR 44
TC 5
PU KLUWER ACADEMIC PUBL
PI DORDRECHT
PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS
SN 0022-2461
J9 J MATER SCI
JI J. Mater. Sci.
PD AUG
PY 1999
VL 34
IS 15
BP 3659
EP 3667
PG 9
SC Materials Science, Multidisciplinary
GA 222UZ
UT ISI:000081804900014
ER

PT J
AU Mota, FD
   Justo, JF
   Fazzio, A
TI Hydrogen role on the properties of amorphous silicon nitride
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID ELECTRONIC-STRUCTURE; MOLECULAR-DYNAMICS; SI; BETA-SI3N4; CHEMISTRY;
   DISILANE; SYSTEMS; FILMS; MODEL; BOND
AB We have developed an interatomic potential to investigate structural
   properties of hydrogenated amorphous silicon nitride. The interatomic
   potential used the Tersoff functional form to describe the Si-Si, Si-N,
   Si-H, N-H, and H-H interactions. The fitting parameters for all these
   interactions were found with a set of ab initio and experimental
   results of the silicon nitride crystalline phase, and of molecules
   involving hydrogen. We investigated the structural properties of
   unhydrogenated and hydrogenated amorphous silicon nitride through Monte
   Carlo simulations. The results show that depending on the nitrogen
   content, hydrogen has a different chemical preference to bind to either
   nitrogen or silicon, which is corroborated by experimental findings.
   Besides, hydrogen incorporation reduced considerably the concentration
   of undercoordinated atoms in the material, and consequently the
   concentration of dangling bonds. (C) 1999 American Institute of
   Physics. [S0021-8979(99)00616-7].
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   UFBa, Inst Fis, BR-40210340 Salvador, BA, Brazil.
RP Mota, FD, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR 1985, JANAF THERMOCHEMICAL
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   DYSON AJ, 1996, SURF SCI, V355, P140
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   GRUN R, 1979, ACTA CRYSTALLOGR B, V35, P800
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   TERSOFF J, 1989, PHYS REV B, V39, P5566
   TERSOFF J, 1991, PHYS REV B, V44, P12039
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NR 33
TC 12
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD AUG 15
PY 1999
VL 86
IS 4
BP 1843
EP 1847
PG 5
SC Physics, Applied
GA 221HD
UT ISI:000081720600010
ER

PT J
AU Hollauer, E
   Rocco, MLM
   Lopes, MCA
   de Souza, GGB
TI An ab initio study of the valence excitation of methyl methacrylate as
   observed by EELS
SO JOURNAL OF ELECTRON SPECTROSCOPY AND RELATED PHENOMENA
LA English
DT Article
DE methyl methacrylate; ab initio calculations; electron energy loss
   spectroscopy; valence-shell
ID SAC-CI THEORIES; EXCITED-STATES; ELECTRON; SPECTROSCOPY; MOLECULE; ACID
AB Ab initio calculations have been carried out in order to assign the
   main bands observed in a recent electron energy-loss study of the
   methyl methacrylate molecule. We employed the Dunning-Huzinaga
   double-zeta basis set for the early steps of geometry optimization but
   for the excited states Rydberg p functions were added to the conjugated
   heavy atoms. Both isomers, the s-cis and s-trans, had its vertical
   spectrum calculated in order to evaluate possible conformation effects
   on the VUV spectrum. SAC (Symmetry Adapted Cluster)-CI calculations
   pointed to the ethylenic pi orbital (8.99 eV) as the HOMO for s-cis
   while the n sigma orbital is predicted around 1 eV more stable. For the
   n pi orbital, although it was not possible to obtain a SAC-CI
   estimative, Koopmans' ionization potentials place it 1.68 eV more
   stable than the pi orbital. The lowest observable transitions have been
   assigned by SAC-CI calculations as to ethylenic pi-pi* (7.10 eV) and n
   pi-pi* (7.97 eV) for the cis isomer. For the trans isomer similar
   values were obtained (7.37 eV and 7.93 eV, respectively). Oscillator
   strengths have been calculated showing acceptable agreement with the
   experimental results. Previous assignments have been revised. (C) 1999
   Elsevier Science B.V. All rights reserved.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Fed Fluminense, Inst Quim, Dept Fisicoquim, BR-24020150 Niteroi, RJ, Brazil.
   Univ Fed Juiz de Fora, Dept Fis ICE, BR-36036330 Juiz de Fora, MG, Brazil.
RP Rocco, MLM, Univ Fed Rio de Janeiro, Inst Quim, Dept Fisicoquim, Cidade
   Univ,Ilha Fundao, BR-21949900 Rio De Janeiro, Brazil.
CR BAKER BL, 1995, J MOL STRUCT, V356, P95
   DUNNING TH, 1977, METHODS ELECT STRUCT
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   NAKATSUJI H, 1979, CHEM PHYS LETT, V67, P334
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   NAKATSUJI H, 1987, THEOR CHIM ACTA, V71, P201
   NAKATSUJI H, 1990, J CHEM PHYS, V93, P1865
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NR 16
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0368-2048
J9 J ELECTRON SPECTROSC RELAT PH
JI J. Electron Spectrosc. Relat. Phenom.
PD JUL
PY 1999
VL 104
IS 1-3
BP 31
EP 39
PG 9
SC Spectroscopy
GA 213ZP
UT ISI:000081303400002
ER

PT J
AU Bechepeche, AP
   Treu, O
   Longo, E
   Paiva-Santos, CO
   Varela, JA
TI Experimental and theoretical aspects of the stabilization of zirconia.
SO JOURNAL OF MATERIALS SCIENCE
LA English
DT Article
ID NEUTRON POWDER DIFFRACTION; X-RAY-ABSORPTION; ELECTRONIC-STRUCTURE;
   DEFECT STRUCTURE; 3 PHASES; ZRO2; SIMULATION; POLYMORPHS; CRYSTALS;
   DOPANTS
AB Using the Rietveld method, phases of ceria-doped zirconia, calcined at
   temperatures of 600 and 900 degrees C, were quantitatively analysed for
   different concentrations of ceria. The results show that the
   stabilization of zirconia depends on the dopant concentration and
   calcination temperature. Moreover, the theoretical calculation using
   the ab initio Hartree-Fock-Roothaan method indicates that the most
   stable phases for ceria-stabilized zirconia are cubic or tetragonal, in
   accordance with experimental results. (C) 1999 Kluwer Academic
   Publishers.
C1 UFSCAR, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   UNESP, Inst Quim, BR-14800900 Araraquara, SP, Brazil.
RP Bechepeche, AP, UFSCAR, Dept Quim, POB 676, BR-13565905 Sao Carlos, SP,
   Brazil.
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NR 30
TC 5
PU KLUWER ACADEMIC PUBL
PI DORDRECHT
PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS
SN 0022-2461
J9 J MATER SCI
JI J. Mater. Sci.
PD JUN 1
PY 1999
VL 34
IS 11
BP 2751
EP 2756
PG 6
SC Materials Science, Multidisciplinary
GA 211VD
UT ISI:000081181800036
ER

PT S
AU Ellis, DE
   Guenzburger, D
TI The discrete variational method in density functional theory and its
   applications to large molecules and solid-state systems
SO ADVANCES IN QUANTUM CHEMISTRY, VOL 34
SE ADVANCES IN QUANTUM CHEMISTRY
LA English
DT Review
DE density functional; electronic structure; molecules; solids
ID CHARGE-TRANSPORT-PROPERTIES; TRANSITION-METAL COMPLEXES; EFFECTIVE CORE
   POTENTIALS; EMBEDDED-ATOM-METHOD; ELECTRONIC-STRUCTURE;
   MOSSBAUER-SPECTROSCOPY; OPTICAL-PROPERTIES; SPIN-DENSITY; GAMMA-FE;
   CORRELATION ENERGIES
C1 Northwestern Univ, Dept Chem, Evanston, IL 60208 USA.
   Northwestern Univ, Ctr Mat Res, Evanston, IL 60208 USA.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
RP Ellis, DE, Northwestern Univ, Dept Chem, 2145 Sheridan Rd, Evanston, IL
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NR 177
TC 31
PU ACADEMIC PRESS INC
PI SAN DIEGO
PA 525 B STREET, SUITE 1900, SAN DIEGO, CA 92101-4495 USA
SN 0065-3276
J9 ADVAN QUANTUM CHEM
PY 1999
VL 34
BP 51
EP 141
PG 91
GA BN22K
UT ISI:000081150800002
ER

PT J
AU Da Silva, SC
   Franco, DW
TI Metastable excited state and electronic structure of [Ru(NH3)(5)NO](3+)
   and [Ru(NH3)(4)(-)(OH)NO](2+)
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE nitrosyl; ruthenium; DFT; metastable state; electronic structure
ID INFRARED-ABSORPTION SPECTRA; LIGHT; NITROPRUSSIDE; COMPLEXES
AB Light-induced metastable excited states of complexes
   [RuO(NH3)(5)NO](3+) and [Ru(NH3)(4)(OH)NO](2+) were investigated by
   FTIR spectroscopy. Both systems showed only one metastable excited
   state (MSI), with decay temperatures higher than 200 K. MSI formation
   occurs upon irradiation in the visible band (450-500 nm). According to
   ab initio density functional theory (DFT) molecular orbital analysis
   and ZINDO semi empirical C.I. calculation, MSI originates from the
   charge transfer transition 2b(2)(dxy) --> 7e(pi*NO). Since irradiation
   in regions other than the charge transfer transition causes fast
   depopulation of the metastable excited state, this light-induced decay
   is tentatively assigned to light absorption by the systems in the
   excited state. (C) 1999 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Sao Paulo, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
RP Franco, DW, Univ Fed Sao Paulo, Inst Quim Sao Carlos, Caixa Postal 780,
   BR-13560970 Sao Carlos, SP, Brazil.
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NR 22
TC 24
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JUL
PY 1999
VL 55
IS 7-8
BP 1515
EP 1525
PG 11
SC Spectroscopy
GA 209AY
UT ISI:000081025900021
ER

PT J
AU Segala, M
   Domingues, NS
   Livotto, PR
   Stefani, V
TI Heterocyclic dyes displaying excited-state intramolecular
   proton-transfer reactions (ESIPT): computational study of the
   substitution effect on the electronic absorption spectra of 2-(2
   '-hydroxyphenyl)-1,3-benzoxazole derivatives
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID AB-INITIO; PHOTOELECTRON-SPECTRA; TRANSIENT ABSORPTION; TRANSFER LASER;
   2-(2'-HYDROXYPHENYL)BENZOXAZOLE; SPECTROSCOPY; MODEL; MOLECULES
AB Semi-empirical molecular-orbital methods were used to simulate the
   electronic absorption spectra of a series of
   2-(2'-hydroxyphenyl)-1,3-benzoxazole derivatives, namely AMI and
   MNDO-PM3 for geometry optimization and INDO/S-CI and HAM/3 for
   spectroscopic features. Wavelengths of maximum absorption that agree
   better with experimental data were found when INDO/S-CI was applied to
   PM3-generated inputs. Chemical substitution redshifted the absorption
   spectrum of all the model compounds, a feature discussed based on the
   calculated energy levels of frontier orbitals and charge redistribution
   upon electronic excitation.
C1 Univ Fed Rio Grande Sul, Inst Quim, BR-91501970 Porto Alegre, RS, Brazil.
RP Stefani, V, Univ Fed Rio Grande Sul, Inst Quim, Av Bento Goncalves
   9500, BR-91501970 Porto Alegre, RS, Brazil.
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   WOOLFE GJ, 1983, CHEM PHYS, V77, P213
NR 45
TC 6
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD JUN
PY 1999
IS 6
BP 1123
EP 1127
PG 5
SC Chemistry, Organic; Chemistry, Physical
GA 208GD
UT ISI:000080981900012
ER

PT J
AU Mundim, KC
   Ellis, DE
TI Stochastic classical molecular dynamics coupled to functional density
   theory: Applications to large molecular systems
SO BRAZILIAN JOURNAL OF PHYSICS
LA English
DT Article
ID OPTIMIZATION
AB A hybrid approach is described, which combines stochastic classical
   molecular dynamics and first principles Density Functional theory to
   model the atomic and electronic structure of large molecular and
   solid-state systems. The stochastic molecular dynamics using
   Generalized Simulated Annealing (GSA) is based on the nonextensive
   statistical mechanics and thermodynamics. Examples are given of
   applications in linear-chain polymers, structural ceramics, impurities
   in metals, and pharmacological molecule-protein interactions.
C1 Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
   Northwestern Univ, Dept Chem, Evanston, IL 60208 USA.
   Northwestern Univ, Mat Res Ctr, Evanston, IL 60208 USA.
RP Mundim, KC, Univ Fed Bahia, Inst Phys, Salvador, BA, Brazil.
CR ALDER BJ, 1957, J CHEM PHYS, V27, P1208
   ALDER BJ, 1970, PHYS REV           A, V1, P18
   ALLINGER NL, 1982, ACS MONOGRAPH, V177
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   CEPERLEY D, 1986, SCIENCE, V231, P555
   CURADO EMF, 1991, J PHYS A, V24, P3187
   CURADO EMF, 1991, J PHYS A, V24, L69
   DELLANAY F, 1987, J MATER SCI, V22, P1
   DORFMAN S, 1996, COMPOS PART A-APPL S, V27, P697
   DORFMAN S, 1996, COMPOSITE INTERFACES, V3, P431
   ELLIS DE, 1995, ELECT DENSITY FUNCTI, P263
   ELLIS DE, 1998, IN PRESS P 9 CIMTEC
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   GANGOPADHYAY U, 1995, J MATER SCI, V30, P94
   GUO CK, UNPUB
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   MORET MA, 1998, J COMPUT CHEM, V19, P647
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   MUNDIM KC, 1998, PHYSICA A, V252, P405
   PASCUTTI PG, 1999, IN PRESS J COMP CHEM
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   TSALLIS C, 1988, J STAT PHYS, V52, P479
   TSALLIS C, 1996, PHYSICA A, V233, P395
NR 28
TC 6
PU SOCIEDADE BRASILEIRA FISICA
PI SAO PAULO
PA CAIXA POSTAL 66328, 05315-970 SAO PAULO, BRAZIL
SN 0103-9733
J9 BRAZ J PHYS
JI Braz. J. Phys.
PD MAR
PY 1999
VL 29
IS 1
BP 199
EP 214
PG 16
SC Physics, Multidisciplinary
GA 205RY
UT ISI:000080835400018
ER

PT J
AU Rodrigues, JAR
   de Oliveira, AP
   Moran, PJS
   Custodio, R
TI Regioselectivity of the nitration of phenol by acetyl nitrate adsorbed
   on silica gel
SO TETRAHEDRON
LA English
DT Article
DE nitration; nitric acid and derivatives; phenols; regioselection
ID NITROGEN-DIOXIDE; SUBSTITUTION; DERIVATIVES; CATALYSTS; AROMATICS;
   ESTERS; ACID
AB The reaction of phenol with acetyl nitrate in chloroform gives
   nitrophenol with an ortho/para ratio of 1.8. This ratio increase to
   13.3 when the reaction was carried out with acetyl nitrate pre-adsorbed
   on dry silica gel. Silica may be acting as a template to bring phenol
   close to acetyl nitrate by hydrogen bonds forming a ternary complex,
   which undergoes a six-center rearrangement to o-nitrophenol. The
   formation of this ternary complex is evaluated by ab initio molecular
   orbital calculation, (C) 1999 Elsevier Science Ltd. All rights reserved.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP Rodrigues, JAR, Univ Estadual Campinas, Inst Quim, BR-13083970
   Campinas, SP, Brazil.
CR CLARK JH, 1992, SUPPORTED REAGENTS P
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   TAYLOR R, 1990, ELECTROPHILIC AROMAT
   VOGEL A, 1978, TXB PRACTICAL ORGANI
NR 28
TC 16
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD OX5 1GB, ENGLAND
SN 0040-4020
J9 TETRAHEDRON
JI Tetrahedron
PD MAY 28
PY 1999
VL 55
IS 22
BP 6733
EP 6738
PG 6
SC Chemistry, Organic
GA 201DK
UT ISI:000080579600002
ER

PT J
AU Alves, HWL
   Alves, JLA
   Castineira, JLP
   Leite, JR
TI Lattice dynamics of boron nitride
SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED
   TECHNOLOGY
LA English
DT Article
DE boron nitride; LAPW method; lattice dynamics; frozen phonons; shell
   model
ID BN; SEMICONDUCTORS; BP
AB Using the density-functional theory within the full potential linear
   augmented plane-wave (FP-LAPW) method, we have calculated ab initio the
   equation of state and the principal phonon modes in cubic boron nitride
   (c-BN), including their pressure dependence and the amplitude of the
   eigendisplacements. A good agreement with the experiments is obtained,
   whenever a comparison is possible: in fact, most of the results are
   predictions. A ten-parameter valence overlap shell model (VOSM) was
   constructed and we obtained the phonon dispersion curves, elastic
   constants and effective charges. Our results were compared with
   calculated theoretical data for c-BN and for other III-V materials and
   we found that the lattice dynamics properties for cubic boron nitride
   is very close to those of diamond. (C) 1999 Elsevier Science S.A. All
   rights reserved.
C1 FUNREI, Dept Ciencias Nat, BR-36300000 Sao Koao Del Rei, MG, Brazil.
   Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
   Univ Sao Paulo, Inst Fis, Dept Fis Mat & Mecan, LNMS, BR-05389970 Sao Paulo, Brazil.
RP Alves, HWL, FUNREI, Dept Ciencias Nat, Praca D Helvecio 74, BR-36300000
   Sao Koao Del Rei, MG, Brazil.
CR ALVES HWL, 1992, J PHYS-CONDENS MAT, V4, P6603
   BILZ H, 1979, PHONON DISPERSION RE, P101
   BLAHA P, 1995, COMPUTER CODE WIEN95
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   CEPERLEY DM, 1981, PHYS REV B, V23, P5048
   COHEN ML, 1998, ELECT STRUCTURE OPTI
   EDGAR JH, 1994, PROPERTIES GROUP 3 N
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   KUNC K, 1983, AB INITIO CALCULATIO, P65
   KUNC K, 1985, ELECT STRUCTURE DYNA, P227
   MADELUNG O, 1982, LANDOLTBORNSTEIN N A, V17
   MADELUNG O, 1989, LANDOLTBORNSTEIN N A, V22
   PAINE RT, 1990, CHEM REV, V90, P73
   SANJURJO JA, 1983, PHYS REV B, V28, P4579
   WENTZCOVITCH RM, 1986, PHYS REV B, V34, P1071
   WENTZCOVITCH RM, 1987, PHYS REV B, V36, P6058
NR 18
TC 5
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0921-5107
J9 MATER SCI ENG B-SOLID STATE M
JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol.
PD MAY 6
PY 1999
VL 59
IS 1-3
BP 264
EP 267
PG 4
SC Materials Science, Multidisciplinary; Physics, Condensed Matter
GA 203CB
UT ISI:000080689000057
ER

PT J
AU Pliego, JR
   De Almeida, WB
TI A new mechanism for the reaction of carbenes with OH groups
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID LASER-FLASH-PHOTOLYSIS; CORRELATED MOLECULAR CALCULATIONS;
   GAUSSIAN-BASIS SETS; SPECTROSCOPIC DETECTION; YLIDE FORMATION;
   ETHYL-ACETATE; AB-INITIO; H BOND; FLUORENYLIDENE; INSERTION
AB The reaction pathway for the 2H(2)O + CCl2 reaction through a cyclic
   five-atom transition structure was studied using ab initio molecular
   orbital theory. The MP2 method in conjunction with the DZP basis set
   was used for geometry optimizations, and single point energy
   calculations were performed at MP2 and MP4 levels with the cc-pVDZ and
   cc-pVTZ basis sets. The solvent effect on the activation free energy
   was evaluated by Monte Carlo statistical mechanics calculations. The
   new mechanism has a high rate constant, and we predict a lifetime of
   seven nanoseconds for dichlorocarbene in aqueous solution. We have
   proposed that this mechanism occurs for the reaction of dichlorocarbene
   with water, and possibly may be involved in many reactions of carbenes
   with alcohols. We have also shown that it can explain the following
   experimental facts: (a) alteration of the product isotopic effect on
   addition of a second alcohol, (b) difference between product and
   kinetic isotopic effects, and (c) no linear dependence of the observed
   rate constant for carbene decay on alcohol concentration.
C1 Univ Fed Minas Gerais, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Minas Gerais, Dept Quim, ICEx, BR-31270901 Belo Horizonte, MG, Brazil.
RP Pliego, JR, Univ Fed Minas Gerais, Lab Quim Computac & Modelagem Mol,
   BR-31270901 Belo Horizonte, MG, Brazil.
CR ADMASU A, 1997, J PHYS CHEM A, V101, P3832
   BELT ST, 1993, J AM CHEM SOC, V115, P2200
   BETHELL D, 1971, J CHEM SOC B, P23
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
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   CHATEAUNEUF JE, 1991, J CHEM SOC CHEM 1015, P1437
   CURTISS LA, 1991, J CHEM PHYS, V94, P7221
   CURTISS LA, 1992, J CHEM PHYS, V96, P9030
   DUNNING TH, 1989, J CHEM PHYS, V90, P1007
   DUNNING TH, 1997, METHODS ELECT STRUCT
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   GONZALEZ C, 1990, J PHYS CHEM-US, V94, P5523
   GONZALEZ C, 1996, J AM CHEM SOC, V118, P5408
   GRILLER D, 1982, J AM CHEM SOC, V104, P5549
   JORGENSEN WL, 1985, J CHEM PHYS, V83, P3050
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   JORGENSEN WL, 1995, BOSS VERSION 3 5
   KIRMSE W, 1990, J AM CHEM SOC, V112, P6399
   KIRMSE W, 1993, J AM CHEM SOC, V115, P8918
   MOSS RA, 1988, TETRAHEDRON LETT, V29, P6417
   MOSS RA, 1989, ACCOUNTS CHEM RES, V22, P15
   NOBES RH, 1982, CHEM PHYS LETT, V89, P497
   OLSON DR, 1996, J PHYS ORG CHEM, V9, P759
   PLATZ MS, 1996, J PHYS ORG CHEM, V9, P689
   PLIEGO JR, 1996, CHEM PHYS LETT, V249, P136
   PLIEGO JR, 1996, J PHYS CHEM-US, V100, P12410
   PLIEGO JR, 1997, J CHEM PHYS, V106, P3582
   PLIEGO JR, 1997, J CHEM SOC FARADAY T, V93, P1881
   PLIEGO JR, 1997, J CHEM SOC PERK  NOV, P2365
   PLIEGO JR, 1998, CHEM PHYS LETT, V285, P121
   PLIEGO JR, 1998, J BRAZIL CHEM SOC, V9, P181
   SOUNDARARAJAN N, 1988, TETRAHEDRON LETT, V29, P3419
   VOLATRON F, 1983, J AM CHEM SOC, V105, P2359
   WANG JL, 1995, J AM CHEM SOC, V117, P5477
   WOON DE, 1993, J CHEM PHYS, V98, P1358
   YAMAGUCHI Y, 1993, J AM CHEM SOC, V115, P5790
   ZUPANCIC JJ, 1985, TETRAHEDRON, V41, P1471
NR 38
TC 23
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAY 20
PY 1999
VL 103
IS 20
BP 3904
EP 3909
PG 6
SC Chemistry, Physical
GA 200XK
UT ISI:000080565300015
ER

PT J
AU Ribeiro, MCC
   Almeida, LCJ
TI Fluctuating charge model for polyatomic ionic systems: A test case with
   diatomic anions
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MOLECULAR-DYNAMICS SIMULATIONS; SOLID ALKALI CYANIDES; FORCE-FIELDS;
   POLARIZABILITY; DENSITY; POTENTIALS; CRYSTALS; WATER
AB The fluctuating charge (FQ) model proposed by Rick et al. [(J. Chem.
   Phys. 101, 6141 (1994)] for molecular dynamics (MD) simulation of water
   is applied to a test case for polyatomic ionic systems. A system
   resembling alkali cyanide crystals, with two partial charges on the
   atomic sites of the polarizable anions, is considered. The need for
   charge fluctuation considerations in such a simple system is
   demonstrated by ab initio calculations of the partial charges in the
   cyanide ion with different orientations within a fixed octahedral
   environment of sodium ions. It is shown that the charge distributions
   in the crystal obtained with the FQ model are sensitive to changes in
   the environment in such a way that the anions become more polarizable
   as the lattice parameter increases. Conversely, the charge
   distributions shrink with increasing repulsive short-range
   interactions. Furthermore, a well-known polarization effect, that is,
   the reduction in the frequencies of longitudinal optic modes of the
   crystal, is also obtained with the FQ model. (C) 1999 American
   Institute of Physics. [S0021-9606(99)50423-6].
C1 Univ Sao Paulo, Inst Quim, Lab Espectroscopia Mol, BR-05599970 Sao Paulo, Brazil.
RP Ribeiro, MCC, Univ Sao Paulo, Inst Quim, Lab Espectroscopia Mol, CP
   26077, BR-05599970 Sao Paulo, Brazil.
CR ALLEN MP, 1987, COMPUTER SIMULATION
   ASTRAND PO, 1998, J PHYS CHEM A, V102, P7686
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
   BULJAN A, 1997, J PHYS CHEM A, V101, P1393
   CHELLI R, 1997, J CHEM PHYS, V107, P8041
   FERRARIO M, 1986, J CHEM PHYS, V84, P3975
   FRISCH MJ, 1995, GAUSSIAN 94
   FUMI FG, 1964, J PHYS CHEM SOLIDS, V25, P31
   GREADY JE, 1978, CHEM PHYS, V31, P467
   JACUCCI G, 1976, PHYS REV A, V13, P1581
   JEMMER P, 1998, J PHYS CHEM A, V102, P8377
   KATO T, 1993, J CHEM PHYS, V99, P3966
   KLEIN ML, 1983, J CHEM PHYS, V79, P2333
   LADD MFC, 1977, J CHEM SOC DA, V3, P220
   LESAR R, 1982, J CHEM PHYS, V77, P3682
   LIU YP, 1998, J CHEM PHYS, V108, P4739
   LYNDENBELL RM, 1983, MOL PHYS, V48, P1093
   MADDEN PA, 1991, J CHEM PHYS, V95, P1980
   MADDEN PA, 1993, J PHYS CONDENS MATT, V5, P2687
   MADDEN PA, 1996, CHEM SOC REV, V25, P339
   MATSUI M, 1998, J CHEM PHYS, V108, P3304
   MULLIKEN RS, 1955, J CHEM PHYS, V23, P1833
   RAPPE AK, 1991, J PHYS CHEM-US, V95, P3358
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   RICK SW, 1994, J CHEM PHYS, V101, P6141
   RICK SW, 1997, J PHYS CHEM B, V101, P10488
   SANGSTER MJL, 1976, ADV PHYS, V25, P247
   TISSEN JTWM, 1990, MOL PHYS, V71, P413
   WIBERG KB, 1992, J PHYS CHEM-US, V96, P671
NR 29
TC 11
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD JUN 15
PY 1999
VL 110
IS 23
BP 11445
EP 11448
PG 4
SC Physics, Atomic, Molecular & Chemical
GA 200CH
UT ISI:000080521200039
ER

PT J
AU Wilson, M
   Madden, PA
   Jemmer, P
   Fowler, PW
   Batana, A
   Bruno, J
   Munn, RW
   Monard, MC
TI Models of environmental effects on anion polarizability
SO MOLECULAR PHYSICS
LA English
DT Article
ID REFRACTIVE-INDEX; ALKALI-HALIDES; DIPOLE POLARIZABILITY; FLUORIDE-ION;
   CRYSTALS; PRESSURE; DERIVATIVES; PARAMETERS; SIMULATION; NABR
AB This paper deals with three different approaches to the representation
   of environmental effects on anion polarizability in cubic crystals of
   the stoichiometry MX, where M is an alkali metal and X is a halogen. Ab
   initio embedded cluster calculations of the variation in anion
   polarizability with pressure in a fixed crystal type are presented and
   compared with experiment. The results are then used in a scaled nb
   initio model used to predict further values for the pressure dependence
   of the in-crystal anion polarizability. This scaled model is compared
   with a fully empirical 'universal' model due to Batana el nl. based on
   polarizability change with ionic radius [1997, Molec. Phys., 92, 1029].
   The assumptions of the two models differ substantially and the central
   purpose of this paper is to contrast these differences and highlight
   their consequences for prediction. Although the empirical model
   typically overestimates the experimental pressure derivatives, and the
   nb initio calculations Somewhat underestimate them, it is shown that
   the assumption of incompressible cations in the scaled ab
   initio-derived model has a firmer physical basis than the empirical
   picture in which all ions are compressible.
C1 Univ Oxford, Phys & Theoret Chem Lab, Oxford OX1 3QZ, England.
   Univ Exeter, Dept Chem, Exeter EX4 4QD, Devon, England.
   Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Quim Inorgan Analit & Quim Fis, RA-1428 Buenos Aires, DF, Argentina.
   UMIST, Dept Chem, Manchester M60 1QD, Lancs, England.
   Univ Sao Paulo, Dept Ciencias Comp & Estatist, Inst Ciencias Matemat & Comp, BR-13560970 Sao Carlos, Brazil.
RP Wilson, M, Univ Oxford, Phys & Theoret Chem Lab, S Parks Rd, Oxford OX1
   3QZ, England.
CR AMOS RD, 1995, CADPAC CAMBRIDGE ANA
   BATANA A, 1997, MOL PHYS, V92, P1029
   BENDOW B, 1974, APPL OPTICS, V13, P2382
   DIERCKSEN GHF, 1981, CHEM PHYS LETT, V84, P390
   DIERCKSEN GHF, 1982, MOL PHYS, V47, P33
   FONTANELLA J, 1972, PHYS REV B, V6, P582
   FOWLER PW, 1983, MOL PHYS, V49, P913
   FOWLER PW, 1984, MOL PHYS, V53, P865
   FOWLER PW, 1984, PHYS REV B, V29, P1035
   FOWLER PW, 1984, PHYS REV B, V30, P6131
   FOWLER PW, 1985, MOL PHYS, V54, P129
   FOWLER PW, 1985, P ROY SOC LOND A MAT, V398, P377
   FOWLER PW, 1985, PHYS REV B, V31, P5443
   FOWLER PW, 1990, J CHEM SOC FARADAY T, V86, P1019
   HARDING JH, 1995, PHIL MAG LETT, V71, P113
   JEMMER P, 1998, J PHYS CHEM A, V102, P8377
   JOHANNSEN PG, 1997, PHYS REV B, V55, P6856
   JOHANNSEN PG, 1997, PHYS REV B, V55, P6865
   LAZZERETTI P, 1991, 167 CNR
   MADDEN PA, 1991, J CHEM PHYS, V94, P918
   MAHAN GD, 1980, SOLID STATE IONICS, V1, P29
   MAHAN GD, 1990, LOCAL DENSITY THEORY
   MULLER U, 1993, INORGANIC STRUCTURE
   PYPER NC, 1991, ADV SOLID STATE CHEM, V2, P223
   PYPER NC, 1997, J PHYS-CONDENS MAT, V9, P471
   SHANKER J, 1979, PHILOS MAG B, V39, P405
   SINGH AV, 1978, PHYSICA B, V94, P331
   SRINIVASAN R, 1973, PHYS STATUS SOLIDI B, V57, P757
   TESSMAN JR, 1983, PHYS REV, V49, P913
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   WERNER HJ, 1980, J CHEM PHYS, V73, P2319
NR 31
TC 6
PU TAYLOR & FRANCIS LTD
PI LONDON
PA ONE GUNPOWDER SQUARE, LONDON EC4A 3DE, ENGLAND
SN 0026-8976
J9 MOL PHYS
JI Mol. Phys.
PD MAY 20
PY 1999
VL 96
IS 10
BP 1457
EP 1467
PG 11
SC Physics, Atomic, Molecular & Chemical
GA 198LW
UT ISI:000080426500003
ER

PT J
AU Wang, F
   Tao, WA
   Gozzo, FC
   Eberlin, MN
   Cooks, RG
TI Synthesis of B- and P-heterocycles by reaction of cyclic acetals and
   ketals with borinium and phosphonium ions
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID RESONANCE MASS-SPECTROMETER; DICOORDINATED BORON CATIONS; GAS-PHASE;
   EFFICIENT DEPROTECTION; TRIMETHYL BORATE; ACYLIUM IONS; CHEMISTRY;
   AFFINITIES; REAGENT; BONDS
AB Tricoordinated cyclic boron cations result from gas-phase ion/molecule
   reactions of dicoordinated borinium ions with neutral acetals and
   ketals and thiazolidine. The reaction, which proceeds via initial
   cationic binding to a heteroatom followed by a consecutive ring-opening
   and ring-reclosing process, resembles the Eberlin transacetalization of
   acylium ions (Eberlin, M. N.; Cooks, R. G. Org. Mass Spectrom. 1993,
   28, 679). The cyclic structure of the tricoordinated boron cation is
   demonstrated by tandem mass spectrometry and further confirmed by
   comparison with authentic cyclic tricoordinated boron cations.; The
   five-membered cyclic boron cations dissociate by ethylene oxide loss to
   thus reform the reactant-dicoordinated borinium ion; the six-membered
   boron cations fragment instead by ethylene loss. Consistent with the
   proposed mechanism, the ion/molecule reaction efficiency falls in the
   order CH3OB+C2H5 > CH3OB+OCH3 much greater than CH3B+CH3; i.e., the
   higher the nucleophilicity of the borinium ion, the higher the reaction
   efficiency. A potential energy surface is calculated for the reaction
   of CH3OB+OCH3 with 2-methyl-1,3-dioxolane, and the reaction is found to
   be 43.3 kcal/mol exothermic due to initial formation of a strong B-O
   bond. The analogous reactivity displayed by phosphonium ions is also
   investigated by both experiment and ab initio calculations. In contrast
   to the borinium ions, the phosphonium ions exhibit higher
   regioselectivity for sulfur compared to nitrogen and oxygen. Finally,
   the present findings indicate that the reaction exothermicity and the
   regioselectivity are controlled by both the Lewis acidity of the
   reactant cations and the leaving ability of the released neutrals in
   the rate-limiting nucleophilic-induced recyclization step.
C1 Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
   State Univ Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Cooks, RG, Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
CR CARVALHO M, 1998, CHEM-EUR J, V4, P1161
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NR 58
TC 29
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD APR 30
PY 1999
VL 64
IS 9
BP 3213
EP 3223
PG 11
SC Chemistry, Organic
GA 194BA
UT ISI:000080171200043
ER

PT J
AU Jardim, IN
   Treu, O
   Martines, MAU
   Davolos, MR
   Jafelicci, M
   Pinheiro, JC
TI Ab initio study of high tridymite by the formalism generator coordinate
   Hartree-Fock
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE electronic properties of high tridymite; IR Spectrum of high tridymite;
   generator coordinate HF method
ID CONTRACTED GAUSSIAN-BASIS; SLATER-TYPE BASES; BASIS-SETS;
   DIATOMIC-MOLECULES; ATOMS H; EQUATIONS; VERSION; SYSTEMS; CHOICE
AB The Generator Coordinate Hartree-Fock (GCHF) Method is applied to
   generate extended 14s 8p and 17s 11p Gaussian basis sets for the atoms
   O and Si, respectively. The role of the weight functions in the
   assessment of the numerical integration range of the GCHF is shown. The
   Gaussian basis sets are contracted to [6s4p] O atom and [8s5p] Si atom
   by the Dunning's segmented contraction scheme. To evaluate the quality
   of our contracted [6s4p] and [8s5p] bases in molecular calculations we
   accomplish calculations of total and orbital energies in the
   Hartree-Fock-Roothaan method for O-2 and SiO molecules. We compare the
   results obtained with the our (14s 8p) and (17s 11p) bases sets with
   the of 6-311G basis and with values from the literature. The addition
   of one d polarization function in the silicon basis and its utilization
   with the basis for oxygen leads to the calculation of electronic
   properties and IR Spectrum of high tridymite in space group D-3d. (C)
   1999 Elsevier Science B.V. All rights reserved.
C1 Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, BR-66075110 Belem, Para, Brazil.
   UNESP, Inst Quim, BR-14801970 Araraquara, SP, Brazil.
RP Jardim, IN, Fed Univ Para, Ctr Ciencias Exatas & Nat, Dept Quim, CP
   11101, BR-66075110 Belem, Para, Brazil.
CR CUSTODIO R, 1992, CAN J CHEM, V70, P580
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NR 33
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 J MOL STRUC-THEOCHEM
JI Theochem-J. Mol. Struct.
PD MAY 18
PY 1999
VL 464
IS 1-3
BP 15
EP 21
PG 7
SC Chemistry, Physical
GA 192KC
UT ISI:000080076700004
ER

PT J
AU Bolivar-Marinez, LE
   Galvao, DS
   Caldas, MJ
TI Geometric and spectroscopic study of some molecules related to
   eumelanins. 1. Monomers
SO JOURNAL OF PHYSICAL CHEMISTRY B
LA English
DT Article
ID INTERMEDIATE NEGLECT; DIFFERENTIAL OVERLAP; MODEL POLYMERS; MELANINS;
   POLYMERIZATION; PARAMETERS; MECHANISM; STATES
AB We have carried out ab initio and semiempirical PM3 (parametric method
   3) and ZINDO (Zerner's intermediate neglect of differential overlap)
   calculations on neutral and charged 5,6-indolequinone and its reduced
   forms semiquinone and hydroquinone. These molecules are believed to
   compose the major part of the active material of eumelanin, a
   biological pigment present in illuminated and nonilluminated areas in
   living organisms. Our results show that these molecules can behave as
   electron accepters and that their electronic behavior is consistent
   with that of the semiconductor models proposed for melanins. The
   relationship between electronic behavior and biological functions is
   also addressed.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Estadual Campinas, UNICAMP, Inst Fis, BR-13081970 Campinas, SP, Brazil.
RP Caldas, MJ, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
CR BLOIS MS, 1964, BIOPHYS J, V4, P471
   BLOIS MS, 1969, SOLID STATE BIOPHYSI, P243
   BUCCI P, 1974, J AM CHEM SOC, V96, P1305
   CHEDEKEL MR, 1982, PHOTOCHEM PHOTOBIOL, V35, P881
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   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   GALVAO DS, 1988, J CHEM PHYS, V88, P4088
   GALVAO DS, 1989, PHYS REV LETT, V63, P786
   GALVAO DS, 1990, J CHEM PHYS, V92, P2630
   GALVAO DS, 1990, J CHEM PHYS, V93, P2848
   GIACOMONI PU, 1995, J PHOTOCH PHOTOBIO B, V29, P87
   JELLINGER K, 1971, ACTA NEUROPATHOL, V17, P553
   LONGUETHIGGINS HC, 1960, ARCH BIOCHEM BIOPHYS, V86, P231
   MASON HS, 1967, ADV BIOL SKIN, V3, P293
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   MCGINNESS JE, 1974, SCIENCE NY, V183, P853
   NAPOLITANO A, 1996, J MED CHEM, V39, P5192
   NICOLAUS RA, 1968, MELANINS
   PROCTOR P, 1974, J THEOR BIOL, V183, P853
   PROTA G, 1992, MELANINS MELANOGENES
   PULLMAN A, 1961, BIOCHIM BIOPHYS ACTA, V54, P384
   PULLMAN B, 1963, QUANTUM BIOCH
   RIDLEY J, 1973, THEOR CHIM ACTA, V32, P111
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NR 34
TC 18
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5647
J9 J PHYS CHEM B
JI J. Phys. Chem. B
PD APR 15
PY 1999
VL 103
IS 15
BP 2993
EP 3000
PG 8
SC Chemistry, Physical
GA 189YN
UT ISI:000079934100025
ER

PT J
AU Quintao, AD
   Vianna, RO
   Mohallem, JR
TI Resonating Valence Bond calculations on small anionic lithium clusters
SO EUROPEAN PHYSICAL JOURNAL D
LA English
DT Article
ID METALS
AB We recast the Resonating Valence Bond theory, first introduced bq Linus
   Pauling, in a nonorthogonal ab initio Valence Bond formalism and apply
   the method to study some properties of the anionic clusters Li-n(-) (2
   less than or equal to n less than or equal to 5). We show how to choose
   appropriate structures and orbitals, and also how to use the so-called
   metallic orbitals. The problem of interpreting the role of a specific
   Valence Bond structure looking up its weight in the general wave
   function is elucidated. Information about the excited states of the
   systems is obtained. The theory can make good qualitative predictions
   on the electronic behaviour of the clusters by using a wave function
   that is a linear combination of a small set of structures. Pauling's
   theory is shown to be quite appropriate for describing anionic systems.
   specially the small ones, where the loosely bounded electron largely
   influences the properties of the systems. We verify the preference of
   some clusters for linear geometries.
C1 UFMG, Inst Ciencias Exatas, Dept Fis, BR-30161970 Belo Horizonte, MG, Brazil.
RP Quintao, AD, UFMG, Inst Ciencias Exatas, Dept Fis, CP 702, BR-30161970
   Belo Horizonte, MG, Brazil.
CR BOUSTANI I, 1988, J CHEM PHYS, V88, P5657
   FRISCH MJ, 1993, GAUSSIAN 92 DFT REVI
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   MCWEENY R, 1992, METHODS MOL QUANTUM
   MOHALLEM JR, 1997, Z PHYS D ATOM MOL CL, V42, P135
   PAULING L, 1949, P ROY SOC LOND A MAT, V196, P343
   PAULING L, 1960, NATURE CHEM BOND
   PAULING L, 1984, J SOLID STATE CHEM, V54, P297
   PRESS WH, 1992, NUMERICAL RECIPES
   PULAY P, 1980, CHEM PHYS LETT, V73, P393
   QUINTAO AD, UNPUB EUR PHYS J D
   VIANNA RO, 1998, J CHEM PHYS, V109, P23
   WU W, 1994, J CHEM PHYS, V101, P4826
NR 17
TC 5
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1434-6060
J9 EUR PHYS J D
JI Eur. Phys. J. D
PD APR
PY 1999
VL 6
IS 1
BP 89
EP 97
PG 9
SC Physics, Atomic, Molecular & Chemical
GA 188UA
UT ISI:000079865800011
ER

PT J
AU Gozzo, FC
   Eberlin, MN
TI 2-pyridyl and 2-pyrimidyl cations: Stable o-hetarynium ions in the gas
   phase
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID MASS-SPECTROMETRY; ACYLIUM IONS; CHEMISTRY; BENZYNE
AB As indicated by high-level CBS-Q ab initio calculations, extensive
   overlap occurs in the 2-pyridyl and 2-pyrimidyl cations between the
   fully occupied sp(2) orbital of nitrogen and the adjacent, coplanar,
   and empty spl orbital of the C2-carbon. Such effective orbital overlap
   results in o-aryne-like structures with substantially shorter N-C+ bond
   lengths and N-C+ bond orders of 1.9-2.1. Therefore. the 2-pyridyl and
   2-pyrimidyl cations are best represented, and can be regarded as,
   o-hetarynium ions, being more stable than their positional,
   nonconjugated isomers by as much as 18-28 kcal/mol. The 4-pyrimidyl
   cation also displays characteristic o-hetarynium ion structure with
   substantial orbital overlap. However, the ion easily isomerizes by
   charge-induced ring opening, as indicated by both the calculations and
   the ion's lack of o-hetarynium-like reactivity. A high energy barrier
   of 62.8 kcal/mol hampers isomerization by H-ring walking of the
   3-pyridyl cation to the far more stable 2-pyridyl cation. For the
   related 2-furanyl, 2-thiophenyl, and 2-pyrrolyl cations, little or none
   of the extra orbital overlap occurs; hence, they display energies
   close, and structures similar, to those of their 3-isomers.
   Collision-induced dissociation of collisionally quenched precursor ions
   performed via triple-stage QqQqQ mass spectrometric (MSS) experiments
   confirms the greater stability of the 2-pyridyl and 2-pyrimidyl cations.
C1 State Univ Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, State Univ Campinas, Inst Chem, CP 6154, BR-13083970
   Campinas, SP, Brazil.
CR BORDEN WT, 1982, DIRADICALS
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   FORESMAN JB, 1993, EXPLORING CHEM ELECT
   FRIEDMAN L, 1969, J ORG CHEM, V34, P3089
   FRISCH MJ, 1995, GAUSSIAN94 REVISION
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   HEANEY H, 1962, CHEM REV, V62, P81
   HEHRE WJ, 1997, GUIDE MOL MECH MOL O
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   KAUFFMANN T, 1965, ANGEW CHEM INT EDIT, V4, P543
   KAUFFMANN T, 1971, ANGEW CHEM INT EDIT, V10, P20
   LAING JW, 1976, J AM CHEM SOC, V98, P660
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   MCLAFFERTY FW, 1989, WILEY NBS REGISTRY M
   MENDES MA, 1998, J AM CHEM SOC, V120, P7869
   MORAES LAB, 1996, J ORG CHEM, V61, P8726
   MORAES LAB, 1997, J ORG CHEM, V62, P5096
   NASH JJ, 1996, J AM CHEM SOC, V118, P11872
   OCHTERSKI JW, 1996, J CHEM PHYS, V104, P2598
   OHKURA K, 1989, TETRAHEDRON LETT, V30, P3433
   ROBERTS JD, 1956, J AM CHEM SOC, V78, P601
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   SPARRAPAN R, UNPUB
   SPARRAPAN R, 1998, J PHYS CHEM A, V102, P5189
   WITTIG G, 1955, ANGEW CHEM, V67, P348
NR 34
TC 13
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD APR 2
PY 1999
VL 64
IS 7
BP 2188
EP 2193
PG 6
SC Chemistry, Organic
GA 185UW
UT ISI:000079690100013
ER

PT J
AU Pliego, JR
   De Almeida, WB
TI A theoretical ab initio and Monte Carlo simulation study of the
   pyridine plus CCl2 reaction kinetics in the gas phase and in carbon
   tetrachloride solution using canonical flexible transition state theory
SO PHYSICAL CHEMISTRY CHEMICAL PHYSICS
LA English
DT Article
ID LASER FLASH-PHOTOLYSIS; POTENTIAL-ENERGY SURFACES; RATE CONSTANTS;
   CHEMICAL-REACTIONS; THERMAL-DECOMPOSITION; YLIDE FORMATION; PATH;
   DYNAMICS; ENERGETICS; HYDRATION
AB The potential energy surface for the pyridine + CCl2 reaction was
   studied at the ab initio MP4/6-311G(2df,p) //MP2/6-31G((*)) level of
   theory. The MP4/6-311G(2df,p) energies were evaluated by the additivity
   approximation E[MP4/6-311G(2df,p)] approximate to E[MP4/6-31G((*))] +
   E[MP2/6-311G(2df,p)] - E[MP2/6-31G((*))]. The first step proceeds by
   the addition of CCl2 to pyridine forming a dipolar ylide structure
   without an activation barrier. Then this species rearranges to a more
   stable biradical like ylide on a picosecond time scale. The generalized
   transition state for dipolar ylide formation occurs at a large center
   of mass distance between the species, and to calculate the reaction
   rate constant we have used canonical flexible transition state theory.
   The configurational integral was solved by Monte Carlo simulation and
   statistical perturbation theory, and the potential of mean force in the
   gas phase was obtained. This procedure was extended to the liquid phase
   by including the solvent coordinates in the configurational integral.
   The activation free energy in the gas phase and in carbon tetrachloride
   solution was calculated as 1.44 and 2.62 kcal mol(-1), respectively.
   The corresponding rate constants are 5.5 x 10(11) and 7.5 x 10(10) l
   mol(-1) s(-1). The last value is in reasonable agreement with the
   experimental result of 7 x 10(9) l mol(-1) s(-1) determined in
   isooctane solution.
C1 Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim
   Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR ADMASU A, 1997, J PHYS CHEM A, V101, P3832
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   COLLINS MA, 1996, ADV CHEM PHYS, V93, P389
   DUAN XF, 1995, J CHEM PHYS, V102, P6121
   DUNNING TH, 1988, SCIENCE, V240, P453
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   FUKUI K, 1981, ACCOUNTS CHEM RES, V14, P363
   GARRETT BC, 1979, J PHYS CHEM-US, V83, P1052
   GLASSTONE S, 1941, THEORY RATE PROCESSE
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   PLIEGO JR, 1998, CHEM PHYS LETT, V285, P11
   PLIEGO JR, 1999, IN PRESS J PHYS CH A
   ROBERT M, 1996, J PHYS CHEM-US, V100, P18426
   ROBERT M, 1998, J PHYS CHEM A, V102, P1507
   ROBERTSON SH, 1995, FARADAY DISCUSS, V102, P65
   ROBERTSON SH, 1995, J CHEM PHYS, V103, P2917
   SMITH SC, 1991, J CHEM PHYS, V95, P3404
   SMITH SC, 1993, J PHYS CHEM-US, V97, P7034
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NR 51
TC 7
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON RD,, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 1463-9076
J9 PHYS CHEM CHEM PHYS
JI PCCP Phys. Chem. Chem. Phys.
PD MAR 15
PY 1999
VL 1
IS 6
BP 1031
EP 1036
PG 6
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 182PX
UT ISI:000079508300013
ER

PT J
AU Borin, AC
   Serrano-Andres, L
   Fulscher, MP
   Roos, BO
TI A theoretical study of the electronic spectra of N-9 and N-7 purine
   tautomers
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID MOLECULAR-ORBITAL THEORY; AB-INITIO MP2; MATRIX-ISOLATION;
   EXCITED-STATES; GAS-PHASE; ADENINE; 2-CHLOROADENINE; SPECTROSCOPY;
   ABSORPTION
AB The complete active space (CAS) SCF method and multiconfigurational
   second-order perturbation theory (CASPT2) have been used to study
   electronic spectra of the N(9)H and N(7)H tautomers of purine. The
   calculations include vertical excitation energies, oscillator
   strengths, dipole moments, and transition moment directions in gas
   phase. In accord with experiment in nonpolar solvents, the two lowest
   pi --> pi* excited singlet valence states are predicted to be located
   at 4.7 and 5.1 eV. The latter is expected to shift to the red in
   aqueous solutions. A satisfactory interpretation of the electronic
   spectra above 5.5 eV is obtained if the experimental data are assumed
   to consist of the superposition of the spectra of the N(9)H and N(7)H
   tautomers, Two bands reported at 6.2 and 6.6 eV in nonpolar solvents
   match the corresponding B-1(b) and B-1(a) states of the N(9)H purine,
   respectively. The absence of the 6.2 eV-band in water can be explained
   by the predominance in aqueous solution of the N(7)H form, which has a
   weak B-1(b) transition at 6.4 eV overlapped by a strong B-1(a)
   transition at 6.6 eV.
C1 Chem Ctr Lund, Dept Theoret Chem, S-22100 Lund, Sweden.
   Univ Sao Paulo, Inst Quim, BR-05599970 Sao Paulo, Brazil.
   Univ Valencia, Dept Quim Fis, E-46100 Burjassot, Spain.
RP Fulscher, MP, Chem Ctr Lund, Dept Theoret Chem, POB 124, S-22100 Lund,
   Sweden.
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   BROO A, 1997, J PHYS CHEM A, V101, P3589
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NR 41
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAR 25
PY 1999
VL 103
IS 12
BP 1838
EP 1845
PG 8
SC Chemistry, Physical
GA 182JV
UT ISI:000079496600021
ER

PT J
AU Dias, LC
   Custodio, R
   Pessine, FBT
TI Theoretical studies of Nile Red by ab initio and semiempirical methods
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID CHARGE-TRANSFER; MO THEORY; FLUORESCENCE; STATES; SOLVENTS; HAM-3; AM1
AB Ab initio and semiempirical calculations were carried out for the Nile
   Red (NR) molecule to study the possible occurrence of the twisted
   intramolecular charge transfer process. The results showed that NR is
   planar in the ground state (using the CEP-31g basis set) with a high
   barrier to rotation of the diethylamine group by 90 degrees (0.334 and
   0.381 eV with AM1 and CEP-31g, respectively). CIS calculations showed
   that the charge transfer decreases after the twisting, in contrast to
   the TICT prediction. The solvatochromic effect was justified through
   the dipole moments calculated for the first excited state. (C) 1999
   Elsevier Science B.V. All rights reserved.
C1 Univ Fed Parana, Dept Quim, BR-81531970 Curitiba, Parana, Brazil.
   Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP Pessine, FBT, Univ Fed Parana, Dept Quim, BR-81531970 Curitiba, Parana,
   Brazil.
CR ASBRINK L, 1977, CHEM PHYS LETT, V52, P63
   ASBRINK L, 1977, CHEM PHYS LETT, V52, P72
   ASBRINK L, 1980, QCPE, V12, P292
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   DUTTA AK, 1996, CHEM PHYS LETT, V258, P369
   DUTTA AK, 1996, J PHOTOCH PHOTOBIO A, V93, P57
   FRISCH MJ, 1995, GAUSSIAN 94
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   STEVENS WJ, 1984, J CHEM PHYS, V81, P6026
NR 20
TC 8
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAR 26
PY 1999
VL 302
IS 5-6
BP 505
EP 510
PG 6
SC Physics, Atomic, Molecular & Chemical
GA 180CM
UT ISI:000079367600021
ER

PT J
AU Miwa, RH
   Schmidt, TM
TI DX centers in GaAs/Si-delta/AlAs heterostructure
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID DOPED GAAS; ELECTRONIC-STRUCTURE; ALXGA1-XAS ALLOYS; NEGATIVE-U; SI
AB Microscopic mechanisms of impurity spreading in GaAs/Si-delta/AlAs
   heterostructure have been investigated using an ab initio
   pseudopotential total energy calculation. Our results showed that
   silicon atoms can move from the delta-doped plane occupying
   interstitial positions, favored by the high doped concentration,
   forming DX centers. The silicon impurity position, out of the delta
   plane in the AlAs layers, presents an energetically stable
   configuration, and in the GaAs layers, presents a metastable
   configuration. As a consequence a silicon doping limit is reached due
   to the presence of localized deep states inside the band gap, when
   silicon atoms are in interstitial positions. (C) 1999 American
   Institute of Physics. [S0003-6951(99)01214-0].
C1 Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Miwa, RH, Univ Fed Uberlandia, Dept Ciencias Fis, CP 593, BR-38400902
   Uberlandia, MG, Brazil.
CR ASHWIN MJ, 1993, J APPL PHYS, V73, P633
   BRANDT O, 1991, APPL PHYS LETT, V59, P2730
   CHADI DJ, 1973, PHYS REV B, V8, P5747
   CHADI DJ, 1988, PHYS REV LETT, V61, P873
   GHOSH S, 1992, PHYS REV B, V46, P7533
   KLEINMAN L, 1982, PHYS REV LETT, V48, P1425
   MAGUIRE J, 1987, APPL PHYS LETT, V50, P516
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NR 20
TC 6
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD APR 5
PY 1999
VL 74
IS 14
BP 1999
EP 2001
PG 3
SC Physics, Applied
GA 182DM
UT ISI:000079483300023
ER

PT J
AU Zeng, Z
   Guenzburger, D
   Ellis, DE
TI Electronic structure, spin couplings, and hyperfine properties of
   nanoscale molecular magnets
SO PHYSICAL REVIEW B
LA English
DT Article
ID WATER OXIDATION CENTER; FERRITIN CORES; MAGNETIZATION; CLUSTERS;
   TRANSITION; COMPLEXES; MODELS; STATE; NANOMAGNET; EXCHANGE
AB First-principles self-consistent spin-polarized electronic structure
   calculations were performed for the nanoscale magnetic molecules
   Mn12O12(CH3COO)(16)(H2O)(4) and Fe11O6(OH)(6)(O2CPh)(15). The numerical
   discrete variational method was employed, within density-functional
   theory. Charges and magnetic moments were obtained for the atoms, as
   well as density of states diagrams, and charge- and spin-density maps.
   For Mn12O12(CH3COO)(16)(H2O)(4), values of the Heisenberg exchange
   parameters J were derived from the calculations; Mossbauer hyperfine
   parameters were calculated for Fe11O6(OH)(6)(O2CPh)(15) and compared to
   reported experimental values. [S0163-1829(99)05709-4].
C1 Acad Sinica, Inst Solid State Phys, Hefei 230031, Peoples R China.
   Ctr Brasileiro Pesquisas Fis, BR-22290180 Rio De Janeiro, Brazil.
   Northwestern Univ, Dept Phys & Astron, Evanston, IL 60208 USA.
   Northwestern Univ, Ctr Mat Res, Evanston, IL 60208 USA.
RP Zeng, Z, Acad Sinica, Inst Solid State Phys, Hefei 230031, Peoples R
   China.
CR AWSCHALOM DD, 1992, SCIENCE, V258, P414
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NR 45
TC 19
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD MAR 1
PY 1999
VL 59
IS 10
BP 6927
EP 6937
PG 11
SC Physics, Condensed Matter
GA 177WG
UT ISI:000079233600048
ER

PT J
AU Mathon, J
   Umerski, A
   Villeret, M
   Muniz, RB
TI Quantum oscillations of the spin density in magnetic multilayers
SO PHYSICAL REVIEW B
LA English
DT Article
ID NONMAGNETIC METALLIC LAYER; AB-INITIO CALCULATIONS; WELL STATES; FE/CU
   MULTILAYERS; EXCHANGE; CU; POLARIZATION; SPACER; CO/CU/CO(001); COPPER
AB An asymptotic stationary phase formula is derived for the oscillatory
   spin density induced in a nonmagnetic spacer sandwiched between two
   semi-infinite ferromagnets. It gives an explicit dependence for the
   polarization on the spacer layer thickness and on the distance from the
   ferromagnet-spacer interface. Both dependences are shown to oscillate
   with thr same periods as the exchange coupling between the
   ferromagnetic layers. The magnitude of the polarization is governed by
   the degree of confinement of carriers in the spacer quantum well and by
   the curvature of the spacer Fermi surface. The formula is applied to a
   Co/Cu/Co (001) trilayer described by tight-binding bands fitted to an
   ab initio band structure. Its validity is tested against a fully
   numerical calculation using the same band structure. As in the case of
   the oscillatory exchange coupling, the induced polarization is
   dominated by the contribution of the Cu Fermi surface neck extrema
   leading to a short period oscillation of 2.6 atomic planes. An
   interesting non-Ruderman-Kittel-Kasuya-Yosida initial decay of the
   induced polarization is discussed. [S0163-1829 (99)06309-2].
C1 City Univ London, Dept Math, London EC1V 0HB, England.
   Univ Fed Fluminense, Dept Fis, Niteroi, RJ, Brazil.
RP Mathon, J, City Univ London, Dept Math, London EC1V 0HB, England.
CR BLANC JAC, 1994, INTRO ELECT MAGNETIC, V1
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   DRCHAL V, 1996, PHYS REV B, V53, P15036
   EDWARDS DM, 1991, J MAGN MAGN MATER, V93, P85
   EDWARDS DM, 1991, J PHYS-CONDENS MAT, V3, P4941
   JIN QY, 1994, PHYS REV LETT, V72, P768
   KUDRNOVSKY J, 1994, PHYS REV B, V50, P16105
   KUDRNOVSKY J, 1996, PHYS REV B, V53, P5125
   LANG P, 1993, PHYS REV LETT, V71, P1927
   LANG P, 1996, PHYS REV B, V53, P9092
   MATHON J, 1992, J PHYS-CONDENS MAT, V4, P9873
   MATHON J, 1995, PHYS REV LETT, V74, P3696
   MATHON J, 1997, PHYS REV B, V56, P11797
   MORUZZI VL, 1978, CALCULATED ELECT PRO
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   ORTEGA JE, 1993, PHYS REV B, V47, P1540
   PAPACONSTANTOPO.DA, 1986, HDB BAND STRUCTURE E
   PARKIN SSP, 1990, PHYS REV LETT, V64, P2304
   PIZZINI S, 1995, PHYS REV LETT, V74, P1470
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   SEGOVIA P, 1996, PHYS REV LETT, V77, P3455
   UMERSKI A, UNPUB
   UMERSKI A, 1997, PHYS REV B, V55, P5266
NR 28
TC 9
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD MAR 1
PY 1999
VL 59
IS 9
BP 6344
EP 6350
PG 7
SC Physics, Condensed Matter
GA 178EX
UT ISI:000079254300054
ER

PT J
AU Schiavon, RP
   Barbuy, B
TI The temperature scale of metal-rich M giants based on TiO bands:
   Population synthesis in the near-infrared
SO ASTROPHYSICAL JOURNAL
LA English
DT Article
DE infrared : stars; molecular data; stars : atmospheres; stars :
   fundamental parameters; stars : late-type
ID OLD STELLAR POPULATIONS; GLOBULAR-CLUSTERS; OSCILLATOR-STRENGTHS; MODEL
   ATMOSPHERES; STARS; SPECTRA; SPECTROSCOPY; GALAXIES; SYSTEMS; LIBRARY
AB We have computed a grid of high-resolution synthetic spectra for cool
   stars (2500 < T-eff < 6000K) in the wavelength range 6000-10200
   Angstrom by employing an updated line list of atomic and molecular
   lines together with state-of-the-art model atmospheres. As a
   by-product, by fitting TiO band heads in spectra of well-known M
   giants, we have derived the electronic oscillator strengths of the TiO
   gamma', delta, epsilon, and phi systems. The derived oscillator
   strengths for the gamma' epsilon and phi systems differ from the
   laboratory and ab initio values found in the literature, but they are
   consistent with the model atmospheres and line lists employed,
   resulting in a good match to the observed spectra of M giants of known
   parameters. The behavior of TiO bands as a function of the stellar
   parameters T-eff log g and [Fe/H] is presented,and the use of TiO
   spectral indices in stellar population studies is discussed.
C1 Univ Sao Paulo, Inst Astron & Geofis, Dept Astron, BR-01060970 Sao Paulo, Brazil.
RP Schiavon, RP, CNPq, Observ Nacl, Dept Astron, Rua Gen Jose Cristino 77,
   BR-20921400 Rio De Janeiro, Brazil.
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   BARBUY B, 1999, UNPUJB
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   LUNDEVALL C, 1998, IN PRESS J MOL SPECT
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NR 50
TC 16
PU UNIV CHICAGO PRESS
PI CHICAGO
PA 5720 SOUTH WOODLAWN AVE, CHICAGO, IL 60637-1603 USA
SN 0004-637X
J9 ASTROPHYS J
JI Astrophys. J.
PD JAN 10
PY 1999
VL 510
IS 2
PN Part 1
BP 934
EP 943
PG 10
SC Astronomy & Astrophysics
GA 176NJ
UT ISI:000079157600039
ER

PT J
AU Tabata, A
   Lima, AP
   Teles, LK
   Scolfaro, LMR
   Leite, JR
   Lemos, V
   Schottker, B
   Frey, T
   Schikora, D
   Lischka, K
TI Structural properties and Raman modes of zinc blende InN epitaxial
   layers
SO APPLIED PHYSICS LETTERS
LA English
DT Article
ID ELECTRON-MICROSCOPY; ELASTIC-CONSTANTS; GAN; NITRIDE; FILMS; PHASE;
   ALN; SPECTROSCOPY
AB We report on x-ray diffraction and micro-Raman scattering studies on
   zinc blende InN epitaxial films. The samples were grown by molecular
   beam epitaxy on GaAs(001) substrates using a InAs layer as a buffer.
   The transverse-optical (TO) and longitudinal-optical phonon frequencies
   at Gamma of c-InN are determined and compared to the corresponding
   values for c-GaN. Ab initio self-consistent calculations are carried
   out for the c-InN c-GaN lattice parameters and TO phonon frequencies. A
   good agreement between theory and experiment is found. (C) 1999
   American Institute of Physics. [S0005-6951(99)00503-3].
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Campinas, SP, Brazil.
   Univ Gesamthsch Paderborn, FB Phys 6, D-33098 Paderborn, Germany.
RP Tabata, A, Univ Sao Paulo, Inst Fis, Caixa Postal 66318, BR-05315970
   Sao Paulo, Brazil.
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NR 21
TC 52
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0003-6951
J9 APPL PHYS LETT
JI Appl. Phys. Lett.
PD JAN 18
PY 1999
VL 74
IS 3
BP 362
EP 364
PG 3
SC Physics, Applied
GA 158TW
UT ISI:000078133800012
ER

PT J
AU Martins, LMMD
   Arbilla, G
   da Silva, EC
TI Unimolecular decomposition of formaldehyde: H2CO -> H-2+CO. Part I: Ab
   initio reaction path and variational transition state rate constants
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID PHOTOFRAGMENTATION DYNAMICS; PHOTO-DISSOCIATION; ENERGY; DISTRIBUTIONS;
   SURFACE; H2CO; PHOTODISSOCIATION; PHOTOCHEMISTRY; FEATURES; PRODUCT
AB Features of the ground-state potential energy surface of formaldehyde
   relevant to its dissociation to H-2 and CO were analyzed by means of ab
   initio calculations. The multiconfigurational self-consistent field
   (MCSCF) calculation gave a critical energy of 83.22 kcal/mol. Accurate
   structures are presented for H2CO(X(1)A(1)) and the saddle point. The
   reaction path was determined and the coupling between reaction
   coordinate and normal modes was analyzed along it, with two different
   levels of calculation (Hartree-Fock and MCSCF). Using these data, the
   transition state was located and the rate constants were calculated for
   the temperature range 200-4500 K using the generalized transition state
   theory.
C1 Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis, BR-21949900 Rio De Janeiro, Brazil.
RP Arbilla, G, Univ Fed Rio de Janeiro, Inst Quim, Dept Quim Fis,
   BR-21949900 Rio De Janeiro, Brazil.
CR BAKER J, 1986, J COMPUT CHEM, V7, P385
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NR 39
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD DEC 24
PY 1998
VL 102
IS 52
BP 10805
EP 10812
PG 8
SC Chemistry, Physical
GA 153MT
UT ISI:000077837400030
ER

PT J
AU Miwa, RH
TI Theoretical study of Si-Ge mixed dimers on Si(001) surfaces
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculation; growth process; pseudopotential; Si and
   Ge
ID DENSITY-FUNCTIONAL THEORY; ATOMIC-STRUCTURE; GROUND-STATE; GROWTH
AB We have studied the atomic geometry of mixed Si-Ge dimers on Si(001)
   surface, using first-principle total energy calculations. Our results
   indicate that the formation of mixed Si-Ge dimers, with the Si atoms in
   a "down" position and the Ge atoms in an "up" position, is an
   energetically more favourable surface topology with respect to the
   switching between Si and Ge atoms, where the Si atoms occupy an "up"
   position and the Ge atoms occupy a "down" position. The formation of
   pure Si-Si and Ge-Ge buckled dimers was also considered, and our
   results indicate that this structure is not energetically favourable
   against formation of mixed Si-Ge buckled dimers. For a 2 x 4 surface
   covered by mixed Si-Ge buckled dimers in an antiphase topology, our
   total energy calculations indicate that this configuration is
   energetically equivalent to the 2 x 4 surface in a semi-antiphase
   topology. (C) 1998 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Uberlandia, Dept Ciencias Fis, BR-38400902 Uberlandia, MG, Brazil.
RP Miwa, RH, Univ Fed Uberlandia, Dept Ciencias Fis, CR 593, BR-38400902
   Uberlandia, MG, Brazil.
EM hiroki@inga.ufu.br
CR CAR R, 1985, PHYS REV LETT, V55, P2471
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CHEN X, 1997, PHYS REV B, V55, R7319
   CHO JH, 1994, PHYS REV B, V49, P13670
   CHO JH, 1994, PHYS REV B, V50, P17139
   DABROWSKI J, 1992, APPL SURF SCI, V56, P15
   FONTES E, 1993, PHYS REV LETT, V70, P2790
   GONZE X, 1991, PHYS REV B, V44, P8503
   HOHENBERG P, 1964, PHYS REV B, V864, P136
   JENKINS SJ, 1997, SURF SCI, V377, P887
   KLEINMAN L, 1982, PHYS REV LETT, V48, P1425
   LIN DS, 1991, PHYS REV LETT, V67, P2187
   NEUGEBAUER J, 1992, PHYS REV B, V46, P16067
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   YEON HW, 1997, SURF SCI, V381, L533
NR 18
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD NOV 27
PY 1998
VL 418
IS 1
BP 55
EP 63
PG 9
SC Chemistry, Physical
GA 148VM
UT ISI:000077554300014
ER

PT J
AU Morgon, NH
   Riveros, JM
TI Calculation of the proton and electron affinity of simple Ge-containing
   species using density functional theory
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID ION-MOLECULE REACTIONS; GAS-PHASE ACIDITIES; DISSOCIATION-ENERGY;
   ATOMS; BOND; TETRAMETHYLGERMANE; APPROXIMATION; METHYLGERMANE; ANIONS;
   GEH5+
AB Basis sets developed using the generator coordinate method and a
   pseudopotential have been adapted to density functional theory to
   calculate the proton affinity of GeH4, GeH3-, GeF3-, CH3GeH2-, and
   Ge(OH)(3)(-) and the electron affinity of .GeH3 and .GeF3. The proton
   affinity of GeH4 is calculated to be 673.9 kJ mol(-1) at 298 K, while
   values for GeH3- (1505.0 kJ mol(-1)) and CH3GeH2- (1529.0 kJ mol(-1))
   are in excellent agreement with experimental values. The electron
   affinity of .GeF3 is predicted to be in the range of 3.5-3.7 eV by
   calculations using different functionals and ab initio methods. The
   present calculations reveal that the B3P86 method can yield proton
   affinities comparable to those obtained with other high-quality methods
   but consistently overestimates electron affinities of simple Ge
   radicals.
C1 UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
   Univ Sao Paulo, Inst Chem, BR-05599970 Sao Paulo, Brazil.
RP Riveros, JM, UNICAMP, Inst Chem, Caixa Postal 6154, BR-13083970
   Campinas, SP, Brazil.
EM jmrnigra@quim.iq.usp.br
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   MOC J, 1990, CHEM PHYS LETT, V173, P557
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   OPERTI L, 1993, ORGANOMETALLICS, V12, P4509
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   XAVIER LA, INT J MASS SPECTROM
NR 42
TC 12
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD DEC 10
PY 1998
VL 102
IS 50
BP 10399
EP 10403
PG 5
SC Chemistry, Physical
GA 148QP
UT ISI:000077543700028
ER

PT J
AU Araujo, RCMU
   Ramos, MN
TI An ab initio MP2 study of HCN-HX hydrogen bonded complexes
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE ab initio MP2; binding energy; infrared parameters; hydrogen bond
ID INFRARED-SPECTROSCOPY; MOLECULAR-PROPERTIES; ROTATIONAL SPECTRUM;
   PERTURBATION-THEORY; GAS-PHASE; ACETYLENE; INTENSITIES; ENERGIES;
   ABINITIO; DIMER
AB An ab initio MP2/6-311++G* * study has been performed to obtain
   geometries, binding energies and vibrational properties of HCN-HX
   H-bonded complexes with X = F, Cl, NC, CN and CCH. These MP2/6-311++G**
   results have revealed that: (i) the calculated H-bond lengths are in
   very good agreement with the experimental ones; (ii) the H-bond
   strength is associated with the intermolecular charge transfer and
   follows the order: HCN-HNC approximate to HCN-HF > HCN-HCl approximate
   to HCN-HCN > HCN-HCCH; (iii) BSSE correction introduces an average
   reduction of 2.4 kJ/mol on the MP2/6-311++G** binding energies, i.e.
   11% of the uncorrected binding energy; (iv) the calculated zero-point
   energies reduce the stability of these complexes and show a good
   agreement with the available experimental values; (v) the H-X
   stretching frequency is shifted downward upon H-bond formation. This
   displacement is associated with the H-bond length; (vi) The more
   pronounced effect on the infrared intensities occurs with the H-X
   stretching intensity. It is much enhanced after complexation due to the
   charge-flux term; (vii) the calculated intermolecular stretching
   frequencies are in very good agreement with the experimental ones; and,
   finally, (viii) the results obtained for the HCN-HX complexes follow
   the same profile as those found for the acetylene-HX series but, in the
   latter case, the effects on the properties of the free molecules due to
   complexation are less pronounced than those in KCN-HX.
C1 Univ Fed Paraiba, Dept Quim, BR-58036300 Joao Pessoa, Paraiba, Brazil.
   Univ Fed Pernambuco, Dept Quim Fundamental, BR-50739901 Recife, PE, Brazil.
RP Araujo, RCMU, Univ Fed Paraiba, Dept Quim, BR-58036300 Joao Pessoa,
   Paraiba, Brazil.
CR ARAUJO RCM, UNPUB J CHEM SOC F2
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NR 39
TC 10
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PD SEP-OCT
PY 1998
VL 9
IS 5
BP 499
EP 505
PG 7
SC Chemistry, Multidisciplinary
GA 148FR
UT ISI:000077494800015
ER

PT J
AU Duarte, HA
   Paniago, EB
   Carvalho, S
   De Almeida, WB
TI Interaction of N-hydroxyacetamide with vanadate: A density functional
   study
SO JOURNAL OF INORGANIC BIOCHEMISTRY
LA English
DT Article
DE vanadate; N-hydroxyacetamide; density functional; metal-ligand
   interaction
ID HYDROXAMIC ACIDS; AB-INITIO; APPROXIMATION; OPTIMIZATION; ENERGY; BOND;
   MO
AB The interaction between N-hydroxyacetamide (HL) and vanadate (VO3-) has
   been theoretically studied using density functional theory. All
   possible tautomers and conformations of two complexes formed have been
   fully optimized and vibrational analysis performed. From reported
   experimental results these two complexes have been shown to be in
   equilibrium in acidic aqueous solution: VO2LH2O and VO2(HL)L. The
   pentacoordinated VO2LH2O species having an intramolecular proton
   transferred from the coordinating H2O ligand to the oxo group, is the
   most stable. Seemingly, the most stable hexacoordinated VO2(HL)L
   species also has an oxo group protonated. Based on the analysis of the
   dipole moments of the species, the solvent effects within the continuum
   model are unlikely to change the relative stabilities of the different
   tautomers and conformers. The experimental infra-red spectrum of the
   VO2LH2O species has been measured and compared directly to the
   calculated frequencies. The most important peaks have been assigned to
   the corresponding normal modes. From the Mulliken population analysis,
   it is shown that the net charge on the vanadium atom and the oxygens
   surrounding the metal center are similar in the two species. The
   different coordination numbers may explain the differences of the
   reported V-51 NMR chemical shifts exhibited by these two species. (C)
   1998 Elsevier Science Inc. All rights reserved.
C1 Lab Quim Computac & Modelagem Mol, Belo Horizonte, MG, Brazil.
   Univ Fed Minas Gerais, ICEx, Dept Quim, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Fed Ouro Preto, ICEB, Dept Quim, Ouro Preto, MG, Brazil.
RP Duarte, HA, Lab Quim Computac & Modelagem Mol, Belo Horizonte, MG,
   Brazil.
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   FITZPATRICK NJ, 1989, POLYHEDRON, V8, P2255
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NR 31
TC 9
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010 USA
SN 0162-0134
J9 J INORG BIOCHEM
JI J. Inorg. Biochem.
PD OCT
PY 1998
VL 72
IS 1-2
BP 71
EP 77
PG 7
SC Chemistry, Inorganic & Nuclear; Biochemistry & Molecular Biology
GA 147RA
UT ISI:000077578800009
ER

PT J
AU Marquardt, R
   Quack, M
TI Global analytical potential hypersurfaces for large amplitude nuclear
   motion and reactions in methane. I. Formulation of the potentials and
   adjustment of parameters to ab initio data and experimental constraints
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID MONTE-CARLO CALCULATIONS; TRANSITION-STATE THEORY; DIPOLE-MOMENT
   FUNCTION; ADIABATIC CHANNEL MODEL; VIBRATION ENERGY-LEVELS; THERMAL
   RATE-CONSTANT; QUARTIC FORCE-FIELD; CH CHROMOPHORE; H+CH3->CH4
   RECOMBINATION; CORRELATED WAVEFUNCTIONS
AB Analytical representations of the global potential energy surface of
   XYn molecules are developed and applied to model the potential surface
   of methane in the electronic ground state. The generic analytical
   representation allows for a compact, robust, and flexible description
   of potentials fur XYn systems irrespective of the specific nature of
   the atomic interactions. The functions are global in that structures
   near several minima of the potential hypersurface as well as saddle
   points and dissociation limits are well described. Clusters of atoms
   Y-n can be represented as well by this type of function. Care is taken
   to implement conditions resulting from the symmetric group S-n and to
   construct positive definite bilinear forms of special functional forms
   of certain coordinates (such as bond lengths and bond angles), in order
   to avoid artifacts in exceptional ranges of the potential hypersurface.
   These special functional forms include intrinsic, symmetry allowed
   couplings between coordinates such as bending and stretching. We
   include linear potential terms in bond angle coordinates, which result
   in effectively quadratic potential terms for highly symmetric
   structures. True logical multidimensional 01-switching functions
   S-sw(r) of bond lengths r are used to interpolate between limiting
   ranges in the hypersurface. The particular form S-sw(r) similar to
   exp(-(r(sw)/r)(nsw)) allows us to describe the potential as a multipole
   expansion representation in the lirlit of large r(ix). In the
   application to methane, first the representations are fitted to data
   from high level ab initio calculations using multireference
   configuration interaction techniques. Additional conditions which help
   to improve the description of experimental data are considered during
   the fit. Typically, these conditions involve some parameters or
   parameter groups and refer to the equilibrium geometry and harmonic
   force field. Other constraints apply to the energies of dissociation
   channels. We describe the model potentials METPOT 1 to METPOT 4 in the
   present work. (C) 1998 American Institute of Physics.
   [S0021-9606(98)01045-9].
C1 ETH Zentrum, Chem Phys Lab, CH-8092 Zurich, Switzerland.
RP Marquardt, R, Univ Fed Rio Grande Sul, Inst Fis, BR-91501970 Porto
   Alegre, RS, Brazil.
CR *AIP, JCPSA6109010845 AIP
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NR 97
TC 20
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD DEC 22
PY 1998
VL 109
IS 24
BP 10628
EP 10643
PG 16
SC Physics, Atomic, Molecular & Chemical
GA 148QB
UT ISI:000077542400011
ER

PT J
AU Almeida, AL
   Martins, JBL
   Taft, CA
   Longo, E
   Lester, WA
TI Theoretical study of water coverage on MgO surfaces
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE water coverage; MgO; ab initio; adsorption; surface
ID TEMPERATURE-PROGRAMMED DESORPTION; CORE POTENTIAL DEPENDENCE; LARGE
   CLUSTER-MODELS; 0001 ZNO SURFACES; MAGNESIUM-OXIDE; MOLECULAR CLUSTER;
   MGO(100) SURFACE; BASIS-SET; ADSORPTION; METHANE
AB Ab initio and semiempirical calculations have been performed on an
   (MgO)(16) cluster model in order to study the effects of water coverage
   on pure MgO (100) surfaces. The geometries of various adsorbed water
   molecules have been optimized and the binding energies, charge
   transfer, and preferential sites of interaction analyzed. We have used
   Mulliken and natural bond population analysis methods in order to
   analyze charge distributions and the direction of charge transfer
   processes. We have also investigated the effects of low and high
   coverage on energy gaps, density of states, self-consistent field (SCF)
   orbital energies, and stretching frequencies. (C) 1999 John Wiley &
   Sons, Inc.
C1 Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA.
   Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estatist, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
RP Lester, WA, Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci,
   Berkeley, CA 94720 USA.
CR ALMEIDA AL, 1996, 23 QTEL QUIM TEOR EX
   ALMEIDA AL, 1996, 4 WORLD C THEOR OR C
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   DURIEZ C, 1990, SURF SCI, V230, P123
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   GREENLAND DJ, 1978, CHEM SOIL CONSTITUEN
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   JONES CF, 1984, J CHEM SOC FARAD T 1, V80, P2609
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   KNOZINGER E, 1993, SURF SCI, V290, P388
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   KURODA Y, 1988, J CHEM SOC F1, V84, P2421
   LEMBERTON JL, 1984, J CATAL, V89, P69
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   LONGO E, 1985, LANGMUIR, V1, P456
   LONGO E, 1987, HIGH TECH CERAMICS, P399
   MARTINS JBL, 1994, J MOL STRUCT, V303, P19
   MARTINS JBL, 1995, THEOCHEM, V330, P301
   MARTINS JBL, 1995, THEOCHEM, V330, P347
   MARTINS JBL, 1996, INT J QUANTUM CHEM, V57, P861
   MARTINS JBL, 1996, THEOCHEM-J MOL STRUC, V363, P249
   MCCARTHY MI, 1996, J PHYS CHEM-US, V100, P16990
   ONISHI H, 1987, SURF SCI, V191, P479
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   PAVAO AC, 1995, SURF SCI, V323, P40
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NR 48
TC 10
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD JAN 15
PY 1999
VL 71
IS 2
BP 153
EP 165
PG 13
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA 147MW
UT ISI:000077572100004
ER

PT J
AU Prudente, FV
   Acioli, PH
   Neto, JJS
TI The fitting of potential energy surfaces using neural networks:
   Application to the study of vibrational levels of H-3(+)
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID QUANTUM MONTE-CARLO; DIATOMIC-MOLECULES; MOMENT SURFACES; H-3+
AB A back-propagation neural network is utilized to fit the potential
   energy surfaces of the H-3(+) ion, using the ab initio data points of
   Dykstra and Swope, and the Meyer, Botschwina, and Burton ab initio data
   points. We used the standard back-propagation formulation and have also
   proposed a symmetric formulation to account for the symmetry of the
   H-3(+) molecule. To test the quality of the fits we computed the
   vibrational levels using the correlation function quantum Monte Carlo
   method. We have compared our results with the available experimental
   results and with results obtained using other potential energy
   surfaces. The vibrational levels are in very good agreement with the
   experiment and the back-propagation fitting is of the same quality of
   the available potential energy surfaces. (C) 1998 American Institute of
   Physics. [S0021-9606(98)30644-3].
C1 Univ Brasilia, Inst Fis, BR-70910900 Brasilia, DF, Brazil.
RP Prudente, FV, Univ Brasilia, Inst Fis, CP 04455, BR-70910900 Brasilia,
   DF, Brazil.
EM fred@fis.unb.br
CR ACIOLI PH, IN PRESS J MOL STRUC
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   DYKSTRA CE, 1979, J CHEM PHYS, V70, P1
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   MACKAY DJC, 1992, NEURAL COMPUT, V4, P415
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NR 31
TC 14
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD NOV 22
PY 1998
VL 109
IS 20
BP 8801
EP 8808
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 139QE
UT ISI:000077039900010
ER

PT J
AU Wang, F
   Ma, S
   Wong, P
   Cooks, RG
   Gozzo, FC
   Eberlin, MN
TI Gas phase agostic bonding in pyridine SiFn+ (n = 1, 3) cluster ions
   investigated by the kinetic method
SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY
LA English
DT Article
DE kinetic method; agostic bonding; cluster ions; SiF3+; SiF+; Lewis
   acidity
ID MOLECULAR-ORBITAL METHODS; CHARGE-TRANSFER REACTIONS; MS(3)
   MASS-SPECTROMETRY; TRANSITION-METAL BONDS; BASIS SETS; AFFINITIES;
   THERMOCHEMISTRY; SILICON; DISSOCIATION; CATION
AB Loosely bonded cluster ions, Py1SiF3+Py2 and Py1SiF+Py2, where Py-1 and
   Py-2 represent substituted pyridines, are formed by ion/molecule
   reactions between mass-selected SiF3+ or SiF+ and a mixture of
   pyridines. The clusters are hown to have loosely bound symmetric
   structures by MS3 experiments and ab initio calculations. The
   SiF3+/pyridine dimer is shown to have a trigonal bipyrimidal structure.
   Relative SiF3+ and SiF+ affinities of the constituent pyridines are
   measured by the kinetic method, and excellent linear correlations with
   the proton affinity of meta- and para-substituted pyridines are
   observed. Gas-phase stereoelectronic parameters (S-k) for SiF3+ SiF+
   are also experimentally measured and show that the binding of the
   ortho-substituted pyridines is governed by two opposing effects, steric
   hindrance and agostic bonding. Agostic bonding of the form C-H --- Si+,
   is evident in the SiF+ system, just as it is in the corresponding
   SiCl+/pyridine dimers. On the other hand, steric hindrance plays a key
   role in weakening the strength of the interaction of the central SiF3+
   ion and the ortho-substituted pyridines compared with that in
   SiF+-bound cluster ions. The relatively larger Lewis acidity of
   fluorinated siliconium ions compared with the corresponding chlorinated
   species shortens the Si-N bond and makes overall steric effects larger
   in the SiFn+ (n = 1, 3) systems than in the SiCln+ (n = 1, 3) systems.
   The potential application of the kinetic method in recognizing agostic
   bonding in transition metal systems in the gas phase is also
   demonstrated in this study. (Int J Mass Spectrom 179/180 (1998)
   195-205). (C) 1998 Elsevier Science B.V.
C1 Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
   State Univ Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Cooks, RG, Purdue Univ, Dept Chem, W Lafayette, IN 47907 USA.
CR ABBOUD JLM, 1996, J AM CHEM SOC, V118, P1126
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   CAMPBELL S, 1995, J AM CHEM SOC, V117, P12840
   CECCHI P, 1996, ANGEW CHEM INT EDIT, V35, P2522
   CERDA BA, 1996, J AM CHEM SOC, V118, P11884
   CIPOLLINI R, 1995, J CHEM SOC CHEM COMM, P773
   COBURN JW, 1982, AM VACUUM SOC MONOGR
   COOKS RG, 1991, RAPID COMMUN MASS SP, V5, P93
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   EBERLIN MN, 1994, J AM CHEM SOC, V116, P2457
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   KETVIRTIS AE, 1998, J PHYS CHEM A, V102, P1162
   KICKEL BL, 1993, J PHYS CHEM-US, V97, P10198
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NR 55
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 1387-3806
J9 INT J MASS SPECTROM
JI Int. J. Mass Spectrom.
PD NOV 23
PY 1998
VL 180
BP 195
EP 205
PG 11
SC Physics, Atomic, Molecular & Chemical; Spectroscopy
GA 140RD
UT ISI:000077101400021
ER

PT J
AU Lino, JLS
   Germano, JSE
   da Silva, EP
   Lima, MAP
TI Elastic cross sections and annihilation parameter for e(+)-H-2
   scattering using the Schwinger multichannel method
SO PHYSICAL REVIEW A
LA English
DT Article
ID POSITRONS; COLLISIONS
AB We report detailed results for positron-H-2 collisions obtained with
   the Schwinger multichannel method. Our calculations include
   annihilation parameter, differential, integral, and momentum transfer
   cross sections for energies below the positronium formation threshold.
   The calculations were carried out in the static-plus-polarization
   approximation with symmetry-resolved cross sections. Energy
   (temperature) dependence and symmetry-resolved contributions for the
   annihilation parameter Z(eff) are also reported. Our ab initio integral
   cross sections are found to be in good agreement with the experimental
   data. [S1050-2947(98)04409-6].
C1 Ctr Tecn Aeronautica, Inst Tecnol Aeronaut, Dept Fis, BR-12228900 Sao Jose Dos Campos, Brazil.
   Univ Fed Ceara, Dept Fis, BR-60455760 Fortaleza, Ceara, Brazil.
   UNICAMP, Inst Fis, BR-13083970 Campinas, SP, Brazil.
RP Lino, JLS, Ctr Tecn Aeronautica, Inst Tecnol Aeronaut, Dept Fis,
   BR-12228900 Sao Jose Dos Campos, Brazil.
CR ARMOUR EAG, 1990, J PHYS B ATOM MOL PH, V23, P3057
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   TAKATSUKA K, 1981, PHYS REV A, V24, P2473
NR 17
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD NOV
PY 1998
VL 58
IS 5
BP 3502
EP 3506
PG 5
SC Physics, Atomic, Molecular & Chemical; Optics
GA 138FT
UT ISI:000076961300022
ER

PT J
AU Moraes, LAB
   Eberlin, MN
TI Dehydrobenzoyl cations: Distonic ions with dual free radical and
   acylium ion reactivity
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID CHARGED PHENYL RADICALS; GAS-PHASE; MASS-SPECTROMETRY; MOLECULE
   REACTIONS; BIMOLECULAR REACTIONS; CYCLOTRON RESONANCE; SUBSTITUTION;
   TRANSACETALIZATION; CHEMISTRY; ANILINE
AB In the gas phase, m- and p-dehydrobenzoyl cations display strong
   duality of chemical behavior. The ions react selectively as either free
   radicals or acylium ions, depending on the choice of the neutral
   reaction partner. Transacetalization with 2-methyl-1,3-dioxolane,
   ketalization with 2-methoxyethanol, and epoxide ring expansion with
   epichlorohydrin demonstrate their acylium ion reactivity, whereas
   (SCH3)-S-. abstraction with dimethyl disulfide demonstrates their free
   radical reactivity. In one-pot reactions with gaseous mixtures of
   epichlorohydrin and dimethyl disulfide, the m- and p-dehydrobenzoyl
   cations react selectively at either site to form the two
   monoderivatized ions in variable but controlled yields; further
   reaction at either the remaining radical or the acylium charge site
   forms a single biderivatized ion as the final product. The
   o-dehydrobenzoyl cation also displays the expected radical and acylium
   ion reactivities. But for the ortho isomer, binding of the nucleophilic
   neutral to the free or derivatized C+=O group facilitates reactions at
   the radical site. Hence, the ortho isomer displays a unique behavior;
   its acylium ion reactions either occur simultaneously with, or are
   followed by, H-abstraction radical reactions. As shown by ab initio
   calculations, the three isomers display sigma-localized odd-spin and
   pi-delocalized charge densities, which characterize distonic structures
   with molecular orbital-separated radical and charge sites. The
   dehydrobenzoyl cations are also, according to the calculations, the
   most stable among 19 of the most feasible C7H4O+. isomers.
C1 UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, UNICAMP, Inst Chem, CP 6154, BR-13083970 Campinas, SP,
   Brazil.
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NR 55
TC 23
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD NOV 4
PY 1998
VL 120
IS 43
BP 11136
EP 11143
PG 8
SC Chemistry, Multidisciplinary
GA 136JE
UT ISI:000076855000015
ER

PT J
AU Dal Colle, M
   Distefano, G
   Modelli, A
   Jones, D
   Guerra, M
   Olivato, PR
   Ribeiro, DD
TI UV-photoelectron, electron transmission, and dissociative electron
   attachment spectroscopies of acetone oximes
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID PI-STAR ORBITALS; ULTRAVIOLET PHOTOELECTRON; INTRAMOLECULAR
   INTERACTIONS; THIO GROUPS; TERT-BUTYL; AB-INITIO; X-ALPHA; DERIVATIVES;
   AFFINITIES; BENZENE
AB The conformation and the electronic structure of several
   alpha-heterosubstituted acetone oximes XCH2(CH3)C= NOH (X = H (1), F
   (2), Cl (3), CH3O (4), C2H5S (5), and (CH3)(2)N (6)) have been
   determined by means of a multidisciplinary approach based on
   ultraviolet photoelectron (UP), electron transmission (ET), and
   dissociative electron attachment (DEA) spectroscopies and fully
   optimized ab initio 6-31G** and MP2/6-31G** calculations. The vertical
   ionization energy (IE) and electron affinity (EA) values related to the
   HOMO (pi(C=N)) and LUMO (pi*(C=N)) have been determined by the Delta
   SCF and Delta MP2 (IE only) procedures. The compounds studied prefer an
   anti (E) configuration between the OH and the CH2X group and a gauche
   conformation of the C-X bond with respect to the double bond, except 2
   and 4 for which a syn (Z) planar structure is nearly degenerate with
   the E one. The spectral data, coupled with the results of the
   calculations, indicate that the properties of the acetone oximes are
   mainly governed by the mixing between the orbitals localized at the X
   and C=N fragments and by electrostatic interactions between hydrogen
   and the electronegative atoms. When X has poor donor and poor mesomeric
   acceptor properties (X = F and OMe), the prevailing interaction is the
   strong charge-transfer mixing of the hydroxyl oxygen lone pair with the
   pi*(C=N) orbital and the X group moves in the main molecular plane.
C1 Univ Ferrara, Dipartimento Chim, I-44100 Ferrara, Italy.
   Univ Bologna, Dipartimento Chim G Ciamician, I-40127 Bologna, Italy.
   CNR, ICoCEA, I-40126 Bologna, Italy.
   Univ Sao Paulo, Inst Quim, Sao Paulo, Brazil.
RP Distefano, G, Univ Ferrara, Dipartimento Chim, Via Borsari 46, I-44100
   Ferrara, Italy.
CR BIERLEIN TK, 1951, ACTA CRYSTALLOGR, V4, P450
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   DARGELOS A, 1977, J CHEM PHYS, V67, P3011
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   DISTEFANO G, 1997, J MOL STRUCT THEOCHE, V418, P99
   FRISCH MJ, 1995, GAUSSIAN 94
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NR 30
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD OCT 8
PY 1998
VL 102
IS 41
BP 8037
EP 8043
PG 7
SC Chemistry, Physical
GA 132EF
UT ISI:000076616800022
ER

PT J
AU Resende, SM
   Wagner, B
TI Analysis of the reaction paths to dissociation of dichloro-ethylenes
   into Cl-2 and C2H2
SO CHEMICAL PHYSICS
LA English
DT Article
ID AB-INITIO; PHOTOCHEMISTRY
AB The reaction paths to dissociation of dichloro-ethylenes (DCE) into
   Cl-2 and acetylene (C2H2) in the gas phase were studied, at the
   CCSD(T)/6-311G(d,p)//CASSCF(6,6)/6-31G(d) level of theory, including
   zero point energy correction. The structures and energies of reactants,
   transition states and products were determined through ab initio
   calculations. There are two principal paths to dissociation. One of
   them involves a number of transition states and intermediates where
   internal rotations, H and Cl migrations are involved until the
   dissociation into Cl and C2H2Cl radicals. The activation energy to this
   path is about 97 kcal/mol. On the other hand, C2H2Cl radicals were also
   predicted to be formed directly from cis- and trans-DCE. In addition,
   we have determined several paths to isomerization among the trans-,
   cis- and 1,1-dichloro-ethylene. We have concluded that these
   isomerization paths have activation energies below to the dissociation
   reaction. Therefore, the dissociation process can proceed from every
   dichloro-ethylene. (C) 1998 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
RP Wagner, B, Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac &
   Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR BALDRIDGE KK, 1989, J PHYS CHEM-US, V93, P5107
   FRISCH MJ, 1995, GAUSSIAN 94
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   LAURSEN SL, 1990, J PHYS CHEM-US, V94, P8175
   LEE TJ, 1989, INT J QUANTUM CHEM S, V23, P199
   LIDE DR, 1993, CRC HDB CHEM PHYSICS
   RESENDE SM, 1997, MOL PHYS, V91, P635
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   RIEHL JF, 1994, J CHEM PHYS, V101, P5942
   SCHMIDT M, 1993, J COMPUT CHEM, V14, P1346
NR 12
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD NOV 1
PY 1998
VL 238
IS 1
BP 11
EP 20
PG 10
SC Physics, Atomic, Molecular & Chemical
GA 132AW
UT ISI:000076608400002
ER

PT J
AU Capaz, RB
   Dal Pino, A
   Joannopoulos, JD
TI Theory of carbon-carbon pairs in silicon.
SO PHYSICAL REVIEW B
LA English
DT Article
ID INTERSTITIAL-CARBON; IRRADIATED SILICON; DEFECTS
AB Interstitial-substitutional carbon pairs (CiCs) in silicon display
   interesting metastable behavior associated with two different
   structural configurations. In this work, we perform extensive ab initio
   calculations on this system. Our results show the following. (i) The
   metastable configuration for the neutral charge state displays C-1h
   symmetry and it is reminiscent of the isolated interstitial carbon
   configuration, i.e., a split interstitial C-Si pair with the
   substitutional carbon bonded to the silicon interstitial. (ii) The
   ground-state configuration also has C-1h symmetry, but it consists;of a
   single silicon interstitial twofold coordinated in an unusual bridge
   configuration between two substitutional carbon atoms. With an
   activation energy of 0.07 eV, this configuration becomes a
   motional-averaged state with C-3v symmetry. (iii) The ground state is
   lower in; energy by 0.11 eV with respect to the metastable state. The
   jump from one configuration to the other corresponds to a simple
   ''bond-switching'' mechanism with a calculated energy barrier of 0.13
   eV. (iv) Both configurations have two electronic-states in the gap,
   with gap-state wave functions consistent with the local bonding of the
   defect complex in each case. (v) Analysis of local-mode vibrations on
   the ground-state configuration indicates a stronger component in one of
   the carbon atoms, which explains the experimentally observed isotope
   splittings. Vibrational frequencies for the metastable configuration
   are also predicted. All of these results are in satisfactory agreement
   with experiments. [S0163-1829(98)07236-1].
C1 Univ Fed Rio de Janeiro, Inst Fis, BR-21945970 Rio De Janeiro, Brazil.
   Inst Tecnol Aeronaut, BR-12225 Sao Jose Dos Campos, Brazil.
   MIT, Dept Phys, Cambridge, MA 02139 USA.
RP Capaz, RB, Univ Fed Rio de Janeiro, Inst Fis, Caixa Postal 68528,
   BR-21945970 Rio De Janeiro, Brazil.
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NR 25
TC 8
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD OCT 15
PY 1998
VL 58
IS 15
BP 9845
EP 9850
PG 6
SC Physics, Condensed Matter
GA 129WJ
UT ISI:000076486800050
ER

PT J
AU Dos Santos, HF
   O'Malley, PJ
   De Almeida, WB
TI Gas phase and water solution conformational analysis of the herbicide
   diuron (DCMU): an ab initio study
SO THEORETICAL CHEMISTRY ACCOUNTS
LA English
DT Article
DE DCMU; diuron; conformational analysis; solvent effect; ab initio
   calculation
ID PHOTOSYNTHETIC REACTION CENTER; PHOTOSYSTEM-II; AQUEOUS-SOLUTION; D1
   PROTEIN; INHIBITORS; ENERGIES; BINDING
AB In the present work, the conformational equilibrium for the herbicide
   diuron (DCMU) has been investigated using high level ab initio
   calculations. The solvent effect was included through two different
   continuum models: (1) the real cavity IPCM method and (2) the standard
   dipole Onsager model SCRF. The effect due to solute-solvent
   hydrogen-bond interactions was analyzed considering a hybrid
   discreet-continuum model. At the Hartree-Fock level, the gas phase
   results showed that only the trans forms (A and B) are present in the
   equilibrium mixture, with the relative concentrations found to be 33%
   (A) and 67% (B) (HF/6-311+G**//6-31G**). When the electronic
   correlation effect is included (MP2/6-31G*//HF/6-31G*), a relative
   stabilization of the cis forms was observed, with the conformational
   distribution calculated as 38% (A), 50% (B), 6% (C) and 6% (D). The
   trans conformations were found to be completely planar, which has been
   considered to be a prerequisite for the herbicide binding. In water
   solution, the ri ans conformation A should be the most abundant
   conformer, the IPCM and SCRF values being ca. 100% and ca. 85%
   respectively. The IPCM calculations with the isodensity level set to
   0.0005 present a conformational distribution close to that obtained
   from the hybrid model [92% (A) and 8% (B)], which has been considered
   our best solvent approach. Regarding the biological action of urea-type
   herbicides, the results presented here are important, because some QSAR
   studies have suggested that the partition coefficient is related to the
   herbicide activity, so the conformational equilibrium may play a role
   in the biological action.
C1 Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Manchester, Inst Sci & Technol, Dept Chem, Manchester M60 1QD, Lancs, England.
RP Dos Santos, HF, Univ Fed Minas Gerais, ICEx, Dept Quim, Lab Quim
   Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR BOWYER J, 1990, Z NATURFORSCH C, V45, P379
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   KARELSON M, 1996, CHEM REV, V96, P1027
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NR 28
TC 7
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1432-881X
J9 THEOR CHEM ACC
JI Theor. Chem. Acc.
PD SEP
PY 1998
VL 99
IS 5
BP 301
EP 311
PG 11
SC Chemistry, Physical
GA 125RC
UT ISI:000076250000004
ER

PT J
AU de Brito Mota, F
   Justo, JF
   Fazzio, A
TI Structural properties of amorphous silicon nitride
SO PHYSICAL REVIEW B
LA English
DT Article
ID ELECTRONIC-STRUCTURE; INTERATOMIC POTENTIALS; MOLECULAR-DYNAMICS;
   BETA-SI3N4; CHEMISTRY; SYSTEMS; BOND
AB We developed an empirical potential for interactions between Si and N
   to describe silicon nitride systems using the Tersoff functional form.
   The fitting parameters were found using a set of ab initio and
   experimental results of the crystalline phase. Using this empirical
   model, we explored the structural properties of amorphous silicon
   nitride through Monte Carlo simulations, and compared them to available
   experimental data. The good description of the a-SiNx system for a wide
   range of nitrogen contents (0 < x < 1.5) shows the reliability of this
   model.
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   UFBA, Inst Fis, BR-40210340 Salvador, BA, Brazil.
RP de Brito Mota, F, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao
   Paulo, Brazil.
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NR 33
TC 32
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD OCT 1
PY 1998
VL 58
IS 13
BP 8323
EP 8328
PG 6
SC Physics, Condensed Matter
GA 125HU
UT ISI:000076232100036
ER

PT J
AU Resende, SM
   Pliego, JR
   De Almeida, WB
TI Free radical mechanism of the Cl-2 addition to acetylene
SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
LA English
DT Article
ID MOLECULAR ELECTRONIC WAVEFUNCTIONS; ATOMS; SUBSTITUTIONS; INTERMEDIATE;
   COMPLEXES; CHLORINE; SIGMA; C2H2
AB The free radical mechanism for the addition of Cl-2 to acetylene in the
   gas phase has been studied. The structures and energies of reactants,
   transition states and products were determined through ab initio
   calculations of the stationary points on the potential-energy surface
   (PES) for the interaction of these two molecules. Using BD(T)/6-311 +
   G(2df,2p)//CASSCF(6,6)/6-31G(d,p) level of theory, the reaction rate
   for the initiation step (Cl-2 + C2H2 --> Cl + C2H2Cl) was estimated as
   10(-18) 1 mol(-1) s(-1) (at 298.15 K). This leads to the formation of a
   small quantity of Cl and C2H2Cl radicals, the chain propagators, and
   the following steps will only occur to an appreciable extent after an
   induction period, which generates a measurable amount of these
   radicals. The following steps were studied at the UCCSD(T)/6-311 +
   G(2df,2p)//UMP2/6-31G(d,p) level of theory. The propagation reaction
   C2H2 + Cl --> C2H2Cl occurs with an activation energy of -1.22 kcal
   mol(-1), and produces a radical C2H2Cl, where the two hydrogens are on
   opposite sides of the molecule (trans-isomer). This reaction has a rate
   constant 2.85 x 10(10) 1 mol(-1) s(-1) at 298.15 K. The interconversion
   of the two isomers of the C2H2Cl radical (cis-trans) is very fast, with
   a rate constant 4.75 x 10(10) s(-1) and so these species can be
   considered to be in equilibrium. The rate constants for the reaction
   C2H2Cl + Cl-2 --> C2H2Cl2 + Cl, where the products trans- and
   cis-1,2-dichloroethylenes are formed, are 1.95 x 10(10) and 3.63 x
   10(9) 1 mol-l s(-1), respectively, and those for the two polymerization
   reactions C2H2 + C2H2Cl --> C2H2C2H2Cl are ca. 10(2) 1 mol(-1) s(-1).
   Hence, the latter reactions will not compete with the formation of
   C2H2Cl2, and the polymerization products will not be produced in
   meaningful amounts. Analysis of the kinetics data gives 97.3% of the
   trans-1,2-dichloroethylene and 2.7% of the cis-1,2-dichloroethylene
   products.
C1 UFMG, Dept Quim, Lab Quim Computac & Modelagem Mol, ICEX, BR-31270901 Belo Horizonte, MG, Brazil.
RP Resende, SM, UFMG, Dept Quim, Lab Quim Computac & Modelagem Mol, ICEX,
   BR-31270901 Belo Horizonte, MG, Brazil.
CR BARTLETT RJ, 1989, J PHYS CHEM-US, V93, P1697
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NR 24
TC 4
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE CB4 0WF,
   CAMBS, ENGLAND
SN 0956-5000
J9 J CHEM SOC FARADAY TRANS
JI J. Chem. Soc.-Faraday Trans.
PD OCT 7
PY 1998
VL 94
IS 19
BP 2895
EP 2900
PG 6
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA 126HM
UT ISI:000076287900004
ER

PT J
AU Lopez-Castillo, A
TI Nonlinear dynamics of the hydrogen molecule
SO PHYSICAL REVIEW A
LA English
DT Article
ID 3-BODY COULOMB PROBLEM; HELIUM ATOM; QUANTUM DEFECTS; STATES;
   QUANTIZATION; H-2; MODEL
AB The hydrogen molecule (H-2) contains the basic ingredients for
   understanding the chemical bond, even more so than the hydrogen
   molecule ion. H-2 is studied in the context of nonlinear dynamics. The
   classical mechanics of H-2 is studied in three dimensions with nine,
   six, and three degrees of freedom and in one dimension (two degrees of
   freedom). The semiclassical quantization is made using the
   Bohr-Sommerfeld rules and the Gutzwiller formula to calculate the
   eigenvalues of the doubly occupied symmetric excited states of H-2. An
   ab initio quantum calculation is performed and compared with
   semiclassical results. The difficulties that appear in those
   calculations are discussed, and a proposal of the experimental measure
   is made.
C1 Univ Fed Sao Carlos, Dept Matemat, Ctr Ciencias & Tecnol, BR-13560970 Sao Paulo, Brazil.
RP Lopez-Castillo, A, Univ Fed Sao Carlos, Dept Matemat, Ctr Ciencias &
   Tecnol, Caixa Postal 676, BR-13560970 Sao Paulo, Brazil.
CR BARANGER M, 1987, ANN PHYS-NEW YORK, V177, P330
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NR 29
TC 4
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1050-2947
J9 PHYS REV A
JI Phys. Rev. A
PD SEP
PY 1998
VL 58
IS 3
BP 1846
EP 1858
PG 13
SC Physics, Atomic, Molecular & Chemical; Optics
GA 116MY
UT ISI:000075730200031
ER

PT J
AU De Almeida, WB
   Dos Santos, HF
   Zerner, MC
TI A theoretical study of the interaction of anhydrotetracycline with
   Al(III)
SO JOURNAL OF PHARMACEUTICAL SCIENCES
LA English
DT Article
ID SOLVENT; TETRACYCLINE; ALUMINUM; PRODUCT; AM1
AB In this article the complexation of anhydrotetracycline (AHTC), the
   major toxic decomposition product of the antibiotic tetracycline, with
   Al(III) has been investigated using the AM1 semiempirical and ab initio
   Hartree-Fock levels of theory. Different modes of complexation have
   been considered with the structure of tetra- and pentacoordinated
   complexes being fully optimized, In the gas phase, processes ii and
   iii, which lead to the complexes with stoichiometry MHL2+, are favored.
   Structure II ([AlLH2(OH)(H2O)](2+)) has the metal coordinated to the
   O-11 and O-12 groups and the O-3 group protonated and is the global
   minimum on the potential energy surface for the interaction. In water
   solution, the Al(III) is predicted to form predominantly a
   tetracoordinated complex at the O-am and O-3 site (V) of the AHTC with
   the stoichiometry MH2L3+ (process i). The experimental proposal is the
   complexed form with the metal ion coordinated to the O-11-O-12 moiety
   (site II). The intramolecular proton transfer, which leads to the most
   stable Al(III)-AHTC MHL2+ complex, has not been considered by the
   experimentalists. The experimental structure was found to be
   unfavorable in our calculations in both gas phase and water solution.
   All the semiempirical results are in perfect agreement with the ab
   initio calculations. So, we suggest that the experimental assignments
   should be revised, taking into account the results obtained in the
   present study.
C1 UFMG, ICEx, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
   Univ Florida, Quantum Theory Project, Gainesville, FL 32611 USA.
RP De Almeida, WB, UFMG, ICEx, Dept Quim, Lab Quim Computac & Modelagem
   Mol, BR-31270901 Belo Horizonte, MG, Brazil.
CR ALVAREZFERNANDE.A, 1969, J PHARM SCI, V58, P443
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   HASAN T, 1985, J ORG CHEM, V50, P1755
   KARELSON M, 1993, J PHYS CHEM-US, V97, P11901
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NR 19
TC 13
PU AMER PHARMACEUTICAL ASSN
PI WASHINGTON
PA 2215 CONSTITUTION AVE NW, WASHINGTON, DC 20037 USA
SN 0022-3549
J9 J PHARM SCI
JI J. Pharm. Sci.
PD SEP
PY 1998
VL 87
IS 9
BP 1101
EP 1108
PG 8
SC Chemistry, Medicinal; Chemistry, Multidisciplinary; Pharmacology &
   Pharmacy
GA 117MQ
UT ISI:000075785600012
ER

PT J
AU Aleman, C
   Casanovas, J
   Galembeck, SE
TI PAPQMD parametrization of molecular systems with cyclopropyl rings:
   Conformational study of homopeptides constituted by
   l-aminocyclopropane-l-carboxylic acid
SO JOURNAL OF COMPUTER-AIDED MOLECULAR DESIGN
LA English
DT Article
DE MM and MD techniques; homopeptides; parametrization
ID FORCE-FIELD PARAMETRIZATION; ELECTROSTATIC POTENTIALS; NUCLEIC-ACIDS;
   AMINO-ACIDS; AB-INITIO; C-ALPHA,ALPHA-DIALKYLATED GLYCINES; STRUCTURAL
   VERSATILITY; ORGANIC-MOLECULES; ENERGY FUNCTIONS; ATOMIC CHARGES
AB The suitability of ab initio, semiempirical and density functional
   methods as sources of stretching and bending parameters has been
   explored using the PAPQMD (Program for Approximate Parametrization from
   Quantum Mechanical Data) strategy. Results show that semiempirical
   methods provide parameters comparable to those compiled on empirical
   force fields. In this respect the AMI method seems to be a good method
   to obtain parameters at a minimum computational cost. On the other
   hand, harmonic force fields initially developed for proteins and DNA
   have been extended to include compounds containing highly strained
   three-membered rings, Like 1-aminocyclopropane-1-carboxylic acid. For
   this purpose the cyclopropyl ring has been explicitly parametrized at
   the AMI level considering different chemical environments. Finally, the
   new set of parameters has been used to investigate the conformational
   preferences of homopeptides constituted by
   1-aminocyclopropane-1-carboxylic acid. Results indicate that such
   compounds tend to adopt a helical conformation stabilized by
   intramolecular hydrogen bonds between residues i and i + 3. This
   conformation allows the arrangement of the cyclic side chains without
   steric clashes.
C1 Univ Politecn Catalunya, ETS Enginyers Ind, Dept Enginyeriia Quim, E-08028 Barcelona, Spain.
   Univ Rovira & Virgili, Fac Quim, Dept Quim Fis & Inorgan, E-43005 Tarragona, Spain.
   Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Pret, Dept Quim, BR-14049901 Ribeirao Preto, Brazil.
RP Aleman, C, Univ Politecn Catalunya, ETS Enginyers Ind, Dept Enginyeriia
   Quim, Av Diagonal 647, E-08028 Barcelona, Spain.
CR ALEMAN C, 1991, J COMPUT CHEM, V12, P664
   ALEMAN C, 1992, BIOPOLYMERS, V32, P621
   ALEMAN C, 1992, J COMPUT AID MOL DES, V6, P331
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   ALEMAN C, 1993, J COMPUT CHEM, V14, P799
   ALEMAN C, 1994, BIOPOLYMERS, V34, P941
   ALEMAN C, 1994, J CHEM SOC P2, P563
   ALEMAN C, 1995, J ORG CHEM, V60, P910
   ALEMAN C, 1996, J POLYM SCI POL PHYS, V34, P963
   ALEMAN C, 1997, J PHYS CHEM B, V101, P5046
   ALEMAN C, 1997, PROTEINS, V28, P83
   ALEMAN C, 1997, PROTEINS, V29, P575
   ALHAMBRA C, 1994, J COMPUT CHEM, V15, P12
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NR 84
TC 9
PU KLUWER ACADEMIC PUBL
PI DORDRECHT
PA SPUIBOULEVARD 50, PO BOX 17, 3300 AA DORDRECHT, NETHERLANDS
SN 0920-654X
J9 J COMPUT AID MOLEC DESIGN
JI J. Comput.-Aided Mol. Des.
PD MAY
PY 1998
VL 12
IS 3
BP 259
EP 273
PG 15
SC Computer Science, Interdisciplinary Applications; Biochemistry &
   Molecular Biology; Biophysics
GA 116PR
UT ISI:000075734200004
ER

PT J
AU Sambrano, JR
   de Sousa, AR
   Queralt, JJ
   Andres, J
   Longo, E
TI A theoretical analysis on the intramolecular proton transfer of
   alpha-alanine in an aqueous medium
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID AXES ELLIPSOIDAL CAVITY; GAS-PHASE; AB-INITIO; NONPERFECT
   SYNCHRONIZATION; ABINITIO; GLYCINE; SOLVENT; ACETALDEHYDE; ZWITTERION;
   ALGORITHM
AB Intramolecular proton transfer from oxygen to nitrogen atoms in the
   alpha-alanine amino acid has been studied by ab initio methods at the
   HF/6-31G*, HF/6-31 ++ G** and MP2/6-31 ++ G** levels of calculation
   including the solvent effects by means of self-consistent reaction
   field theory. An analysis of the results based on the natural bond
   orbital charges shows that the transition structure presents an
   imbalance in the sense that the charge shift lags behind the proton
   transfer and that the bond formation is always in advance with respect
   to the bond cleavage. All calculation levels show that the barrier
   height associated with the conformational change on alpha-alanine is
   larger than the proton transfer process. (C) 1998 Elsevier Science B.V.
   All rights reserved.
C1 Univ Jaume I, Dept Ciencias Expt, Castello 12080, Spain.
   Univ Estadual Paulista, Dept Matemat, BR-17030360 Bauru, SP, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
RP Queralt, JJ, Univ Jaume I, Dept Ciencias Expt, Apartat 224, Castello
   12080, Spain.
EM queralt@vents.uji.es
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NR 33
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD SEP 11
PY 1998
VL 294
IS 1-3
BP 1
EP 8
PG 8
SC Physics, Atomic, Molecular & Chemical
GA 118WP
UT ISI:000075864200001
ER

PT J
AU Almeida, AL
   Martins, JBL
   Taft, CA
   Longo, E
   Lester, WA
TI Ab initio and semiempirical studies of the adsorption and dissociation
   of water on pure, defective, and doped MgO (001) surfaces
SO JOURNAL OF CHEMICAL PHYSICS
LA English
DT Article
ID LARGE CLUSTER-MODELS; MAGNESIUM-OXIDE; CO INTERACTION;
   ELECTRONIC-STRUCTURE; OXIDATIVE DIMERIZATION; CHARGE-DISTRIBUTION;
   3D-METAL SURFACES; SOLID HYDROXIDES; ZNO SURFACES; HYDROGEN
AB Ab initio and semiempirical calculations of large cluster models have
   been performed in order to study water adsorption and dissociation on
   pure, defective (vacancies) and doped (Li, Na, K, Ca, Fe) MgO (001)
   surfaces. The geometries of the adsorbed and dissociated molecules have
   been optimized preparatory to analysis of binding energies, stretching
   frequencies, charge transfers, preferential sites of interaction, and
   bond distances. We have used Mulliken, natural bond order, and
   electrostatic-derived atomic and overlap populations to analyze charge
   distributions in the clusters. We have also investigated transition
   structures, activation energies, energy gaps, HOMO, density of states,
   SCF orbital energies as well as the acid-base properties of our cluster
   model. Numerical results are compared, where possible, with experiment,
   interpreted in the framework of various analytical models, and
   correlated with site coordination numbers, corner and edge site
   preferential locations, and direction of charge transfer. A thorough
   charge analysis indicates substantial charge redistribution in the
   magnesium oxide crystal as a result of water adsorption and
   dissociation in pure, defective, and doped MgO crystals. The
   introduction of heavier impurities and vacancies could produce
   substantial changes in the physical and chemical properties of the
   catalyst and increase the binding and dissociation energies. Some of
   the largest changes originate from the introduction of vacancies. Two
   and three-dimensional potential energy surfaces are used to investigate
   activation energies of hydroxylation on the MgO surface. Stretching
   frequencies are correlated with magnesium and oxygen coordination
   numbers. (C) 1998 American Institute of Physics.
C1 Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estat, BR-22290180 Rio De Janeiro, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
   Univ Calif Berkeley, Dept Chem, Berkeley, CA 94720 USA.
   Univ Calif Berkeley, Lawrence Berkeley Lab, Div Chem Sci, Berkeley, CA 94720 USA.
RP Almeida, AL, Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis
   Estat, Rua Dr Xavier Sigaud 150, BR-22290180 Rio De Janeiro, Brazil.
CR ALMEIDA AL, 1996, UNPUB 4 WORLD C THEO
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NR 80
TC 16
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY
   11797-2999 USA
SN 0021-9606
J9 J CHEM PHYS
JI J. Chem. Phys.
PD SEP 1
PY 1998
VL 109
IS 9
BP 3671
EP 3685
PG 15
SC Physics, Atomic, Molecular & Chemical
GA 114ZP
UT ISI:000075639300042
ER

PT J
AU Mendes, MA
   Moraes, LAB
   Sparrapan, R
   Eberlin, MN
   Kostiainen, R
   Kotiaho, T
TI Oxygen atom transfer to positive ions: A novel reaction of ozone in the
   gas phase
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID MASS-SPECTROMETRY; ACYLIUM IONS; RADICAL-CATION; KINETICS; CHEMISTRY;
   O3; MECHANISMS; ATMOSPHERE; O-3(-); NO2
AB In the gas phase, neutral ozone (O-3) transfers an oxygen atom to
   several positive ions, i.e. the radical cations of pyridines (R-Py+.; R
   = H, CH3, C2H5, and Cl), pyrimidine (Pi(+).), and alkyl halides
   (CH3X+.; X = Cl and I), and the halogen cations (X+; X = Cl, Br, and
   I). Reactivity changes drastically within the halogen series (Cl+ much
   less than Br+ less than or equal to I+), whereas no O-transfer occurs
   to F+. The oxide derivatives R-Py+-O ., Pi(+)-O ., CH3X+-O ., and XO+
   are formed, as demonstrated by pentaquadrupole (QqQqQ) double- and
   triple-stage mass spectrometry. No oxygen atom transfer occurs,
   however, in "inverse" reactions, i.e., those of ionized ozone (O-3(+).)
   with the corresponding neutrals; and charge transfer dominates. Ab
   initio calculations suggest that O-transfer from ozone to ionized
   pyridine yields ionized pyridine N-oxide via simple nucleophilic
   addition of ozone as opposed to 1,3-dipolar cycloaddition. Similar
   nucleophilic addition followed by Oz loss is also the most likely
   mechanism for O-transfer from ozone to the ionized alkyl halides and
   halogen cations. This novel O-transfer reaction to positive ions, which
   expands our knowledge of the rich chemistry of ozone, introduces a new
   pathway for the gas-phase oxidation of halogen atoms, pyridines,
   pyrimidines, alkyl halides, and analogues, and consequently for the
   gas-phase generation of their chemically interesting but difficult to
   access ionized oxides.
C1 UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
   Univ Helsinki, Dept Pharm, Div Pharmaceut Chem, FIN-00014 Helsinki, Finland.
   VTT Chem Technol, FIN-02044 Espoo, Finland.
RP Eberlin, MN, UNICAMP, Inst Chem, CP6154, BR-13083970 Campinas, SP,
   Brazil.
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NR 47
TC 16
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD AUG 12
PY 1998
VL 120
IS 31
BP 7869
EP 7874
PG 6
SC Chemistry, Multidisciplinary
GA 111CQ
UT ISI:000075420100023
ER

PT J
AU Justo, JF
   Bazant, MZ
   Kaxiras, E
   Bulatov, VV
   Yip, S
TI Interatomic potential for silicon defects and disordered phases
SO PHYSICAL REVIEW B
LA English
DT Article
ID MOLECULAR-DYNAMICS SIMULATIONS; 90-DEGREES PARTIAL DISLOCATION;
   CONCERTED-EXCHANGE MECHANISM; PURE AMORPHOUS-SILICON; LIQUID SILICON;
   FORCE-FIELDS; ELECTRONIC-PROPERTIES; SELF-DIFFUSION; BULK PHASES; SI
AB We develop an empirical potential for silicon which represents a
   considerable improvement over existing models in describing local
   bonding for bulk defects and disordered phases. The model consists of
   two- and three-body interactions with theoretically motivated
   functional forms that capture chemical and physical trends as explained
   in a companion paper. The numerical parameters in the functional form
   are obtained by fitting to a set of ab initio results from
   quantum-mechanical calculations based on density-functional theory in
   the local-density approximation, which include various bulk phases and
   defect structures. We test the potential by applying it to the
   relaxation of point defects, core properties of partial dislocations
   and the structure of disordered phases, none of which are included in
   the fitting procedure. For dislocations, our model makes predictions in
   excellent agreement with ab initio and tight-binding calculations. It
   is the only potential known to describe both the 30 degrees- and 90
   degrees-partial dislocations in the glide set {111}. The structural and
   thermodynamic properties of the liquid and amorphous phases are also in
   good agreement with experimental and ab initio results. Our potential
   is capable of simulating a quench directly from the liquid to the
   amorphous phase, and the resulting amorphous structure is more
   realistic than with existing empirical preparation methods. These
   advances in transferability come with no extra computational cost,
   since force evaluation with our model is faster than with the popular
   potential of Stillinger-Weber, thus allowing reliable atomistic
   simulations of very large atomic systems. [S0163-1829(98)04026-0].
C1 Univ Sao Paulo, Inst Fis, BR-05315970 Sao Paulo, Brazil.
   Harvard Univ, Dept Phys, Cambridge, MA 02138 USA.
   MIT, Dept Mech Engn, Cambridge, MA 02139 USA.
   MIT, Dept Nucl Engn, Cambridge, MA 02139 USA.
RP Justo, JF, Univ Sao Paulo, Inst Fis, CP 66318, BR-05315970 Sao Paulo,
   Brazil.
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NR 71
TC 128
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD AUG 1
PY 1998
VL 58
IS 5
BP 2539
EP 2550
PG 12
SC Physics, Condensed Matter
GA 108UQ
UT ISI:000075284300040
ER

PT J
AU Augusti, R
   Gozzo, FC
   Moraes, LAB
   Sparrapan, R
   Eberlin, MN
TI The simplest azabutadienes in their N-protonated forms. Generation,
   stability, and cycloaddition-reactivity in the gas phase
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID DIELS-ALDER REACTION; PENTAQUADRUPOLE MASS-SPECTROMETER;
   MOLECULAR-ORBITAL METHODS; RADICAL-CATION; CARBONYL-COMPOUNDS; ACYLIUM
   IONS; BASIS SETS; ISOMERS; TANDEM; DISSOCIATION
AB The simplest azabutadienes, i.e. 1-aza-1,3-butadiene and
   2-aza-1,3-butadiene, are generated in their N-protonated forms 1 and 2
   via gas-phase dissociative electron ionization of allylamine and
   piperidine; respectively. Formation of 1 and 2 is suggested by simple
   dissociation mechanisms, and supported by high-accuracy G2 ab initio
   calculations, which show the ions to be stable, non-interconverting
   species. Whereas 1 and 2 are unreactive toward ethylene and
   cyclohexene, 2 reacts with alkenes activated by electron-donating
   (OC2H5), electron-withdrawing (CN; COCH3), and vinyl and phenyl
   substituents most likely by polar [4(+) + 2] cycloaddition, as
   suggested by MS3 experiments and ab initio calculations. The
   cycloadduct of 2 with ethyl vinyl ether is unstable and dissociates
   promptly by ethanol loss; hence, net C2H2 addition occurs. This novel
   vinylation reaction is proposed as a potential structurally diagnostic
   test for both 2-azabutadienes and vinyl ethers. Isomer 1 is in general
   much less reactive, and abundant adducts are only formed in reactions
   with alkenes activated by electron-withdrawing substituents. In
   reactions of 1 and 2 with esters (methyl acetate and dimethyl
   carbonate), hydrogen-bridged ion-neutral complexes are formed as the
   most abundant and stable products, as suggested by the ab initio
   calculations. Acetone, fluoroacetone and acetonitrile form abundant
   adducts with-bath 1 and 2; However, the experimental and theoretical
   results on these adducts provide nb clear structural information.
   Reactions of 1 with DMSO occur almost exclusively by proton transfer,
   whereas 2 forms an abundant complex with DMSO. Limited reactivity is
   observed for I and 2 with acetyl chloride and thionyl chloride; the
   minor products observed were those of either dissociative proton
   transfer or charge exchange.;The distinctive reactivities of 1 and 2
   with styrene, ethyl vinyl ether, and dimethyl sulfoxide contrast to
   their identical low energy CID behavior, and allow their
   straightforward differentiation in the gas phase.
C1 State Univ Campinas, UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
   Univ Fed Minas Gerais, Dept Chem, BR-31270901 Belo Horizonte, MG, Brazil.
RP Eberlin, MN, State Univ Campinas, UNICAMP, Inst Chem, CP 6154,
   BR-13083970 Campinas, SP, Brazil.
CR ABBOUD JLM, 1993, J AM CHEM SOC, V115, P12468
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NR 55
TC 21
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD JUL 24
PY 1998
VL 63
IS 15
BP 4889
EP 4897
PG 9
SC Chemistry, Organic
GA 108JQ
UT ISI:000075263100008
ER

PT J
AU Carvalho, M
   Gozzo, FC
   Mendes, MA
   Sparrapan, R
   Kascheres, C
   Eberlin, MN
TI Locating the charge site in heteroaromatic cations
SO CHEMISTRY-A EUROPEAN JOURNAL
LA English
DT Article
DE ab initio calculations; collision-induced dissociation; in-molecule
   reactions; mass spectrometry
ID GAS-PHASE; SOOT FORMATION; IONS; C3H3+; CHEMISTRY
AB Low-energy collision-induced dissociation (CID) and ion-molecule
   reactions with 2-methyl-1,3-dioxolane (MD) performed by pentaquadrupole
   (QqQqQ) mass spectrometry were applied to locate the charge site in
   isomeric heteroaromatic cations. The 2-, 3-, and 4-pyridyl cations are
   indistinguishable by CID. However, as suggest ed by MS3 experiments and
   ab initio calculations, the 2-pyridyl cation reacts extensively with MD
   by a transacetalization-like mechanism to afford a bicyclic
   dihydrooxazolopyridyl cation. The 3- and 4-pyridyl cations, on the
   contrary react predominantly with MD by proton transfer, as does the
   analogous phenyl cation. The 2-. 4-, and 5-pyrimidyl cations display
   characteristic CID behavior. In addition, the 2-pyrimidyl cation reacts
   extensively with MD by the transacetalization-like mechanism, whereas
   proton transfer occurs predominantly for the 4- and 5-pyrimidyl
   cations. The ions thought to be the 2- and 3-furanyl and 2- and
   3-thiophenyl cations show indistinguishable CID and ion-molecule
   behavior. This is most likely the result of their inherent instability
   in the gas phase and their spontaneous isomerization to the
   corresponding butynoyl and butynethioyl cations HC=CHCH2C=O+ and
   HC=CHCH2C=S+. These isomerizations, which are considerably exothermic
   according to G2(MP2) ab initio calculations, are indicated by a series
   of experimental results. The ions dissociate upon CID by loss of CO or
   CS and undergo transacetalization with MD. Most informative is the
   participation of HC=CHCH2C=S+ in a transacetalization/dissociation
   sequence with replacement of sulfur by oxygen, which is structurally
   diagnostic for thioacylium ions. It is therefore possible to locate the
   charge site of the 2-pyridyl and the three 2-, 4-, and 5-pyrimidyl
   cations and to identify the isomeric precursors from which they are
   derived. However, rapid isomerization to the common HC=CHCH2-C=O(S)(+)
   ion eliminates characteristic chemical behavior that could result from
   different charge locations in the heteroaromatic 2- and 3-furanyl and
   2- and 3-thiophenyl cations.
C1 UNICAMP, State Univ Campinas, Inst Chem, BR-13083970 Campinas, SP, Brazil.
RP Eberlin, MN, UNICAMP, State Univ Campinas, Inst Chem, CP 6154,
   BR-13083970 Campinas, SP, Brazil.
EM eberlin@iqm.unicamp.br
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NR 39
TC 27
PU WILEY-V C H VERLAG GMBH
PI BERLIN
PA MUHLENSTRASSE 33-34, D-13187 BERLIN, GERMANY
SN 0947-6539
J9 CHEM-EUR J
JI Chem.-Eur. J.
PD JUL
PY 1998
VL 4
IS 7
BP 1161
EP 1168
PG 8
SC Chemistry, Multidisciplinary
GA 103ZD
UT ISI:000074987000005
ER

PT J
AU Aleman, C
   Ishiki, HM
   Armelin, EA
   Junior, OA
   Galembeck, SE
TI Free energies of solvation for peptides and polypeptides using SCRF
   methods
SO CHEMICAL PHYSICS
LA English
DT Article
ID AQUEOUS SOLVATION; HYDROGEN-BOND; AB-INITIO; SOLVENT; MODEL; MOLECULES;
   COMPLEXES; CONTINUUM; POLYMERS; RESIDUES
AB The effects of the aqueous solvent in the conformational preferences of
   peptides and homopeptides have been investigated using two different
   and widely used self-consistent reaction-field models. The free
   energies of solvation were predicted using the polarizable continuum
   model developed by Tomasi and co-workers and adapted to semi-empirical
   hamiltonians by Orozco and Luque, and the solvation model developed by
   Cramer and Truhlar. The set of compounds investigated is constituted by
   five dipeptides with different chemical nature and structural
   properties as well as by two homopeptides in which the size of the
   polypeptidic chain was varied. Results provided by the different
   methods are compared and discussed. (C) 1998 Elsevier Science B.V. All
   rights reserved.
C1 Univ Politecn Catalunya, ETS Engn Ind Barcelona, Dept Engn Quim, E-08028 Barcelona, Spain.
   Univ Fed Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, Ribeirao Preto, SP, Brazil.
RP Aleman, C, Univ Politecn Catalunya, ETS Engn Ind Barcelona, Dept Engn
   Quim, Diagonal 647, E-08028 Barcelona, Spain.
CR AGUILAR M, 1993, CHEM PHYS, V174, P397
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NR 51
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD JUL 15
PY 1998
VL 233
IS 1
BP 85
EP 96
PG 12
SC Physics, Atomic, Molecular & Chemical
GA ZZ999
UT ISI:000074790600008
ER

PT J
AU Sparrapan, R
   Mendes, MA
   Ferreira, IPP
   Eberlin, MN
   Santos, C
   Nogueira, JC
TI Gas-phase chemistry of the sulfur hexafluoride fragment ions SFn+
   (n=0-5) and SFn2+ (n=2, 4). Ab initio thermochemistry of novel
   reactions of S+. and SF+
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID MASS-SPECTROMETRY; PROTON AFFINITY; KINETIC METHOD; ISOMERS
AB A systematic study of the gas-phase chemistry of the major positively
   charged ions produced by 70 eV dissociative electron ionization of SF6,
   i.e., SFn+ (n = 0-5) and SFn2+ (n = 2, 4), has been performed via
   pentaquadrupole (QqQqQ) mass spectrometric experiments in conjunction
   with G2(MP2) ab initio calculations. Comparison, under exactly the same
   15 eV collision conditions, of the SFn+ proclivities to dissociate by F
   loss was accomplished via a tandem-in-space three-dimensional MS2 scan.
   The experimental SFn+ dissociation proclivities were found to correlate
   perfectly with those expected from G2(MP2) dissociation thresholds.
   Ion/molecule reactions of mass-selected SFn+ and SFn2+ were performed
   with O-2 and the oxygenated neutral gases H2O, CO, CO2, and N2O. The
   ions, under the very low energy (near zero) multiple collision
   conditions employed, undergo either dissociation by F loss or charge
   exchange, or participate in novel reactions that have been corroborated
   by both MS3 experiments and G2(MP2) ab initio thermochemistry.
   O-abstraction takes place in reactions of SF+ with O-2 and CO, and of
   S+. with CO2 and O-2 and the corresponding oxyions F-SO+ and SO+. are
   formed to great extents. CO-abstraction that yields ionized carbon
   oxysulfide (COS+.) also occurs to a minor extent in reactions of S+.
   with CO2. Reactions of SF+ with CO yields a minor COS+. product in a
   net sulfur cation (S+.) transfer reaction. Theory corroborates the
   experimental observations as the respective O-abstraction and S+.
   transfer reactions are predicted by G2(MP2) ab initio thermochemistry
   to be the most favorable processes.
C1 State Univ Campinas, UNICAMP, Inst Chem, BR-13083970 Campinas, SP, Brazil.
   Univ Fed Sao Carlos, Dept Chem, BR-13560 Sao Carlos, SP, Brazil.
RP Eberlin, MN, State Univ Campinas, UNICAMP, Inst Chem, CP 6154,
   BR-13083970 Campinas, SP, Brazil.
CR BABCOCK LM, 1981, J CHEM PHYS, V74, P5700
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NR 48
TC 8
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD JUL 2
PY 1998
VL 102
IS 27
BP 5189
EP 5195
PG 7
SC Chemistry, Physical
GA ZZ640
UT ISI:000074751300006
ER

PT J
AU Casagrande, D
   Srivastava, GP
   Ferraz, AC
TI Theoretical calculations for Si(001)-(2x1)Cl
SO SURFACE SCIENCE
LA English
DT Article
DE adsorption; atomic geometry; chemisorption; semiconductor surfaces;
   surface states
ID CL; PHOTOEMISSION; ADSORPTION; SURFACES; SI
AB We have investigated the atomic geometry, electronic states and bonding
   at the Si(001)-(2 x 1) surface covered with a monolayer of Cl. The
   calculations were performed with ab initio pseudopotentials, using a
   plane wave basis and the local density approximation. We find that the
   adsorption of Cl results in an elongated symmetric Si dimer. The
   calculated Si-Cl, Si-Si (dimer) and Si-Si (back-bond) distances are
   2.08 Angstrom, 2.43 Angstrom and 2.34 Angstrom, respectively. The Si-Cl
   bond is inclined at 20 degrees with respect to the surface normal. Our
   results for atomic geometry and electronic states are in good agreement
   with available experimental data. (C) 1998 Elsevier Science B.V. All
   rights reserved.
C1 Univ Exeter, Dept Phys, Exeter EX4 4QL, Devon, England.
   Univ Sao Paulo, Inst Fis, BR-05389970 Sao Paulo, Brazil.
RP Srivastava, GP, Univ Exeter, Dept Phys, Stocker Rd, Exeter EX4 4QL,
   Devon, England.
EM physics@ac.ex.uk
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NR 9
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD MAY 15
PY 1998
VL 404
IS 1-3
BP 653
EP 657
PG 5
SC Chemistry, Physical
GA ZY342
UT ISI:000074610800134
ER

PT J
AU Esteves, PM
   Mota, CJA
   Ramirez-Solis, A
   Hernandez-Lamoneda, R
TI Mechanism of superacid catalyzed alkane activation: theoretical ab
   initio studies of pentacoordinated carbonium ion rearrangement
SO TOPICS IN CATALYSIS
LA English
DT Article
DE carbonium ion; superacid; rearrangement; alkane activation
ID ELECTROPHILIC REACTIONS; ISOBUTANE CRACKING; ALIPHATIC-HYDROCARBONS;
   DEUTERIUM-EXCHANGE; HYDROGEN-TRANSFER; SINGLE BONDS; Y-ZEOLITES; ACID
   SITE; 3-CENTER; ETHANE
AB A theoretical ab initio study of the interconversion of
   pentacoordinated carbonium ions was carried out. For the isobutonium
   cations it was found that the respective C-carbonium ions were lower in
   energy than the H-isobutonium ions. Nevertheless, the interconversion
   of the 1-H-isobutonium cation in the C-isobutonium ion is a barrierless
   process. This suggests that product arisen from C-C protonation in
   liquid superacid and zeolite catalyzed alkane activation may be formed
   by protonation in the outer and more accessible primary C-H bonds of
   isobutane, rather than by direct protonation of the inner and more
   steric demanding C-C bonds.
C1 Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, BR-21949900 Rio De Janeiro, Brazil.
   Univ Estado Morelos, Fac Ciencias, Cuernavaca 62210, Morelos, Mexico.
RP Mota, CJA, Univ Fed Rio de Janeiro, Dept Quim Organ, Inst Quim, Cidade
   Univ,CT Bloco A, BR-21949900 Rio De Janeiro, Brazil.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
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NR 48
TC 15
PU BALTZER SCI PUBL BV
PI BUSSUM
PA PO BOX 221, 1400 AE BUSSUM, NETHERLANDS
SN 1022-5528
J9 TOPIC CATALYSIS
JI Top. Catal.
PY 1998
VL 6
IS 1-4
BP 163
EP 168
PG 6
SC Chemistry, Applied; Chemistry, Physical
GA ZW644
UT ISI:000074432300019
ER

PT J
AU do Monte, SA
   Braga, M
TI Electronic factor for photoinduced electron transfer in
   porphyrin-bridge-quinone systems
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID PHOTOSYNTHETIC REACTION CENTER; DISTANCE DEPENDENCE;
   RHODOPSEUDOMONAS-VIRIDIS; SPHAEROIDES R-26; FIXED DISTANCES; LONE
   PAIRS; MODEL; BICYCLO<2.2.2>OCTANE; SPACERS
AB Quantum-chemical calculations at a semiempirical level (CNDO/S) are
   used for porphyrin-bridge-quinone systems and at an ab initio and
   semiempirical level for CH2-bridge-CH22- systems. In both cases the
   bridge is constituted by a number of aromatic, saturated or mixed
   units. From these calculations the electronic factor (Delta) is
   obtained, for photoinduced reaction (PET) in the first case and for
   thermal reaction in the second case. The relative efficiency of the
   bridges is discussed. For phenylene and staffane units, a
   non-exponential dependence of Delta with distance is observed for PET,
   while for the other two bridges the exponential behavior prevails. (C)
   1998 Elsevier Science B.V. All rights reserved.
C1 Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540 Recife, PE, Brazil.
RP do Monte, SA, Univ Fed Pernambuco, Dept Quim Fundamental, BR-50740540
   Recife, PE, Brazil.
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NR 26
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD JUN 26
PY 1998
VL 290
IS 1-3
BP 136
EP 142
PG 7
SC Physics, Atomic, Molecular & Chemical
GA ZW963
UT ISI:000074466600022
ER

PT J
AU Martins, JBL
   Taft, CA
   Perez, MA
   Stamato, FMLG
   Longo, E
TI Theoretical study of metiamide, a histamine H-2 antagonist
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
ID GAS-PHASE; MOLECULAR DETERMINANTS; ACTIVATION MECHANISM; RECEPTOR
   MODEL; TAUTOMERISM; HISTAMINE-H2-RECEPTOR; H-2-RECEPTORS;
   2-METHYLHISTAMINE; 4-METHYLHISTAMINE; CONFORMATION
AB The requirements for H-2-antagonist activity so far identified for most
   of the known antagonists of histamine are the presence of a
   heterocyclic ring containing a basic center linked via a methylene
   chain to a substituted guanidine or thiourea polar side chain.
   Metiamide is a potent H-2 antagonist (pA2 = 6.06). We have used the ab
   initio Hartree-Fock (HF) method in order to study the conformational
   properties of the N-3-H tautomers of metiamide molecule; and histamine
   monocation. Three basis set (the 3-21G*, 6-31G**, and 6-31 + G**) were
   used, the results compared, and the geometric parameters fully
   optimized. Our results indicate the preference of metiamide for a
   folded conformation with an intramolecular hydrogen bonding between the
   imidazole ring and one of the NH groups. The optimized geometrical
   parameters and charge distributions of both molecules, using the
   Mulliken, and natural bond order (NBO) analysis, are given and
   discussed. (C) 1998 John Wiley & Sons, Inc.
C1 Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis Estatist, BR-22290180 Rio De Janeiro, Brazil.
   Univ Estadual Ponta Grossa, Ponta Grossa, Parana, Brazil.
   Univ Fed Sao Carlos, Dept Quim, BR-13565905 Sao Carlos, SP, Brazil.
RP Taft, CA, Ctr Brasileiro Pesquisas Fis, Dept Mat Condensada & Fis
   Estatist, R Xavier Sigaud 150, BR-22290180 Rio De Janeiro, Brazil.
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NR 49
TC 9
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD JUL 15
PY 1998
VL 69
IS 1
BP 117
EP 128
PG 12
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA ZV457
UT ISI:000074306500013
ER

PT J
AU Rocha, WR
   De Almeida, WB
TI Theoretical study of the olefin insertion reaction in the
   heterobimetallic Pt(H)(PH3)(2)(SnCl3)(C2H4) compound
SO ORGANOMETALLICS
LA English
DT Article
ID ASYMMETRIC HYDROFORMYLATION; BERRY PSEUDOROTATION; CRYSTAL-STRUCTURE;
   BASIS-SETS; COMPLEXES; REARRANGEMENT; PHOSPHORUS; MOLECULES; NMR; MO
AB Ab initio MO calculations at the MP4(SDQ)//MP2 level of theory were
   carried out to investigate the energies and reaction mechanism for the
   olefin insertion reaction (first step in the olefin hydroformylation
   catalytic cycle) using heterobimetallic trans-Pt(H)(PH3)(2)(SnCl)(3) as
   the active catalytic species. The electronic effects of SnCl3 on the
   trigonal-bipyramidal intermediates formed were analyzed through the
   charge decomposition analysis method. The results show that the major
   role of the SnCl3 ligand is to stabilize the pentacoordinated
   intermediates as well as to weaken the Pt-H bond trans to it, favoring
   the insertion.
C1 UFMG, Dept Quim, Lab Quim Computac & Modelagem Mol, ICRx, BR-31270901 Belo Horizonte, MG, Brazil.
RP De Almeida, WB, UFMG, Dept Quim, Lab Quim Computac & Modelagem Mol,
   ICRx, BR-31270901 Belo Horizonte, MG, Brazil.
CR AGBOSSOU F, 1995, CHEM REV, V95, P2485
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NR 38
TC 21
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 0276-7333
J9 ORGANOMETALLICS
JI Organometallics
PD MAY 11
PY 1998
VL 17
IS 10
BP 1961
EP 1967
PG 7
SC Chemistry, Inorganic & Nuclear; Chemistry, Organic
GA ZP802
UT ISI:000073789900015
ER

PT J
AU Ishiki, HM
   Aleman, C
   Galembeck, SE
TI Conformational preferences of flavone and isoflavone in the gas phase,
   aqueous solution and organic solution
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; AB-INITIO; MODEL; PARAMETRIZATION;
   PARAMETERS; SOLVENT; STATES; ENERGY
AB Flavone and isoflavone are an important class of secondary metabolites
   that are widely distributed in nature. In this Letter we have
   determined the conformational preferences of each compound in the gas
   phase, aqueous solution and organic solution. Gas-phase calculations
   were performed using AM1, MNDO, HF/3-21G, HF/6-31G(d) and
   B3-LYP/6-31G(d) calculations. Besides solution calculations were
   performed using the MST solvation model. (C) 1998 Elsevier Science B.V.
   All rights reserved.
C1 Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Pret, Dept Quim, Lab Modelagem Mol, BR-14049902 Ribeirao Preto, SP, Brazil.
   Univ Politecn Catalunya, ETS Engn Ind Barcelona, Dept Engn Quim, E-08028 Barcelona, Spain.
RP Galembeck, SE, Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao
   Pret, Dept Quim, Lab Modelagem Mol, Ave Bandelrantes 3900, BR-14049902
   Ribeirao Preto, SP, Brazil.
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NR 34
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 8
PY 1998
VL 287
IS 5-6
BP 579
EP 584
PG 6
SC Physics, Atomic, Molecular & Chemical
GA ZP121
UT ISI:000073718500016
ER

PT J
AU Prudente, FV
   Neto, JJS
TI The fitting of potential energy surfaces using neural networks.
   Application to the study of the photodissociation processes
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DISCRETE VARIABLE REPRESENTATION; CROSS-SECTIONS; SCATTERING; MOLECULES
AB A back-propagation neural network is utilized to fit potential energy
   surfaces and the transition dipole moment of the HCl+ ion, using the ab
   initio electronic energies calculated by Pradhan, Kirby and Dalgarno.
   These surfaces are used in the study of the photodissociation process.
   The photodissociation cross section is calculated utilizing the equally
   spaced discrete variable representation and the negative imaginary
   potential method. (C) 1998 Elsevier Science B.V. All rights reserved.
C1 Univ Brasilia, Dept Fis, BR-70910900 Brasilia, DF, Brazil.
RP Prudente, FV, Univ Brasilia, Dept Fis, CP 04455, BR-70910900 Brasilia,
   DF, Brazil.
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   PRADHAN AD, 1991, J CHEM PHYS, V95, P9009
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NR 20
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 8
PY 1998
VL 287
IS 5-6
BP 585
EP 589
PG 5
SC Physics, Atomic, Molecular & Chemical
GA ZP121
UT ISI:000073718500017
ER

PT J
AU Sambrano, JR
   Andres, J
   Beltran, A
   Sensato, F
   Longo, E
TI Theoretical study of the structure and stability of NbxOy, and NbxOy+
   (x = 1-3; y = 2-5, 7, 8) clusters
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DENSITY-FUNCTIONAL THEORY; ELECTRON LOCALIZATION; TOPOLOGICAL ANALYSIS;
   EXACT EXCHANGE; BONDS; IONS
AB Geometric, thermodynamic and electronic properties of cluster neutrals
   NbxOy and cations NbxOy+ (x = 1-3; y = 2-5, 7, 8) have been
   characterized theoretically. A DFT calculation using a hybrid
   combination of B3LYP with contracted Huzinaga basis sets. Numerical
   results of the relative stabilities, ionization potentials and band
   gaps of different clusters are in agreement with experiment. Analysis
   of dissociation channels supports the more stable building blocks as
   formed by NbO2, NbO2+ NbO3 and NbO3+ stoichiometries. The net atomic
   charges suggest that oxygen donor molecules can interact more favorably
   on central niobium atoms of cluster cations, while the interaction with
   oxygen acceptor molecules is more favorable on the terminal oxygen
   atoms of neutral clusters. A topological analysis of the electron
   localization function gradient field indicates that the clusters may be
   described as having a strong ionic interaction between Nb and O atoms.
   Published by Elsevier Science B.V.
C1 Univ Estadual Paulista, Dept Matemat, BR-17030360 Bauru, SP, Brazil.
   Univ Jaume 1, Dept Ciencies Expt, Castello 12080, Spain.
   Univ Fed Sao Carlos, Dept Quim, LIEC, BR-13565905 S Carlos, SP, Brazil.
RP Sambrano, JR, Univ Estadual Paulista, Dept Matemat, CP 473, BR-17030360
   Bauru, SP, Brazil.
CR BADER RFW, 1990, ATOMS MOL
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   HUZINAGA S, 1985, BASIS SET MOL CALCUL
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NR 34
TC 14
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAY 8
PY 1998
VL 287
IS 5-6
BP 620
EP 626
PG 7
SC Physics, Atomic, Molecular & Chemical
GA ZP121
UT ISI:000073718500023
ER

PT J
AU Bettega, MHF
   Oliveira, AJS
   Natalense, APP
   Lima, MAP
   Ferreira, LG
TI Static-exchange cross sections for electron-collisions with B2H6, C2H6,
   Si2H6, and Ge2H6
SO EUROPEAN PHYSICAL JOURNAL D
LA English
DT Article
ID NORM-CONSERVING PSEUDOPOTENTIALS; LOW-ENERGY ELECTRONS;
   INELASTIC-SCATTERING; POLYATOMIC-MOLECULES; ABINITIO; ETHANE;
   EXCITATION; METHANE; SNH4; CH4
AB We report integral and differential cross sections from 5-30 eV for
   elastic scattering of electrons by X2H6 (X=B, C, Si, Ge) obtained using
   the Schwinger Multichannel Method with Pseudopotentials [M.K.F.
   Bettega, L.G. Ferreira, M.A.P. Lima, Phys. Rev. A 47, 1111 (1993)]. We
   compare our results with available experimental data and other
   theoretical results, and also with previous results for XH4 (X=C, Si,
   Ge) [M.H.F. Bettega, A.P.P. Natalense, M.A.P. Lime, L.G. Ferreira, J.
   Chem. Phys. 103, 10566 (1995)]. To our knowledge this is the first ab
   initio calculation of the B2H6 and Ge2H5 electron scattering cross
   sections.
C1 Univ Fed Parana, Dept Fis, BR-81531990 Curitiba, Parana, Brazil.
   Univ Estadual Campinas, Inst Fis Gleb Wataghin, BR-13083970 Sao Paulo, Brazil.
   UFMa, Dept Fis, BR-65040020 Sao Luiz, MA, Brazil.
RP Bettega, MHF, Univ Fed Parana, Dept Fis, Caixa Postal 19081,
   BR-81531990 Curitiba, Parana, Brazil.
CR BACHELET G, 1982, PHYS REV B, V46, P4199
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NR 26
TC 7
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010 USA
SN 1434-6060
J9 EUR PHYS J D
JI Eur. Phys. J. D
PD MAR
PY 1998
VL 1
IS 3
BP 291
EP 296
PG 6
SC Physics, Atomic, Molecular & Chemical
GA ZM841
UT ISI:000073581700010
ER

PT J
AU Kahlal, S
   Saillard, JY
   Hamon, JR
   Manzur, C
   Carrillo, D
TI Molecular orbital analysis of the metal-hydrazide(2-) bonding in
   co-ordination chemistry
SO JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
LA English
DT Review
ID X-RAY CRYSTAL; TUNGSTEN-DINITROGEN COMPLEXES; TRANSITION-METAL
   COMPLEXES; BRIDGING ALKOXO LIGANDS; STRUCTURAL CHARACTERIZATION;
   COORDINATED DINITROGEN; HYDRAZIDO(2-) COMPLEXES; MOLYBDENUM COMPLEXES;
   ELECTRONIC-STRUCTURE; NITROGEN-FIXATION
AB The bonding in mono-and bis-hydrazido metal complexes has been studied
   with the help of EHMO and ab initio calculations on various models as
   well as on free hydrazide. The theoretical results have been analysed
   together with a collection of structural data obtained through a
   Cambridge Data Base search covering 118 compounds. Although generally
   described as being a hydrazide(2-) ligand, its oxidation state is often
   closer -1 in early transition-metal complexes, corresponding to the
   following occupation of its frontier orbitals:
   (sigma(n))(2)(pi(NN))(2)-(pi(sigma))(2)(pi*(NN))(1). The occupied
   hydrazido pi(NN) orbital, which does not interact significantly with
   the metal, is largely responsible for the significant double-bond
   character of the N-N bond. The partial population of the pi*(NN) level,
   which tends to reduce the N-N bond order, is partly balanced by
   depopulation of the somewhat antibonding pi(sigma) orbital. Assuming
   the traditional hydrazido(2-) formal charge, the ligand is a
   six-electron donor in monohydrazido metal species if co-ordinated
   linearly. If significantly bent, it is a four-electron donor. In the
   case of cis bis(hydrazido) species, the two formally hydrazide(2-)
   ligands act generally as a 10-electron donor system.
C1 Valparaiso Univ, Inst Quim, Lab Quim Inorgan, Valparaiso, Chile.
   Univ Rennes 1, UMR CNRS 6511, Chim Solide & Inorgan Mol Lab, F-35042 Rennes, France.
   Univ Rennes 1, UMR CNRS 6509, F-35042 Rennes, France.
RP Saillard, JY, Valparaiso Univ, Inst Quim, Lab Quim Inorgan, Ave Brasil
   2950, Valparaiso, Chile.
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NR 140
TC 25
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE CB4 4WF,
   CAMBS, ENGLAND
SN 0300-9246
J9 J CHEM SOC DALTON TRANS
JI J. Chem. Soc.-Dalton Trans.
PD APR 7
PY 1998
IS 7
BP 1229
EP 1240
PG 12
SC Chemistry, Inorganic & Nuclear
GA ZJ011
UT ISI:000073170600028
ER

PT J
AU Pliego, JR
   Franca, MA
   De Almeida, WB
TI Kinetics of the H2O+CCl2 reaction in gas phase and in solution by an
   insertion mechanism
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID CORRELATED MOLECULAR CALCULATIONS; LASER FLASH-PHOTOLYSIS;
   GAUSSIAN-BASIS SETS; O-H BOND; AB-INITIO; DIMETHOXYCARBENE; ADDITIVITY;
   METHYLENE; HYDRATION; CARBENES
AB The single-step insertion reaction of dichlorocarbene into the water OH
   bond was investigated at the ab initio level of theory. We have used
   additivity approximation to obtain an effective CCSD(T)/cc-pVTZ + diff
   single-point energy calculation on MP2/DZP optimized geometries. The
   solvent effect on the activation free energy was included by performing
   Monte Carlo simulations and statistical perturbation theory. it was
   found that direct insertion should not play an important role in the
   H2O + CCl2 reaction. A mechanism involving two water molecules is
   suggested as a possible alternative reaction pathway. (C) 1998 Elsevier
   Science B.V.
C1 Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Quim, Lab Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
RP Pliego, JR, Univ Fed Minas Gerais, Inst Ciencias Exatas, Dept Quim, Lab
   Quim Computac & Modelagem Mol, BR-31270901 Belo Horizonte, MG, Brazil.
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NR 31
TC 10
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD MAR 13
PY 1998
VL 285
IS 1-2
BP 121
EP 126
PG 6
SC Physics, Atomic, Molecular & Chemical
GA ZF354
UT ISI:000072889100019
ER

PT J
AU Castellano, EE
   Piro, OE
   Caram, JA
   Mirifico, MV
   Aimone, SL
   Vasini, EJ
   Glossman, MD
TI Crystallographic study and molecular orbital calculations of
   1,2,5-thiadiazole 1,1-dioxide derivatives
SO JOURNAL OF PHYSICAL ORGANIC CHEMISTRY
LA English
DT Article
DE 1,2,5-thiadiazole; 1,1-dioxide derivatives; single-crystal x-ray
   diffraction; ab initio MO calculations; structure; conformation;
   reactivity
ID 3,4-DIPHENYL-1,2,5-THIADIAZOLE 1,1-DIOXIDE; CHEMICAL-REACTIVITY;
   CRYSTAL-STRUCTURE; ACETONITRILE; ELECTROREDUCTION; HYDROLYSIS; SOLVENTS
AB Single-crystal x-ray diffraction studies are reported for 3,4-dimethyl
   (I), 3-methyl-4-phenyl (II) and 3,4-diphenyl (III) derivatives of
   1,2,5-thiadiazole 1,1-dioxide. Ab initio MO calculations on the
   electronic structure, conformation and reactivity of I, II and III are
   also reported and compared with the x-ray results. The structural data
   are related to previous kinetic and electrochemical experimental
   results on these compounds. (C) 1998 John Wiley & Sons, Ltd.
C1 Natl Univ La Plata, Fac Ciencias Exactas, Dept Fis, RA-1900 La Plata, Argentina.
   Univ Sao Paulo, Inst Fis Sao Carlos, BR-13560 Sao Carlos, SP, Brazil.
   CONICET, Programa PROFIMO, RA-1900 La Plata, Argentina.
   Natl Univ La Plata, INIFTA, CONICET, RA-1900 La Plata, Argentina.
   Natl Univ La Plata, CEQUINOR, CONICET, RA-1900 La Plata, Argentina.
   Univ Nacl Lujan, Dept Ciencias Basicas, RA-6700 Lujan, Argentina.
RP Piro, OE, Natl Univ La Plata, Fac Ciencias Exactas, Dept Fis, CC 67,
   RA-1900 La Plata, Argentina.
EM Piro@ayelen.fisica.unlp.edu.ar
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NR 40
TC 15
PU JOHN WILEY & SONS LTD
PI W SUSSEX
PA BAFFINS LANE CHICHESTER, W SUSSEX PO19 1UD, ENGLAND
SN 0894-3230
J9 J PHYS ORG CHEM
JI J. Phys. Org. Chem.
PD FEB
PY 1998
VL 11
IS 2
BP 91
EP 100
PG 10
SC Chemistry, Organic; Chemistry, Physical
GA ZD967
UT ISI:000072743700003
ER

PT J
AU Gomes, MG
   Davanzo, CU
   Silva, SC
   Lopes, LGF
   Santos, PS
   Franco, DW
TI cis- and trans-nitrosyltetraammineruthenium(II). Spectral and
   electrochemical properties and reactivity
SO JOURNAL OF THE CHEMICAL SOCIETY-DALTON TRANSACTIONS
LA English
DT Article
ID RUTHENIUM NITROSYL COMPLEXES; REVERSIBLE ELECTRON-TRANSFER;
   NITRIC-OXIDE; CHEMISTRY; BEHAVIOR; LIGAND
AB A synthetic route was developed for the preparation of
   trans-[Ru(NH3)(4)(NO)X](n+), where X = isonicotinamide (isn), pyrazine
   (pyz) or sulfite, and cis-[Ru(NH3)(4)(NO)(NO2)](2+). The complexes have
   been characterized by elemental analysis, UV/VIS, infrared, H-1 NMR and
   ESR spectroscopies, molar conductance measurements and cyclic
   voltammetry. All showed v(NO) in the range characteristic of
   metal-co-ordinated NO+ and do not exhibit any ESR signal, consistent
   with the formulation of Ru-II-NO+. The equilibrium constants K-eq for
   the reaction trans-[Ru(NH3)(4)(NO)X](3+) + 20H(-) reversible arrow
   trans-[Ru(NH3)(4)(NO2)X](+) + H2O are 2.5 x 10(8) and 6 x 10(8) dm(6)
   mol(-2) for X = isn or pyz. Cyclic voltammograms of the complexes in
   aqueous solution exhibited reversible one-electron waveforms in the
   potential range -0.13 to -0.38 V vs. SCE, which were assigned to the
   [Ru(NH3)(4)(No)X](n+) --> [Ru(NH3)(4)(NO)X]((n-1)+) process. Nitric
   oxide and trans-[Ru(NH3)(4)(H2O)X](2+) are the final products of the
   reaction between Eu-II and trans-[Ru(NH3)(4)(NO)X](3+), L = isn or pyz.
   Ab initio molecular orbital calculations performed for
   trans-[Ru(NH3)(4)(NO)(pyz)](3+) and trans-[Ru(NH3)(4)(NO)(pyz)](2+),
   and the products of the trans-[Ru(NH3)(4)(NO)(pyz)](3+) one-electron
   electrochemical or chemical reduction, strongly suggest the added
   electron is localized mainly on the nitrosyl ligand. A correlation was
   observed between v(NO) and E-1/2 for the reversible reduction wave.
   These results indicate that the nitric oxide reduction is facilitated
   by strong pi-acceptor ligands trans to the NO. Nitric oxide and
   trans-[Ru(NH3)(4)(H2O)X](3+) were formed when solutions containing
   trans-[Ru(NH3)(4)(NO)X](3+) were irradiated in the range 310-370 nm.
C1 USP, Inst Quim Sao Carlos, BR-13560970 Sao Carlos, SP, Brazil.
   Univ Fed Ceara, Dept Quim Analit & Fis Quim, Fortaleza, Ceara, Brazil.
   Univ Estadual Campinas, Inst Quim, BR-13081970 Campinas, SP, Brazil.
   USP, Inst Quim, BR-09500900 Sao Paulo, Brazil.
RP Franco, DW, USP, Inst Quim Sao Carlos, Caixa Postal 780, BR-13560970
   Sao Carlos, SP, Brazil.
CR *HYP INC, 1994, HYPERCHEM 4
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NR 57
TC 44
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE CB4 4WF,
   CAMBS, ENGLAND
SN 0300-9246
J9 J CHEM SOC DALTON TRANS
JI J. Chem. Soc.-Dalton Trans.
PD FEB 21
PY 1998
IS 4
BP 601
EP 607
PG 7
SC Chemistry, Inorganic & Nuclear
GA ZD135
UT ISI:000072654900016
ER

PT J
AU Morgon, NH
TI Theoretical calculation of proton affinities using basis set functions
   defined by the generator coordinate method
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID GAS-PHASE ACIDITIES; COMPACT EFFECTIVE POTENTIALS; EXPONENT BASIS-SETS;
   OPTIMIZATION TECHNIQUE; GAUSSIAN-2 THEORY; EFFICIENT; ENERGIES;
   1ST-ROW; ATOMS; IONS
AB Ab initio calculations have been performed to determine the molecular
   structure and proton affinity of a set of molecules. The basis sets
   were developed for pseudopotentials using the GCM procedure, This
   technique is potentially useful for large molecules for which similar
   procedures (such as the G2 method and variations) were not feasible.
   This method achieves performance similar to the G2 method at a lower
   computational cost, The mean absolute deviation and the mean deviation
   of the results from experimental are 3.5 and 1.7 kJ mol(-1),
   respectively, compared with 4.6 and 2.2 kJ mol(-1) for the G2 method.
C1 Univ Estadual Campinas, Inst Quim, BR-13083970 Campinas, SP, Brazil.
RP Morgon, NH, Univ Estadual Campinas, Inst Quim, CP 6154, BR-13083970
   Campinas, SP, Brazil.
EM nelson@iqm.unicamp.br
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NR 28
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036 USA
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD MAR 12
PY 1998
VL 102
IS 11
BP 2050
EP 2054
PG 5
SC Chemistry, Physical
GA ZC830
UT ISI:000072622400023
ER

PT J
AU Rocha, WR
   Pliego, JR
   Resende, SM
   dos Santos, HF
   de Oliveira, MA
   de Almeida, WB
TI Ab initio conformational analysis of cyclooctane molecule
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE ab initio conformational analysis; cyclooctane molecule; potential
   energy surface; Hartree-Fock theory; Moller-Plesset theory
ID GAUSSIAN-TYPE BASIS; ORBITAL METHODS; ORGANIC-MOLECULES; MECHANICS;
   SPACE; OXOCANES; MINIMUM
AB The potential energy surface (PES) for the cyclooctane molecule was
   comprehensively investigated at the Hartree-Fock (HF) level of theory
   employing the 3-21G, 6-31G, and 6-31G* basis sets. Six distinct true
   minimum energy structures (named B, BB, BC, CROWN, TBC, and TCC1),
   characterized through harmonic frequency analysis, were located on the
   multidimensional PES. Two transition state structures were also located
   on the PES for the cyclooctane molecule. Electron correlation effects
   were accounted for using the Moller-Plesset second-order perturbation
   theory (MP2) approach. The predicted global minimum energy structure on
   the ab initio PES for the cyclooctane molecule is the BC conformer. A
   gas phase electron diffraction study at 300 K suggested a
   conformational mixture while an NMR study in solution at 161.5 K
   predicted the BC conformer as the predominant form. The equilibrium
   constants reported in the present study, which were evaluated from the
   nb initio calculated total Gibbs free energy change values, were in
   good agreement with both experimental investigations. The ab initio
   results showed that the low temperature condition significantly favored
   the BC conformer while above room temperature both BC and CROWN
   structures can coexist. (C) 1998 John Wiley & Sons, Inc.
C1 UFMG, ICEx, Dept Quim, LQC MM, BR-31270901 Belo Horizonte, MG, Brazil.
RP Rocha, WR, Univ Florida, Quantum Theory Project, 362 Williamson Hall,
   Gainesville, FL 32611 USA.
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   BRECKNELL DJ, 1985, J MOL STRUCT THEOCHE, V124, P343
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NR 23
TC 15
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012 USA
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD APR 15
PY 1998
VL 19
IS 5
BP 524
EP 534
PG 11
SC Chemistry, Multidisciplinary
GA ZC849
UT ISI:000072624700005
ER

PT J
AU Alves, JLA
   Alves, HWL
   de Oliveira, C
   Valadao, RDSC
   Leite, JR
TI Zinc-blende GaN: ab initio calculations
SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED
   TECHNOLOGY
LA English
DT Article
DE zinc-blende; wide-gap device concepts; molecular cluster calculations
ID EFFECTIVE CORE POTENTIALS; SEMICONDUCTOR COMPOUNDS; MOLECULAR
   CALCULATIONS; ZINCBLENDE GAN; 110 SURFACE; RECONSTRUCTION; ORBITALS
AB The purpose of this paper is to contribute, on a theoretical basis, an
   understanding of future wide-gap device concepts and applications based
   on III-V nitride semiconductors. The electronic properties of
   zinc-blende structure GaN and their (110), (100) and (111) surfaces are
   investigated using ab initio calculations based on the full potential
   linear augmented plane-wave (FPLAPW) method within the large unit cell
   approach, and on the molecular Gaussian-92 code. Lattice constant,
   cohesive energy, bulk modulus are obtained from total energy
   calculations. Light-hole and heavy-hole effective masses along (100),
   (111) and (110) directions and electron masses at Gamma point are
   extracted from band structure calculations and compared with previous
   ones based on pseudopotential methods. The hydrostatic pressure
   dependence of the Gamma Gamma, Gamma X and Gamma L energy gaps are also
   obtained. Comparing our band structure and 'molecular cluster'
   calculations, the relaxations of the surfaces are found to be mostly
   determined by local rehybridization or valence effects and are
   basically independent of energy band features. (C) 1997 Elsevier
   Science S.A.
C1 DCNAT FUNREI, BR-36300000 Sao Joao Del Rei, MG, Brazil.
   DFMM IFUSP, BR-05389970 Sao Paulo, SP, Brazil.
RP Alves, JLA, DCNAT FUNREI, CP 110, BR-36300000 Sao Joao Del Rei, MG,
   Brazil.
EM arestrup@dedalus.lcc.ufmg.br
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   CHANG KJ, 1984, SOLID STATE COMMUN, V50, P105
   EDGAR JH, 1994, DATAREVIEWS SERIES
   FAN WJ, 1996, J APPL PHYS, V79, P188
   FANCIULLI M, 1993, PHYS REV B, V48, P15144
   FIORENTINI V, 1993, PHYS REV B, V47, P13353
   FRISCH MJ, 1992, GAUSSIAN 92
   HAY PJ, 1985, J CHEM PHYS, V82, P270
   HAY PJ, 1985, J CHEM PHYS, V82, P299
   JAFFE JE, 1996, PHYS REV B, V53, R4209
   JHI SH, 1995, PHYS STATUS SOLIDI B, V191, P367
   LAMBRECHT WRL, 1992, MATER RES SOC S P, V242, P367
   MADELUNG O, 1982, LANDOLTBORNSTEIN N A, V17
   MONKHORST HJ, 1976, PHYS REV B, V13, P5188
   PALUMMO M, 1992, PHYSICS SEMICONDUCTI, V1, P89
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NR 21
TC 4
PU ELSEVIER SCIENCE SA
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0921-5107
J9 MATER SCI ENG B-SOLID STATE M
JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol.
PD DEC 18
PY 1997
VL 50
IS 1-3
BP 57
EP 60
PG 4
SC Materials Science, Multidisciplinary; Physics, Condensed Matter
GA YW795
UT ISI:000071974800014
ER

PT J
AU Ishiki, HM
   Donate, PM
   Galembeck, SE
TI Electronic structure of chromone and its hydroxylated derivatives on
   positions 2 and 3
SO JOURNAL OF MOLECULAR STRUCTURE-THEOCHEM
LA English
DT Article
DE computational study; electronic structure; flavonoids; reactivity;
   resonance
ID MOLECULAR-ORBITAL METHODS; INTRAMOLECULAR PROTON-TRANSFER;
   GAUSSIAN-TYPE BASIS; CONFORMATIONAL-ANALYSIS; SEMIEMPIRICAL METHODS;
   BASIS-SETS; ORGANIC-MOLECULES; OPTIMIZATION; FLAVONOIDS; PARAMETERS
AB The electronic structure of chromone (1) and those of its 2-hydroxy (2)
   and 5-hydroxy (3) derivatives were studied by semiempirical and ab
   initio molecular orbital methods. Several electronic parameters show
   that the A-ring is an aromatic system, whereas the C-ring does not
   present conjugation. In the C-ring, the double bonds are located in the
   carbonyl group and between C(2)-C(3). These results were confirmed by
   comparison with geometries of chromone derivatives which were
   determined by X-ray diffraction data. The relative stability of
   compounds (2) and (3) was explained and the sites of acid, basic,
   nucleophilic and electrophilic attack were also determined. (C) 1998
   Elsevier Science B.V.
C1 Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao Preto, Dept Quim, BR-14049901 Ribeirao Preto, SP, Brazil.
RP Galembeck, SE, Univ Sao Paulo, Fac Filosofia Ciencias & Letras Ribeirao
   Preto, Dept Quim, Ave Bandeirantes 3900, BR-14049901 Ribeirao Preto,
   SP, Brazil.
EM segalemb@usp.br
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NR 36
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD FEB 2
PY 1998
VL 423
IS 3
BP 235
EP 243
PG 9
SC Chemistry, Physical
GA YX315
UT ISI:000072027900009
ER

PT J
AU Hollauer, E
   Olabe, JA
TI A HF/CI-SD study of the low-lying states of nitroprusside ion
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE ab initio (SCF, CI-SD); nitroprusside; excited states; metastable
   states; Na-2[Fe(CN)(5)NO]; pentacyanonitrosylferrate
ID TRANSPARENT MOLECULAR SYSTEMS; COMPACT EFFECTIVE POTENTIALS; METASTABLE
   ELECTRONIC STATE; EXPONENT BASIS-SETS; OPTICAL DISPERSION;
   SODIUM-NITROPRUSSIDE; POLARIZED-LIGHT; SINGLE-CRYSTAL; RAMAN-SPECTRA;
   TGA-DTA
AB Since the discovering of two photoexcited metastable states of
   crystalline sodium nitroprusside, Na-2[Fe(CN)(5)NO]..2H(2)O (SNP)
   showing rather long lifetimes at temperatures below 160 K, much effort
   has been devoted toward the study of its electronic structure. Despite
   this tremendous effort the nature of the frontier orbitals and the
   related low energy excitations remains controversial. Early
   calculations, EHT, showed the HOMO as mainly the metallic 3d orbital
   while the LUMO had a major pi* (NO) contribution. However INDO
   calculations, clearly set the metal d orbital many electron-volts deep
   in core. The vertical electronic spectrum have been estimated through
   ab initio HF/CI-SD with a double-zeta quality basis set. The ab initio
   results support Bottomley and Grein's interpretations and assign the
   first electronic transitions to ligand-to-ligand charge-transfer
   excitation from trans-cyano to nitrosyl ligands. The corresponding
   oscillator strengths have been calculated showing comparable intensity
   with the experimental results. The excitation energy of the metal -->
   NO charge-transfer transition, 8e --> 13e (d(xz),d(yz) --> pi* NO) have
   been estimated to be at 4.52 eV and show a rather intense absorption
   band. The second CT excitation, 1b(2) --> 13e (d(xy) --> pi* NO),
   pointed by previous works as a typical CT band, exhibits a small
   intensity at 5.04 eV. In the calculations it was observed that SCF
   orbital ordering are rather dependent on the metal basis set used.
   Metallic minimal basis set show results in close agreement with EHT
   early calculations while double-zeta basis set pushes the metallic d
   orbitals deep away from the HOMO's. The HF orbital ordering has been
   used to interpret photochemical and thermoanalysis experiments on SNP
   and the results seem to fit properly with the calculated properties.
C1 Univ Fed Fluminense, Inst Quim, Dept Fisicoquim, BR-24210150 Niteroi, RJ, Brazil.
   Univ Buenos Aires, Fac Ciencias Exactas & Nat, Dept Quim Inorgan Analit & Quim Fis Inquimae, RA-1428 Buenos Aires, DF, Argentina.
EM gfqholl@vm.uff.br
   olabe@ayelen.q3.fcen.uba.ar
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NR 50
TC 5
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PD SEP-OCT
PY 1997
VL 8
IS 5
BP 495
EP 504
PG 10
SC Chemistry, Multidisciplinary
GA YT741
UT ISI:000071640400010
ER

PT J
AU Olivato, PR
   Mondino, MG
   Yreijo, MH
   Wladislaw, B
   Bjorklund, MB
   Marzorati, L
   Distefano, G
   Dal Colle, M
   Bombieri, G
   Del Pra, A
TI Spectroscopic and theoretical studies on the conformation of some
   alpha-sulfinylacetophenones
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID SUBSTITUTED CARBONYL-COMPOUNDS; ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY;
   ELECTRONIC INTERACTION; INTRAMOLECULAR INTERACTIONS; ACETOPHENONES;
   SPECTRA
AB IR nu(CO) and nu(SO) frequencies of some alpha-sulfinylacetophenones
   [PhC(O)CH2S(O)R: R = Me 1, Et 2, Pr-i 3, Ph 4 and Bu' 5] have been
   measured and their conformations are estimated with the help of ab
   initio 6-31G** calculations and X-ray diffraction analyses. The
   anomalous negative carbonyl frequency shifts for the cis(2) rotamer
   together with the decrease of the cis:gauche population ratio in
   solvents of increasing polarity for compounds 1-4 support the existence
   of a strong intramolecular interaction between C=O and S=O dipoles,
   which stabilizes the cis(2) rotamer more than the pi(CO)-sigma*(C-SO)
   and pi(CO)*-sigma(C-SO) orbital interactions stabilize the gauche(3)
   rotamer. The stability of the cis(2) rotamer is discussed in terms of
   the electrostatic attraction between the C=O and S=O dipoles along with
   the pi(S=O)*<--n(O(CO)) charge transfer which lead to an O-(C)...
   S-(SO) contact shorter than the sum of the corresponding van der Waals
   radii. The gauche(2) rotamer of 5 is more stable than the cis(2) one in
   which steric strain between the carbonyl oxygen atom and the tert-butyl
   group is present.
C1 Univ Sao Paulo, Inst Quim, BR-05599970 Sao Paulo, Brazil.
   Univ Ferrara, Dipartimento Chim, I-44100 Ferrara, Italy.
   Univ Milan, Ist Chim Farmaceut, I-20131 Milan, Italy.
RP Olivato, PR, Univ Sao Paulo, Inst Quim, Caixa Postal 26-077,
   BR-05599970 Sao Paulo, Brazil.
CR ALCUDIA F, 1988, AN QUIM C-ORG BIOQ, V84, P333
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NR 37
TC 16
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE CB4 4WF,
   CAMBS, ENGLAND
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD JAN
PY 1998
IS 1
BP 109
EP 114
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA YR484
UT ISI:000071499900020
ER

PT J
AU Mohallem, JR
   Vianna, RO
   Quintao, AD
   Pavao, AC
   McWeeny, R
TI Pauling's resonating valence bond theory of metals: some studies on
   lithium clusters
SO ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS
LA English
DT Article
ID ELECTRONIC-STRUCTURE; GEOMETRIC STRUCTURE
AB We report for the first time fully ab initio valence bond (VB)
   calculations with explicit use of the unsynchronized resonance
   structures introduced by Pauling [1]. We show that resonance involving
   these structures largely determines the stability and conformation of
   the Li-4 cluster and plays a central role in a VB explanation of the
   3-center bonds in planar alkali clusters. The theory can make
   qualitative predictions on the behaviour of general metallic clusters,
   and can relate stability and conformation to electronic structure, thus
   indicating the origin of magic numbers. This first ab initio test of
   Pauling's resonating VB theory confirms the importance of the metallic
   orbital and the covalent character of the metal-metal bond.
C1 UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50740540 RECIFE,PE,BRAZIL.
   UNIV PISA,DIPARTIMENTO CHIM & CHIM IND,I-56100 PISA,ITALY.
RP Mohallem, JR, UNIV FED MINAS GERAIS,INST CIENCIAS EXATAS,DEPT FIS,CP
   702,BR-30161970 BELO HORIZONT,MG,BRAZIL.
CR AGUIAR JA, 1992, J MAG MAG MAT, V547, P104
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   GONCALVES CP, UNPUB
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NR 27
TC 8
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0178-7683
J9 Z PHYS D-ATOMS MOL CLUSTERS
JI Z. Phys. D-Atoms Mol. Clusters
PD NOV
PY 1997
VL 42
IS 2
BP 135
EP 143
PG 9
SC Physics, Atomic, Molecular & Chemical
GA YJ528
UT ISI:A1997YJ52800011
ER

PT J
AU Janotti, A
   Fazzio, A
   Piquini, P
   Mota, R
TI Defect complexes in GaAs: First-principles calculations
SO PHYSICAL REVIEW B
LA English
DT Article
ID NATIVE DEFECTS; PSEUDOPOTENTIALS; IRRADIATION
AB The electronic and structural properties of selected defect complexes
   in GaAs, created during electron or ion irradiation, are studied. An ab
   initio calculation based on pseudopotential density-functional theory
   is used. A supercell with 128 atoms is adopted in Car-Parrinello
   scheme. For the antistructure pair (As-Ga+Ga-As), from the total-energy
   calculations, first donor, first acceptor, and second acceptor levels
   are observed, and a comparison is made with earlier, both theoretical
   and experimental, results. Two other possible defect complexes
   (V-As+As-Ga+Ga-i) and V-Ga+Ga-As+As-i), are discussed. It is shown that
   the first one presents a metastable configuration, and the second one
   is unstable presenting a spontaneous recombination. For all defect
   complexes the formation energies and charge densities are discussed.
C1 UNIV FED SANTA MARIA,DEPT FIS,BR-97015900 SANTA MARIA,RS,BRAZIL.
RP Janotti, A, UNIV SAO PAULO,INST FIS,CAIXA POSTAL 66318,BR-05315970 SAO
   PAULO,SP,BRAZIL.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BARAFF GA, 1986, PHYS REV B, V33, P7356
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NR 14
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 15
PY 1997
VL 56
IS 20
BP 13073
EP 13076
PG 4
SC Physics, Condensed Matter
GA YH588
UT ISI:A1997YH58800060
ER

PT J
AU Carvalho, MC
   Juliano, VF
   Kascheres, C
   Eberlin, MN
TI Gas phase chemistry of the heterocumulene cations O=C=N+=C=O and
   O=C=C=N+=O
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID ION-MOLECULE REACTIONS; PENTAQUADRUPOLE MASS-SPECTROMETER; KINETIC
   METHOD; ACYLIUM IONS; ISOMERS; TANDEM; COLLISIONS; AFFINITIES; 3D
AB The low energy collisional dissociation and ion/molecule chemistry of
   the heterocumulene cations O=C=N+=C=O 1 and O=C=C=N+=O 2 have been
   investigated by pentaquadrupole mass spectrometry, and G2(MP2) ab
   initio calculations applied to interrogate their relative stabilities
   and dissociation thresholds, as well as those of six other conceivable
   C2NO2+ isomers 3-8. The calculations show that the acyclic 1 (zero) and
   2 (72.4 kcal mol(-1)) are the most stable isomers, whereas both the
   location of the positive charge mainly at the CO-carbon and the short
   CO bond lengths characterize their acylium ion structures, Two cyclic
   isomers, i.e. 7 (131.3 kcal mol(-1)) and 8 (140.0) kcal mol(-1), were
   also found to be stable, but placed at energy levels considerably
   higher than 1. Exactly as predicted from G2(MP2) energy dissociation
   thresholds, low-energy collisions cause dissociation of 1 exclusively
   by CO loss to yield NCO+ of m/z 42. A more diverse dissociation
   chemistry is predicted and exhibited by 2, which dissociates mainly by
   loss of an oxygen atom (C2NO+ of m/z 54), CO (CNO+ of m/z 42) and C2O
   (NO+ of m/z 30). Both ions are unreactive towards polar [4+2(+)]
   cycloaddition with isoprene. However, they undergo ketalization with
   2-methoxyethanol, and transacetalization with two cyclic neutral
   acetals, i.e. 2-methyl-1,3-dioxolane and 1,3-dioxane, and these
   structurally diagnostic ion/molecule reactions confirm experimentally
   the acylium ion structures of 1 and 2. Cyclic 'ionic ketals', ie.
   1,3-dioxonium ions, are formed in these reactions, as evidenced by
   their MS3 spectra, which show extensive dissociation to re-form the
   reactant ions. Whereas 1 readily forms a stable and covalently bound
   adduct with pyridine, 2 reacts mainly by net CN+ and OCN+ transfer
   via--most likely--the unstable (Py-2)(+) adduct.
C1 STATE UNIV CAMPINAS UNICAMP,INST CHEM,BR-13083970 CAMPINAS,SP,BRAZIL.
CR BEAUGRAND C, 1989, ANAL CHEM, V61, P1447
   BOWERS MT, 1979, GAS PHASE ION CHEM, V1
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   EBERLIN MN, 1992, J AM CHEM SOC, V114, P2884
   EBERLIN MN, 1993, J AM CHEM SOC, V115, P9226
   EBERLIN MN, 1993, ORG MASS SPECTROM, V28, P679
   EBERLIN MN, 1994, J AM CHEM SOC, V116, P2457
   EBERLIN MN, 1997, J AM CHEM SOC, V119, P3550
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   FARRAR JM, 1988, TECHNIQUES STUDY ION
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   VAINIOTALO P, 1996, P 44 ASMS C MASS SPE, P453
   WESDEMIOTIS C, 1987, CHEM REV, V87, P485
   WONG PSH, 1997, J AM SOC MASS SPECTR, V8, P68
   YANG SS, 1995, J MASS SPECTROM, V30, P807
   ZAGOREVSKII DV, 1994, MASS SPECTROM REV, V13, P133
NR 45
TC 17
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD NOV
PY 1997
IS 11
BP 2347
EP 2352
PG 6
SC Chemistry, Organic; Chemistry, Physical
GA YH013
UT ISI:A1997YH01300033
ER

PT J
AU Pliego, JR
   DeAlmeida, WB
TI Reaction of CCl2 with CH2NH and the formation of dipolar and biradical
   ylide structures
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID AB-INITIO; SPECTROSCOPIC DETECTION; 1,2-HYDROGEN MIGRATION;
   POLYATOMIC-MOLECULES; CYCLO-ADDITIONS; RATE CONSTANTS; ABSOLUTE RATE;
   DECOMPOSITION; SELECTIVITIES; PHOTOLYSIS
AB The potential energy surface for the reaction between CH2NH and CCl2
   has been investigated using ab initio methods. We have performed
   geometry optimizations at the MP2/6-31G* level of theory and single
   point calculations at the MP4(SDQ)/6-311+ +G** level. The reaction step
   for ylide formation has a free energy of activation predicted to be 5.0
   kcal mol(-1). The parallel 1,2-cycloaddition reaction has a calculated
   free energy barrier of 16.5 kcal mol(-1), indicating that this second
   pathway is not competitive with ylide formation. The structure of the
   azomethine ylide formed in the first reaction step is similar to that
   found for the ylide resulting from the reaction of methylene with
   ammonia and corresponds to a dipolar species, This is highly unstable
   and rearranges to its more stable isomer, the biradical azomethine
   ylide, which has a structure similar to the corresponding carbonyl
   ylide. This species has a free energy barrier to ring closure
   calculated to be 21.2 kcal mol(-1), so it has reasonable kinetic
   stability, The resulting aziridine has a free energy of 24.1 kcal
   mol(-1) lower than the biradical azomethine ylide, and the activation
   free energy of ring opening is calculated to be 45.3 kcal mol(-1).
C1 UFMG,ICEX,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEN MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR BACH RD, 1995, J ORG CHEM, V60, P4653
   BARTNIK R, 1984, TETRAHEDRON, V40, P2569
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   COOK AG, 1962, J ORG CHEM, V27, P3686
   DU XM, 1990, J AM CHEM SOC, V112, P1920
   FRISH MJ, 1995, GAUSSIAN 94
   GONZALEZ C, 1996, J AM CHEM SOC, V118, P5408
   HOUK KN, 1980, J AM CHEM SOC, V102, P1504
   HOUK KN, 1984, J AM CHEM SOC, V106, P4291
   HOUK KN, 1985, TETRAHEDRON, V41, P1555
   JACKSON JE, 1988, J AM CHEM SOC, V110, P5595
   JACKSON JE, 1989, J AM CHEM SOC, V111, P6874
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   PADWA A, 1991, CHEM REV, V91, P263
   PLIEGO JR, 1996, CHEM PHYS LETT, V249, P136
   PLIEGO JR, 1996, J PHYS CHEM-US, V100, P12410
   PLIEGO JR, 1997, J CHEM PHYS, V106, P3582
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   YAMAGUCHI Y, 1993, J AM CHEM SOC, V115, P5790
NR 29
TC 5
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD NOV
PY 1997
IS 11
BP 2365
EP 2369
PG 5
SC Chemistry, Organic; Chemistry, Physical
GA YH013
UT ISI:A1997YH01300035
ER

PT J
AU Sambrano, JR
   Andres, J
   Beltran, A
   Sensato, FR
   Leite, ER
   Stamato, FMLG
   Longo, E
TI An ab initio study of oxygen vacancies and doping process of Nb and Cr
   atoms on TiO2 (110) surface models
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE ab initio; oxygen vacancy; doping; titanium oxide surface; varistor
   ceramics
ID OXIDE; SOLVENT; VARISTORS; CLUSTERS
AB We theoretically investigated how the formation of oxygen vacancies and
   the addition of niobium and chromium atoms as dopants modify the
   varistor properties of TiO2. The calculations were carried out at the
   HF level using a contracted basis set, developed by Huzinaga et al.. to
   represent the atomic centers on the (110) surface for the large
   (TiO2)(15) cluster model. The change of the values for the net atomic
   charges and band gap after oxygen vacancy formation and the presence of
   dopants in the lattice are analyzed and discussed. It is shown that the
   formation of oxygen vacancies decreases the band gap while an opposite
   effect is found when dopants are located in the reduced surface. The
   theoretical results are compared with available experimental data. A
   plausible explanation of the varistor behavior of this system is
   proposed. (C) 1997 John Wiley & Sons, Inc.
C1 UNIV JAUME 1,DEPT CIENCIES EXPT,CASTELLO 12080,SPAIN.
   UNIV FED SAO CARLOS,DEPT QUIM,LIEC,BR-13565905 SAO CARLOS,SP,BRAZIL.
RP Sambrano, JR, UNIV ESTADUAL PAULISTA,DEPT MATEMAT,CP 473,BR-17030360
   BAURU,SP,BRAZIL.
CR BAGUS PS, 1991, CLUSTER MODELS SUR B, V283, P233
   BERMUDEZ VM, 1981, PROG SURF SCI, V11, P1
   BUENO PR, UNPUB
   BUENO PR, 1996, J MATER SCI LETT, V15, P2048
   CARPENTER JE, 1988, J MOL STRUCT THEOCHE, V169, P41
   EGDELL RG, 1995, J MATER CHEM, V5, P499
   FOSTER JP, 1980, J AM CHEM SOC, V102, P7211
   FRISCH MJ, 1995, GAUSSIAN94 REVISION
   GUPTA TK, 1985, J MATER SCI, V20, P4091
   HADJIIVANOV KI, 1996, CHEM SOC REV, V25, P61
   HAGFELDT A, 1992, INT J QUANTUM CHEM, V44, P477
   HAGFELDT A, 1994, INT J QUANTUM CHEM, V49, P97
   HEILAND G, 1984, CHEM PHYSICS SOLID S, V3
   HENRICH VE, 1983, PROG SURF SCI, V14, P175
   HENRICH VE, 1985, REP PROG PHYS, V48, P11
   HUZINAGA S, 1984, GAUSSIAN BASIS SETS
   HUZINAGA S, 1985, COMPUT PHYS REP, V2, P279
   INAMADA M, 1978, JPN J APPL PHYS, V17, P1
   LEITE ER, 1992, J MATER SCI, V27, P5325
   MARTINS JBL, 1993, INT J QUANTUM CHEM, V27, P643
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P301
   MARTINS JBL, 1995, J MOL STRUCT THEOCHE, V330, P447
   MARUCCO JF, 1981, J PHYS CHEM SOLIDS, V42, P363
   MASUYAMA T, 1968, JPN J APPL PHYS, V7, P1294
   PENNEWISS J, 1982, MATER LETT, V40, P536
   PENNEWISS J, 1990, MATER LETT, V40, P219
   PETTERSSON LGM, 1993, THEOR CHIM ACTA, V85, P345
   PIANARO SA, 1995, J MATER SCI LETT, V14, P692
   RANTALA TS, 1994, PHYS SCRIPTA, V54, P252
   REED AE, 1985, J CHEM PHYS, V83, P735
   REED AE, 1988, CHEM REV, V88, P899
   RINALDI D, 1992, J COMPUT CHEM, V13, P675
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   SAKAI Y, 1982, J COMPUT CHEM, V3, P6
   SANON G, 1991, PHYS REV, V44, P5681
   TAPIA O, 1975, MOL PHYS, V29, P1653
   TAPIA O, 1992, THEORETICAL MODELS C, P435
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   WATANABE Y, 1994, J NON-CRYST SOLIDS, V178, P84
   YANG SL, 1995, J MATER RES, V10, P345
NR 41
TC 9
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD DEC 5
PY 1997
VL 65
IS 5
BP 625
EP 631
PG 7
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA YG650
UT ISI:A1997YG65000028
ER

PT J
AU Rocha, WR
   DeAlmeida, WB
TI Reaction path for the insertion reaction of SnCl2 into the Pt-Cl bond:
   An ab initio study
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
ID COMPACT EFFECTIVE POTENTIALS; EXPONENT BASIS-SETS; ASYMMETRIC
   HYDROFORMYLATION; ORGANIC SYNTHESES; OLEFIN HYDROFORMYLATION;
   ELECTRONIC-STRUCTURE; MOLECULAR-STRUCTURE; CRYSTAL-STRUCTURE;
   TRANSITION-METAL; COMPLEXES
AB The reaction pathway for the insertion reaction of SnCl2 into the Pt-Cl
   bond on the cis-Pt(Cl)(2)(PH3)(2) compound was investigated at the ab
   initio MO level of theory. The optimized structure obtained for the
   transition state indicates that this reaction proceeds through a
   three-center transition state, and the formed intermediate
   cis-Pt(Cl)(PH3)(2)(SnCl3) easily isomerizes to the
   trans-Pt(Cl)(PH3)(2)(SnCl3) compound. The nature of the bonds was
   investigated with the charge decomposition analysis (CDA) method and
   this method indicates that the SnCl3 group is a stronger trans director
   than is the PH3 group. (C) 1997 John Wiley & Sons, Inc.
C1 UFMG,ICEF,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR ALBINATI A, 1985, J ORGANOMET CHEM, V295, P239
   ANDERSON GK, 1980, CHEM SOC REV, V9, P185
   BAERENDS EJ, 1986, NATO ASI SER C-MATH, V176, P159
   BAGUS PS, 1984, J CHEM PHYS, V80, P4378
   BAGUS PS, 1984, J CHEM PHYS, V81, P1966
   BAGUS PS, 1992, J CHEM PHYS, V96, P8962
   BARDI R, 1982, J ORGANOMET CHEM, V224, P407
   BARDI R, 1982, J ORGANOMET CHEM, V234, P107
   BASOLO F, 1967, MECH INORGANIC REACT
   BERRY RS, 1960, J CHEM PHYS, V32, P933
   CAVINATO G, 1983, J ORGANOMET CHEM, V241, P275
   CHATT J, 1953, J CHEM SOC, P2939
   DAPPRICH S, 1994, CDA 2 1
   DAPPRICH S, 1995, J PHYS CHEM-US, V99, P9352
   DELPRA A, 1979, J CHEM SOC DA, P1862
   DEWAR MJS, 1951, B SOC CHIM FR, V18, C79
   EHLERS AW, 1996, ORGANOMETALLICS, V15, P105
   FRISCH MJ, 1995, GAUSSIAN 94 REVISION
   FUJIMOTO H, 1974, J CHEM PHYS, V60, P572
   FUJIMOTO H, 1981, J AM CHEM SOC, V103, P752
   GOMEZ M, 1991, ORGANOMETALLICS, V10, P4036
   HEHRE WJ, 1972, J CHEM PHYS, V56, P2257
   HOLLWARTH A, 1993, CHEM PHYS LETT, V208, P237
   HSU CY, 1975, J AM CHEM SOC, V97, P3553
   KATO S, 1974, J AM CHEM SOC, V94, P2024
   KOLLAR L, 1987, J ORGANOMET CHEM, V330, P305
   KOLLAR L, 1988, J ORGANOMET CHEM, V350, P277
   OZAWA F, 1981, B CHEM SOC JPN, V54, P1868
   PAONESSA RS, 1982, J AM CHEM SOC, V104, P3529
   PARRINELLO G, 1987, J AM CHEM SOC, V109, P7122
   PETTIT LD, 1971, Q REV, P1
   PREGOSIN PS, 1978, HELV CHIM ACTA, V61, P1848
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
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   STEVENS WJ, 1992, CAN J CHEM, V70, P612
   STILLE JK, 1983, J MOL CATAL, V21, P203
   WISNER JM, 1986, J AM CHEM SOC, V108, P347
   ZIEGLER T, 1977, THEOR CHIM ACTA, V46, P1
   ZIEGLER T, 1992, NATO ASI SER C, V378, P367
NR 39
TC 9
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD DEC 5
PY 1997
VL 65
IS 5
BP 643
EP 650
PG 8
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA YG650
UT ISI:A1997YG65000030
ER

PT J
AU Cordeiro, JMM
TI C-H center dot center dot center dot O and N-H center dot center dot
   center dot O hydrogen bonds in liquid amides investigated by Monte
   Carlo simulation
SO INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY
LA English
DT Article
DE Monte Carlo simulation; amides; hydrogen bond; radial distribution
   functions
ID X-RAY-DIFFRACTION; MOLECULAR-DYNAMICS SIMULATIONS; MO-SCF CALCULATIONS;
   FORMAMIDE; METHYLFORMAMIDE; GEOMETRY; N,N-DIMETHYLFORMAMIDE; PEPTIDES;
   MIXTURES; NEUTRON
AB Monte Carlo simulations of liquid formamide, N-methylformamide (MF),
   and N,N-dimethylformamide (DMF) have been performed in the isothermal
   and isobaric ensemble at 298 K and 1 atm, aiming to investigate the C-H
   ... O and N-H ... O hydrogen bonds. The interaction energy was
   calculated using the classical 6-12 Lennard-Jones pairwise potential
   plus a Coulomb term on a rigid six-site molecular model with the
   potential parameters being optimized in this work. Theoretical values
   obtained for heat of vaporization and liquid densities are in good
   agreement with the experimental data. The radial distribution function
   [RDF, g(r)] obtained compare well with R-X diffraction data available.
   The RDF and molecular mechanics (MM2) minimization show that the C-H
   ... O interaction has a significant role in the structure of the three
   liquids. These results are supported by ab initio calculations. This
   Interaction is particularly important in the structure of MF. The
   intensity of the N-H ... O hydrogen bond is greater in the MF than
   formamide. This could explain some anomalous properties verified in MF.
   (C) 1997 John Wiley & Sons, Inc.
RP Cordeiro, JMM, UNESP,FAC ENGN ILHA SOLTEIRA,DEPT QUIM & FIS,AV BRASIL
   56,BR-15385000 ILHA SOLTEIRA,SP,BRAZIL.
CR *SER SOFTW, PCMODEL PROGR
   ALLEN MP, 1987, COMPUTER SIMULATIONS
   BERTOLASI V, 1995, ACTA CRYSTALLOGR B 6, V51, P1004
   CARLSON HA, 1993, J COMPUT CHEM, V14, P1240
   COURNOYER ME, 1984, MOL PHYS, V51, P119
   DESIRAJU GR, 1990, J CHEM SOC CHEM COMM, V179, P454
   DESIRAJU GR, 1991, ACCOUNTS CHEM RES, V24, P290
   FANTONI AC, 1996, J CHEM SOC FARADAY T, V92, P343
   FREITAS LCG, DIADORIM FORTRAN COD
   FREITAS LCG, 1995, THEOCHEM-J MOL STRUC, V335, P189
   FRISH MJ, 1992, GAUSSIAN REVISION A
   GIBSON KD, 1990, J COMPUT CHEM, V11, P468
   HAGLER AT, 1974, J AM CHEM SOC, V96, P5319
   JORGENSEN WL, 1985, J AM CHEM SOC, V107, P569
   JORGENSEN WL, 1991, CHEMTRACTS ORG CHEM, V4, P91
   KALMAN E, 1983, Z NATURFORSCH A, V38, P231
   LADANYI BM, 1993, ANNU REV PHYS CHEM, V44, P335
   LIDE DR, 1992, CRC HDB PHYSICS CHEM
   METROPOLIS N, 1953, J CHEM PHYS, V21, P108
   NEUEFEIND J, 1992, MOL PHYS, V76, P143
   OHTAKI H, 1983, B CHEM SOC JPN, V56, P2116
   OHTAKI H, 1983, B CHEM SOC JPN, V56, P3406
   OHTAKI H, 1986, B CHEM SOC JPN, V59, P271
   RADNAI T, 1988, B CHEM SOC JPN, V61, P3845
   RAO BG, 1990, J AM CHEM SOC, V112, P3803
   SAGARIK KP, 1987, J CHEM PHYS, V86, P5117
   SCHOESTER PC, 1995, Z NATURFORSCH A, V50, P38
   SINOTI ALL, 1996, J BRAZIL CHEM SOC, V7, P133
   STEINER T, 1994, J CHEM SOC CHEM COMM, P2341
   STRAATSMA TP, 1992, ANNU REV PHYS CHEM, V43, P407
   TAYLOR R, 1982, J AM CHEM SOC, V104, P5063
   YASHONATH S, 1991, CHEM PHYS, V155, P351
NR 32
TC 10
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0020-7608
J9 INT J QUANTUM CHEM
JI Int. J. Quantum Chem.
PD DEC 5
PY 1997
VL 65
IS 5
BP 709
EP 717
PG 9
SC Chemistry, Physical; Mathematics, Interdisciplinary Applications;
   Physics, Atomic, Molecular & Chemical
GA YG650
UT ISI:A1997YG65000037
ER

PT J
AU Mathon, J
   Villeret, M
   Umerski, A
   Muniz, RB
   Castro, JD
   Edwards, DM
TI Quantum-well theory of the exchange coupling in magnetic multilayers
   with application to Co/Cu/Co(001)
SO PHYSICAL REVIEW B
LA English
DT Article
ID NONMAGNETIC METALLIC LAYER; AB-INITIO CALCULATIONS; TORQUE METHOD;
   OSCILLATIONS; SUPERLATTICES; STATES; MAGNETORESISTANCE; FERROMAGNETS;
   CONFINEMENT; INTERFACES
AB Two parallel calculations of the-exchange coupling in a Co/Cu/Co(001)
   trilayer, both using the same realistic s, p, and d tight-binding bands
   with parameters determined from the ab initio band structures of bulk
   Cu and Co, are reported. The coupling is first calculated within the
   framework of the quantum-well (QW) formalism in which the periodic
   behavior of the spectral density is exploited to derive an analytic
   formula for the coupling valid for large spacer thicknesses. On the
   other hand, an alternative expression for the coupling, referred to as
   cleavage formula, is derived that allows accurate and efficient
   numerical evaluation of the coupling. An analytic approximation to this
   expression, valid in the asymptotic region of large spacer thickness,
   is also obtained. These two approaches are discussed in relation to
   other existing theoretical formulations of the coupling. The numerical
   results for the coupling obtained from the cleavage formula are first
   compared with the analytical QW calculation. The agreement between the
   two calculations is impressive and entirely justifies the analytical QW
   approach. The numerical calculation fully confirms the result of the QW
   formalism that, for trilayers with thick Co layers, the short-period
   oscillation due to the minority electrons from the vicinity of the Cu
   Fermi-surface (FS) necks is dominant, the contribution of the
   long-period oscillation being negligible. This is shown, in the
   analytical QW formalism, to be due to the existence of bound states for
   the minority-spin electrons at the Cu FS necks in the ferromagnetic
   configuration. The dominant short-period oscillation has been confirmed
   by spin-polarized scanning electron microscopy and observed directly in
   the most recent photoemission experiments. The full confinement of the
   minority electrons at the neck of the Cu FS also leads to a strong
   temperature dependence of the short-period oscillation and an initial
   decay of the coupling with spacer thickness N that is much slower than
   predicted by the usual 1/N-2 law. For the electrons at the belly of the
   Cu FS, the confinement is weak in both spin channels and the
   long-period oscillation hardly changes between zero and room
   temperatures. In addition, the belly contribution to the coupling
   decreases at T=0 K following the usual 1/N-2 dependence. The amplitude
   of the calculated coupling approximate to 1.2 mJ/m(2) at the first
   antiferromagnetic peak of Cu is only a factor of 3 larger than the
   observed coupling strength. Finally, the coupling for 2 ML of Co
   embedded in Cu has also been evaluated from the cleavage formula. A
   large initial coupling strength (3.4 mJ/m(2)) and comparable
   contributions from the shea-and long-oscillation periods are obtained.
   This is in complete agreement with theoretical results reported by
   other groups. [S0163-1829(97)04138-6].
C1 UNIV FED FLUMINENSE,DEPT FIS,NITEROI,RJ,BRAZIL.
   UNIV LONDON IMPERIAL COLL SCI & TECHNOL,DEPT MATH,LONDON SW7 2BZ,ENGLAND.
RP Mathon, J, CITY UNIV LONDON,DEPT MATH,LONDON EC1V 0HB,ENGLAND.
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   NORDSTROM L, 1994, PHYS REV B, V50, P13058
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   PARKIN SSP, 1990, PHYS REV LETT, V64, P2304
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   SLONCZEWSKI JC, 1989, PHYS REV B, V39, P6995
   STILES MD, 1993, PHYS REV B, V48, P7238
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   VANSCHILFGAARDE M, 1995, PHYS REV LETT, V74, P4063
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NR 43
TC 35
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 1
PY 1997
VL 56
IS 18
BP 11797
EP 11809
PG 13
SC Physics, Condensed Matter
GA YF528
UT ISI:A1997YF52800068
ER

PT J
AU Enderlein, R
   Sipahi, GM
   Scolfaro, LMR
   Leite, JR
TI Density functional theory for holes in semiconductors
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID DELTA-DOPED GAAS; FERMI-EDGE SINGULARITY; NIPI-SUPERSTRUCTURE;
   QUANTUM-WELLS; CRYSTALS; GAS
AB A long standing problem of solid state theory is solved, being the
   derivation of a set of self-consistent one-particle equations for the
   interacting multicomponent hole gas of a semiconductor in an external
   potential. Combining effective mass theory with density functional
   theory, the Hohenberg-Kohn theorem is generalized and a set of
   generalized Kohn-Sham equations is obtained for the multicomponent gas.
   It is demonstrated how the exchange-correlation potential matrix may be
   calculated by the local density approximation. Explicit results are
   given for the Gamma(8) valence band holes of zinc blende type
   semiconductors. [S0031-9007(97)04490-6].
RP Enderlein, R, UNIV SAO PAULO,INST FIS,CAIXA POSTAL 66318,BR-05315970
   SAO PAULO,BRAZIL.
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   DOHLER GH, 1972, PHYS STATUS SOLIDI, V52, P79
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NR 15
TC 22
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD NOV 10
PY 1997
VL 79
IS 19
BP 3712
EP 3715
PG 4
SC Physics, Multidisciplinary
GA YF186
UT ISI:A1997YF18600042
ER

PT J
AU Moraes, LAB
   Eberlin, MN
TI Transacetalization of 1,3-dioxane with acylium and sulfinyl cations in
   the gas phase
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID ION-MOLECULE REACTIONS; MASS-SPECTROMETRY; ORBITAL METHODS; BASIS SETS;
   ISOMERS; 1,3-DIOXOLANES; SUBSTITUTION; INSTRUMENT; SCANS; 3D
AB Transacetalization occurs extensively In gas phase ion-molecule
   reactions of 1,3-dioxane with a variety of acylium ions [R-C+=O; R =
   CH3, C2H5, Ph, CH3O, Cl, CH2=CH, (CH3)(2)N] and a sulfur analogue, the
   thioacetyl ion CH3-C+=S. Six-membered 1,3-dioxanylium ions and
   analogues, i.e. cyclic 'ionic (thio)ketals', are formed, as evidenced
   by pentaquadrupole triple-stage collision-dissociation mass spectra and
   MP2/6-311G(d,p)//6-311G(d,p) + ZPE ab initio calculations, as well as
   by O-18 labelling experiments. Transacetalization with 1,3-dioxane is
   not a general reaction for sulfinyl cations (R-S+=O). They react either
   moderately (CH3-S+=O) or extensively (CH2=CH-S+=O) by
   transacetalization, form abundant intact adducts (Ph-S+=O) or undergo
   mainly proton transfer and/or hydride abstraction reactions (Cl-S+=O,
   CH3O-S+=O and C2H5O-S+=O). Competitive MS2 experiments are employed to
   compare the transacetalization reactivity of different acylium ions,
   and that of two cyclic neutral acetals, that is 1,3-dioxane and
   1,3-dioxolane. All the cyclic 'ionic ketals) dissociate exclusively
   under low-energy collision conditions to regenerate the original
   reactant ion species, a simple dissociation chemistry that is amply
   demonstrated to be a very general characteristic of the
   transacetalization products. The cyclic 'ionic thioketal' formed in
   transacetalization with CH3-C+=S is found, however, to dissociate
   exclusively to the oxygen analogue ion CH3-C+=O, a triple-stage mass
   spectrometric(MS3) experiment that constitutes a novel gas-phase
   strategy for conversion of thioacylium ions into acylium ions.
C1 UNICAMP,INST CHEM,BR-13083970 CAMPINAS,SP,BRAZIL.
CR ATTINA M, 1983, J AM CHEM SOC, V105, P1122
   CAREY FA, 1984, ADV ORGANIC CHEM
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NR 37
TC 18
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD OCT
PY 1997
IS 10
BP 2105
EP 2111
PG 7
SC Chemistry, Organic; Chemistry, Physical
GA YB261
UT ISI:A1997YB26100035
ER

PT J
AU Jorge, FE
   deCastro, EVR
   daSilva, ABF
TI A universal Gaussian basis set for atoms Cerium through Lawrencium
   generated with the generator coordinate Hartree-Fock method
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
DE universal Gaussian basis set; generator coordinate Hartree-Fock method;
   heavy atoms
ID SLATER-TYPE BASES; LYING EXCITED-STATES; COULOMB CALCULATIONS;
   HEAVY-ATOMS; EQUATIONS; VERSION
AB The generator coordinate Hartree-Fock method is applied to generate a
   universal Gaussian basis set for the heavy atoms from Ce (Z = 58)
   through Lr (Z = 103). The Hartree-Fock energies obtained with our
   universal Gaussian basis set are compared with the new numerical
   Hartree-Fock results of Koga et al., when available, and with
   geometrical Gaussian basis sets results available in the Literature.
   The universal Gaussian basis set presented here is generated taking
   into account the shell constraint (the sharing of exponential functions
   between all s, p, d, and f atomic orbitals), and can be used as
   starting basis set in ab initio relativistic Hartree-Fock-Roothaan
   calculations. (C) 1997 John Wiley & Sons, Inc.
C1 UNIV SAO PAULO, INST QUIM DE SAO CARLOS, DEPT QUIM & FIS MOL, BR-13560970 SAO CARLOS, SP, BRAZIL.
   UNIV FED DO ESPIRITO SANTO, CCE, DEPT QUIM, VITORIA, ES, BRAZIL.
   UNIV FED DO ESPIRITO SANTO, CCE, DEPT FIS, VITORIA, ES, BRAZIL.
CR CLEMENTI E, 1991, MOTECC MODERN TECHNI, P58
   DACOSTA HFM, 1987, MOL PHYS, V62, P91
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   FISCHER CF, 1977, HARTREEFOCK METHOD A
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   MATSUOKA O, 1987, CHEM PHYS LETT, V140, P567
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NR 18
TC 11
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD OCT
PY 1997
VL 18
IS 13
BP 1565
EP 1569
PG 5
SC Chemistry, Multidisciplinary
GA YA494
UT ISI:A1997YA49400001
ER

PT J
AU Guimaraes, TC
   Pavao, AC
   Taft, CA
   Lester, WA
TI Interaction mechanism of N-2 with the Cr (110) surface
SO PHYSICAL REVIEW B
LA English
DT Article
ID ANGLE-RESOLVED PHOTOEMISSION; RAY-ABSORPTION-SPECTRA; HIGHER
   EXCITED-STATES; ELECTRONIC-STRUCTURE; CHEMISORBED MOLECULES; 3D-METAL
   SURFACES; TRANSITION-METALS; CO CHEMISORPTION; DISSOCIATION; PRECURSOR
AB The interaction:of N-2 With the Cr (110) surface is analyzed using the
   ab initio Hartree-Fock method and a Cr5N2 cluster. Our results indicate
   that the tilted state is energetically favored over perpendicular
   adsorption. The Mulliken surface-->N-2 charge transfer, overlap
   populations as well as N-N distances increase in the tilted
   configuration. We also analyze the stretching frequencies, geometrical
   parameters, natural bond orbital populations, density of states,
   orbital energies,charge-density distribution and orbital contours. We
   propose a model to explain the catalytic dissociation of N-2 On the Cr
   (110) surface.
C1 CTR BRASILEIRO PESQUISAS FIS,BR-22290180 RIO JANEIRO,BRAZIL.
   UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,DIV CHEM SCI,BERKELEY,CA 94720.
   UNIV CALIF BERKELEY,DEPT CHEM,BERKELEY,CA 94720.
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NR 60
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD SEP 15
PY 1997
VL 56
IS 11
BP 7001
EP 7010
PG 10
SC Physics, Condensed Matter
GA XY806
UT ISI:A1997XY80600093
ER

PT J
AU Aleman, C
   Galembeck, SE
TI Intramolecular electronic and hydrogen-bonding interactions in
   N,N'-dimethyl-2,3-di-O-methyl-L-tartaramide
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID L-TARTARIC ACID; MST-SCRF CALCULATIONS; CONFORMATIONAL-ANALYSIS;
   PSEUDOROTATIONAL EQUILIBRIUM; PENTOFURANOSE MOIETY; POLY(ETHYLENE
   OXIDE); ENERGY CALCULATIONS; COUPLING-CONSTANTS; FURANOSE RING;
   FORCE-FIELD
AB The changes in energy of the
   N,N'-dimethyl-2,3-di-O-methyl-L-tartaramide, model compound of
   polytartaramides based on 2,3-di-O-methyl-L-tartaric acid and
   1,n-alkanediamine, have been analyzed by ab initio quantum mechanical
   calculations. The influences of the gauche oxygen effect have been
   investigated in the gas phase as well as in aqueous, chloroform, and
   carbon tetrachloride solutions. The results indicate that polarizable
   environments enhance the gauche oxygen effect, but the amount of
   stabilization depends on the electronic characteristics of the solvent.
C1 UNIV SAO PAULO,FAC FILOSOFIA CIENCIAS & LETRAS RIBEIRAO PRET,DEPT QUIM,BR-14049901 RIBEIRAO PRET,SP,BRAZIL.
RP Aleman, C, UNIV POLITECN CATALUNYA,ETS ENGN IND BARCELONA,DEPT ENGN
   QUIM,DIAGONAL 647,E-08028 BARCELONA,SPAIN.
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NR 52
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD SEP 19
PY 1997
VL 62
IS 19
BP 6562
EP 6567
PG 6
SC Chemistry, Organic
GA XX490
UT ISI:A1997XX49000024
ER

PT J
AU Martins, JBL
   Taft, CA
   Longo, E
   Andres, J
TI Ab initio study of CO and H-2 interaction on ZnO surfaces using a small
   cluster model
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE ab initio; adsorption; ZnO
ID OXIDE SURFACES; ZINC-OXIDE; ABINITIO CALCULATIONS; METHANOL SYNTHESIS;
   CARBON-MONOXIDE; METAL; PHOTOELECTRON; ADSORPTION; POTENTIALS; SITES
AB We have studied the adsorption of H-2 and CO molecules, as well as the
   dissociation of H-2, on the (ZnO)(6) cluster model using the ab initio
   Hartree-Fock method. The effective core potential was used for Zn, C,
   and O atoms at double-zeta-type valence basis set level, whereas for H
   we used Dunning's basis set, We have also added polarization and
   diffuse functions to the O, C, and H basis set. The CO molecule
   interacts with the lowest coordination zinc sites which are located on
   the edge between the (0001) and (10 (1) over bar 0) surfaces. The
   decrease in CO bond length upon adsorption on ZnO surfaces is
   associated with the charge transfer from CO to the surface, Our
   calculations indicate the 5 sigma orbital from adsorbed CO stabilized
   to a 1.56 eV deeper energy, Of all the configurations investigated, the
   molecular H-2 interaction has the lowest binding energy with a decrease
   in H-2 bond strength, The H-2 molecule also dissociates on the zinc and
   oxygen sites of the ZnO cluster, and the preferential dissociation site
   is the oxygen which has a coordination number of two. The H-2
   dissociation shows a large stabilization energy for the most stable
   adsorption site which is the lowest coordination site. Molecular CO and
   H-2 adsorption yields a smaller change in the estimated energy gaps and
   ionization potentials, We have also analysed the geometry of the
   adsorbed molecules, the Mulliken charge, the orbital SCF energies, and
   also the molecular orbital densities and contour plots. Our results are
   compared with the available experimental data, (C) 1997 Elsevier
   Science B.V.
C1 UNIV FED SAO CARLOS,DEPT QUIM,BR-13560905 SAO CARLOS,SP,BRAZIL.
   UNIV JAUME 1,DEPT CIENCIAS EXPT,CASTELLO DE PLANA,SPAIN.
RP Martins, JBL, CTR BRASILEIRO PESQUISAS FIS,DEPT MAT CONDENSADA & FIS
   ESTATIST,RUA XAVIER SIGAUD 150,BR-22290 RIO JANEIRO,BRAZIL.
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   KLIER K, 1982, ADV CATAL, V31, P243
   LIN JY, 1991, J AM CHEM SOC, V113, P8312
   LIN JY, 1992, INORG CHEM, V31, P686
   MARTINS JBL, IN PRESS J MOL STRUC
   MARTINS JBL, 1994, J MOL STRUCT, V303, P19
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P301
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P347
   MARTINS JBL, 1996, THEOCHEM-J MOL STRUC, V363, P249
   MAVRIDIS A, 1989, J AM CHEM SOC, V111, P2482
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   SCARANO D, 1992, SURF SCI, V276, P281
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   SPANHEL L, 1991, J AM CHEM SOC, V113, P2826
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NR 33
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD JUN 30
PY 1997
VL 398
BP 457
EP 466
PG 10
SC Chemistry, Physical
GA XV714
UT ISI:A1997XV71400050
ER

PT J
AU Gong, XG
   Guenzburger, D
   Saitovitch, EB
TI Structure and dynamic properties of neutral and ionized SiH5 and Si2H3
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID SPECTROSCOPY; SPECTRUM; ENTHALPIES; MOLECULES; DISILYNE; RADICALS;
   SILANE; CATION; BANDS; ATOMS
AB The equilibrium structures and dynamical properties of neutral and
   ionized SiH5, and Si2H3 have been studied using the ab initio molecular
   dynamics method. The obtained equilibrium structures are in good
   agreement with other highly precise methods. In SiH5+, we have clearly
   observed that H-2 rotates about the C-3 axis. In Si2H3+, we have found
   that H atoms can interchange positions frequently and also the
   structure changes. The different dynamical behaviors of the Si-H and
   C-H molecules has been addressed. (C) 1997 Published by Elsevier
   Science B.V.
C1 CTR BRASILEIRO PESQUISAS FIS,URCA,RJ,BRAZIL.
RP Gong, XG, NANJING UNIV,INST SOLID STATE PHYS,NATL LAB SOLID STATE
   MICROSTRUCT,NANJING 210093,PEOPLES R CHINA.
CR BACHELET GB, 1982, PHYS REV B, V26, P4199
   BECERRA R, 1992, J PHYS CHEM-US, V96, P10856
   BETRENCOURT M, 1986, J CHEM PHYS, V84, P4121
   BOGEY M, 1991, PHYS REV LETT, V66, P413
   BOO DW, 1993, CHEM PHYS LETT, V211, P358
   BOO DW, 1995, J CHEM PHYS, V103, P514
   BORRMANN A, 1996, CHEM PHYS LETT, V252, P1
   BUDA F, 1989, PHYS REV LETT, V63, P294
   CAO YB, 1993, J PHYS CHEM-US, V97, P5215
   CAR R, 1985, PHYS REV LETT, V55, P2471
   COLEGROVE BT, 1990, J CHEM PHYS, V93, P7230
   COLEGROVE BT, 1990, J PHYS CHEM-US, V94, P5593
   CURTISS LA, 1991, J CHEM PHYS, V95, P2433
   DAVIES PB, 1994, J CHEM PHYS, V100, P6166
   DEMOLLIENS A, 1989, J AM CHEM SOC, V111, P5623
   GONG XG, IN PRESS
   HOHENBERG P, 1964, PHYS REV B, V136, P864
   HU CH, 1992, CHEM PHYS LETT, V190, P543
   KHANNA SN, 1995, PHYS REV B, V51, P13705
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NR 32
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD AUG 29
PY 1997
VL 275
IS 3-4
BP 392
EP 398
PG 7
SC Physics, Atomic, Molecular & Chemical
GA XV887
UT ISI:A1997XV88700038
ER

PT J
AU Morgon, NH
   Linnert, HV
   deSouza, LAG
   Riveros, JM
TI Gas-phase nucleophilic reactions in SO2F2: experiment and theory
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID COMPACT EFFECTIVE POTENTIALS; EXPONENT BASIS-SETS; OPTIMIZATION
   TECHNIQUE; ADDITION-ELIMINATION; IONS; FLUORIDE; SULFUR; ATOMS;
   THERMOCHEMISTRY; SUBSTITUTION
AB The gas-phase ion-molecule reactions of simple anions (HO-, CH3O-,
   NH2-) with SO2F2 proceed with rate constants close to the collision
   limit. The energy surface for the OH-/SO2F2 reaction has been
   characterized by ab initio calculations using basis functions adapted
   for a pseudopotential and corrected for anionic systems by the
   generator coordinate method (GCM) at the QCISD(T)/(ECP/TZV/GCM) level.
   The calculations indicate that reaction occurs by initial addition of
   the anion to SO2F2 to form a hypervalent sulfur species. The high
   efficiency of the reaction is associated with a low energy barrier
   separating the initial adduct from the product side ion-neutral
   complex. (C) 1997 Elsevier Science B.V.
C1 UNIV SAO PAULO,INST CHEM,BR-05599970 SAO PAULO,BRAZIL.
RP Morgon, NH, UNIV CAMPINAS,INST CHEM,CAMPINAS,SP,BRAZIL.
CR ALKORTA I, 1994, THEOR CHIM ACTA, V89, P1
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   LARSON JW, 1987, INORG CHEM, V26, P4018
   LIAS SG, 1988, J PHYS CHEM S1, V235, P436
   MCKEE ML, 1996, J PHYS CHEM-US, V100, P3473
   MCLEAN AD, 1980, J CHEM PHYS, V72, P5639
   MILLER KJ, 1979, J AM CHEM SOC, V101, P7206
   MORGON NH, 1995, CHEM PHYS LETT, V235, P436
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   MORGON NH, 1995, THEOCHEM-J MOL STRUC, V335, P11
   OKUYAMA T, 1990, CHEM SULPHINIC ACIDS, P623
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   ROZAS I, 1996, J CHEM SOC PERK  MAR, P461
   SMITH D, 1977, INT J MASS SPECTROM, V23, P123
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   STEVENS WJ, 1992, CAN J CHEM, V70, P612
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NR 34
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD SEP 5
PY 1997
VL 275
IS 5-6
BP 457
EP 462
PG 6
SC Physics, Atomic, Molecular & Chemical
GA XV888
UT ISI:A1997XV88800004
ER

PT J
AU Srivastava, RM
   Seabra, GM
TI Preparation and reactions of 3-[3-(aryl)-1,2,4-oxadiazol-5-yl]
   propionic acids
SO JOURNAL OF THE BRAZILIAN CHEMICAL SOCIETY
LA English
DT Article
DE arylamidoximes; bis-1,2,4-oxadiazoles; diaryl-1,2,4-oxadiazoles;
   ab-initio sto-3g calculations
AB The synthesis of title compounds 3a-g, from arylamidoximes 1a-g and
   succinic anhydride in high yields is described. 1,2,4-Oxadiazoles 3a-f
   were also obtained by carrying out the reaction in a domestic microwave
   oven. Preliminary pharmacological evaluations demonstrated that 3b-e
   possess analgesic properties. Ab initio molecular orbital calculations
   of the type STO-3G have been performed for compounds 3a, 4a, 5a and 6a.
C1 UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50670901 RECIFE,PE,BRAZIL.
CR AFIATPOUR P, 1994, BRAZ J MED BIOL RES, V27, P1403
   ARBASINO M, 1963, ATTI ACCAD NAZL SFMN, V34, P532
   BALLARD RE, 1968, SPECTROCHIM ACTA A, V24, P1975
   BARRANS J, 1959, CR HEBD ACAD SCI, V249, P1096
   BLATT AH, 1943, ORG SYNTH, V2, P165
   BRAM G, 1991, CHEM IND-LONDON, P396
   FRISCH MJ, 1992, GAUSSAIN 92
   HIROTA T, 1994, ACTA CRYSTALLOGR C, V50, P807
   KALINOWSKI HO, 1984, 13C NMR SPECTROSKOPI, P183
   LEITE LFC, 1983, THESIS U FEDERAL PER
   LEITE LFCD, 1989, B SOC CHIM BELG, V98, P203
   LOPEZ JP, 1983, J MOL STRUCT, V94, P203
   MILLER JA, 1989, CHEM BER, V22, P243
   MILLER JA, 1989, CHEM BER, V22, P2796
   MOUSSEBOIS C, 1964, HELV CHIM ACTA, V47, P942
   PARK CH, 1977, HAKSUL YONGUCHI CHUN, V4, P133
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   SRIVASTAVA RM, 1977, J ORG CHEM, V42, P1555
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   SRIVASTAVA RM, 1984, J CHEM ENG DATA, V29, P221
   SRIVASTAVA RM, 1989, QUIM NOVA, V12, P221
   SRIVASTAVA RM, 1992, J BRAZIL CHEM SOC, V3, P117
   SRIVASTAVA RM, 1993, J BRAZIL CHEM SOC, V4, P84
NR 24
TC 9
PU SOC BRASILEIRA QUIMICA
PI SAO PAULO
PA CAIXA POSTAL 26037, 05599-970 SAO PAULO, BRAZIL
SN 0103-5053
J9 J BRAZIL CHEM SOC
JI J. Braz. Chem. Soc.
PY 1997
VL 8
IS 4
BP 397
EP 405
PG 9
SC Chemistry, Multidisciplinary
GA XV685
UT ISI:A1997XV68500013
ER

PT J
AU Pfannes, HD
TI Simple theory of superparamagnetism and spin-tunneling in Mossbauer
   spectroscopy
SO HYPERFINE INTERACTIONS
LA English
DT Article
ID MAGNETIC-RELAXATION; SPECTRA; MOLECULES; DISSIPATION; SYSTEMS
AB The magnetic relaxation of isolated small (< 100 Angstrom) monodomain
   magnetic particles is due to superparamagnetic relaxation (predominant
   at high temperatures) and eventually quantum tunneling of the magnetic
   moment (at low temperatures). The superparamagnetic relaxation process
   can be formally described by an (multiple phonon absorption and
   emission) Orbach process with an anisotropy Hamiltonian due to
   crystalline or form anisotropy (H) over cap(Ion) = S-z(2) and a usual
   dynamical spin-Hamiltonian for the spin-phonon interaction. From this
   Mossbauer spectra can be calculated using ab-initio or stochastic
   methods. Phonon-assisted tunneling and its influence on Mossbauer
   spectra are discussed.
RP Pfannes, HD, UNIV FED MINAS GERAIS,DEPT FIS,CP 702,BR-30123970 BELO
   HORIZONT,MG,BRAZIL.
CR BROWN WF, 1959, J APPL PHYS, V30, S130
   BROWN WF, 1963, PHYS REV, V130, P1677
   CALDEIRA AO, 1981, PHYS REV LETT, V46, P211
   CALDEIRA AO, 1983, ANN PHYS-NEW YORK, V149, P374
   CHUDNOVSKY EM, 1994, PHYS REV LETT, V72, P3433
   CIANCHI L, 1986, REP PROG PHYS, V49, P1243
   DATTAGUPTA S, 1977, PHYS REV B, V16, P3893
   GARG A, 1994, J APPL PHYS 2, V76, P6168
   HARTMANNBOUTRON F, 1995, J PHYS I, V5, P1281
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   HARTMANNBOUTRON F, 1996, J PHYS I, V6, P137
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   ORBACH R, 1972, ELECT PARAMAGNETIC R, P121
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   POLITI P, 1995, PHYS REV LETT, V75, P537
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   STONER EC, 1991, IEEE T MAGN, V27, P3475
   VILLAIN J, 1994, EUROPHYS LETT, V27, P159
NR 19
TC 7
PU BALTZER SCI PUBL BV
PI AMSTERDAM
PA ASTERWEG 1A, 1031 HL AMSTERDAM, NETHERLANDS
SN 0304-3843
J9 HYPERFINE INTERACTIONS
JI Hyperfine Interact.
PY 1997
VL 110
IS 1-2
BP 127
EP 134
PG 8
SC Physics, Atomic, Molecular & Chemical; Physics, Condensed Matter;
   Physics, Nuclear
GA XV680
UT ISI:A1997XV68000015
ER

PT J
AU daSilva, JBP
   Ramos, MN
   Suto, E
   Bruns, RE
TI Transferability of the cis- and trans-dichloroethylene atomic polar
   tensors
SO JOURNAL OF PHYSICAL CHEMISTRY A
LA English
DT Article
ID PHASE INTENSITY MEASUREMENTS; PRINCIPAL COMPONENT ANALYSIS;
   DIPOLE-MOMENT DERIVATIVES; EFFECTIVE CHARGES; INFRARED INTENSITIES;
   DIFLUOROETHYLENE
AB The isotopic invariance criterion, ab initio molecular orbital results,
   and principal component analysis are used to resolve the sign
   ambiguities of the dipole moment derivatives for cis-dichloroethylene
   and the out-of-plane derivatives of trans-dichloroethylene. Atomic
   polar tensors (APTs) for CiS-C2H2Cl2 and cis-C2D2Cl2 as well as
   out-of-plane polar tensor elements for trans-C2H2Cl2 and trans-C2D2Cl2
   are reported. Mean dipole moment derivatives of the difluoro-and
   dichloroethylenes are compared and interpreted as atomic charges. The
   APTs of cis-dichloroethylene are transferred to trans-dichloroethylene
   to calculate its infrared fundamental vibrational intensities. These
   intensities are in much better agreement with the experimental
   intensities than those calculated by a MP2/6-311++G(d,p) wave function.
   The transferability of mean dipole moment derivatives between the cis
   and trans-dichloroethylenes is demonstrated using a simple potential
   model and carbon and chlorine core electron binding energies obtained
   by ESCA spectroscopy.
C1 UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13083970 CAMPINAS,SP,BRAZIL.
   UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50739901 RECIFE,PE,BRAZIL.
CR BASSI ABM, 1975, THESIS U ESTADUAL CA
   BIARGE JF, 1961, ANALES REAL SOC ES A, V57, P81
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   FRISCH MJ, 1992, GAUSSIAN 92
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   HOPPER MJ, 1983, J CHEM PHYS, V79, P19
   KAGEL RO, 1983, J CHEM PHYS, V78, P7029
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   NEWTON JH, 1976, J CHEM PHYS, V64, P3036
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   SCHAFER L, 1986, J MOL STRUCT, V145, P135
   SIEGBAHN K, 1969, ESCA APPLIED FREE MO
   SUTO E, 1991, J COMPUT CHEM, V12, P885
   SUTO E, 1991, J PHYS CHEM-US, V95, P9716
   SUTO E, 1993, J PHYS CHEM-US, V97, P6161
NR 22
TC 4
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 1089-5639
J9 J PHYS CHEM A
JI J. Phys. Chem. A
PD AUG 28
PY 1997
VL 101
IS 35
BP 6293
EP 6298
PG 6
SC Chemistry, Physical
GA XT955
UT ISI:A1997XT95500020
ER

PT J
AU Ma, SG
   Wong, P
   Cooks, RG
   Gozzo, FC
   Eberlin, MN
TI Stereoelectronic effects in phosphorus dichloride cation pyridine
   complexes
SO INTERNATIONAL JOURNAL OF MASS SPECTROMETRY AND ION PROCESSES
LA English
DT Article
DE kinetic method; stereoelectronic effects; cation affinity; PCL2+;
   thermochemistry; agostic effects
ID MS(3) MASS-SPECTROMETRY; GAS-PHASE BASICITIES; AMMONIUM ION AFFINITIES;
   TRANSITION-METAL BONDS; PROTON-BOUND DIMERS; KINETIC METHOD;
   ELECTRON-AFFINITIES; PCL2 RADICALS; ACIDITIES; AM1
AB The kinetic method is applied to order the relative affinities of a
   group of substituted pyridines towards PC2+ relationships with the
   affinities towards other cations. The absolute affinities are estimated
   with the aid of AM1 molecular orbital calculations while the PCl2+
   affinity of pyridine itself is also estimated by ab initio calculations
   at MP2/6-31G(d,p)//6-31G(d,p) level to be 76.0 kcal mol(-1). The
   experiments employ the PCl2+-bound dimer of two pyridines generated via
   ion/ molecule reactions between the mass-selected PCl2+ ion and a
   mixture of pyridines. The dimers, examined using MS3 experiments,
   fragment exclusively to yield the pyridine/PCl2+ monomers and this is
   consistent with ab initio RHF/6-31G(d,p) and AM1 molecular orbital
   calculations which show a tetrahedral complex with a N-P-N angle of 129
   degrees. For meta- and parasubstituted pyridines, there is an excellent
   linear correlation (slope 0.69) between the logarithm of the ratio of
   the two fragment ion abundances and the proton affinity of the
   corresponding substituted pyridine. Similar correlations are observed
   for other cations (SiCl3+, Cl+, SF3+ and SiCl+) and it is shown that
   both the number of degrees of freedom in the dimer and the cation
   affinity control this correlation.
   Dimers comprising ortho-substituted pyridines show decreased affinities
   due to stereoelectronic interactions between the ortho-substituted
   alkyl group and the central PCl2+ cation. A set of gas phase
   stereoelectronic parameters (S-k) is determined and ordered as 2-MePy
   (-0.38) < 2,4-diMePy (-0.84) < 2,6-diMePy (-0.86) < 2,5-diMePy (-1.08)
   < 2,3-diMePy (-1.26). AM1 calculations show that the eclipsed
   conformation of 2-methylpyridine/PCl2+ adduct is more stable than the
   staggered conformation by approx. 3 kcal mol(-1) and this is suggested
   to be due to a favorable agostic interaction between the hydrogen of
   the ortho methyl group and the central phosphorus atom. The most stable
   conformation is found when the two chlorines face the two hydrogens of
   the ortho methyl substituent in a ''face-to-face'' interaction. This
   novel type of interaction is also the reason for the relatively small
   magnitude of S-k, the stereoelectronic parameter, in
   2,6-dimethylpyridine. The overall stereoelectronic effects of the
   ortho-substituent(s) on PCl2+ affinities indicate that steric effects
   dominate electronic effects in this system. The PCl2+ ion behaves
   similarly in its steric and agostic effects to SF3+ and very
   differently to SiCl+ which displays uniquely strong agostic effects.
   (C) 1997 Elsevier Science B.V.
C1 PURDUE UNIV,DEPT CHEM,W LAFAYETTE,IN 47907.
   STATE UNIV CAMPINAS,INST CHEM,BR-13083970 CAMPINAS,SP,BRAZIL.
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   BROOKHART M, 1988, PROG INORG CHEM, V36, P1
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   BURINSKY DJ, 1984, J AM CHEM SOC, V106, P2770
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   YANG SS, 1996, J AM SOC MASS SPECTR, V7, P198
NR 48
TC 17
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0168-1176
J9 INT J MASS SPECTROM ION PROC
JI Int. J. Mass Spectrom. Ion Process.
PD APR
PY 1997
VL 163
IS 1-2
BP 89
EP 99
PG 11
SC Physics, Atomic, Molecular & Chemical; Spectroscopy
GA XL627
UT ISI:A1997XL62700008
ER

PT J
AU Moraes, LAB
   Gozzo, FC
   Eberlin, MN
   Vainiotalo, P
TI Transacetalization with acylium ions. A structurally diagnostic
   ion/molecule reaction for cyclic acetals and ketals in the gas phase
SO JOURNAL OF ORGANIC CHEMISTRY
LA English
DT Article
ID MOLECULAR-ORBITAL METHODS; MASS-SPECTROMETRY; BASIS SETS; SUBSTITUTION;
   ISOMERS
AB Transacetalization takes place in high yields in gas phase ion/molecule
   reactions of acylium ions (RC+=O) with a variety of cyclic acetals and
   ketals, that is, five-, six-, and seven-membered 1,3-O,O-heterocycles
   and their mono-sulfur and nitrogen analogues. A general, structurally
   diagnostic method for the gas phase characterization of cyclic acetals
   and ketals is therefore available. Transacetalization occurs via
   initial O(or S)-acylation, followed by a ring-opening/ring-re-forming
   process in which a neutral carbonyl compound is eliminated and cyclic
   ''ionic ketals'' (that is, cyclic 1,3-dioxonium ions and analogues) are
   formed. The nature of the substituents at the 2-position, which are
   eliminated in the course of the reaction, is found to affect
   considerably the extent of transacetalization. Substituents not at the
   2-position remain in the ionic products; hence positional isomers
   produce different cyclic ''ionic ketals'' and are easily
   differentiated. The triple-stage (MS3) mass spectra of the cyclic
   ''ionic ketals'' show in all cases major dissociation to re-form the
   reactant acylium ion, a unique dissociation chemistry that is
   equivalent to the hydrolysis of neutral acetals and ketals and which is
   then determined to be a very general characteristic of cyclic ''ionic
   ketals''. Additionally, the O-18-labeled transacetalization product of
   1,3-dioxolane shows dissociation to both CH3C+=O-18 and CH3C+=O to the
   same extent, which confirms its cyclic ''ionic ketal'' structure and
   the ''oxygen-scrambling'' mechanism of transacetalization. Ab initio
   MP2/6-31G(d,p)//6-31G-(d,p) + ZPE energy surface diagrams show that
   transacetalization is the most exothermic, thermodynamically favorable
   process in reactions of CH3C+=O with 1,3-dioxolane and 1,3-oxathiolane,
   whereas 1,3-dithiolane is unreactive due to the endothermicity of the
   initial acylation step.
C1 UNICAMP,INST CHEM CP6154,BR-13083970 CAMPINAS,SP,BRAZIL.
   UNIV JOENSUU,DEPT CHEM,FIN-80101 JOENSUU,FINLAND.
CR ATTINA M, 1983, J AM CHEM SOC, V105, P1122
   BOGERT MT, 1933, J AM CHEM SOC, V55, P3741
   CAREY FA, 1984, ADV ORGANIC CHEM
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   CHATFIELD DA, 1976, J AM CHEM SOC, V98, P6492
   CREASER CS, 1996, J CHEM SOC PERK  MAR, P427
   EBERLIN MN, IN PRESS MASS SPECTR
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   EBERLIN MN, 1997, J AM CHEM SOC, V119, P3550
   FRISCH MJ, 1984, J CHEM PHYS, V80, P3265
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   MORAES LA, IN PRESS J CHEM S P2
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   OLAH GA, 1976, CARBONIUM IONS, V5, P2084
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   STALEY RH, 1977, J AM CHEM SOC, V99, P5964
   VAINIOTALO P, 1996, P 44 ASMS C MASS SPE, P453
NR 38
TC 47
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3263
J9 J ORG CHEM
JI J. Org. Chem.
PD JUL 25
PY 1997
VL 62
IS 15
BP 5096
EP 5103
PG 8
SC Chemistry, Organic
GA XN357
UT ISI:A1997XN35700035
ER

PT J
AU Gong, XG
TI Structure and stability of cluster-assembled solid Al12C(Si): A
   first-principles study
SO PHYSICAL REVIEW B
LA English
DT Article
ID MAGNETIC-PROPERTIES; METALLIC CLUSTERS; ALUMINUM CLUSTERS; CRYSTALS;
   SYSTEMS; C-60
AB We have proposed a possible crystal structure for the cluster-assembled
   solid Al12C(Si), and its electronic structures and stability have been
   studied in the framework of density functional theory and ab initio
   molecular dynamics. We find that Al12C(Si) clusters are condensed by
   van der Waals force, with a very small cohesive energy of similar to
   1.1 eV. The combined steepest descent on ions shows that upon the
   formation of solid the relaxation of atomic distances in the Al12C(Si)
   cluster is very small. The stability of the Al12C solid is also
   confirmed by a dynamical simulation at low temperature.
C1 ACAD SINICA,INST SOLID STATE PHYS,HEFEI 230031,PEOPLES R CHINA.
   CTR BRASILEIRO PESQUISAS FIS,RIO JANEIRO,BRAZIL.
RP Gong, XG, NANJING UNIV,INST SOLID STATE PHYS,NATL LAB SOLID STATE
   MICROSTRUCT,NANJING 210093,PEOPLES R CHINA.
CR *JENA P, 1992, PHYSICS CHEM FINITE
   BACHELET GB, 1982, PHYS REV B, V26, P4199
   BENOIT M, 1996, PHYS REV LETT, V76, P2934
   CAR R, 1985, PHYS REV LETT, V55, P2471
   CHENG HP, 1991, PHYS REV B A, V43, P10647
   GONG XG, 1993, PHYS REV LETT, V70, P2078
   HOHENBERG P, 1964, PHYS REV, V136, B864
   HOHENBERG P, 1995, PHYS REV, V140, A1133
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   KAWAI R, UNPUB
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   KHANNA SN, 1994, CHEM PHYS LETT, V219, P479
   KHANNA SN, 1995, PHYS REV B, V51, P13705
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   KUMAR V, UNPUB
   LIU F, 1996, CHEM PHYS LETT, V248, P213
   PERDEW JP, 1981, PHYS REV B, V23, P5048
   SAITO S, 1991, PHYS REV LETT, V66, P2637
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   SUN DY, 1996, PHYS REV B, V54, P17051
   WHITTEN RL, 1990, MRS LATE NEWS SESSIO
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   YOU JQ, 1995, PHYS REV B, V51, P1358
   ZHANG GW, 1994, J APPL PHYS 2, V76, P7037
NR 26
TC 23
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 1098-0121
J9 PHYS REV B
JI Phys. Rev. B
PD JUL 15
PY 1997
VL 56
IS 3
BP 1091
EP 1094
PG 4
SC Physics, Condensed Matter
GA XM766
UT ISI:A1997XM76600035
ER

PT J
AU Srivastava, RM
   Pavao, AC
   Seabra, GM
   Brown, RK
TI Anomeric effect enhancement in C-5-substituted 2-methoxytetrahydropyrans
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE anomeric effect; 2-methoxytetrahydropyran; conformation; AM1
   calculations; HF/6-31g** basis set
AB cis- and trans-2,5-Dimethoxytetrahydropyrans,
   cis-2,5-dimethoxy-6-methyltetrahydropyran and
   2-methoxy-5-methyltetrahydropyran have been examined to see the effect
   of an OCH3 group at position 5 on the degree of anomeric effect in
   substituted 2-methoxytetrahydropyrans. The present study shows that
   this group stabilises the C-2 electronegative substituent in the axial
   position. Semi-empirical and ab initio molecular orbital calculations
   support this view. AM1 calculation gives lower enthalpies as well as
   lower dipole moments for the compounds having an OCH3 group in the
   axial position at C-2 over the equatorial form in
   2-methoxytetrahydropyrans. This enhanced stabilisation is attributed to
   the electrostatic interaction between the partial positive charge at
   C-5 and the partial negative charge of the aglycone oxygen atom. (C)
   1997 Elsevier Science B.V.
C1 UNIV ALBERTA,DEPT CHEM,EDMONTON,AB,CANADA.
RP Srivastava, RM, UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50670901
   RECIFE,PE,BRAZIL.
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   BOOTH H, 1992, TETRAHEDRON, V48, P6151
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   DESCOTES G, 1970, B SOC CHIM FR, P3730
   DESLONGCHAMPS P, 1983, STEREOELECTRONIC EFF
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   FRISCH MJ, 1992, GAUSSIAN 92
   GELIN M, 1970, B SOC CHIM FR, P3723
   HALL SS, 1978, J ORG CHEM, V43, P667
   JUARISTI E, 1992, TETRAHEDRON, V48, P5019
   JUARISTI E, 1995, ANOMERIC EFFECT
   KIRBY AJ, 1983, ANOMERIC EFFECT RELA
   LEMIEUX RU, 1969, CAN J CHEM, V47, P4427
   LEMIEUX RU, 1971, PURE APPL CHEM, V25, P527
   MONNERET C, 1978, CARBOHYD RES, V65, P35
   MONNERET C, 1987, J CARBOHYD CHEM, V6, P221
   PIERSON GO, 1968, J ORG CHEM, V33, P2572
   PRALY JP, 1987, CAN J CHEM, V65, P213
   PULAG P, 1977, MODERN THEORETICAL C, V4
   SOUZA AMA, 1986, THESIS U FEDERAL PER
   SRIVASTAVA RM, 1970, CAN J CHEM, V48, P2334
   STEWART JJP, 1990, J COMPUT AID MOL DES, V4, P1
   STEWART JJP, 1993, MOPAC 9300 MANUAL
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   TVAROSKA I, 1981, CARBOHYD RES, V90, P173
   TVAROSKA I, 1989, ADV CARBOHYD CHEM, P75
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   WIBERG KB, 1989, J AM CHEM SOC, V111, P4821
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   WOODS RJ, 1991, J CHEM SOC CHEM COMM, P334
   WOODS RJ, 1995, J PHYS CHEM-US, V99, P3832
NR 37
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD JUL 7
PY 1997
VL 412
IS 1-2
BP 51
EP 58
PG 8
SC Chemistry, Physical
GA XL894
UT ISI:A1997XL89400006
ER

PT J
AU Glaser, MA
   Clark, NA
   Garcia, E
   Walba, DM
TI Quantum chemistry based force fields for soft matter
SO SPECTROCHIMICA ACTA PART A-MOLECULAR AND BIOMOLECULAR SPECTROSCOPY
LA English
DT Article
DE liquid crystal; modeling; force fields; quantum chemistry
ID FERROELECTRIC LIQUID-CRYSTALS; HIGH SPONTANEOUS POLARIZATION; OPLS
   POTENTIAL FUNCTIONS; MONTE-CARLO SIMULATIONS;
   NUCLEAR-MAGNETIC-RESONANCE; MOLECULAR-DYNAMICS
AB We describe the use of ab initio electronic structure calculations in
   the development of high-quality classical interaction potentials for
   liquid crystal modeling. Our focus is on methods for the rapid,
   on-demand creation of force fields for use in mean field theory based
   calculations of materials properties, employed for routine
   pre-synthesis evaluation of novel liquid crystalline materials. The
   role of quantum chemistry in the development of intermolecular
   interaction potentials for large-scale simulations of soft matter is
   also discussed, and directions for future work are outlined. The
   utility of quantum chemistry derived force fields for liquid crystal
   modeling is illustrated by two example applications: mean field theory
   based prediction of the spontaneous polarization density P of
   ferroelectric liquid crystals, and large-scale simulation studies of
   the nanosegregation of polymer precursors in smectic liquid crystal
   hosts. (C) 1997 Elsevier Science B.V.
C1 UNIV BRAZILIA,DEPT CHEM,BRASILIA,BRAZIL.
   UNIV COLORADO,DEPT CHEM & BIOCHEM,BOULDER,CO 80309.
RP Glaser, MA, UNIV COLORADO,DEPT PHYS,CONDENSED MATTER LAB,BOULDER,CO
   80309.
CR 1996, LIQCRYST DATABASE 5
   *BIOS MOL SIM, 1995, CERIUS2
   *WAV INC, SPART
   BAHR C, 1986, MOL CRYST LIQ CRYST, V4, P31
   BAHR C, 1987, MOL CRYST LIQ CRYST, V148, P29
   BERENDSEN HJC, 1984, J CHEM PHYS, V81, P3684
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
   BRIGGS JM, 1990, J COMPUT CHEM, V11, P958
   BRIGGS JM, 1991, J PHYS CHEM-US, V95, P3315
   DEMUS D, 1983, WISSENSCHAFTL BEITRA, V41, P18
   FRISCH MJ, 1995, GAUSSIAN 94
   GLASER MA, UNPUB
   GLASER MA, 1995, MOL PHYS REP, V10, P26
   GLASER MA, 1996, UNPUB
   GUYMON CA, 1997, SCIENCE, V275, P57
   HEHRE WJ, 1995, PRACTICAL STRATEGIES
   HO MS, 1993, FERROELECTRICS, V138, P51
   JORGENSEN WL, 1984, J AM CHEM SOC, V106, P6638
   JORGENSEN WL, 1993, J COMPUT CHEM, V14, P206
   KELLER P, 1985, J PHYS PARIS G, V4, P2203
   LIDE DR, 1996, CRC HDB CHEM PHYSICS
   MAYO SL, 1990, J PHYS CHEM-US, V94, P8897
   POON CD, 1989, J CHEM PHYS, V91, P7392
   POON CD, 1989, LIQ CRYST, V5, P1159
   PRICE SL, 1991, COMPUTER SIMULATION, P183
   RAPPE AK, 1991, J PHYS CHEM-US, V95, P3358
   RAPPE AK, 1992, J AM CHEM SOC, V114, P10024
   SEXTON JC, 1992, NUCL PHYS B, V380, P665
   SIEPMANN JI, 1993, NATURE, V365, P330
   SMITH GD, 1995, MACROMOLECULES, V28, P5804
   STONE AJ, 1991, HYDROGEN BONDED LIQU, P25
   TUCKERMAN M, 1992, J CHEM PHYS, V97, P1990
   WATANABE M, 1993, J CHEM PHYS, V99, P8063
   YOSHINO K, 1987, MOL CRYST LIQ CRYST, V144, P87
NR 34
TC 10
PU PERGAMON-ELSEVIER SCIENCE LTD
PI OXFORD
PA THE BOULEVARD, LANGFORD LANE, KIDLINGTON, OXFORD, ENGLAND OX5 1GB
SN 1386-1425
J9 SPECTROCHIM ACTA PT A-MOL BIO
JI Spectroc. Acta Pt. A-Molec. Biomolec. Spectr.
PD JUL 30
PY 1997
VL 53
IS 8
BP 1325
EP 1346
PG 22
SC Spectroscopy
GA XL198
UT ISI:A1997XL19800024
ER

PT J
AU Resende, SM
   DeAlmeida, WB
TI Ab initio study of the formation of molecular complexes between Cl-2
   and C2H2
SO MOLECULAR PHYSICS
LA English
DT Article
ID ROTATIONAL SPECTROSCOPY; HYDROGEN-FLUORIDE; ABINITIO; PHOTOCHEMISTRY;
   INTERMEDIATE; SURFACE; WATER
AB The intermolecular potential energy surface (PES) for the interaction
   between the Cl-2 and C2H2 molecules has been comprehensively
   investigated using nb initio methods, aiming to locate the possible
   stationary points. The calculations were performed with the double zeta
   plus double polarization (DZ2P), triple zeta plus polarization (TZP)
   and triple zeta plus double polarization (TZ2P) basis sets, including
   electron correlation at the second-order Moller-Plesset (MP2) level,
   and basis set superposition error correction. Six stationary points
   were located on the PES: a T-shaped form where one chlorine atom is
   attached to the acetylene triple bond (b pi-a sigma type), a parallel
   form, a slipped parallel form, a crossed form and an inclined and a
   symmetric inverse T-shaped forms, where the van der Waals bond is
   between one of the H atoms of the acetylene and the Cl-Cl bond. At the
   MP2/TZ2P//MP2/TZP level of calculation, only the T-shaped and the
   parallel forms are minimum energy structures, and their stabilization
   energies are 2.002 and 0.422 kcal mol(-1) respectively. The two inverse
   T-shaped forms and the slipped parallel form are predicted to be
   first-order transition states at this level of calculation, and their
   stabilization energies are 0.709 kcal mol(-1) for the inclined form,
   0.694 kcal mol(-1) for the symmetric form, and 0.624 kcal mol(-1) for
   the slipped parallel form, which suggest that the intermolecular PES is
   very flat in this region. The crossed form is a second-order transition
   state, and it is stabilized by 0.390 kcal mol(-1). The shifts of the
   intramolecular frequencies upon complexation are also discussed. The
   global minimum is the T-shaped bn-ao structure, and the geometry, the
   intermolecular stretching force constant and the charge redistribution
   on complex formation lead to a classification of the outer (weak) type
   according to Mulliken. These results show the weakness of this
   interaction, which is dominated by dispersion forces, characteristic of
   the complexes between molecules without a permanent electric dipole,
   such as C2H2 and Cl-2.
RP Resende, SM, UNIV FED MINAS GERAIS,ICEX,DEPT QUIM,LAB QUIM COMPUTAC &
   MODELAGEM MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR ANDREWS L, 1983, J CHEM PHYS, V79, P3670
   AULT BS, 1987, J PHYS CHEM-US, V91, P4723
   BLAKE JF, 1989, J AM CHEM SOC, V111, P1919
   BLOEMINK H, 1995, J CHEM SOC CHEM COMM, V18, P1833
   BLOEMINK HI, 1994, CHEM PHYS LETT, V223, P162
   BLOEMINK HI, 1995, J CHEM SOC FARADAY T, V91, P1891
   BOYS SF, 1970, MOL PHYS, V19, P533
   DEALMEIDA WB, 1989, CHEM PHYS, V137, P143
   DEALMEIDA WB, 1990, CHEM PHYS, V141, P297
   DEALMEIDA WB, 1993, J PHYS CHEM-US, V97, P2560
   FRISCH MJ, 1995, GAUSSIAN 94
   HOBZA P, 1988, CHEM REV, V88, P871
   INGOLD CK, 1969, STRUCTURE MECHANISM
   KANG HC, 1996, CHEM PHYS LETT, V254, P135
   LAURSEN SL, 1989, J PHYS CHEM-US, V93, P2328
   LAURSEN SL, 1990, J PHYS CHEM-US, V94, P8175
   LEGON AC, 1995, J CHEM SOC FARADAY T, V91, P1881
   MULLIKEN RS, 1952, J PHYS CHEM-US, V56, P801
   NOVOA JJ, 1994, CHEM PHYS, V186, P175
   PLIEGO JR, 1996, CHEM PHYS LETT, V249, P136
   PLIEGO JR, 1996, J PHYS CHEM-US, V100, P12410
   PLIEGO JR, 1996, THEOR CHIM ACTA, V93, P333
   RESENDE SM, 1996, CHEM PHYS, V206, P1
   RESENDE SM, 1997, IN PRESS J PHYS CHEM
   SCHMIDT M, 1993, J COMPUT CHEM, V14, P1346
NR 25
TC 5
PU TAYLOR & FRANCIS LTD
PI LONDON
PA ONE GUNPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE
SN 0026-8976
J9 MOL PHYS
JI Mol. Phys.
PD JUL
PY 1997
VL 91
IS 4
BP 635
EP 641
PG 7
SC Physics, Atomic, Molecular & Chemical
GA XK031
UT ISI:A1997XK03100005
ER

PT J
AU Martins, JBL
   Longo, E
   Taft, CA
   Andres, J
TI Ab initio and semiempirical MO studies using large cluster models of CO
   and H-2 adsorption and dissociation on ZnO surfaces with the formation
   of ZnH and OH species.
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE ab initio; semiempirical MO study; cluster model
ID ZINC-OXIDE SURFACES; METHANOL SYNTHESIS; PHOTOELECTRON-SPECTROSCOPY;
   ROOM-TEMPERATURE; CARBON-MONOXIDE; HYDROGEN; MECHANISMS; POTENTIALS;
   PARAMETERS; CATALYST
AB We have used ab initio MO as well as MNDO, AM1 and PM3 semiempirical
   methods with large (ZnO)(60) clusters to study the H-2 and CO
   adsorption, as well as the H-2 dissociation, on ZnO surfaces with the
   formation of ZnH and OH species. From the optimized adsorption and
   dissociation geometries, we analyse Mulliken populations, binding
   energies, band gaps, and bonding distances. The calculated SCF orbital
   energies, density of states and stretch frequencies are compared with
   infrared and ultraviolet photoelectron experiments. We analyse the
   effect of cluster size on our calculations, hydrogen bonding, and
   heterolytic dissociation, as well as the diversity and stability of the
   bonding sites, and compare our results obtained using both ab initio
   and semiempirical methods. (C) 1997 Elsevier Science B.V.
C1 UNIV FED SAO CARLOS,DEPT QUIM,BR-13565905 SAO CARLOS,SP,BRAZIL.
   UNIV JAUME 1,DEPT CIENCIAS EXPT,CASTELLO DE PLANA 12080,SPAIN.
RP Martins, JBL, CTR BRASILEIRO PESQUISAS FIS,DEPT MAT CONDENSADA & FIS
   ESTATIST,RUA XAVIER SIGAUD 150,BR-22290180 RIO JANEIRO,BRAZIL.
CR AU CT, 1988, SURF SCI, V197, P391
   BOCCUZZI F, 1978, J CATAL, V51, P150
   BOLIS V, 1989, J CHEM SOC FARAD T 1, V85, P855
   CHANG CC, 1973, J PHYS CHEM-US, V77, P2634
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   DENT AL, 1969, J PHYS CHEM-US, V73, P3772
   DEWAR MJS, 1977, J AM CHEM SOC, V99, P4899
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   EISCHENS RP, 1962, J CATAL, V1, P180
   FRISCH MJ, 1992, GAUSSIAN 92
   FUBINI B, 1982, J CHEM SOC F1, V78, P153
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   LONGO E, 1984, ADV CERAM, V10, P526
   LONGO E, 1985, LANGMUIR, V1, P456
   MARTINS JBL, 1993, INT J QUANTUM CHEM, V27, P643
   MARTINS JBL, 1994, J MOL STRUCT, V303, P19
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P301
   MARTINS JBL, 1995, J MOL STRUC-THEOCHEM, V330, P347
   MARTINS JBL, 1996, INT J QUANTUM CHEM, V57, P861
   MARTINS JBL, 1996, J MOL STRUCT, V363, P249
   MOLLER PJ, 1995, SURF SCI, V323, P102
   SEANOR DA, 1965, J CHEM PHYS, V42, P2967
   SOLOMON EI, 1993, CHEM REV, V93, P2623
   SPANHEL L, 1991, J AM CHEM SOC, V113, P2826
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   ZERNER MC, 1991, REV COMPUTATIONAL CH
NR 39
TC 9
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD JUN 2
PY 1997
VL 397
BP 147
EP 157
PG 11
SC Chemistry, Physical
GA XJ804
UT ISI:A1997XJ80400015
ER

PT J
AU Acioli, PH
TI Review of quantum Monte Carlo methods and their applications
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE quantum Monte Carlo; correlation energy; jellium model; variational
   Monte Carlo; diffusion Monte Carlo
ID GENERALIZED GRADIENT APPROXIMATION; LOCAL-DENSITY APPROXIMATION;
   METAL-SURFACES; GROUND-STATE; EXCHANGE-ENERGY; WAVE-FUNCTIONS;
   GREEN-FUNCTION; ELECTRON-GAS; MOLECULES; SOLIDS
AB Correlation energy makes a small but very important contribution to the
   total energy of an electronic system. Among the traditional methods
   used to study electronic correlation are coupled clusters (CC),
   configuration interaction (CI) and many-body perturbation theory (MBPT)
   in quantum chemistry, and density functional theory (DFT) in solid
   state physics. An alternative method, which has been applied
   successfully to systems ranging from the homogeneous electron gas, to
   atoms, molecules, solids and clusters is quantum Monte Carlo (QMC). In
   this method the Schrodinger equation is transformed to a diffusion
   equation which is solved using stochastic methods. In this work we
   review some of the basic aspects of QMC in two of its variants,
   variational (VMC) and diffusion Monte Carlo (DMC). We also review some
   of its applications, such as the homogeneous electron gas, atoms and
   the inhomogeneous electron gas (jellium surface). The correlation
   energy obtained by Ceperley and Alder (D.M. Ceperley and B.J. Alder,
   Physical Review, 45 (1980) 566), as parameterized by Perdew and Zunger
   (J.P. Perdew and A. Zunger, Phys. Rev. B23 (1980) 5469), is one of the
   most used in DFT calculations in the local density approximation (LDA).
   Unfortunately, the use of the LDA in inhomogeneous systems is
   questionable, and better approximations are desired or even necessary.
   We present results of the calculations performed on metallic surfaces
   in the jellium model which can be useful to obtain better
   approximations for the exchange and correlation functionals. We have
   computed the electronic density, work function, surface energy and pair
   correlation functions for a jellium slab at the average density of
   magnesium (r(s) = 2.66). Since there is an exact expression for the
   exchange and correlation functional in terms of the pair correlation
   functions, the knowledge of such functions near the edge of the surface
   may be useful to obtain exchange and correlation functionals valid for
   inhomogeneous systems. From the exchange and correlation functional we
   can conclude that the exchange-correlation hole is nearly spherical in
   the bulk region but elongated in the direction perpendicular to the
   surface as the electron approaches the edge of the surface, showing the
   anisotropic character of the electronic correlation near the surface.
   (C) 1997 Elsevier Science B.V.
RP Acioli, PH, UNIV BRASILIA,DEPT FIS,BR-70910900 BRASILIA,DF,BRAZIL.
CR ACIOLI PH, UNPUB
   ACIOLI PH, 1994, J CHEM PHYS, V100, P8169
   ACIOLI PH, 1996, PHYS REV B, V54, P17199
   ANDERSON JB, 1995, INT REV PHYS CHEM, V14, P85
   BACHELET GB, 1989, PHYS REV LETT, V62, P2088
   BECKE AD, 1988, PHYS REV A, V38, P3098
   BOSIN A, UNPUB
   BOYS SF, 1969, P ROY SOC LOND A MAT, V31, P43
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   CEPERLEY D, 1978, PHYS REV B, V18, P3126
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CEPERLEY DM, 1981, RECENT PROGR MANY BO, P262
   CEPERLEY DM, 1984, J CHEM PHYS, V81, P5833
   CEPERLEY DM, 1986, J STAT PHYS, V43, P815
   CHASE MW, 1985, J PHYS CHEM REF D S1, V14, P535
   CHEN B, IN PRESS
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   FAHY S, 1990, PHYS REV B, V42, P3503
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   HAMMOND BL, 1994, MONTE CARLO METHODS
   HANDY NC, 1973, J CHEM PHYS, V58, P279
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   VEILLARD A, 1968, J CHEM PHYS, V49, P2415
   ZHANG ZY, 1990, PHYS REV B, V41, P5674
NR 54
TC 4
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD MAY 2
PY 1997
VL 394
IS 2-3
BP 75
EP 85
PG 11
SC Chemistry, Physical
GA XF583
UT ISI:A1997XF58300002
ER

PT J
AU Mota, CJA
   Esteves, PM
   RamirezSolis, A
   HernandezLamoneda, R
TI Protonated isobutane. A theoretical ab initio study of the isobutonium
   cations
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID HYDROGEN-DEUTERIUM EXCHANGE; ELECTROPHILIC REACTIONS; ELECTROSTATIC
   POTENTIALS; PROTOLYSIS DEUTEROLYSIS; ELECTRONIC-STRUCTURE;
   CARBONIUM-IONS; SINGLE BONDS; CARBOCATIONS; 3-CENTER; MOLECULES
AB The structure and energy of the isobutonium cations, protonated
   isobutane, were studied by ab initio methods. At MP2(full)/6-31G**
   level, besides the C-isobutonium cation (5), the 2-H-isobutonium cation
   (6), and the 1-H-isobutonium cation (7), two additional structures,
   representing the van der Wads complex between methane and isopropyl.
   cation (8) and hydrogen plus tert-butyl cation (9), could also be
   characterized. The,energy increases in the order 9 < 8 < 5 < 6 < 7,
   indicating the lower energy of the van der Waals complexes. The
   experimental proton affinity of isobutane is in good agreement with the
   calculated values for the van der Waals complexes 8 and 9, indicating
   the facility of rupture of the three center bond in 5 and 6. On the
   other hand, the relative order of stability of the isobutonium cations
   can explain the experimental gas phase protonation of isobutane by
   small electrophiles, such as H-3(+) and H3O+, as well as the H-D
   exchange in liquid superacid.
C1 UNIV AUTONOMA ESTADO MORELOS,FAC CIENCIAS,CUERNAVACA 62210,MORELOS,MEXICO.
RP Mota, CJA, UNIV FED RIO DE JANEIRO,DEPT QUIM ORGAN,INST
   QUIM,BR-21949900 RIO JANEIRO,BRAZIL.
CR AQUILANTI V, 1968, J CHEM PHYS, V48, P4310
   BISCHOF PK, 1975, J AM CHEM SOC, V97, P2278
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   BURWELL RL, 1954, J AM CHEM SOC, V76, P5822
   CARNEIRO JWD, 1994, J AM CHEM SOC, V116, P3483
   CHIRLIAN LE, 1987, J COMPUT CHEM, V8, P894
   COLLINS SJ, 1994, CHEM PHYS LETT, V228, P246
   CORMA A, 1993, CATAL REV, V35, P483
   DEKOCK RL, 1988, J CHEM EDUC, V65, P194
   DUPUIS M, 1994, HONDO 8 5 CHEM STATI
   DYCZMONS V, 1970, CHEM PHYS LETT, V5, P361
   FIELD FH, 1968, ACCOUNTS CHEM RES, V1, P42
   FRISCH MJ, 1995, GUASSIAN 94 REVISION
   HACHOUMY M, 1995, THESIS U L PASTEUR
   HIRAO K, 1984, CHEM PHYS, V89, P237
   HIRAOKA K, 1975, CAN J CHEM, V53, P970
   HIRAOKA K, 1975, J CHEM PHYS, V63, P394
   HIRAOKA K, 1976, J AM CHEM SOC, V98, P6119
   HIRAOKA K, 1978, INT J MASS SPEC ION, V27, P139
   HOBZA P, 1995, J COMPUT CHEM, V16, P1315
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   HOGEVEEN H, 1969, RECL TRAV CHIM PAY B, V88, P703
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   LIDE DR, 1994, CRC HDB CHEM PHYSICS
   LOMBARDO EA, 1988, J CATAL, V112, P565
   MCMURRY JE, 1992, ACCOUNTS CHEM RES, V25, P47
   MOTA CJA, 1996, J PHYS CHEM-US, V100, P12418
   OLAH GA, 1968, J AM CHEM SOC, V90, P2726
   OLAH GA, 1969, J AM CHEM SOC, V91, P3261
   OLAH GA, 1971, J AM CHEM SOC, V93, P1251
   OLAH GA, 1972, J AM CHEM SOC, V94, P808
   OLAH GA, 1973, ANGEW CHEM INT EDIT, V12, P171
   OLAH GA, 1973, ANGEW CHEM INT EDIT, V12, P173
   OLAH GA, 1973, J AM CHEM SOC, V95, P4960
   OLAH GA, 1987, HYPERCARBON CHEM
   OLAH GA, 1987, HYPERCARBON CHEM, P222
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   POIRIER RA, 1982, J MOL STRUCT THEOCHE, V88, P343
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   SCHELEYER PV, 1992, J COMPUT CHEM, V13, P997
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
   SHERTUKDE PV, 1992, J CATAL, V136, P446
   SOMMER J, 1992, J AM CHEM SOC, V114, P5884
   SOMMER J, 1997, J AM CHEM SOC, V119, P32474
   STEVENSON DP, 1952, J AM CHEM SOC, V74, P3269
   TALROZE VL, 1952, DOKL AKAD NAUK SSSR, V86, P909
NR 49
TC 38
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD JUN 4
PY 1997
VL 119
IS 22
BP 5193
EP 5199
PG 7
SC Chemistry, Multidisciplinary
GA XC669
UT ISI:A1997XC66900016
ER

PT J
AU Pliego, JR
   DeAlmeida, WB
TI Absolute proton affinity and basicity of the carbenes CH2, CF2, CCl2,
   C(OH)(2), FCOH, CPh2 and fluorenylidene
SO JOURNAL OF THE CHEMICAL SOCIETY-FARADAY TRANSACTIONS
LA English
DT Article
ID O-H BOND; POLYATOMIC-MOLECULES; ION
AB Ab initio molecular orbital calculations were performed in order to
   determine the absolute proton affinity and basicity of some carbenes.
   For the species CH2, CF2, CCl2 C(OH)(2), and FCOH, the G2(MP2) method
   was utilized, and we have obtained the values 207.0, 177.4, 209.6,
   217.3 and 199.9 kcal mol(-1), respectively, for the absolute proton
   affinities. For CPh2 and fluorenylidene the calculation was performed
   at the HF/DZ + (P)/HF/DZ and MP2/DZ/HF/DZ levels of theory. For CPh2 we
   have obtained an absolute proton affinity of 275.0 kcal mol(-1) and,
   for fluorenylidene, the value is 272.4 kcal mol(-1). The implication of
   these results for the carbene reaction mechanism with PH groups is
   discussed.
C1 UFMG,ICEX,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR BETHELL D, 1971, J CHEM SOC B, P23
   CEYER ST, 1979, J CHEM PHYS, V70, P14
   CHATEAUNEUF JE, 1991, J CHEM SOC CHEM 1015, P1437
   CURTISS LA, 1993, J CHEM PHYS, V98, P1293
   DIXON DA, 1991, J PHYS CHEM-US, V95, P4180
   DU XM, 1990, J AM CHEM SOC, V112, P1920
   FRISCH MJ, 1995, GAUSSIAN 94
   GONZALEZ C, 1996, J AM CHEM SOC, V118, P5408
   GRILLER D, 1983, J AM CHEM SOC, V104, P5849
   HILLEBRAND C, 1996, J PHYS CHEM-US, V100, P9698
   KIRMSE W, 1964, CARBENE CHEM
   KIRMSE W, 1981, J AM CHEM SOC, V103, P5935
   KIRMSE W, 1990, J AM CHEM SOC, V112, P6399
   LEE C, 1996, J PHYS CHEM-US, V100, P7398
   LEVI BA, 1977, J AM CHEM SOC, V99, P8454
   LIAS SG, 1988, J PHYS CHEM REF D S1, V17
   NG CY, 1977, J CHEM PHYS, V67, P4235
   PLIEGO JR, 1996, CHEM PHYS LETT, V249, P136
   PLIEGO JR, 1996, J PHYS CHEM-US, V100, P12410
   POPLE JA, 1983, J AM CHEM SOC, V105, P6389
   VOGT J, 1975, J AM CHEM SOC, V97, P6682
   WALCH SP, 1993, J CHEM PHYS, V98, P3163
   ZUPANCIC JJ, 1985, TETRAHEDRON, V41, P1471
NR 23
TC 10
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK, MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0956-5000
J9 J CHEM SOC FARADAY TRANS
JI J. Chem. Soc.-Faraday Trans.
PD MAY 21
PY 1997
VL 93
IS 10
BP 1881
EP 1883
PG 3
SC Chemistry, Physical; Physics, Atomic, Molecular & Chemical
GA XC287
UT ISI:A1997XC28700004
ER

PT J
AU Zeng, Z
   Duan, Y
   Guenzburger, D
TI Magnetism, chemical bonding, and hyperfine properties in the nanoscale
   antiferromagnet [Fe(OMe)(2)(O2CCH2Cl)](10)
SO PHYSICAL REVIEW B
LA English
DT Article
ID ELECTRONIC-STRUCTURE; CLUSTER; TRANSITION; PARTICLES; ARRAYS; WHEEL;
   STATE
AB The electronic and magnetic properties of the nanometer-size
   antiferromagnet [Fe(OMe)(2)(O2CCH2Cl)](10) are investigated with the
   first-principles spin-polarized discrete variational method, in the
   framework of density-functional theory. Magnetic moments, densities of
   slates, and charge- and spin-density maps are obtained. The Mossbauer
   hyperfine parameters isomer shift, quadrupole splitting, and hyperfine
   field are obtained from the calculations and compared to reported
   experimental values when available.
RP Zeng, Z, CTR BRASILEIRO PESQUISAS FIS,CBPF,RUA DR XAVIER SIGAUD
   150,BR-22290180 RIO JANEIRO,BRAZIL.
CR AWSCHALOM DD, 1992, PHYS REV LETT, V68, P3092
   AWSCHALOM DD, 1992, SCIENCE, V258, P414
   AWSCHALOM DD, 1995, PHYS TODAY, V48, P43
   BAERENDS EJ, 1973, CHEM PHYS, V2, P41
   BARBARA B, 1990, PHYS LETT A, V145, P205
   BENCINI A, 1995, J CHEM SOC DA, P963
   CANESCHI A, 1996, INORG CHIM ACTA, V243, P295
   CAO PL, 1982, PHYS REV B, V25, P2124
   DELFS C, 1993, INORG CHEM, V32, P3099
   DELLEY B, 1982, J CHEM PHYS, V76, P1949
   DUFEK P, 1995, PHYS REV LETT, V75, P3545
   ELLIS DE, 1968, INT J QUANTUM CHEM S, V2, P35
   ELLIS DE, 1970, PHYS REV           B, V2, P2887
   ELLIS DE, 1994, ELECT DENSITY FUNCTI
   GATTESCHI D, 1994, SCIENCE, V265, P1054
   GATTESCHI D, 1996, INORG CHEM, V35, P1926
   GREENWOOD NN, 1971, MOSSBAUER SPECTROSCO
   GUENZBURGER D, 1980, PHYS REV B, V22, P4203
   GUENZBURGER D, 1987, PHYS REV B, V36, P6971
   KENT AD, 1994, J APPL PHYS 2, V76, P6656
   MELDRUM FC, 1992, SCIENCE, V257, P522
   MICHAEL RD, 1992, J MAGN MAGN MATER, V111, P29
   PAPAEFTHYMIOU GC, 1992, PHYS REV B, V46, P10366
   PARR RG, 1989, DENSITY FUNCTIONAL T
   POWELL AK, 1995, J AM CHEM SOC, V117, P2491
   SESSOLI R, 1993, NATURE, V365, P141
   SHENOY GK, 1978, MOSSBAUER ISOMER SHI
   SMYTH JF, 1991, J APPL PHYS, V69, P5262
   STPIERRE TG, 1987, J MAGN MAGN MATER, V69, P276
   TAFT KL, 1990, J AM CHEM SOC, V112, P9629
   TAFT KL, 1994, J AM CHEM SOC, V116, P823
   TERRA J, 1991, PHYS REV B, V44, P8584
   TERRA J, 1995, J PHYS CHEM-US, V99, P4935
   UMRIGAR C, 1980, PHYS REV B, V21, P852
   VONBARTH U, 1972, J PHYS C SOLID STATE, V5, P1629
   ZIOLO RF, 1992, SCIENCE, V257, P219
NR 36
TC 10
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD MAY 1
PY 1997
VL 55
IS 18
BP 12522
EP 12528
PG 7
SC Physics, Condensed Matter
GA XA260
UT ISI:A1997XA26000081
ER

PT J
AU Ferraz, AC
   Srivastava, GP
TI Atomic geometry and electronic structure of S/InP(001)
SO SURFACE SCIENCE
LA English
DT Article
DE adatoms; density functional calculations; indium phosphide; sulfur;
   surface electronic phenomena; surface relaxation and reconstruction
ID PASSIVATED INP(100)-(1X1) SURFACE
AB We have performed ab initio pseudopotential calculations of the atomic
   geometry and electronic states for a monolayer S-covered (001) surface
   of InP. It is found that for the 1 x 1 periodicity with S in the bridge
   site, the overlayer-substrate distance between S and In is 1.3 Angstrom
   and the In-S-In angle is 113.8 degrees. While the calculated In-S-In
   angle is close to the experimentally deduced value, we find that our
   prediction of overlayer-substrate distance is smaller than the value
   obtained from LEED analysis. We also discuss the energetics of
   formation of long and short dimer bonds for the 1 x 2, 2 x 1 and 2 x 2
   reconstructions of the surface.
C1 UNIV EXETER,DEPT PHYS,EXETER EX4 4QL,DEVON,ENGLAND.
RP Ferraz, AC, UNIV SAO PAULO,INST FIS,CP 66318,BR-05389970 SAO
   PAULO,SP,BRAZIL.
CR GONZE X, 1991, PHYS REV B, V44, P8503
   JIN JM, 1995, PHYS REV LETT, V75, P878
   LU ZH, 1992, APPL PHYS LETT, V60, P2773
   NEUGEBAUER J, 1992, PHYS REV B, V46, P16067
   PERDEW JP, 1981, PHYS REV B, V23, P5048
   TAO Y, 1992, APPL PHYS LETT, V60, P2669
   WARREN OL, 1995, PHYS REV B, V52, P2959
NR 7
TC 7
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD APR 20
PY 1997
VL 377
IS 1-3
BP 121
EP 124
PG 4
SC Chemistry, Physical
GA WZ496
UT ISI:A1997WZ49600027
ER

PT J
AU Urquhart, SG
   Turci, CC
   Tyliszczak, T
   Brook, MA
   Hitchcock, AP
TI Core excitation spectroscopy of phenyl- and methyl-substituted silanol,
   disiloxane, and disilane compounds: Evidence for pi-delocalization
   across the Si-C-phenyl bond
SO ORGANOMETALLICS
LA English
DT Article
ID ABSOLUTE OSCILLATOR-STRENGTHS; INNER-SHELL SPECTROSCOPY;
   HIGH-RESOLUTION; K-EDGE; ELECTRON-EXCITATION; GAS-PHASE; SPECTRA;
   MOLECULES; PHOTOABSORPTION; MONOCHROMATOR
AB The Si 1s and 2p solid state photoabsorption (total electron yield)
   spectra of triphenylsilanol, hexaphenyldisiloxane, and
   hexaphenyldisilane and the Si 1s spectra (total ion yield) of gaseous
   trimethylsilanol, hexamethyldisiloxane, hexamethyldisilane, and
   trimethylmethoxysilane have been recorded using synchrotron radiation.
   These spectra are compared to inner shell electron energy loss spectra
   of gaseous triphenylsilanol, hexaphenyldisilane,
   trimethylmethoxysilane, hexamethyldisiloxane, and hexamethyldisilane in
   the Si 2p and C 1s regions, measured under scattering conditions where
   electric dipole transitions dominate (2.5 keV residual energy, theta
   less than or equal to 2 degrees). Comparison of the Si 1s and Si 2p
   spectra of the Ph3Si-X and Me3Si-X species shows there are low-lying
   transitions at Si which occur exclusively in the Ph3Si-X species. These
   transitions are attributed to (Si 1s(-1),pi*Si-Ph) and (Si
   2p(-1),pi*Si-Ph) states in which the core excited electron is
   delocalized across the Si-C(phenyl) bond into the pi* levels ofthe
   phenylring. Extended Huckel and ab initio molecular orbital
   calculations of the core excitation spectra support this
   interpretation. Transitions characteristic of Si-Si and Si-O bonds are
   also identified.
C1 MCMASTER UNIV,DEPT CHEM,HAMILTON,ON L8S 4M1,CANADA.
   UNIV FED RIO JANEIRO,INST QUIM,BR-21910900 RIO JANEIRO,BRAZIL.
CR *WAV INC, 1994, SPART VERS 4 0
   AGREN H, 1995, CHEM PHYS, V195, P47
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   BADER RFW, 1990, ATOMS MOL QUANTUM TH
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   BODEUR S, 1990, PHYS REV A, V41, P252
   BOUISSET E, 1991, J PHYS B ATOM MOL PH, V24, P1609
   BOZEK JD, 1990, CHEM PHYS, V145, P131
   BRION CE, 1982, AIP C P, V94, P429
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   COOPER G, 1995, CHEM PHYS, V196, P293
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   WINKLER DC, 1994, CHEM PHYS LETT, V222, P1
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NR 62
TC 7
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0276-7333
J9 ORGANOMETALLICS
JI Organometallics
PD MAY 13
PY 1997
VL 16
IS 10
BP 2080
EP 2088
PG 9
SC Chemistry, Inorganic & Nuclear; Chemistry, Organic
GA WY882
UT ISI:A1997WY88200014
ER

PT J
AU Cerqueira, M
   Nasar, RS
   Longo, E
   Varela, JA
   Beltran, A
   Llusar, R
   Andres, J
TI Piezoelectric behaviour of PZT doped with calcium: A combined
   experimental and theoretical study
SO JOURNAL OF MATERIALS SCIENCE
LA English
DT Article
ID MORPHOTROPIC PHASE-BOUNDARY; PERTURBED-ION; CRYSTALS; SEPARABILITY;
   SIMULATION; CERAMICS; FILMS; MODEL
AB An experimental and theoretical study on the piezoelectric behaviour of
   PZT doped with a range of calcium ion concentrations is presented. A
   systematic study of the effect on the piezoelectric properties of PZT
   doped with various concentrations of CaO at constant sintering
   temperature and sintering time was carried out. The remanent
   polarization, planar coupling factor and frequency-thickness constant
   increase with calcium concentration. Ab initio perturbed ion
   calculations show that the lattice energy decreases with calcium
   addition for both tetragonal and rhombohedral phases of PZT.
C1 UNIV JAUME 1,DEPT CIENCIES EXPT,CASTELLO 12080,SPAIN.
   UFSCAR,DEPT QUIM,LAB INTERDISCIPLINAR ELECTROQUIM & CERAM,BR-13565 SAO CARLOS,SP,BRAZIL.
   UNESP,INST QUIM,BR-14800900 ARARAQUARA,SP,BRAZIL.
CR ANDRES J, 1993, INT J QUANTUM CHEM S, V27, P175
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NR 44
TC 4
PU CHAPMAN HALL LTD
PI LONDON
PA 2-6 BOUNDARY ROW, LONDON, ENGLAND SE1 8HN
SN 0022-2461
J9 J MATER SCI
JI J. Mater. Sci.
PD MAY 1
PY 1997
VL 32
IS 9
BP 2381
EP 2386
PG 6
SC Materials Science, Multidisciplinary
GA WY350
UT ISI:A1997WY35000020
ER

PT J
AU deMelo, CP
   Fonseca, TL
TI Polarizabilities of defect-bearing polyenic chains
SO SYNTHETIC METALS
LA English
DT Article
DE ab initio quantum chemical methods and calculations
AB We investigate the effect of the presence of conformational defects on
   the polarization response of conjugated chains. Our ab initio results
   for the polarizabilities of small C2n+1H2n+3+, and C2nH2n+2++ oligomers
   of polyacetylene confirm previous suggestions that the nonlinear
   optical properties of these systems are highly dependent on the type of
   conformational defect introduced. Especially, we call attention to the
   fact that the first hyperpolarizability of soliton bearing chains has
   opposite signs' for positive and negative defects.
RP deMelo, CP, UNIV FED PERNAMBUCO,DEPT FIS,BR-50670901 RECIFE,PE,BRAZIL.
CR ANDERSON T, 1994, BRAZ J PHYS, V24, P756
   DEMELO CP, UNPUB CHEM PHYS LETT
   DEMELO CP, 1988, J CHEM PHYS, V88, P2567
   DUCASSE L, 1993, SYNTHETIC MET, V55, P4536
   FRISCH MJ, 1992, GAUSSIAN 92 REVISION
   KIRTMAN B, 1995, J CHEM PHYS, V102, P5350
   LINDSAY GA, 1995, POLYM 2 ORDER NONLIN
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
NR 8
TC 4
PU ELSEVIER SCIENCE SA LAUSANNE
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD FEB 15
PY 1997
VL 85
IS 1-3
BP 1085
EP 1086
PG 2
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA WX708
UT ISI:A1997WX70800028
ER

PT J
AU DelNero, J
   Laks, B
   Custodio, R
TI Polycarbonitrile: A semiempirical, ab initio and density functional
   study of molecular stability
SO SYNTHETIC METALS
LA English
DT Article
DE polycarbonitrile; semiempirical; ab initio; density functional method;
   conformational structure
ID POLYMETHINEIMINE; POLYMERS
AB The theoretical literature data with respect to the electronic
   properties of this compound is quite scarce and makes use of the planar
   all-trans structure as the most stable for the calculations. In this
   work semiempirical (AMI and PM3), ab initio (at the Hartree-Fock level)
   and density functional theory (using the correlation functional of
   Vosko, Wille and Nussair) were used to analyse the conformational
   stability of the all-trans and all-cis dimers, trimers and tetramers of
   polycarbonitrile. The semiempirical and ab initio calculations at the
   Hartree-Fock level showed in general that the all-trans structure with
   respect to other conformers is the most unstable structure. The
   inclusion of electronic correlation energy through the MP2 calculations
   or the VWN functional method suggest that the trans structure is the
   most stable. The relative energies calculated at the correlated level
   presented differences around 2 kcal/mol among the different conformers.
   While the all-cis compounds presented a planar structure for any of the
   three methods, the all-trans polymer showed a strong deviation of
   planarity with a set of local minima in its energy surface. These
   results suggest that further calculations on the electronic properties
   of this polymer can be significantly different of those actually
   available in the literature.
C1 UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13083970 CAMPINAS,SP,BRAZIL.
RP DelNero, J, UNIV ESTADUAL CAMPINAS,INST FIS,BR-13083970
   CAMPINAS,SP,BRAZIL.
CR BREDAS JL, 1983, J CHEM PHYS, V78, P6137
   KARPFEN A, 1979, CHEM PHYS LETT, V64, P299
   MOLLER C, 1934, PHYS REV, V46, P618
   SPRINGBORG M, 1991, SYNTHETIC MET, V41, P4393
   VOSKO SH, 1980, CAN J PHYS, V58, P1200
NR 5
TC 6
PU ELSEVIER SCIENCE SA LAUSANNE
PI LAUSANNE
PA PO BOX 564, 1001 LAUSANNE, SWITZERLAND
SN 0379-6779
J9 SYNTHET METAL
JI Synth. Met.
PD FEB 15
PY 1997
VL 85
IS 1-3
BP 1127
EP 1128
PG 2
SC Materials Science, Multidisciplinary; Physics, Condensed Matter;
   Polymer Science
GA WX708
UT ISI:A1997WX70800049
ER

PT J
AU Eberlin, MN
   Sorrilha, AEPM
   Gozzo, FC
   Pimpim, RS
TI Novel [3+2] 1,3-cycloaddition of the ionized carbonyl ylide +CH2OCH2
   center dot with carbonyl compounds in the gas phase
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID DISTONIC RADICAL CATIONS; ION-MOLECULE REACTIONS; CATALYZED
   DIELS-ALDER; MASS-SPECTROMETRY; PERICYCLIC-REACTIONS; ORBITAL METHODS;
   DIMETHYL ETHER; ETHYLENE-OXIDE; ACYLIUM IONS; BASIS SETS
AB For the first time [3 + 2] 1,3-cycloaddition of an ionized carbonyl
   ylide has been observed in gas phase ion-molecule reactions of
   (+CH2OCH2.) (1) with several carbonyl compounds. The reaction, which
   competes with electrophilic addition that leads to net CH2.+ transfer,
   occurs across the C=O double bond of acetaldehyde and several acyclic
   ketones yielding ionized 4,3-dialkyl-1,3-dioxolanes as unstable
   cycloadducts. Rapid dissociation of the nascent cycloadducts by loss of
   a 4-alkyl substituent as a radical leads to the observed products, that
   is cyclic 3-alkyl-1,3-dioxolanylium ions. Cycloaddition of 1 with
   cyclic ketones yields bicyclic spiro adducts, which also undergo rapid
   dissociation. Cyclobutanone yields ionized 1,3-dioxaspiro[4,3]octane,
   which dissociates exclusively by neutral ethene loss to ionized
   4-methylene-1,3-dioxolane. Ionized 1,3-dioxaspiro[4,4]nonane is formed
   in reactions with cyclopentanone, and its rapid dissociation by loss of
   C3H6 and C2H5. yields the ionized 4-methylene-1,3-dioxolanylium and the
   4-ethenyl-1,3-dioxolanylium product ions, respectively. A systematic
   study of this novel reaction and characterization of the product ions
   carried out via pentaquadrupole (QqQqQ) multiple stage (MS-(1) and MS3)
   mass spectrometric experiments provide experimental evidence for the
   cycloaddition mechanism. The dissociation chemistry observed for the
   cycloaddition products correlate well with their proposed structures
   and was compared to that of both isomeric and reference ions. Ab initio
   MP2/6-31G(d,p)//HF/6-31G(d,p) + ZPE potential energy surface diagrams
   for the reactions of 1 with acetone, fluoroacetone, and
   1,1,1-trifluoroncetone support the operation of the two competitive
   reaction pathways, that is CH2.+ transfer and [3 + 2]
   1,3-cyclonddition/dissociation, and show that the cycloaddition process
   is favored by electron-withdrawing substituents.
RP Eberlin, MN, UNIV CAMPINAS,INST CHEM,CP 6154,BR-13083970
   CAMPINAS,SP,BRAZIL.
CR AUDIER H, 1964, B SOC CHIM FR, P1880
   BASHER MM, IN PRESS
   BAULD NL, 1987, ACCOUNTS CHEM RES, V20, P371
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   BELLVILLE DJ, 1981, J AM CHEM SOC, V103, P718
   BIANCHI G, 1977, CHEM DOUBLE BON 1 SA, P369
   BLAIR AS, 1973, CAN J CHEM, V51, P703
   BOGER DL, 1987, HETERO DIELSALDER ME
   BOUCHOUX G, 1988, MASS SPECTROM REV, V7, P1
   BOUMA WJ, 1979, J AM CHEM SOC, V101, P5540
   BOUMA WJ, 1980, ADV MASS SPECTROM A, V8, P178
   BOUMA WJ, 1980, J AM CHEM SOC, V102, P2246
   BOUMA WJ, 1983, J AM CHEM SOC, V105, P1743
   BOWERS MT, 1970, J PHYS CHEM-US, V74, P2583
   BUDZIKIEWICZ H, 1967, MASS SPECTROMETRY OR
   CASTLE LW, 1989, ORG MASS SPECTROM, V24, P637
   DASS C, 1990, MASS SPECTROM REV, V9, P1
   DOMINH T, 1970, J AM CHEM SOC, V92, P1402
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   EBERLIN MN, 1993, P 41 ASMS C MASS SPE, P975
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   EBERLIN MN, 1995, J AM SOC MASS SPECTR, V6, P1
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   FRASERMONTEIRO ML, 1982, J PHYS CHEM-US, V86, P739
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   GOZZO FC, 1995, J AM SOC MASS SPECTR, V6, P554
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   GROENEWOLD GS, 1984, J AM CHEM SOC, V106, P539
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   KOTIAHO T, 1993, J AM CHEM SOC, V115, P1004
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   MOLLER C, 1934, PHYS REV, V46, P618
   MORAES LAB, UNPUB J ORG CHEM
   MORAES LAB, 1996, J ORG CHEM, V61, P8726
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   NOURSE BD, 1992, ORG MASS SPECTROM, V27, P453
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   SHAY BJ, 1992, J AM SOC MASS SPECTR, V3, P518
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   STIRK KM, 1992, CHEM REV, V92, P1649
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NR 71
TC 27
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD APR 16
PY 1997
VL 119
IS 15
BP 3550
EP 3557
PG 8
SC Chemistry, Multidisciplinary
GA WU272
UT ISI:A1997WU27200017
ER

PT J
AU Morgon, NH
   Argenton, AB
   daSilva, MLP
   Riveros, JM
TI Experimental and theoretical characterization of FSi(OCH3)(2)(OCH2)(-):
   A gas phase fluoride-siloxirane adduct
SO JOURNAL OF THE AMERICAN CHEMICAL SOCIETY
LA English
DT Article
ID OPTIMIZATION TECHNIQUE; SUBSTITUTED SILANES; BASIS-SETS; H SYSTEM;
   ANIONS; THERMOCHEMISTRY; CHEMISTRY; IONS; AFFINITIES; MOLECULES
AB The structural characteristics and reactivity of the gas-phase
   FSi(OCH3)(2)(OCH2)(-) ion were investigated by a combination of ab
   initio calculations and FT-ICR techniques. The theoretical calculations
   for different possible structures reveal that carbanion and alkoxide
   ion type structures lead to ring closure upon geometry optimization to
   yield two different cyclic fluoride-siloxirane structures. The
   FSi(OCH3)(2)(cyc-OCH2)(-) ions containing the elusive siloxirane ring
   are estimated to be extremely stable with respect to F-(69 kcal
   mol(-1)) dissociation in agreement with earlier calculations on simpler
   systems. Experimentally, this ion is formed as a minor product (7%) in
   the gas-phase ion/molecule reaction of F- with Si(OMe)(4) and is
   observed to undergo readily fluoride transfer to the parent neutral.
   This strongly suggests an ion with a structure corresponding to a
   fluoride adduct of a siloxirane species, Reaction of
   FSi(OCH3)(2)(OCH2)(-) with BF3, hexafluorobenzene, and gas-phase acids
   more acidic than ethanol further suggests that this ion is capable of
   reacting as an alkoxide type nucleophile or base. This latter behavior
   has been associated with the possibility of ring opening of the
   siloxirane in the collision complex that mediates this ion/molecule
   reaction.
C1 UNIV SAO PAULO,INST CHEM,BR-05599970 SAO PAULO,BRAZIL.
CR ALLENDORF MD, 1992, J PHYS CHEM-US, V96, P428
   ALLENDORF MD, 1995, J PHYS CHEM-US, V99, P15285
   BARTMESS JE, 1993, NIST STANDARD REFERE
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   SKANCKE PN, 1994, J PHYS CHEM-US, V98, P3154
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NR 49
TC 16
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0002-7863
J9 J AMER CHEM SOC
JI J. Am. Chem. Soc.
PD FEB 19
PY 1997
VL 119
IS 7
BP 1708
EP 1716
PG 9
SC Chemistry, Multidisciplinary
GA WJ097
UT ISI:A1997WJ09700025
ER

PT J
AU Varella, MTD
   Bettega, MHF
   Lima, MAP
TI Cross sections for rotational excitations of CH4, SiH4, GeH4, SnH4 and
   PbH4 by electron impact
SO ZEITSCHRIFT FUR PHYSIK D-ATOMS MOLECULES AND CLUSTERS
LA English
DT Article
ID TEMPERATURE; SCATTERING; MOLECULES
AB We report differential and integral cross sections for rotational
   excitation of XH(4) molecules (X: C, Si, Ge, Sn, Pb) from 7.5-30 eV by
   electron impact. These cross sections were derived from fixed-nuclei
   scattering amplitudes (Bettega et al. 1995) obtained using the
   Schwinger Multichannel Method with Pseudopotentials (SMCPP) (Bettega et
   al. 1993). Our results represent the first rotational excitation cross
   sections for molecules as large as GeH4, SnH4 and PbH4 using entirely
   ab initio procedures. The cross sections for CH4 and SiH4 obtained with
   pseudopotentials are in very good agreement with all-electron
   calculations and with other theoretical results. A comparison between
   our calculated cross sections and experimental data for CH4 is in
   general encouraging, but some discrepancies remain. We found inelastic
   rotational cross sections and momentum transfer cross sections to be
   larger for SiH4, GeH4, SnH4 and PbH4 than for CH4. We could explain
   this feature.
C1 UNIV FED PARANA,DEPT FIS,BR-81531990 CURITIBA,PARANA,BRAZIL.
RP Varella, MTD, UNIV ESTADUAL CAMPINAS,INST FIS GLEB WATAGHIN,BR-13083970
   CAMPINAS,SP,BRAZIL.
CR ABULSABI N, 1983, J CHEM PHYS, V78, P1213
   BETTEGA MHF, 1993, PHYS REV A, V47, P1111
   BETTEGA MHF, 1995, J CHEM PHYS, V103, P10566
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   GARSCADDEN A, 1992, Z PHYS D ATOM MOL CL, V24, P97
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   GIANTURCO FA, 1995, PHYS REV A, V52, P1257
   JAIN A, 1983, J PHYS B-AT MOL OPT, V16, P3077
   JAIN A, 1991, Z PHYS D ATOM MOL CL, V21, P153
   MULLER R, 1985, J PHYS B ATOM MOL PH, V18, P3971
   NATALENSE APP, 1995, PHYS REV A, V52, R1
   ROSE ME, 1957, ELEMENTARY THEORY AN
   SHIMAMURA I, 1984, ELECT MOL COLLISIONS
NR 13
TC 13
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0178-7683
J9 Z PHYS D-ATOMS MOL CLUSTERS
JI Z. Phys. D-Atoms Mol. Clusters
PD JAN
PY 1997
VL 39
IS 1
BP 59
EP 67
PG 9
SC Physics, Atomic, Molecular & Chemical
GA WF781
UT ISI:A1997WF78100011
ER

PT J
AU Tostes, JR
   Seidl, PR
   Taft, CA
   Lie, SK
   Carneiro, JWD
   Brown, W
   Lester, WA
TI Carbon-carbon and carbon-hydrogen hyperconjugation in neutral alcohols
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE hyperconjugation; neutral alcohol; carbon-carbon bonding;
   carbon-hydrogen bonding; charge distribution
ID MOLECULAR-ORBITAL THEORY; NEGATIVE HYPERCONJUGATION;
   ELECTRONIC-STRUCTURE; CHARGE-DISTRIBUTION; AB-INITIO; METHYL;
   CONFORMATIONS; CONSEQUENCES; SUBSTITUENTS; SPECTROSCOPY
AB A short review of hyperconjugation is presented emphasizing
   carbon-carbon and carbon-hydrogen hyperconjugation in neutral alcohols
   of different sizes and geometries. Charge distribution and geometrical
   parameters, involving adjacent 'acceptor' carbon-hydrogen and
   carbon-carbon bonds such as those found on methanol ethanol, 2-propanol
   t-butanol, exo and endo norbornol as well as their tetra-penta- and
   hexacyclic analogs in different conformations provide sensitive probes
   for hyperconjugation.
C1 UNIV FED FLUMINENSE,DEPT QUIM GERAL & INORGAN,BR-24249 NITEROI,RJ,BRAZIL.
   UNIV FED FLUMINENSE,DEPT FIS,BR-24249 NITEROI,RJ,BRAZIL.
   UNIV FED RIO DE JANEIRO,ESCOLA QUIM,RIO JANEIRO,BRAZIL.
   CTR BRASILEIRO PESQUISAS FIS,BR-22290 RIO JANEIRO,BRAZIL.
   UNIV CALIF BERKELEY,LAWRENCE BERKELEY LAB,DIV CHEM SCI,BERKELEY,CA 94720.
   UNIV CALIF BERKELEY,DEPT CHEM,BERKELEY,CA 94720.
RP Tostes, JR, UNIV FED FLUMINENSE,DEPT QUIM FIS,BR-24249
   NITEROI,RJ,BRAZIL.
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NR 64
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD DEC 11
PY 1996
VL 388
BP 85
EP 95
PG 11
SC Chemistry, Physical
GA WE809
UT ISI:A1996WE80900013
ER

PT J
AU Lins, JOMDL
   Nascimento, MAC
TI Theoretical investigation of the methane activation reaction on
   protonated zeolite from generalized valence-bond plus configuration
   interaction calculations
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE activation energy; methane activation; transition state; zeolite
ID MOLECULAR ELECTROSTATIC POTENTIALS; DISSOCIATION ENERGIES; ATOMIC
   CHARGES; EXCHANGE; DEHYDROGENATION; DENSITY; CD4
AB Generalized valence-bond plus configuration interaction calculations
   are performed to study the activation of methane by a protonated model
   zeolite. The resulting transition state exhibits carbenium-like ion
   character, with a positively charged methyl group and an almost neutral
   hydrogen molecule to be formed. The nature of the transition state is
   similar to that obtained with density functional theory (DFT), in spite
   of significant differences in the geometry of the optimized model
   clusters. The activation barrier for the dehydrogenation process was
   found to be 74.8 kcal mol(-1), which compares well with the DFT value
   of 82.0 kcal mol(-1).
C1 UNIV FED RIO DE JANEIRO,DEPT FISICOQUIM,INST QUIM,BR-21949900 RIO JANEIRO,BRAZIL.
CR BLASZKOWSKI SR, 1994, J PHYS CHEM-US, V98, P12938
   BRENEMAN CM, 1990, J COMPUT CHEM, V11, P361
   BROBOWICZ FW, 1977, MODERN THEORETICAL C, CH4
   CARTER EA, 1988, J CHEM PHYS, V88, P3132
   CHIANG AS, 1984, CHEM ENG SCI, V39, P1451
   CHIRLIAN LE, 1987, J COMPUT CHEM, V8, P894
   DAVIS ME, 1991, IND ENG CHEM RES, V30, P1675
   DAVIS ME, 1995, STUD SURF SCI CATAL, V97, P35
   ESTEVES PM, UNPUB
   EVLETH EM, 1994, J PHYS CHEM-US, V98, P1421
   HIROTA E, 1979, J MOL SPECTROSC, V77, P213
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   KRAMER GJ, 1995, J AM CHEM SOC, V117, P1766
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   MULLIKEN RS, 1955, J CHEM PHYS, V23, P1833
   NASCIMENTO MAC, UNPUB J PHYS CHEM
   RAPPE AK, 1988, GRADGVB PROGRAM
   SILVA SC, 1993, THEOCHEM-J MOL STRUC, V101, P51
   STACH H, 1986, ZEOLITES, V6, P74
   STEFANADIS C, 1991, J MOL CATAL, V67, P363
   VANSANTEN RA, 1995, CHEM REV, V95, P637
   WANG LS, 1993, CATAL LETT, V21, P35
   WOODS RJ, 1990, J COMPUT CHEM, V11, P297
NR 23
TC 5
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD NOV 18
PY 1996
VL 371
BP 237
EP 243
PG 7
SC Chemistry, Physical
GA WD890
UT ISI:A1996WD89000027
ER

PT J
AU Rocha, WR
   DeAlmeida, WB
TI Quantum-mechanical and molecular mechanics conformational analysis of
   1,5-cyclooctadiene
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
ID GAUSSIAN-TYPE BASIS; MM3 FORCE-FIELD; SEMIEMPIRICAL METHODS;
   ORGANIC-MOLECULES; ORBITAL METHODS; OPTIMIZATION; PARAMETERS
AB The 1,5-cyclooctadiene (COD) molecule can easily form complexes with
   transition metals with the molecular structure of various of these
   complexes being proposed with the aid of X-ray diffraction methods. The
   fact that the complexes exhibit weak metal-GOD bonds makes it very
   important in inorganic synthesis and catalysis. In this work the
   potential energy surface (PES) for the GOD molecule was comprehensively
   investigated first with molecular mechanics (casing the MM3 force
   field); and, in a second stage, at the ab initio Hartree-Fock level of
   theory employing the 3-21G*, 6-31G, and 6-31G* basis sets and also
   including electron correlation effects at the Moller-Plesset
   second-order perturbation theory level. This work revealed that there
   are three distinct conformers of the COD molecule with the predicted
   lowest energy conformation being in agreement with the proposed
   structure based on experimental electron diffraction data. (C) 1997 by
   John Wiley & Sons, Inc.
C1 UFMG,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM MOL,ICEX,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR ALLINGER NL, 1975, TETRAHEDRON, V31, P21
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   ANET FAL, 1973, J AM CHEM SOC, V95, P3407
   DEALMEIDA WB, 1996, IN PRESS ANN 3 LAT A
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   DITCHFIELD R, 1971, J CHEM PHYS, V54, P724
   DOSSANTOS HF, IN PRESS INF TECNOL
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   STEWART JJP, 1989, J COMPUT CHEM, V10, P221
   VANDENHENDE JH, 1963, J AM CHEM SOC, V85, P1009
NR 23
TC 7
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD JAN 30
PY 1997
VL 18
IS 2
BP 254
EP 259
PG 6
SC Chemistry, Multidisciplinary
GA WB112
UT ISI:A1997WB11200009
ER

PT J
AU Wong, PSH
   Ma, SG
   Yang, SS
   Cooks, RG
   Gozzo, FC
   Eberlin, MN
TI Sulfur trifluoride cation (SF3+) affinities of pyridines determined by
   the kinetic method: Stereoelectronic effects in the gas phase
SO JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
LA English
DT Article
ID MS(3) MASS-SPECTROMETRY; BOND-DISSOCIATION ENERGIES; TRANSITION-METAL
   BONDS; PROTON AFFINITY; CHEMISTRY; CARBONYL; SF6
AB Ion/molecule reactions performed by pentaquadrupole mass spectrometry
   are used to generate cluster ions in which neutral pyridines are bound
   to the polyatomic cation SF3+. The dimeric ions Py(1)SF(3)(+)Py(2),
   where Py(1) and Py(2) represent substituted pyridines, are shown to
   have loosely bound structures by collision-induced dissociation (MS(3))
   experiments and by semiempirical AM1 and ab initio RHF/G-S1G(d, p)
   molecular orbital calculations. In the case of dimers comprised of
   meta- and/or para-substituted pyridines (unhindered pyridines), there
   is an excellent Linear correlation between the logarithm of the
   fragment ion abundance ratio In{[Py(1)(SF3+)]/[Py(SF3+)]} and the
   proton affinities (PA) of the constituent pyridines. Semiempirical
   calculations are used to estimate the SF3+ affinities of pyridines
   which are found to be in the range of 25-31 kcal/mol. The SF3+
   affinities show an excellent linear correlation with the proton
   affinities of the pyridines, and the relationship SF3+ affinity
   (kcal/mol) = 0.73PA - 135.8 between the two affinities is derived. The
   effective temperature of the dimeric ions is determined to be 595 +/-
   69 K, which is in good agreement with values of around 600 K obtained
   experimentally in studies on many other systems activated under similar
   conditions. Ortho-substituted pyridines show lower than expected
   affinities due to stereoelectronic effects that decrease the cation
   affinities. Gas-phase stereoelectronic parameters (S-k) are measured
   from the deviation from the PA correlation and are ordered as 2-MePy
   (-1.09) < 2,6-diMePy (-1.11) < 2-EtPy (-1.91) < 2,3-diMePy (-2.15) <
   2,5-diMePy (-2.25) < 2,4-diMePy (-2.40). Overall, the steric effects
   are larger than those in the corresponding Cl+-bound dimers but smaller
   than those in the bulky [OCNCO+] system. Calculations show evidence for
   agostic bonding that offsets the steric effects in some eases. The
   eclipsed conformation of 2-methylpyridine/SF3+ adduct is found to be
   more stable than the staggered form by 0.8 kcal/mol, due to auxiliary
   agostic bonding between the hydrogen of the ortho methyl substituent
   and the sulfur atom. Calculations on atomic charge distribution reveal
   that the positive charge is mainly on the sulfur atom (+1.99) and the
   charge on the bonding hydrogen S-H-C (+0.07) is considerably lower than
   that on the other two methyl hydrogens (+0.14), which appears to be a
   good indication of agostic binding. The most stable form of the
   2-ethylpyridine/SF3+ adduct is found when the N-C-1-C-alpha-C-beta
   dihedral angle is approximately 60 degrees, where the ethyl hydrogen is
   directed toward the SF3 group via an interesting six-membered ring
   alignment. The experiments show a remarkably small steric effect in
   2,6-dimethylpyridine, probably due to strong agostic bonding enhanced
   by the buttressing effect that shortens the S-H distance. In addition,
   the face-to-face interactions of the F atoms and the H atoms further
   stabilize this form. (C) 1997 American Society for Mass Spectrometry
C1 PURDUE UNIV,BROWN LAB,DEPT CHEM,W LAFAYETTE,IN 47907.
   UNICAMP,INST CHEM,CAMPINAS,SP,BRAZIL.
CR AYNG SS, 1996, J AM SOC MASS SPECTR, V7, P198
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   COOKS RG, 1989, ADV MASS SPECTROM, V11, P33
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   EBERLIN MN, 1994, J AM CHEM SOC, V116, P2457
   FEHSENFELD FC, 1971, J CHEM PHYS, V54, P438
   FRANKLIN JL, 1972, ION MOL REACTIONS
   FUTRELL JH, 1986, GASEOUS ION CHEM MAS
   GREEN MLH, 1984, PURE APPL CHEM, V56, P47
   HARRISON AG, 1983, CHEM IONIZATION MASS
   HERRON JT, 1987, J PHYS CHEM REF DATA, V16, P1
   HO Y, 1992, J AM CHEM SOC, V114, P10961
   JENKINS HDB, 1994, TETRAHEDRON LETT, V34, P6543
   JONES RW, 1982, J PHYS CHEM-US, V86, P1387
   JULIANO VF, 1996, ANAL CHEM, V68, P1328
   KOGA N, 1984, J AM CHEM SOC, V106, P4625
   LATIMER DR, 1994, J CHEM PHYS, V101, P3410
   LIAS SG, 1975, ION MOL REACTIONS TH
   MACKAY GI, 1992, INT J MASS SPECTROM, V117, P38
   MAJUMDAR TK, 1992, J AM CHEM SOC, V114, P2897
   MCLUCKEY SA, 1981, J AM CHEM SOC, V103, P1313
   NOURSE BD, 1991, INT J MASS SPECTROM, V106, P249
   OPERTI L, 1988, J AM CHEM SOC, V110, P3847
   SCHWARTZ JC, 1990, ANAL CHEM, V62, P1809
   SCHWARTZ JC, 1990, INT J MASS SPECTROM, V101, P1
   STONE JA, 1989, INT J MASS SPECTROM, V94, P269
   TAMURA A, 1987, APPL PHYS LETT, V51, P1503
   YANG SS, 1995, J MASS SPECTROM, V30, P184
   YANG SS, 1995, J MASS SPECTROM, V30, P807
   ZANGERLE R, 1993, INT J MASS SPECTROM, V129, P117
NR 40
TC 20
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010
SN 1044-0305
J9 J AMER SOC MASS SPECTROM
JI J. Am. Soc. Mass Spectrom.
PD JAN
PY 1997
VL 8
IS 1
BP 68
EP 75
PG 8
SC Chemistry, Analytical; Chemistry, Physical; Spectroscopy
GA WA210
UT ISI:A1997WA21000010
ER

PT J
AU Olivato, PR
   Rittner, R
TI Conformational and electronic interaction studies of some
   alpha-mono-heterosubstituted carbonyl compounds
SO REVIEWS ON HETEROATOM CHEMISTRY
LA English
DT Article
DE alpha-heterosubstituted carbonyl compounds; conformational isomerism;
   electronic interactions
ID SOLUTION-STATE CONFORMATIONS; VIBRATIONAL ASSIGNMENT;
   INTERNAL-ROTATION; ULTRAVIOLET PHOTOELECTRON; ABINITIO CALCULATIONS;
   MOLECULAR-MECHANICS; MICROWAVE-SPECTRUM; IR SPECTROSCOPY;
   FLUOROACETONE; DERIVATIVES
AB nu(CO) frequencies and intensities of some alpha-heterosubstituted
   carbonyl compounds [XCH(2)C(O)Y: X = F, OMe, NR(2), Cl, Br, SEt, or I;
   and Y = Me, Ph, SR, OMe or NEt(2)], together with molecular mechanics
   calculations indicated the existence of cis-gauche rotational
   isomerism. In solvents of low polarity the gauche rotamers predominate
   over the cis ones, except for the fluoro and methoxy derivatives of
   acetophenone and methyl acetate series. The progressive increase in the
   gauche rotamer population in each series, on going from the fluoro to
   the iodo derivative has been mainly ascribed to the increasing
   contribution of the pi*(CO)/sigma(C-X) and pi*(CO)/n(X) orbital
   interactions. The carbonyl frequency shifts of the cis rotamers are
   interpreted as being due to the substituent field and inductive
   effects, while the corresponding shifts of the gauche rotamers have
   been attributed to an interplay of inductive and hyperconjugative
   effects. The carbonyl shifts induced by inductive (Delta nu(I)), field
   (Delta nu(F)) and hyperconjugative effects (Delta nu(H)) were estimated
   separately for the acetone derivatives. The larger negative carbonyl
   gauche shifts (Delta nu(g)) along with a higher non-additivity effect
   (Delta delta) of the alpha-methylene carbon chemical shifts can be
   associated with stronger pi*(CO)/sigma(C-X) and pi*(CO)/n(X) orbital
   interactions. The higher stabilization of the gauche rotamers for the
   alpha-akylthio carbonyl compounds, the larger nu(CO) gauche shifts and
   the lower non-additivity effect for the alpha-methylene carbon have
   been interpreted as being due to the simultaneous occurrence of
   pi*(CO)/sigma(C-S) and pi(CO)/sigma*(C-S) orbital interactions. The
   progressive bathochromic shifts of n(O) --> pi*(CO) transition for the
   alpha-heterosubstituted ketones, on going from the fluorine to the
   iodine substituent, were mainly ascribed to a contribution of the
   hyperconjugative interaction (pi*(CO)/sigma*(C-X)). Ab initio
   calculations, and photoelectron and electron transmission
   spectroscopies have supported, in general, the mentioned orbital
   interactions.
C1 UNIV SAO PAULO,INST QUIM,BR-05599970 SAO PAULO,BRAZIL.
   UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13083970 CAMPINAS,SP,BRAZIL.
CR ABRAHAM RJ, 1981, TETRAHEDRON, V37, P575
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NR 65
TC 16
PU MYU K K
PI TOKYO
PA SCIENTIFIC PUBLISHING DIV, 2-32-3 SENDAGI, BUNKYO-KU, TOKYO 113, JAPAN
SN 0915-6151
J9 REV HETEROATOM CHEM
JI Rev. Heteroatom Chem.
PY 1996
VL 15
BP 115
EP 159
PG 45
SC Chemistry, Multidisciplinary
GA VV529
UT ISI:A1996VV52900006
ER

PT J
AU Camargo, AC
   Igualada, JA
   Beltran, A
   Llusar, R
   Longo, E
   Andres, J
TI An ab initio perturbed ion study of structural properties of TiO2,
   SnO2, and GeO2 rutile lattices
SO CHEMICAL PHYSICS
LA English
DT Article
ID VANADIUM-DOPED ZIRCON; PERIODIC HARTREE-FOCK; TITANIUM-DIOXIDE;
   ELECTRONIC-STRUCTURE; CRYSTAL-STRUCTURES; OXIDE; PRINCIPLES;
   POLYMORPHS; DYNAMICS; SURFACES
AB This work describes a theoretical quantum mechanical study on TiO2,
   SnO2 and GeO2 rutile structures in order to characterize the geometric,
   mechanical, thermodynamic and electronic properties of these systems.
   The doping processes of V4+ at the sixfold-coordinated site have been
   studied with the aim of determining the relative stability of pure and
   doped structures. Ab initio perturbed ion calculations with Slater-type
   orbitals for representing atomic centers and large cluster models have
   been used. Local geometry optimizations have been performed to
   determine the lattice energy, lattice parameters and bulk modulus, as
   well as the force constant and vibrational frequencies (nu) of the
   breathing vibrational modes, a(1g), in the sixfold-coordinated site.
   Numerical results are analyzed and compared with experimental data, the
   geometrical distances obtained by computer simulation being in
   agreement with the reported experimental values. The difference in
   energy for the substitution of Ti4+, Sn4+ and Ge4+ for V4+ in TiO2,
   SnO2 and GeO2, respectively is very dependent on the method used to
   represent these doping processes. The TiO2, SnO2 lattices show a
   decrease in the nu value from the pure to the doped structure while a
   opposite trend is obtained for the GeO2 structure. The validity of the
   methodology is discussed.
C1 UNIV JAUME 1,DEPT EXPT SCI,CASTELLO 12080,SPAIN.
   UNIV FED SAO CARLOS,DEPT CHEM,BR-131560 SAO CARLOS,BRAZIL.
CR ANDRES J, 1994, CHEM PHYS LETT, V221, P249
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NR 59
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD DEC 1
PY 1996
VL 212
IS 2-3
BP 381
EP 391
PG 11
SC Physics, Atomic, Molecular & Chemical
GA VV617
UT ISI:A1996VV61700010
ER

PT J
AU Teles, LK
   Scolfaro, LMR
   Enderlein, R
   Leite, JR
   Josiek, A
   Schikora, D
   Lischka, K
TI Structural properties of cubic GaN epitaxial layers grown on beta-SiC
SO JOURNAL OF APPLIED PHYSICS
LA English
DT Article
ID MOLECULAR-BEAM EPITAXY; GALLIUM NITRIDE; AB-INITIO; INTERFACES
AB Self-consistent Eight-binding total energy calculations are performed
   to study the deposition of a few layers of cubic GaN on (100) beta-SiC
   substrates. Cohesion energies, atomic displacements, dangling bond
   occupancies and surface reconstructions are calculated for a variety of
   epitaxial systems including monolayers of either Ga or N as well as
   single and double bilayers of GaN on either Si or C terminated
   substrates. The SiC substrates and Ga-N epitaxial layers are
   represented by 2x2 supercells of 9 Si and C monolayers plus the
   respective number of monolayers of Ga and N atoms. Depending on the
   system, surface atoms dimerize either symmetrically or asymmetrically
   resulting in either 2x1, c-2x2, or 2x2 surface reconstructions. At the
   substrate-epitaxial-layer interfaces, N binds stronger than Ga to
   either Si or C. Interface mixing is found to be energetically not
   advantageous for both C- and Si-terminated substrates, although for the
   latter the obtained small energy differences may suggest the
   possibility of mixing. (C) 1996 American Institute of Physics.
C1 UNIV BORDEAUX 1,LAB COMPOSITES THERMOSTRUCT,F-33600 PESSAC,FRANCE.
   UNIV GESAMTHSCH PADERBORN,FB PHYS 6,D-33098 PADERBORN,GERMANY.
RP Teles, LK, UNIV SAO PAULO,INST FIS,CAIXA POSTAL 66318,BR-05389970 SAO
   PAULO,BRAZIL.
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NR 25
TC 9
PU AMER INST PHYSICS
PI WOODBURY
PA CIRCULATION FULFILLMENT DIV, 500 SUNNYSIDE BLVD, WOODBURY, NY 11797-2999
SN 0021-8979
J9 J APPL PHYS
JI J. Appl. Phys.
PD DEC 1
PY 1996
VL 80
IS 11
BP 6322
EP 6328
PG 7
SC Physics, Applied
GA VV267
UT ISI:A1996VV26700036
ER

PT J
AU Zeng, Z
   Ellis, DE
   Guenzburger, D
   BaggioSaitovitch, E
TI Spin density and magnetism of rare-earth nickel borocarbides:
   RNi(2)B(2)C
SO PHYSICAL REVIEW B
LA English
DT Article
ID ANTIFERROMAGNETIC SUPERCONDUCTOR HONI2B2C; ELECTRONIC-STRUCTURE; BORIDE
   CARBIDE; R=RARE EARTH; INTERMETALLIC COMPOUNDS; QUATERNARY COMPOUNDS;
   SINGLE-CRYSTALS; ENERGY-GAP; B-C; YNI2B2C
AB The rare-earth spin moments in quarternary borocarbides RNi(2)B(2)C,
   R=Pr, Nd, Sm, Gd, Ho, Tm are determined by self-consistent density
   functional theory, using the embedded cluster formalism. Spin-polarized
   electronic structure calculations considering antiferromagnetic
   coupling between R-C layers are performed. Spin polarization of the
   lattice is examined in detail and related to observed ferromagnetic
   ordering in R-C layers and antiferromagnetic ordering between layers.
   The observed superconductivity of Y, Lu, Tm, Er, and Ho compounds and
   regions of coexistence with antiferromagnetism in Tm and Ho is
   discussed in terms of the magnitude of R moments, differences in R
   4f-5d hybridization, and resulting lattice polarization.
RP Zeng, Z, CTR BRASILEIRO PESQUISAS FIS,RUA XAVIER SIGAUD 150,BR-22290180
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NR 72
TC 6
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD NOV 1
PY 1996
VL 54
IS 18
BP 13020
EP 13029
PG 10
SC Physics, Condensed Matter
GA VT682
UT ISI:A1996VT68200060
ER

PT J
AU Morgon, NH
   Giroldo, T
   Linnert, HV
   Riveros, JM
TI Isomerization of the molecular ion of allyl bromide
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID DISTONIC RADICAL CATIONS; MASS-SPECTROMETRY NRMS; X = CL; GAS-PHASE;
   AB-INITIO; OPTIMIZATION TECHNIQUE; IONIZATION ENERGIES;
   ORGANIC-MOLECULES; SPECTRA; NEUTRALIZATION
AB The molecular ion of allyl bromide has been characterized by nb initio
   molecular orbital calculations at the MP4(SDTQ) level with optimized
   geometries at the MP2 level in order to account for experimental data
   suggesting the presence of two isomers. The calculations predict the
   existence of an allyl bromide molecular ion with structural parameters
   resembling the neutral species except for a lengthening of the double
   bond. This structure is calculated to be more stable than a cyclic
   bromonium radical cation structure, Rearrangement of the molecular ion
   of allyl bromide to that of 1-bromopropene is shown to be possible
   through a transition state represented by the distonic ion,
   (BrHCCH2CH2.)-Br-+, lying just below the dissociation limit of the
   allyl bromide molecular ion. Studies based on ion/molecule reactivity
   of C3H5Br.+ ions generated from allyl bromide and 1-bromopropene with
   ammonia, methanol, allyl bromide, and charge transfer reactions
   strongly suggest that a small fraction of the molecular ions of allyl
   bromide isomerize to the 1-bromopropene molecular ion as predicted by
   the calculation. These experiments cannot establish unequivocally
   whether the allyl bromide molecular ions retain the structure of the
   parent molecules as predicted by the calculations or undergo
   ion/molecule reactions mediated by a bromonium type complex. Charge
   transfer experiments also suggest the adiabatic ionization energy of
   allyl bromide to be 9.83 +/- 0.07 eV.
C1 UNIV SAO PAULO,INST QUIM,BR-05599970 SAO PAULO,BRAZIL.
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NR 67
TC 10
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD NOV 14
PY 1996
VL 100
IS 46
BP 18048
EP 18056
PG 9
SC Chemistry, Physical
GA VT708
UT ISI:A1996VT70800008
ER

PT J
AU Araujo, RCMU
   Ramos, MN
TI An ab initio study of the molecular properties of the acetylene-HX
   hydrogen complexes
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE ab initio calculation; acetylene; hydrogen bonding; infrared; molecular
   complex
ID VANDERWAALS MOLECULES; ROTATIONAL SPECTRUM; ATOMIC CHARGES; GAS-PHASE;
   ABINITIO; INTENSITIES; DIMER; HCL; HF
AB MP2/6-311++G** ab initio molecular orbital calculations indicate that
   larger Delta Q(corr) intermolecular charge transfer values are
   associated with stronger hydrogen bonds in the acetylene-HX complexes
   where X is F, Cl CN, NC or CCH. The MP2/6-311++G** H-bond lengths are
   in very good agreement with the corresponding experimental values.
   The H-X stretching frequency is shifted downward upon H-bond formation.
   Its displacement shows an excellent linear correlation with the
   intermolecular charge transfer, in agreement with the experimental
   behaviour previously observed in such complexes. As expected, the more
   pronounced effect on the IR intensities occurs with the H-X stretching
   intensity, and it is much enhanced after complexation owing to the
   charge-flux term.
   The new low-frequency vibrational modes arising from complexation show
   several interesting features and their normal modes are schematically
   described herein.
C1 UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50739901 RECIFE,PE,BRAZIL.
RP Araujo, RCMU, UNIV FED PARAIBA,DEPT QUIM,BR-58036300 JOAO
   PESSOA,PARAIBA,BRAZIL.
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NR 24
TC 14
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD AUG 26
PY 1996
VL 366
IS 3
BP 233
EP 240
PG 8
SC Chemistry, Physical
GA VP836
UT ISI:A1996VP83600009
ER

PT J
AU Sorrilha, AEPM
   Gozzo, FC
   Pimpim, RS
   Eberlin, MN
TI Multiple stage pentaquadrupole mass spectrometry for generation and
   characterization of gas-phase ionic species. The case of the
   PyC(2)H(5)(+center dot) isomers
SO JOURNAL OF THE AMERICAN SOCIETY FOR MASS SPECTROMETRY
LA English
DT Article
ID DISTONIC RADICAL CATIONS; MOLECULAR-ORBITAL METHODS; REACTIVE
   COLLISIONS; BASIS SETS; CHEMISTRY; IDENTIFICATION; AMMONIA; OXIDE;
   DERIVATIVES; INSTRUMENT
AB Eleven isomers with the PyC(2)H(5)(+.) composition, which include three
   conventional (1-3) and eight distonic radical cations (4-11), have been
   generated and in most cases successfully characterized in the gas phase
   via tandem-in-space multiple-stage pentaquadrupole MS(2) and MS(3)
   experiments, The three conventional radical cations,that is, the
   ionized ethylpyridines C2H5-C5H4N+.(1-3), were generated via direct
   70-eV electron ionization of the neutrals, whereas sequences of
   chemical ionization and collision-induced dissociation (CID) or
   mass-selected ion-molecule reactions were used to generate the distonic
   ions H2C.-C5H4N+-CH3 (4-6), CH3-C5H4N+-CH2. (7-9), C5H5N+-CH2CH2. (10),
   and C5H5N+-CH.-CH3 (11). Unique features of the low-energy (15-eV) CID
   an ion-molecule reaction chemistry with the diradical oxygen molecule
   of the isomers were used for their structural characterization. All the
   ion-molecule reaction products of a mass-selected ion, each associated
   with its corresponding CID fragments, were collected in a single
   three-dimensional mass spectrum. Ab initio calculations at the
   ROMP2/6-31G(d, p)//6-31G(d, p) + ZPE level of theory were performed to
   estimate the energetics involved in interconversions within the
   PyC(2)H(5)(+.) system, which provided theoretical support for facile 4
   reversible arrow 7 interconversion evidenced in both CID and
   ion-molecule reaction experiments. The ab initio spin densities for the
   alpha-distonic ions 4-9 and 11 were found to be largely on the
   methylene or methyne formal radical sites, which thus ruled out
   substantial odd-spin delocalization throughout the neighboring pyridine
   ring. However, only 8 and 9 (and 10) react extensively with oxygen by
   radical coupling, hence high spin densities on the radical site of the
   distonic ions do not necessarily lead to radical coupling reaction with
   oxygen. The very typical ''spatially separated'' ab initio charge and
   spin densities of 4-11 were used to classify them as distonic ions,
   whereas 1-3 show, as expected, ''localized'' electronic structures
   characteristic of conventional radical ions. (C) 1996 American Society
   for Mass Spectrometry
C1 STATE UNIV CAMPINAS,INST CHEM,BR-13083970 CAMPINAS,SP,BRAZIL.
CR *MINN SUP CTR INC, 1993, XMOL VERS 1 3 1
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NR 71
TC 15
PU ELSEVIER SCIENCE INC
PI NEW YORK
PA 655 AVENUE OF THE AMERICAS, NEW YORK, NY 10010
SN 1044-0305
J9 J AMER SOC MASS SPECTROM
JI J. Am. Soc. Mass Spectrom.
PD NOV
PY 1996
VL 7
IS 11
BP 1126
EP 1137
PG 12
SC Chemistry, Analytical; Chemistry, Physical; Spectroscopy
GA VP553
UT ISI:A1996VP55300006
ER

PT J
AU Silva, CR
   Reilly, JP
TI Theoretical calculations on excited electronic states of benzaldehyde
   and observation of the S-2<-S-0 jet-cooled spectrum
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID PLANE VIBRATIONAL MODES; BAND SYSTEM; ABSORPTION-SPECTRA;
   CARBONYL-COMPOUNDS; MASS-SPECTROMETRY; SUPERSONIC JETS; TRIPLET-STATES;
   GAS-PHASE; IONIZATION; PHOSPHORESCENCE
AB The S-2(pi pi*)<--S-0 spectrum of jet-cooled benzaldehyde has been
   recorded by laser ionization. The O-0(0) band has been located at 35
   191 cm(-1). Ten fundamental vibrations have been assigned following a
   vibrational analysis assisted by theoretical calculations. Ab initio
   molecular orbital methods have been used to examine the electronically
   excited states of benzaldehyde. On pi*<--pi excitation the primary
   geometric distortions are in the formyl group, while on pi*<--pi
   excitation these are mainly in the aromatic ring. Vibrational
   frequencies were found to be in reasonable agreement with the
   experimental data for the states studied (S-0, S-1(n pi*), S-2(pi pi*),
   and T(n pi*)), and the calculations provided a useful guide in
   assigning the observed excited state fundamentals.
C1 INDIANA UNIV,DEPT CHEM,BLOOMINGTON,IN 47405.
   UNIV FED RIO DE JANEIRO,DEPT FISICOQUIM,INST QUIM,BR-21949900 RIO JANEIRO,BRAZIL.
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NR 94
TC 17
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD OCT 24
PY 1996
VL 100
IS 43
BP 17111
EP 17123
PG 13
SC Chemistry, Physical
GA VP261
UT ISI:A1996VP26100006
ER

PT J
AU deMelo, CP
   Fonseca, TL
TI Ab initio polarizabilities of polyenic chains with conformational
   defects
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID VARIATIONAL PERTURBATIONAL TREATMENT; NONLINEAR-OPTICAL PROPERTIES;
   CONJUGATED CHAINS; LINEAR-POLARIZABILITIES; POLYACETYLENE; ABINITIO;
   POLYMERS; HYPERPOLARIZABILITY; SOLITONS; POLYPYRROLE
AB We present an ab initio Hartree-Fock study of the electronic
   polarizabilities of the C2n+1H2n+3+ (2 < n < 11) and C2nH2n+2++ (2 < n
   < 15) oligomers of polyacetylene. After a complete geometry
   optimization implemented through the GAUSSIAN 92 program, the
   longitudinal components of the linear polarizabilities were
   analytically determined and the second hyperpolarizabilities calculated
   through a finite field procedure. While the first hyperpolarizabilities
   of the bipolaron-like structures vanish (since inversion symmetry is
   preserved), the dominant component beta(xxy) of the soliton chains was
   obtained analytically. We confirm that the polarizabilities of these
   polyenic oligomers are quite sensitive to the nature of the
   conformational defect present.
RP deMelo, CP, UNIV FED PERNAMBUCO,DEPT FIS,BR-50670901 RECIFE,PE,BRAZIL.
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NR 29
TC 14
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD OCT 11
PY 1996
VL 261
IS 1-2
BP 28
EP 34
PG 7
SC Physics, Atomic, Molecular & Chemical
GA VL879
UT ISI:A1996VL87900006
ER

PT J
AU Ornellas, FR
   Iwata, S
TI Structures and energetics of new nitrogen and silicon molecules: An ab
   initio study of Si2N2
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID DENSITY-FUNCTIONAL METHODS; SPECTROSCOPIC PROPERTIES; VIBRATIONAL
   FREQUENCIES; INTERSTELLAR CLOUDS; DIAZASILENE SINN; HARTREE-FOCK; BOND;
   CHEMISTRY; SI2H2; ENERGIES
AB New species with molecular formula Si2N2, not yet observed
   experimentally, are described theoretically for the first time. Nine
   different stationary points have been examined and the effects of
   electronic correlation on the structural parameters, harmonic
   frequencies, and relative energies are described at increasingly higher
   levels of correlation treatment (MP2, MP4, CCSD(T)). The global minimum
   corresponds to a linear singlet state ((1) Sigma(g)(+)) SiNNSi. At the
   CCSD(T) level, the next most stable species (at 15.08 kcal/mol) has a
   nonclassical tetrahedral-like structure similar to the global minimum
   of Si2H2. This is followed by another local minimum with a linear
   structure SiNSiN (at 20.25 kcal/mol) and by a rhomboidal-type structure
   (at 21.33 kcal/mol), which is in fact a transition state connecting two
   equivalent tetrahedral-like structures. Another nonclassical structure
   similar to the monobridged one in the case of Si2H2 was also found to
   be a local minimum (at 28.18 kcal/mol). An interconversion path from
   this latter structure to the linear SiNNSi one is likely to occur via
   another transition state located at about 38 kcal/mol. With the
   exception of the linear isomer SiNNSi, the triplet states were found to
   lie very high energetically and to correspond to unstable structures.
   None of these species exhibits any appreciable amount of
   silicon-silicon bonding, and the analogue of cyanogen (NCCN) NSiSiN is
   unstable. The nature of the bonding in the most relevant species is
   also discussed, as well the energetics of dissociation. An analysis of
   the energetics and structural similarities and differences between
   Si2N2, C2N2, Si2H2, and Si2C2 is also carried out. Caution must be
   exercized in generalizing results at a low level of theory since they
   have not been confirmed by the CCSD(T) calculations.
C1 INST MOL SCI,OKAZAKI,AICHI 444,JAPAN.
RP Ornellas, FR, UNIV SAO PAULO,DEPT QUIM FUNDAMENTAL,INST QUIM,CP
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NR 66
TC 12
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD OCT 3
PY 1996
VL 100
IS 40
BP 16155
EP 16161
PG 7
SC Chemistry, Physical
GA VK731
UT ISI:A1996VK73100019
ER

PT J
AU Distefano, G
   DalColle, M
   dePalo, M
   Jones, D
   Bombieri, G
   DelPra, A
   Olivato, PR
   Mondino, MG
TI Experimental and theoretical study of the intramolecular interactions
   determining the conformation of beta-carbonyl sulfoxides
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID ULTRAVIOLET PHOTOELECTRON-SPECTROSCOPY; ELECTRON TRANSMISSION
   SPECTROSCOPY; MOLECULAR-PROPERTIES; IR SPECTROSCOPY; SPECTRA;
   ACETOPHENONES; DERIVATIVES; ACETONES
AB Information on the geometrical and electronic structures of
   alpha-methylsulfinylacetophenone, C6H5C(O)CH2S(O)CH3 2, have been
   obtained from X-ray diffraction analysis, UV photoelectron spectroscopy
   and ab initio 6-31G**calculations. A comparison of the results with
   those obtained from the spectra and the computations on
   alpha-methylthioacetophenone, C6H5C(O)CH2SCH3 1 and
   alpha-methylsulfonylacetophenone, C6H5C(O)CH2SO2CH3 3, together with
   previous results on; beta-keto sulfides and beta-keto sulfones
   indicates that the CH2-S(O) bond in is quasi-cis to the carbonyl group
   in the gas and solid phase, at variance with the other beta-carbonyl
   thioderivatives which adopt a gauche conformation. Eigenvector
   analysis, electron charge distribution at various atoms and/or groups
   and geometric parameters indicate that the cis conformation of 2 is
   stabilized by a strong non-bonded interaction between the negatively
   charged carbonyl oxygen and the positively charged sulfur atom from
   which it is separated by a distance (2.8-2.9 Angstrom much shorter than
   the sum of the the van der Waals radii. The predominant charge transfer
   interaction in 3 and related sulfones occurs in the opposite direction
   (O-SO2-->C-CO). The inversion of We direction of the charge transfer
   (and the change of the cis/gauche orientation of the thio group) from
   sulfone to sulfoxide is associated with an increase of electron
   affinity of the thio group in the latter, and could explain its smaller
   thermal stability.
   Ab initio 3-21G* calculations on several conformations of the
   bis-thioderivatives C6H5C(O)CH(SCH3)S(O)CH3 4, C6H5C(O)CH(SR)SO(2)R (R
   = Me 5 and Ph 6) and C6H5C(O)CH(SOCH3)SO2CH3 7, together with X-ray
   diffraction (4, 6 and 7) and photoelectron spectroscopy (4) analyses
   confirmed the cis (SOR) and gauche (SR and SO(2)R) preferred
   orientation of the thio groups with respect to the carbonyl group as
   observed in the monosubstituted derivatives. In 4 and 7 the S-SO atom
   is about 30 degrees out of the cis plane [O(1)-C(2)C(3)].
C1 CNR,AREA RIC,ICOCEA,I-40129 BOLOGNA,ITALY.
   UNIV MILAN,IST CHIM FARMACEUT,I-2013 MILAN,ITALY.
   UNIV SAO PAULO,INST QUIM,BR-05508 SAO PAULO,BRAZIL.
RP Distefano, G, UNIV FERRARA,DIPARTMENTO CHIM,VIA BORSARI 46,I-44100
   FERRARA,ITALY.
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NR 38
TC 21
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD AUG
PY 1996
IS 8
BP 1661
EP 1669
PG 9
SC Chemistry, Organic; Chemistry, Physical
GA VC214
UT ISI:A1996VC21400019
ER

PT J
AU Alejandre, J
   LozadaCassou, M
   Degreve, L
TI Effect of pore geometry on a confined hard sphere fluid
SO MOLECULAR PHYSICS
LA English
DT Article
ID ELECTRICAL DOUBLE-LAYER; EXTENSION HYPERNETTED-CHAIN; INTEGRAL-EQUATION
   APPROACH; ORNSTEIN-ZERNIKE EQUATION; DENSITY FUNCTIONAL THEORY; 3 POINT
   EXTENSION; MONTE-CARLO; PAIR CORRELATION; CHARGED WALL;
   STATISTICAL-MECHANICS
AB The structure of a hard sphere fluid confined by model slit and
   cylindrical pores is investigated. Results from grand canonical Monte
   Carlo (GCMC) simulations and from the hypernetted chain/mean spherical
   approximation (HNC/MSA) equation are reported. GCMC results are
   compared with those from the HNC/MSA equation, and agreement is good.
   The effect of confinement on liquids at the same chemical potentials is
   that the absorption of the hard sphere fluid into the pores decreases
   with increasing confinement, i.e., when going from planar to
   cylindrical geometry or by narrowing the pores. The adsorption on the
   pore walls has, in general, the opposite behaviour. For high bulk
   concentrations and certain values of cylindrical pore diameter the
   concentration profile is higher at the centre of the pore than next to
   the pore wall. A very strong, but continuous, transition occurs in the
   concentration profile, as a function of the cylinder's diameter. These
   results could be of some interest in catalysis studies.
C1 UNIV AUTONOMA METROPOLITANA IZTAPALAPA,DEPT FIS,MEXICO CITY 09340,DF,MEXICO.
   UNIV SAO PAULO,DEPT QUIM,FAC FILOSOFIA CIENCIAS & LETRAS,BR-14040 SAO PAULO,BRAZIL.
RP Alejandre, J, UNIV AUTONOMA METROPOLITANA IZTAPALAPA,DEPT QUIM,APARTADO
   POSTAL 55-534,MEXICO CITY 09340,DF,MEXICO.
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NR 60
TC 5
PU TAYLOR & FRANCIS LTD
PI LONDON
PA ONE GUNDPOWDER SQUARE, LONDON, ENGLAND EC4A 3DE
SN 0026-8976
J9 MOL PHYS
JI Mol. Phys.
PD AUG 10
PY 1996
VL 88
IS 5
BP 1317
EP 1336
PG 20
SC Physics, Atomic, Molecular & Chemical
GA VB761
UT ISI:A1996VB76100013
ER

PT J
AU Pliego, JR
   DeAlmeida, WB
TI Reaction paths for aqueous decomposition of CCl2
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
AB The potential energy surface (PES) for the H2O + CCl2 reaction was
   investigated at the ab initio SCF and MP2 levels of theory, employing
   the DZP basis set, in order to determine the mechanism of basic aqueous
   decomposition of CCl2. Several possible pathways were considered,
   including reactions with other H2O molecules and OH-. We have found
   that the first step corresponds to insertion of CCl2 into the O-H bond
   of water, resulting in the CHCl2OH species. This molecule loses HCl in
   one elimination reaction catalyzed by OH-, forming ClCHO. Again, OH-
   catalyzes the elimination of other HCl, resulting in CO, the
   decomposition product. The first step is the slow one, and we have used
   transition-state theory to estimate the rate constant for the aqueous
   decomposition of CCl2, The obtained rate constant was used for building
   a general picture of CHCl3, decomposition in basic aqueous solution.
   The results of the present study are in agreement with experimental
   observations.
C1 UNIV FED MINAS GERAIS,ICEX,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR BETHELL D, 1973, ORGANIC REACTIVE INT
   DUNNING TH, 1977, METHODS ELECTRONIC S
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NR 10
TC 34
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD JUL 25
PY 1996
VL 100
IS 30
BP 12410
EP 12413
PG 4
SC Chemistry, Physical
GA UY938
UT ISI:A1996UY93800041
ER

PT J
AU Mota, CJA
   Esteves, PM
   deAmorim, MB
TI Theoretical studies of carbocations adsorbed over a large zeolite
   cluster. Implications on hydride transfer reactions
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID SHAPE-SELECTIVE CATALYSIS; HIGH-SILICA ZEOLITES; HYDROGEN-TRANSFER;
   HYDROXYL-GROUPS; CARBENIUM IONS; DEUTERIUM EXCHANGE; SN2-SN1 SPECTRUM;
   MOLECULAR-MODELS; CARBONIUM-IONS; HY ZEOLITES
AB A semiempirical MNDO study of simple alkylcarbenium ions (Me, Et, i-Pr,
   t-Bu) on a large and more realistic cluster, comprising a hexagonal
   prism and a sodalite unit (3) and simulating different adsorption sites
   on zeolite Y, was carried out. On going from H to bulky alkyl groups,
   there is an increasing tendency to stretch the Al-O bond length and to
   decrease the Si-O-Al bond angle. Nevertheless, the proton and the alkyl
   groups are covalently bonded to the framework, as expressed by the high
   bond orders, near unity. Adsorption on site O-4, located in the
   sodalite, is energetically disfavored by 2-4 kcal/mol relative to
   adsorption on site O-1, in the hexagonal prism. The MNDO calculations
   on cluster 3 showed a reasonable agreement with ab initio calculations
   of carbenium ions adsorbed on smaller clusters 1 and 2, except when
   adsorption on O-4 is considered, indicating that steric strain, due to
   the crystalline structure, plays an important role. Adsorption on
   Si-O-Si sites is about 45 kcal/mol higher in energy than the
   correspondent adsorption on Si-O-Al sites. This result may explain the
   observed experimental dependence of hydride transfer reactions with the
   structural Si/Al ratio, also suggesting the participation of the
   zeolite structure in the transition state.
C1 UNIV FED RIO DE JANEIRO,INST QUIM,BR-21949900 RIO JANEIRO,BRAZIL.
   UNIV FED RIO DE JANEIRO,NPPN,BR-21941540 RIO JANEIRO,BRAZIL.
RP Mota, CJA, PETROBRAS CENPES,ILHA FUNDAO Q 7,BR-21949900 RIO
   JANEIRO,BRAZIL.
CR ABBOT J, 1988, J CATAL, V113, P353
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   BITTENCOURT R, IN PRESS
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   CATLOW CRA, 1992, MODELLING STRUCTURE
   CHANG CD, 1983, HYDROCARBONS METHANO
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   ZHAO YX, 1993, J CATAL, V140, P243
NR 90
TC 23
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD JUL 25
PY 1996
VL 100
IS 30
BP 12418
EP 12423
PG 6
SC Chemistry, Physical
GA UY938
UT ISI:A1996UY93800043
ER

PT J
AU Venezuela, PPM
   Fazzio, A
TI Ab initio study of N impurity in amorphous germanium
SO PHYSICAL REVIEW LETTERS
LA English
DT Article
ID ELECTRONIC-STRUCTURE; MOLECULAR-DYNAMICS; SILICON; NITROGEN; SYSTEMS;
   PSEUDOPOTENTIALS; SEMICONDUCTORS; CARBON; STATE; MODEL
AB The electronic and structural properties of N-atom-doped amorphous
   germanium are obtained by ab initio, total energy calculations. We find
   that the 3-fold coordinated N impurity (N-3) and the 4-fold coordinated
   N impurity (N-4) present negative effective Coulombic interactions.
   Analysis of these results shows that the electrical effect of n-type
   doping due to N atoms is not related only to chemical equilibrium
   between N-3 and N-4.
RP Venezuela, PPM, UNIV SAO PAULO,INST FIS,CP 66318,BR-05389970 SAO
   PAULO,SP,BRAZIL.
CR ANDERSON PW, 1975, PHYS REV LETT, V34, P953
   BACHELET GB, 1982, PHYS REV B, V26, P4199
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   BROWER KL, 1982, PHYS REV B, V26, P6040
   BYER W, 1984, SEMICONDUCTORS SEM C, V21, CH8
   CAR R, 1985, PHYS REV LETT, V55, P2471
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   SPEAR WE, 1975, SOLID STATE COMMUN, V17, P1193
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   ZHOU JH, 1993, J APPL PHYS, V74, P5086
NR 27
TC 7
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0031-9007
J9 PHYS REV LETT
JI Phys. Rev. Lett.
PD JUL 15
PY 1996
VL 77
IS 3
BP 546
EP 549
PG 4
SC Physics, Multidisciplinary
GA UW791
UT ISI:A1996UW79100034
ER

PT J
AU Ferraz, AC
   daSilva, RC
TI Atomic and electronic structures of Te adsorbed on GaAs(100) and
   InAs(100)
SO SURFACE SCIENCE
LA English
DT Article
DE density functional calculations; gallium arsenide; indium arsenide;
   tellurium
ID SURFACES; GAAS; GROWTH
AB We report results of density functional theory total energy and force
   calculations of Te covered GaAs- and InAs(100)-(2 X 1). The adsorption
   is studied for the coverages of 1/2 and 1 monolayer of Te. The atomic
   positions of the adsorbate and the three outermost substrate layers are
   fully relaxed and the equilibrium surface geometries are given. We
   discuss how the adsorption modifies the dean surface geometry and the
   electronic structures.
RP Ferraz, AC, UNIV SAO PAULO,INST FIS,CAIXA POSTAL 66318,BR-05389970 SAO
   PAULO,BRAZIL.
CR CAR R, 1985, PHYS REV LETT, V55, P2471
   CEPERLEY DM, 1980, PHYS REV LETT, V45, P566
   CIBERT J, 1989, PHYS REV B, V39, P12047
   COHENSOLAL G, 1989, APPL PHYS LETT, V49, P1519
   COPEL M, 1989, PHYS REV LETT, V63, P632
   ETGENS VH, 1993, PHYS REV B, V47, P10607
   FELDMAN RD, 1986, APPL PHYS LETT, V48, P248
   GOBIL Y, 1989, SURF SCI, V211, P969
   GONZE X, 1991, PHYS REV B, V44, P8503
   GRANDJEAN N, 1992, PHYS REV LETT, V69, P799
   KIM TW, 1994, APPL PHYS LETT, V64, P2526
   MIWA RH, IN PRESS
   MONCKHORST HJ, 1976, PHYS REV B, V13, P5188
   NEUGEBAUER J, 1992, PHYS REV B, V46, P16067
   OHNO T, 1991, SURF SCI, V255, P229
   PERDEW JP, 1981, PHYS REV B, V23, P5048
   QIAN GX, 1988, PHYS REV B, V38, P7649
   RODRIGUES WN, 1995, IN PRESS SOLID STATE
   SPINDT CJ, 1989, APPL PHYS LETT, V55, P861
NR 19
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0039-6028
J9 SURFACE SCI
JI Surf. Sci.
PD MAY 15
PY 1996
VL 352
BP 379
EP 382
PG 4
SC Chemistry, Physical
GA UV254
UT ISI:A1996UV25400072
ER

PT J
AU Ornellas, FR
   Iwata, S
TI Ab initio studies of silicon and nitrogen clusters: Cyclic or linear
   Si2N?
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID CORRELATED MOLECULAR CALCULATIONS; GAUSSIAN-BASIS SETS;
   PERTURBATION-THEORY; DERIVATIVES; ABINITIO; SPECTRUM; STATES; BOND;
   SICO; SINN
AB Theoretical studies are carried out on the doublet and quartet states
   of three isomeric forms of the species Si2N. Correlation effects on the
   structural parameters, harmonic frequencies, and relative energies are
   investigated at increasingly higher levels of theory (MP2, MP4, and
   CCSD(T)) and basis sets (DZP, cc-pVTZ-f, and cc-pVTZ). At the highest
   level of theory (CCSD(T)/cc-pVTZ) all three isomers are found to be
   thermodynamically stable species with the symmetric linear structure
   (SiNSi) as the global minimum; a symmetric cyclic structure (93.1
   degrees) lies only 4.90 kcal/mol higher in energy, while the asymmetric
   linear isomer (SiSiN) is much higher located (85.23 kcal/mol).
   Dissociation of the most stable isomer into the channels SiN + Si and
   Si-2 + N would require 123 and 148 kcal/mol, respectively, including
   the zero-point energies. Chemical bonding as reflected in bond
   distances indicates a SiN bond character intermediate between that of a
   single and a double bonds in the linear SiNSi isomer (1.644 Angstrom),
   changing then to a single bond in the cyclic structure (1.695 Angstrom)
   and a double bond in SiSiN (1.608 Angstrom). The energetics involved in
   various dissociation channels is also analyzed, as well as the strength
   of the vibronic interaction in the linear isomer estimated by the
   computation of the Renner parameter. A comparison with the molecules
   C2N, Si2C, Si2C-, and Si2O clearly shows structural and stability
   trends among these triatomics.
C1 INST MOLEC SCI,OKAZAKI,AICHI 444,JAPAN.
RP Ornellas, FR, UNIV SAO PAULO,INST QUIM,DEPT QUIM FUNDAMENTAL,CP
   26077,BR-05599970 SAO PAULO,BRAZIL.
CR ANDERSSON K, 1992, J CHEM PHYS, V96, P1218
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   BOLTON EE, 1992, J CHEM PHYS, V97, P5586
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   KAFAFI ZH, 1983, J PHYS CHEM-US, V87, P797
   KISHI R, IN PRESS
   KOLZLOWSKI PM, 1994, CHEM PHYS LETT, V222, P615
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   LEE TJ, 1984, J CHEM PHYS, V81, P356
   LEMBKE RR, 1977, J AM CHEM SOC, V99, P416
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   PRESILLAMARQUEZ JD, 1991, J CHEM PHYS, V95, P5612
   RAGHAVACHARI K, 1989, CHEM PHYS LETT, V157, P479
   RANKIN DW, 1990, J CHEM SOC, A1224
   RENNER R, 1934, Z PHYS, V92, P172
   RITTBY CML, 1991, J CHEM PHYS, V95, P5609
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   SCUSERIA GE, 1991, CHEM PHYS LETT, V176, P27
   TRUONG TN, 1986, J AM CHEM SOC, V108, P1775
   WALTENBURG HN, 1995, CHEM REV, V95, P1589
   WOON DE, 1993, J CHEM PHYS, V98, P1358
NR 47
TC 17
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD JUN 27
PY 1996
VL 100
IS 26
BP 10919
EP 10927
PG 9
SC Chemistry, Physical
GA UU477
UT ISI:A1996UU47700013
ER

PT J
AU Pliego, JR
   Resende, SM
   DeAlmeida, WB
TI Ab initio MP2 study of the HF center dot center dot center dot ClF
   complex using various extended basis sets and bond functions
SO THEORETICA CHIMICA ACTA
LA English
DT Article
DE van der Waals complex; transition states; extended basis sets; bond
   functions; electronic correlation
ID ABINITIO CALCULATIONS; SYSTEMS
AB The stationary points on the intermolecular potential energy surface
   (PES) for the HF ... CIF complex have been investigated at the
   second-order Moller-Plesset perturbation theory (MP2) level using
   various extended bais sets, including diffuse functions, and also bond
   functions. The last ones were placed at different intermolecular
   positions, for distinct stationary points. The basis set superposition
   errors (BSSE) were accounted for using the counterpoise method. Besides
   the anti-H-bonded and H-bonded minimum energy structures, four
   transition state structures were also located on the PES. It was shown
   that higher polarization functions are required for the description of
   the anti H-bonded isomer and diffuse functions had to be included for
   the H-bonded isomer. The bond functions are able to replace the f(Cl,
   F) and d(H) polarization functions at a lower computational cost.
   However, for the H-bonded isomer intramolecuIar electron correlation
   also plays an important role. So we have to use diffuse nucleus
   centered polarization functions for an adequate description of
   intermolecular and intramolecular correlation.
RP Pliego, JR, UFMG,LAB QUIM COMPUTAC & MODELAGEM MOL,DEPT
   QUIM,ICEX,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR BONE RGA, 1990, THEOR CHIM ACTA, V78, P133
   BOYS SF, 1970, MOL PHYS, V19, P533
   CHALASINSKI G, 1988, CHEM REV, V88, P943
   CHALASINSKI G, 1994, CHEM REV, V94, P1723
   DEALMEIDA WB, 1991, THEOCHEM, V228, P191
   DEALMEIDA WB, 1993, J CHEM PHYS, V99, P5917
   DEALMEIDA WB, 1993, THEOCHEM, V285, P277
   DEALMEIDA WB, 1995, SPECTROCHIM ACTA A, V51, P653
   DUNNING TH, 1977, METHODS ELECT STRUCT, P1
   HOBZA P, 1981, CHEM PHYS LETT, V82, P469
   HOBZA P, 1988, CHEM REV, V88, P871
   HOBZA P, 1994, CHEM REV, V94, P1767
   HOBZA P, 1994, THEOR CHIM ACTA, V88, P233
   LEGON AC, 1994, FARADAY DISCUSS, V97, P19
   LEOPOLD KR, 1994, CHEM REV, V94, P1807
   NESBITT DJ, 1988, CHEM REV, V88, P843
   NEUSSER HJ, 1994, CHEM REV, V94, P1829
   NOVICK SE, 1976, J CHEM PHYS, V65, P5115
   RENDELL APL, 1987, J CHEM PHYS, V87, P535
   RESENDE SM, UNPUB
   RESENDE SM, 1995, J CHEM PHYS, V102, P4184
   SCHM, 1993, UJ, V14, P1347
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
   SLANINA Z, 1991, THEOCHEM, V235, P51
   SLANINA Z, 1994, THERMOCHIM ACTA, V231, P55
   TAO FM, 1992, CHEM PHYS LETT, V194, P162
   TAO FM, 1992, J CHEM PHYS, V97, P4989
   TAO FM, 1993, J CHEM PHYS, V98, P3049
   VANDERAVOIRD A, 1994, CHEM REV, V94, P1931
   VANLENTHE JH, 1987, ADV CHEM PHYS, V69, P522
   YAN YB, 1994, CHEM PHYS LETT, V230, P480
   ZHANG DH, 1995, J CHEM PHYS, V102, P2315
NR 32
TC 4
PU SPRINGER VERLAG
PI NEW YORK
PA 175 FIFTH AVE, NEW YORK, NY 10010
SN 0040-5744
J9 THEOR CHIM ACTA
JI Theor. Chim. Acta
PD JUN
PY 1996
VL 93
IS 6
BP 333
EP 342
PG 10
SC Chemistry, Physical
GA UT564
UT ISI:A1996UT56400002
ER

PT J
AU Resende, SM
   DeAlmeida, WB
TI A theoretical study of tunneling in the (HCCH)(2) complex
SO CHEMICAL PHYSICS
LA English
DT Article
ID RESOLUTION INFRARED-SPECTROSCOPY; POTENTIAL-ENERGY SURFACE; ACETYLENE
   DIMER; MICROWAVE; ABINITIO; (HF)2; SPECTRUM; MOTION
AB The internal motion in the acetylene dimer has been investigated at the
   ab initio Moller-Plesset second-order perturbation theory (MP2) level,
   employing the double-zeta plus polarization function (DZP) basis set.
   Basis set superposition errors (BSSE) corrections were included using
   the counterpoise method. A two-dimensional (2D) Hamiltonian for the
   tunneling motion, considering the two bending modes in the dimer plane
   was solved variationally, using as the potential energy function a
   two-dimensional ab initio intermolecular potential energy surface
   (PES), Coupling of the intramolecular vibration and dimer internal
   rotation has been neglected. Also, the synchronized one-dimensional
   (1D) tunneling motion was obtained through a change of variables which
   allowed the separation of the motion along the minimum energy path and
   the one perpendicular to it. Anharmonicity corrections were also added
   to the 1D procedure to reach the 2D results. The calculated splitting
   of transition frequencies are compared with the experimental data. The
   1D Hamiltonian including anharmonicity corrections is shown to be a
   very efficient and computational inexpensive procedure for treating the
   tunneling motion.
C1 UNIV FED MINAS GERAIS,ICEX,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM MOL,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR ALTHORPE SC, 1991, CHEM PHYS LETT, V187, P345
   BERNSTEIN E, 1990, ATOMIC MOL CLUSTERS
   BONE RGA, 1990, THEOR CHIM ACTA, V78, P133
   BOYS SF, 1970, MOL PHYS, V19, P533
   BRYANT GW, 1988, J CHEM SOC F2, V84, P1443
   BUMGARNER RE, 1991, CHEM PHYS LETT, V176, P123
   DEALMEIDA WB, 1993, CHEM PHYS, V169, P185
   DEALMEIDA WB, 1993, J CHEM PHYS, V99, P5617
   DEALMEIDA WB, 1993, J PHYS CHEM-US, V97, P2560
   DEALMEIDA WB, 1993, MOL PHYS, V78, P1351
   DEALMEIDA WB, 1993, MOL STRUCT THEOCHEM, V285, P77
   DEALMEIDA WB, 1994, MOL PHYS, V81, P1397
   DEALMEIDA WB, 1995, SPECTROCHIM ACTA A, V51, P653
   DUNNING TH, 1970, J CHEM PHYS, V53, P2823
   FRASER GT, 1988, J CHEM PHYS, V89, P6028
   FRASER GT, 1989, J CHEM PHYS, V90, P2097
   FRASER GT, 1989, J CHEM PHYS, V90, P6077
   HA TK, 1993, J PHYS CHEM-US, V97, P11415
   HOBZA P, 1988, CHEM REV, V88, P871
   MAKAREWICZ J, 1993, J CHEM PHYS, V99, P3694
   MILLER RE, 1984, J CHEM PHYS, V80, P5453
   MOLLER C, 1934, PHYS REV, V46, P618
   OHSHIMA Y, 1988, CHEM PHYS LETT, V147, P1
   PLIEGO JR, 1996, IN PRESS THEORET CHI
   PRICHARD D, 1987, CHEM PHYS LETT, V135, P9
   PRICHARD DG, 1988, J CHEM PHYS, V89, P115
   RESENDE SM, 1995, J CHEM PHYS, V102, P4184
   RICE JK, 1990, J CHEM PHYS, V92, P6408
   SADLEJ J, 1994, J CHEM PHYS, V100, P4272
   SCHMIDT MW, 1990, QCPE B, V10, P52
   SUNI II, 1993, J CHEM PHYS, V98, P988
   TENNYSON J, 1982, J CHEM PHYS, V77, P5664
   VONPUTTKAMER K, 1987, MOL PHYS, V62, P1047
   ZHANG DH, 1995, J CHEM PHYS, V102, P2315
NR 34
TC 14
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0301-0104
J9 CHEM PHYS
JI Chem. Phys.
PD MAY 15
PY 1996
VL 206
IS 1-2
BP 1
EP 8
PG 8
SC Physics, Atomic, Molecular & Chemical
GA UP170
UT ISI:A1996UP17000001
ER

PT J
AU Alves, JLA
   Alves, HWL
   deCastilho, CMC
TI Hydrogen, oxygen and chlorine adsorption on Ag(110) surface: A cluster
   calculation
SO MATERIALS SCIENCE AND ENGINEERING B-SOLID STATE MATERIALS FOR ADVANCED
   TECHNOLOGY
LA English
DT Article
DE hydrogen; oxygen; chlorine; adsorption; silver
ID EFFECTIVE CORE POTENTIALS; MOLECULAR CALCULATIONS
AB The adsorption of atoms on Ag(110) surfaces has been widely
   investigated both theoretically and experimentally. The importance of
   the (110) face results from the much better catalytic properties of the
   single crystal Ag(110) compared with polycrystalline samples. The aim
   of this work is to study the systems Ag(110): H, O, Cl by means of
   rigorous ab initio quantum-chemical calculations. We have investigated
   several possible binding sites, geometries, elastic constants, binding
   energies and charge distributions for H, O and Cl on Ag(110) surfaces
   simulated by clusters Ag, (n = 3,10).
C1 UNIV FED BAHIA,INST FIS,BR-40210340 SALVADOR,BA,BRAZIL.
RP Alves, JLA, FDN ENSINO SUPER SAO DEL REI,FUNREI,DEPT CIENCIAS NAT,PRACA
   D HELVECIO,74,BR-36300000 SAO JOAO REI,MG,BRAZIL.
CR FRISCH MJ, 1992, GAUSSIAN 92
   HAY PJ, 1985, J CHEM PHYS, V82, P270
   HAY PJ, 1985, J CHEM PHYS, V82, P299
   MARTIN RL, 1983, SURF SCI, V130, P283
   SELMANI A, 1986, INT J QUANTUM CHEM, V29, P829
   SELMANI A, 1988, SURF SCI, V206, P279
   WADT WR, 1985, J CHEM PHYS, V82, P284
NR 7
TC 6
PU ELSEVIER SCIENCE SA LAUSANNE
PI LAUSANNE 1
PA PO BOX 564, 1001 LAUSANNE 1, SWITZERLAND
SN 0921-5107
J9 MATER SCI ENG B-SOLID STATE M
JI Mater. Sci. Eng. B-Solid State Mater. Adv. Technol.
PD FEB
PY 1996
VL 37
IS 1-3
BP 139
EP 141
PG 3
SC Materials Science, Multidisciplinary; Physics, Condensed Matter
GA UM735
UT ISI:A1996UM73500025
ER

PT J
AU Pereira, GK
   Donate, PM
   Galembeck, SE
TI Electronic structure of hydroxylated derivatives of the flavylium cation
SO THEOCHEM-JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
DE anthocyanins; computational study; electronic structure; flavonoids;
   flavylium cation
ID MOLECULAR-ORBITAL METHODS; GAUSSIAN-TYPE BASIS; ORGANIC-MOLECULES;
   BASIS-SETS; ANTHOCYANINS
AB The electronic structure of the flavylium cation (1) and those of some
   of its hydroxylated derivatives were studied by semiempirical and ab
   initio molecular orbital methods. This ion presents a small resonance
   in the pyrylium group (C-ring), which is not conjugated to the phenyl
   group (B-ring). The planarity of the molecule is due to a hydrogen bond
   between the oxygen atom in C-ring and some hydrogen atoms in B-ring.
   There is also a repulsive interaction between hydrogen atoms of these
   rings. The theoretical locations of the sites of nucleophilic and
   electrophilic attack corresponds to those experimentally observed.
   Monohydroxylation does not cause important alterations in the
   electronic structure of the cation (1) except for the substitution on
   C(4'), which causes the appearance of resonance between B- and C-rings.
C1 UNIV SAO PAULO,FAC FILOSOFIA CIENCIAS & LETRAS RIBEIRAO PRET,DEPT QUIM,BR-14049901 RIBEIRAO PRET,SP,BRAZIL.
CR BAKER J, 1986, J COMPUT CHEM, V7, P385
   BENT HA, 1961, CHEM REV, V61, P275
   BESLER BH, 1990, J COMPUT CHEM, V11, P431
   BINKLEY JS, 1980, J AM CHEM SOC, V102, P939
   BROUILLARD R, 1988, FLAVONOIDS ADV RES 1, P525
   BUSETTA PB, 1974, ACTA CRYSTALLOGR B, V30, P1448
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   DITCHFIELD R, 1971, J CHEM PHYS, V54, P724
   FLEMING I, 1976, FRONTIER ORBITALS OR
   GOTO T, 1991, ANGEW CHEM INT EDIT, V30, P17
   GUEDES MC, 1993, THESIS U CAMPINAS CA
   HARBORNE JB, 1988, FLAVONOIDS ADV RES 1, P1
   HEHRE WJ, 1972, J CHEM PHYS, V56, P2257
   HOLTON TA, 1994, TRENDS BIOTECHNOL, V12, P40
   HUHEEY JE, 1972, INORGANIC CHEM PRINC
   IACOBUCCI GA, 1983, TETRAHEDRON, V39, P3005
   KOES RE, 1994, BIOESSAYS, V16, P123
   LISTER CE, 1994, J SCI FOOD AGR, V64, P155
   MERLIN JC, 1994, PHYTOCHEMISTRY, V35, P227
   MERLIN JC, 1994, SPECTROCHIM ACTA A, V50, P703
   NESSLER CL, 1994, TRANSGENIC RES, V3, P109
   RASTELLI G, 1993, J MOL STRUCT THEOCHE, V279, P157
   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
   SCHWINN KE, 1994, PHYTOCHEMISTRY, V35, P145
   STEWART JJP, 1990, J COMPUT AID MOL DES, V4, P1
   UENO K, 1977, ACTA CRYSTALLOGR B, V33, P111
   UENO K, 1977, ACTA CRYSTALLOGR B, V33, P114
NR 27
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0166-1280
J9 THEOCHEM-J MOL STRUCT
JI Theochem-J. Mol. Struct.
PD MAR 29
PY 1996
VL 363
IS 1
BP 87
EP 96
PG 10
SC Chemistry, Physical
GA UH856
UT ISI:A1996UH85600007
ER

PT J
AU Abraham, RJ
   Jones, AD
   Warne, MA
   Rittner, R
   Tormena, CF
TI Conformational analysis .27. NMR, solvation and theoretical
   investigation of conformational isomerism in fluoro- and
   1,1-difluoro-acetone
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID SUBSTITUTED CARBONYL-COMPOUNDS; VIBRATIONAL ASSIGNMENT;
   INTERNAL-ROTATION; ABINITIO CALCULATIONS; ELECTRONIC INTERACTION;
   BARRIERS; STABILITY; FLUOROACETONE; CHLORIDE; SPECTRA
AB The solvent and temperature dependence of the H-1 and C-13 NMR spectra
   of fluoroacetone (FA), 1,1-difluoroacetone (DFA) and
   1,1,1-trifluoroacetone (TFA) are reported and the (4)J(HF), (1)J(CF)
   and (2)J(CF) couplings analysed using ab initio calculations and
   solvation theory.
   In FA the energy difference (E(cis) - E(tr)) between the cis (F-C-C=O 0
   degrees) and trans (F-C-C=O 180 degrees) conformers is 2.2 kcal mol(-1)
   in the vapour, decreasing to 1.0 kcal mol(-1) in CCl4 solution and to
   -0.6 kcal mol(-1) in the pure liquid.
   In DFA the conformational equilibrium is between the less polar cis
   (H-C-C=O 0 degrees) and a gauche conformation (H-C-C=O 104 degrees).
   The energy difference (E(g) - E(cis)) is +0.8 kcal mol(-1) in the
   vapour, decreasing to 0.1 kcal mol(-1) in CCl4 solution and to -0.6
   kcal mol(-1) in the pure liquid.
   The vapour state energy difference for FA compares well with that
   calculated (2.8 kcal mol(-1) at MP4/6-31G*). DFA calculations at this
   level gave only one minimum in the potential surface corresponding to
   the cis form, A minimum for the gauche conformer was only found when
   sol solvation was included in the ab initio calculations, or at much
   larger basis sets (6-311++G**).
   The conformer couplings obtained show that the (4)J(HF) coupling
   (F-C-C-CH3) is proportional to cos(2) theta, where theta is the F-C-C-C
   dihedral angle. The (1)J(CF) and (2)J(CF) couplings also show a
   pronounced orientation dependence which could be of particular utility
   in those cases where other couplings are not present.
C1 UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13083970 CAMPINAS,SP,BRAZIL.
RP Abraham, RJ, UNIV LIVERPOOL,DEPT CHEM,POB 147,LIVERPOOL L69
   3BX,MERSEYSIDE,ENGLAND.
CR ABRAHAM RJ, 1974, INTERNAL ROTATION MO, CH13
   ABRAHAM RJ, 1981, TETRAHEDRON, V37, P575
   ABRAHAM RJ, 1991, J COMPUT AID MOL DES, V5, P21
   ABRAHAM RJ, 1994, J CHEM SOC P2, P949
   ABRAHAM RJ, 1995, J CHEM SOC P2, P1973
   CHOI SC, 1985, CAN J CHEM, V63, P836
   COOK BR, 1967, J CHEM PHYS, V47, P1700
   CROWDER GA, 1967, J CHEM PHYS, V47, P367
   DURIG JR, 1989, J CHEM PHYS, V90, P6840
   DURIG JR, 1989, SPECTROCHIM ACTA A, V45, P1239
   DURIG JR, 1991, J MOL STRUCT, V242, P179
   DURIG JR, 1991, J RAMAN SPECTROSC, V22, P141
   EWING DF, 1972, J CHEM SOC P2, P701
   FOREMAN JB, 1993, EXPLORING CHEM ELECT
   FRISCH MJ, 1992, GAUSSIAN 92
   GUERRERO SA, 1983, J CHEM SOC PERK T 2, P1053
   JONES GIL, 1973, J MOL STRUCT, V18, P1
   JONES VIP, 1970, J CHEM SOC B, P1719
   KAISEN CR, 1982, THESIS U ESTADUAL CA
   KARABATSOS GJ, 1969, J AM CHEM SOC, V91, P1124
   KARABATSOS GJ, 1969, J AM CHEM SOC, V91, P3572
   KHAN AY, 1969, J CHEM PHYS, V50, P1801
   LUMBROSO H, 1987, J MOL STRUCT, V162, P131
   OLIVATO PR, 1992, CAN J APPL SPECTROSC, V37, P37
   PHAN HV, 1993, SPECTROCHIM ACTA A, V49, P1967
   SAEGEBARTH E, 1967, J CHEM PHYS, V46, P3088
   SAEGEBARTH E, 1970, J CHEM PHYS, V52, P3555
   SHAPIRO BL, 1970, J MAGN RESON, V3, P336
   SHAPIRO BL, 1973, J MAGN RESON, V10, P65
   SHAPIRO BL, 1973, J MAGN RESON, V11, P355
   SHAPIRO BL, 1973, J MAGN RESON, V9, P305
   VANEIJCK BP, 1972, J MOL STRUCT, V11, P67
   VEKEN BJV, 1993, J MOL STRUCT, V293, P55
   WEAST RC, HDB CHEM PHYSICS
   WOLFE S, 1972, ACCOUNTS CHEM RES, V5, P102
   WOODWARD AJ, 1970, J MOL SPECTROSC, V35, P127
   WOODWARD AJ, 1970, J PHYS CHEM-US, V74, P798
NR 37
TC 26
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD APR
PY 1996
IS 4
BP 533
EP 539
PG 7
SC Chemistry, Organic; Chemistry, Physical
GA UF122
UT ISI:A1996UF12200010
ER

PT J
AU Gozzo, FC
   Sorrilha, AEPM
   Eberlin, MN
TI The generation, stability, dissociation and ion molecule chemistry of
   sulfinyl cations in the gas phase
SO JOURNAL OF THE CHEMICAL SOCIETY-PERKIN TRANSACTIONS 2
LA English
DT Article
ID MASS-SPECTROMETRY; ELECTRON-IMPACT; ORBITAL METHODS; ACYLIUM IONS;
   BASIS SETS; INTERMEDIATE; SUBSTITUTION; ISOMERS; C2H3O+
AB Sulfinyl cations [R-S+-O (R = CH3, Ph, Cl, CH3O and C2H5O)] have been
   demonstrated by MO calculations in conjunction with pentaquadrupole
   multidimensional (2D and 3D) MS(2) and MS(3) mass spectrometric
   experiments to be stable and easily accessible gas phase species, and
   their dissociation and ion/molecule chemistry have been studied.
   Potential energy surface diagrams indicate that the sulfoxides
   (CH3)(2)S=O, Ph(2)S=O, Cl2S=O, (CH3O)(2)S=O and (C2H5O)(2)S=O do not
   undergo rearrangement upon dissociative ionization, yielding the
   corresponding sulfinyl cations as primary fragments, Ph(CH3)S=O-+., on
   the other hand, is predicted to isomerize to CH3-S-O-Ph(+.) via a
   four-membered ring transition state, yielding upon further CH3. loss
   the isomeric ion S=O+-Ph. The sulfinyl cations were found by ab initio
   calculations to be much more stable than their S=O+-R isomers, hence
   isomerization via [1,2-R] shifts is not expected, Direct cleavage of
   the R-SO+ bonds and/or processes that are preceded by isomerization
   dominate the low-energy collision dissociation chemistry of the
   sulfinyl cations, thus providing limited structural information. On the
   other hand, a general and structurally diagnostic ion/molecule reaction
   with 2-methyl-1,3-dioxolane occurs for all the sulfinyl cations
   yielding abundant net oxirane (C2H4O) addition products. The reaction
   probably occurs via a transketalization-like mechanism that leads to
   cyclic 2-thia-1,3-dioxolanylium ions. This reactivity parallels that of
   several acylium (R-C+=O) and thioacylium ions (R-C+=S), and is not
   shared by the isomeric ions SO+-Ph and CH2=S+-OH. While the
   corresponding acylium ions react extensively with isoprene by [4 +
   2(+)] cycloaddition, only the phenylsulfinyl cation Ph-S+=O yields an
   abundant cycloadduct.
C1 STATE UNIV CAMPINAS UNICAMP,INST CHEM,BR-13083970 CAMPINAS,SP,BRAZIL.
CR *MIN SUP CTR INC, 1993, XMOL VER 1 3 1
   APPEL R, 1966, CHEM BER, V99, P3108
   ATTINA M, 1983, J AM CHEM SOC, V105, P1122
   BAAR BV, 1986, J CHEM SOC CHEM COMM, P1607
   BASHER MM, UNPUB
   BEAUGRAND C, 1989, ADV MASS SPECTROM A, V11, P256
   BLICKE FF, 1942, ORG REACTIONS, V1, P303
   BOGERT MT, 1933, J AM CHEM SOC, V55, P3741
   BOWERS MT, 1979, GAS PHASE ION CHEM
   BOWIE JH, 1966, TETRAHEDRON, V22, P3515
   BUDZIKIEWICZ H, 1967, MASS SPECTROMETRY OR
   BUSH KL, 1989, MASS SPECTROMETRY MA
   CAREY FA, 1983, ADV ORGANIC CHEM
   CARLSEN L, 1988, J AM CHEM SOC, V110, P6701
   CASERIO MC, 1983, J AM CHEM SOC, V105, P6896
   CHAPMAN JR, 1993, PRACTICAL ORGANIC MA
   CHATFIELD DA, 1976, J AM CHEM SOC, V98, P6492
   DEWAR MJS, 1985, J AM CHEM SOC, V107, P3902
   EBERLIN MN, 1992, J AM CHEM SOC, V114, P2884
   EBERLIN MN, 1993, J AM CHEM SOC, V115, P9226
   EBERLIN MN, 1993, ORG MASS SPECTROM, V28, P679
   EBERLIN MN, 1994, J AM CHEM SOC, V116, P2457
   EBERLIN MN, 1995, J AM SOC MASS SPECTR, V6, P1
   FRISCH MJ, 1984, J CHEM PHYS, V80, P3265
   FRISCH MJ, 1992, GAUSSIAN92
   GORDON MS, 1980, CHEM PHYS LETT, V76, P163
   GOZZO FC, 1993, P 41 ASMS C MASS SPE, P974
   GOZZO FC, 1995, J AM SOC MASS SPECTR, V6, P554
   GOZZO FC, 1995, J MASS SPECTROM, V30, P1553
   GU M, 1992, J AM CHEM SOC, V114, P7146
   HARIHARAN PC, 1973, THEOR CHEM ACTA, V72, P650
   HEHRE WJ, 1972, J CHEM PHYS, V56, P2257
   JOHNSTONE RAW, 1979, MASS SPECTROMETRY, V5, P277
   JULIANO VF, IN PRESS ANAL CHEM
   KHMELNITSKII RA, 1977, RUSS CHEM REV, V46, P46
   KIM JK, 1982, J AM CHEM SOC, V104, P4624
   KOTIAHO T, 1993, J AM CHEM SOC, V115, P1004
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   LINDNER E, 1968, ANGEW CHEM INT EDIT, V7, P548
   LIU LK, 1983, ORG MASS SPECTROM, V18, P22
   LU L, 1995, J MASS SPECTROM, V30, P581
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   MCGIBBON GA, 1994, CHEM PHYS LETT, V218, P499
   MCLAFFERTY FW, 1983, TANDEM MASS SPECTROM
   MCLAFFERTY FW, 1993, INTERPRETATION MASS
   MEYERSON S, 1964, ANAL CHEM, V36, P1294
   MOLLER C, 1934, PHYS REV, V46, P618
   MORRISON JD, 1986, 34TH P AM SOC MASS S, P222
   MUKAIYAMA T, 1982, ORG REACTIONS, V28, P203
   NIXON WB, 1978, INT J MASS SPECTROM, V26, P115
   NOBES RH, 1983, J AM CHEM SOC, V105, P309
   OLAH GA, 1964, FRIEDELCRAFTS RELATE, V3
   OLAH GA, 1974, J AM CHEM SOC, V96, P3581
   OLAH GA, 1976, CARBONIUM IONS, V5, P2049
   OLAH GA, 1980, ANGEW CHEM INT EDIT, V19, P812
   PARADISI C, 1988, ORG MASS SPECTROM, V23, P521
   PEERS AM, 1975, INT J MASS SPECTROM, V16, P321
   PIHLAJA K, 1988, CHEM SULPHONES SULPH, P125
   PIHLAJA K, 1988, ORG MASS SPECTROM, V23, P770
   POTZINGER P, 1975, Z NATURFORSCH A, V30, P340
   RAHMAN NA, 1988, ORG MASS SPECTROM, V23, P517
   ROLSTON JH, 1969, J AM CHEM SOC, V91, P1469
   SABLIER M, 1994, TETRAHEDRON LETT, V35, P2895
   SCHWARTZ JC, 1989, INT J MASS SPECTROM, V3, P305
   SCHWARTZ JC, 1990, ANAL CHEM, V62, P1809
   SHAY BJ, 1992, J AM SOC MASS SPECTR, V3, P518
   SPARAPANI C, 1980, J AM CHEM SOC, V102, P3120
   STALEY RH, 1977, J AM CHEM SOC, V99, P5964
   TURECEK F, 1983, ORG MASS SPECTROM, V18, P608
   TURECEK F, 1984, MASS SPECTROM REV, V3, P85
   TURECEK F, 1989, J AM CHEM SOC, V111, P7696
   WEBER R, 1980, ORG MASS SPECTROM, V15, P138
   YANG SS, 1995, J MASS SPECTROM, V30, P807
NR 73
TC 17
PU ROYAL SOC CHEMISTRY
PI CAMBRIDGE
PA THOMAS GRAHAM HOUSE, SCIENCE PARK MILTON ROAD, CAMBRIDGE, CAMBS,
   ENGLAND CB4 4WF
SN 0300-9580
J9 J CHEM SOC PERKIN TRANS 2
JI J. Chem. Soc.-Perkin Trans. 2
PD APR
PY 1996
IS 4
BP 587
EP 596
PG 10
SC Chemistry, Organic; Chemistry, Physical
GA UF122
UT ISI:A1996UF12200020
ER

PT J
AU Blaszkowski, SR
   Nascimento, MAC
   vanSanten, RA
TI Activation of C-H and C-C bonds by an acidic zeolite: A density
   functional study
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID MOLECULAR-SIEVES; OPTIMIZATION; ENERGIES; APPROXIMATION; BEHAVIOR;
   GEOMETRY
AB Density functional theory is used to determine transition states and
   the corresponding energy barriers of the reactions related to C-H bond
   activation of hydrogen exchange and dehydrogenation of ethane catalyzed
   by a protonated zeolite as well as hydride transfer between methanol
   and a methoxide (CH3-zeolite) species. Additionally the C-C bond
   activation involved in the acid catalyzed cracking reaction of ethane
   was investigated. The computed activation barriers are 118 for hydrogen
   exchange, 202 for hydride transfer, 292 for cracking and finally 297
   for dehydrogenation, all in kilojoules per mole. For the cracking
   reaction, two different transition states with the same activation
   barrier have been obtained, dependent on the approach of the ethane
   molecule to the zeolite cluster. A study of the relation between
   acidity and the structure of the zeolite shows that the transition
   state for the hydrogen exchange reaction is rather covalent and its
   geometry resembles the well-known carbonium ion, while the others are
   rather ionic carbenium ions. From the calculated activation barriers as
   well as vibrational, rotational, and translational partition functions,
   reaction rate constants have been evaluated by means of the transition
   state reaction rate theory.
C1 EINDHOVEN UNIV TECHNOL,SCHUIT INST CATALYSIS,INORGAN CHEM LAB,5600 MB EINDHOVEN,NETHERLANDS.
   EINDHOVEN UNIV TECHNOL,CATALYSIS THEORY GRP,5600 MB EINDHOVEN,NETHERLANDS.
RP Blaszkowski, SR, FED UNIV RIO DE JANEIRO,DEPT QUIM FIS,INST QUIM,CIDADE
   UNIV,BLOCO A,BR-21949900 RIO JANEIRO,BRAZIL.
CR ANDZELM J, 1987, CHEM PHYS LETT, V142, P169
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   BECKE AD, 1988, PHYS REV A, V38, P3098
   BLASZKOWSKI SR, 1994, J PHYS CHEM-US, V98, P12938
   BLASZKOWSKI SR, 1995, J PHYS CHEM-US, V99, P11728
   BOHME DK, 1975, INTERACTIONS IONS MO, P489
   CARNEIRO JWD, 1994, J AM CHEM SOC, V116, P3483
   COLLINS SJ, 1995, J CATAL, V153, P94
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   ENGELHARDT J, 1995, J CATAL, V151, P1
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   FAN LY, 1992, J AM CHEM SOC, V114, P10890
   FROST AA, 1961, KINETICS MECHANISMS
   GILBERT RG, 1990, THEORY UNIMOLECULAR
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   HEHRE WJ, 1986, AB INITIO MOL ORBITA
   HOCEVAR S, 1992, J CATAL, V135, P518
   HOHENBERG P, 1964, PHYS REV B, V136, P864
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   KAZANSKY VB, 1994, CATAL LETT, V27, P345
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   STEFANADIS C, 1991, J MOL CATAL, V67, P363
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   VANSANTEN RA, 1995, J CHEM REV, V95, P637
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   WILSON EB, 1955, MOL VIBRATIONS
   YALURIS G, 1995, J CATAL, V153, P65
NR 42
TC 76
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD FEB 29
PY 1996
VL 100
IS 9
BP 3463
EP 3472
PG 10
SC Chemistry, Physical
GA TX766
UT ISI:A1996TX76600024
ER

PT J
AU daSilva, JBP
   daCosta, NB
   Ramos, MN
   Fausto, R
TI Vibrational spectra and structure of the cis and trans conformers of
   methyl nitrite: An ab initio MO study
SO JOURNAL OF MOLECULAR STRUCTURE
LA English
DT Article
ID ABINITIO CALCULATIONS; MICROWAVE-SPECTRA; PHASE
AB The vibrational and conformational properties exhibited by nethyl
   nitrite (CH3ON=O) were studied by ab initio MO methods (HF-SCF and MP2)
   using both the 6-31G and 6-311G basis sets without or with the
   inclusion of diffuse and/or polarization functions, Fully optimized
   geometries, relative stabilities, dipole moments and harmonic force
   fields for both the cis and trans conformers of this molecule were
   determined and the results compared with available experimental data.
   In agreement with the experimental results, the calculations involving
   polarization functions at the MP2 level of theory indicate that the
   most stable conformer of methyl nitrite is the planar cis conformer,
   where the methyl group is eclipsing the N=O bond, while the trans form
   was predicted to have a higher energy than this form by about 4 kJ
   mol(-1) The conformational dependence of some relevant structural
   parameters was used to characterize the most important intramolecular
   interactions present in the studied conformers, and their calculated
   infrared spectra were used to review previous assignments of the
   experimentally observed bands for both the normal and deuterated
   (CD3ON=O) species. Chemometrics methods (principal components and
   two-level factorial designing) were used both to analyze the effect of
   changing the basis set and level of theory used to perform the
   calculations, and to aid comparison between the experimental and
   calculated vibrational spectra.
C1 UNIV COIMBRA,DEPT QUIM,P-3049 COIMBRA,PORTUGAL.
   UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50740250 RECIFE,PE,BRAZIL.
CR *INF INC, 1991, EIN SIGHT PATT REC S
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   CORKILL MJ, 1978, 7 AUST S MOL STRUCT
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   FRISCH MJ, 1992, GAUSSIAN 92
   FUHER F, 1976, NATL RES COUNCIL CAN, V15, P1
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   GRAY P, 1963, T FARADAY SOC, V59, P347
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NR 38
TC 6
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0022-2860
J9 J MOL STRUCT
JI J. Mol. Struct.
PD JAN 22
PY 1996
VL 375
IS 1-2
BP 153
EP 180
PG 28
SC Chemistry, Physical
GA TX261
UT ISI:A1996TX26100014
ER

PT J
AU Tanabe, FKJ
   Morgon, NH
   Riveros, JM
TI Relative gas-phase bromide and iodide affinity of simple solvent
   molecules determined by FT-ICR
SO JOURNAL OF PHYSICAL CHEMISTRY
LA English
DT Article
ID TRANSFORM MASS-SPECTROMETRY; HALIDE-IONS; CHLORIDE-ION; EQUILIBRIA
   MEASUREMENTS; EXCHANGE EQUILIBRIA; IMPULSE EXCITATION; BRONSTED ACIDS;
   BOND STRENGTHS; NEGATIVE-IONS; COMPLEXES
AB The gas-phase ion/molecule reaction of CH3O- with bromo- and
   iodobenzene has been used to generate Br-(CH3OH) and I-(CH3OH) ions in
   an FT-ICR spectrometer. These ions are shown to undergo rapid solvent
   exchange with molecules of comparable or higher halide affinity. The
   equilibrium constants have been determined for these exchange reactions
   and the relative bromide free-energy affinity at 335 K (-Delta G
   degrees/kcal mol(-1)) is shown to increase in the order H2O (0.0) <
   CH3OH (1.07) < CH3CN (1.51) similar to C2H5OH (1.53) < i-C3H7OH (1.88)
   < CH3NO2 (2.34). For I-, a similar trend is observed except that C2H5OH
   < CH3CN. Ab initio calculations were carried out at the MP4(SDTQ) level
   with geometry optimization at the MP2 level and using the generator
   coordinate method to add diffuse functions to the Br basis set. Changes
   in entropies for the gas-phase equilibrium experiments were estimated
   from the calculated vibrational frequencies, and the enthalpies of
   solvation were derived by using the reported value for Br-(CH3OH) as a
   reference point.
C1 UNIV SAO PAULO,INST QUIM,BR-05599970 SAO PAULO,BRAZIL.
CR ABBOUD JLM, 1989, J AM CHEM SOC, V111, P8960
   ARSHADI M, 1970, J PHYS CHEM-US, V74, P1475
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   CASTLEMAN AW, 1986, CHEM REV, V86, P589
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   DUNNING TH, 1977, METHODS ELECTRONIC S, CH1
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   FRISCH C, 1992, GAUSSIAN 92 REVISION
   GONZALEZ C, 1989, J CHEM PHYS, V90, P2154
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   HEHRE WJ, 1986, AB INITIO MOL ORBITA, CH6
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   LINNERT HV, UNPUB
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NR 51
TC 11
PU AMER CHEMICAL SOC
PI WASHINGTON
PA 1155 16TH ST, NW, WASHINGTON, DC 20036
SN 0022-3654
J9 J PHYS CHEM
JI J. Phys. Chem.
PD FEB 22
PY 1996
VL 100
IS 8
BP 2862
EP 2866
PG 5
SC Chemistry, Physical
GA TX257
UT ISI:A1996TX25700014
ER

PT J
AU Schmidt, TM
   Fazzio, A
   Caldas, MJ
TI Germanium negative-U center in GaAs
SO PHYSICAL REVIEW B
LA English
DT Article
ID DX-CENTER; PERSISTENT PHOTOCONDUCTIVITY; ALXGA1-XAS ALLOYS;
   HYDROSTATIC-PRESSURE; DEEP DONORS; GE; SEMICONDUCTORS; STATES; SI;
   ENERGETICS
AB The DX center related to the Ge impurity in GaAs is investigated by ab
   initio pseudopotential calculations within the local-density
   aproximation. Our results indicate that the behavior of the Ge-Ga
   defect is qualitatively different from the broken-bond model usually
   associated to Si-Ga, even if the electronic structure behaves in a very
   similar way. Indeed, for the Ge impurity our calculations show that
   already for breathing-mode relaxations of the Ge neighbors, in T-d
   symmetry, a negative-U behavior is found, and many details of the
   experimental data can be explained.
C1 UNIV FED UBERLANDIA,DEPT CIENCIAS FIS,BR-38400902 UBERLANDIA,MG,BRAZIL.
RP Schmidt, TM, UNIV SAO PAULO,INST FIS,CAIXA POSTAL 66318,BR-05389970 SAO
   PAULO,BRAZIL.
CR BAJ M, COMMUNICATION
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   SCHMIDT TM, UNPUB
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NR 45
TC 10
PU AMERICAN PHYSICAL SOC
PI COLLEGE PK
PA ONE PHYSICS ELLIPSE, COLLEGE PK, MD 20740-3844 USA
SN 0163-1829
J9 PHYS REV B
JI Phys. Rev. B
PD JAN 15
PY 1996
VL 53
IS 3
BP 1315
EP 1321
PG 7
SC Physics, Condensed Matter
GA TU290
UT ISI:A1996TU29000063
ER

PT J
AU Pliego, JR
   DeAlmeida, WB
TI Searching for the ylide structure. An ab initio study of the H2O...CCl2
   complex
SO CHEMICAL PHYSICS LETTERS
LA English
DT Article
ID DICHLOROCARBENE
AB The potential energy surface (PES) for the H2O...CCl2 complex has been
   investigated at the self-consistent field level with a DZP basis set in
   order to search for stationary points and to verify the possible
   formation of an ylide species. Six stationary points were located on
   the PES, being one minimum, three first-order transition sates (TS) and
   two second-order TS structures. A stable ylide species was not found,
   and an explanation for this is given based on electrostatic grounds,
   The unique minimum corresponds to an H-bond structure, with a
   dissociation energy of 845.5 cm(-1), calculated including zero point
   energy correction, a more extended basis set, electron correlation
   effects at the MP2 level and taking into account basis set
   superposition errors employing the counterpoise method.
RP Pliego, JR, UFMG,ICEX,DEPT QUIM,LAB QUIM COMPUTAC & MODELAGEM
   MOLEC,BR-31270901 BELO HORIZONT,MG,BRAZIL.
CR BETHELL D, 1973, ORGANIC REACTIVE INT
   BOYS SF, 1970, MOL PHYS, V19, P553
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   CHALASINSKI G, 1994, CHEM REV, V94, P1723
   CHATEAUNEUF JE, 1990, J AM CHEM SOC, V112, P3217
   DEALMEIDA WB, 1993, J PHYS CHEM-US, V97, P2560
   DEALMEIDA WB, 1994, CHEM PHYS LETT, V231, P283
   DEALMEIDA WB, 1994, MOL PHYS, V81, P1397
   DEALMEIDA WB, 1995, SPECTROCHIM ACTA A, V51, P653
   DUNNING TH, 1977, METHODS ELECTRONIC S
   GOBBI A, 1993, J CHEM SOC CHEM COMM, P1162
   GUTSEV GL, 1991, J PHYS CHEM-US, V95, P7220
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   KIRMSE W, 1964, CARBENE CHEM
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   PLIEGO JR, UNPUB
   RESENDE SM, 1995, J CHEM PHYS, V102, P4184
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   SCHMIDT MW, 1993, J COMPUT CHEM, V14, P1347
NR 22
TC 12
PU ELSEVIER SCIENCE BV
PI AMSTERDAM
PA PO BOX 211, 1000 AE AMSTERDAM, NETHERLANDS
SN 0009-2614
J9 CHEM PHYS LETT
JI Chem. Phys. Lett.
PD JAN 26
PY 1996
VL 249
IS 1-2
BP 136
EP 140
PG 5
SC Physics, Atomic, Molecular & Chemical
GA TR918
UT ISI:A1996TR91800023
ER

PT J
AU Giordan, M
   Custodio, R
   Trigo, JR
TI Pyrrolizidine alkaloids necine bases: Ab initio, semiempirical, and
   molecular mechanics approaches to molecular properties
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
ID BUTTERFLIES DANAUS-PLEXIPPUS; ARCTIID MOTH; PARAMETERS; OPTIMIZATION
AB The structural stabilities of endo and exo conformations of retronecine
   and heliotridine molecules were analyzed using different ab initio,
   semiempirical, and molecular mechanics methods. All electron and
   pseudopotential nb initio calculations at the Hartree-Fock level of
   theory with 6-31G* and CEP-31G* basis sets provided structures in
   excellent agreement with available experimental results obtained from
   X-ray crystal structure and H-1-NMR (nuclear magnetic resonance)
   studies in D2O solutions. The exo conformations showed a greater
   stability for both molecules. The most significant difference between
   the calculations was found in the ring planarity of heliotridine, whose
   distortion was associated with the interaction between the O(11)H group
   and the C(1)-C(2) double bond as well as with a hydrogen bond between
   O(11)H and N(4). The discrepancy between pseudopotential and
   all-electron optimized geometries was reduced after inclusion of the
   innermost electrons of C(1), C(2), and N(4) in the core potential
   calculation. The MNDO, AM1, and PM3 semiempirical results showed poor
   agreement with experimental data. The five-membered rings were observed
   to be planar for AM1 and MNDO calculations. The PM3 calculations for
   exo-retronecine showed a greater stability than the endo conformer, in
   agreement with ab initio results. A good agreement was observed between
   MM3 and nb initio geometries, with small differences probably due to
   hydrogen bonds. While exo-retronecine was calculated to be more stable
   than the endo conformer, the MM3 calculations suggested that
   endo-heliotridine was slightly more stable than the exo form. (C) 1996
   by John Wiley & Sons, Inc.
C1 UNIV ESTADUAL CAMPINAS,INST BIOL,DEPT ZOOL,LAB ECOL QUIM,BR-13081970 CAMPINAS,SP,BRAZIL.
RP Giordan, M, UNIV ESTADUAL CAMPINAS,DEPT FISICOQUIM,INST
   QUIM,BR-13081970 CAMPINAS,SP,BRAZIL.
CR ALLINGER NL, MM392 QCPE IND U
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   FERGUSON DM, 1992, J COMPUT CHEM, V13, P525
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   GELBAUM LT, 1985, ACTA CRYSTALLOGR C, V41, P1342
   HARTMANN T, 1988, CELL CULTURE SOMATIC, V5, P277
   HARTMANN T, 1995, ALKALOIDS CHEM BIOL, V9, P155
   HAY DG, 1982, ACTA CRYSTALLOGR B, V38, P155
   HEHRE WJ, 1986, AB INITIO MOL ORBITA, P137
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   MACKAY MF, 1983, ACTA CRYSTALLOGR C, V39, P785
   MATTOCKS AR, 1972, PHYTOCHEMICAL ECOLOG, P179
   MATTOCKS AR, 1986, CHEM TOXICOLOGY PYRR
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   RIZAK AFM, 1991, NATURALLY OCCURRING, P211
   STELLJES ME, 1990, J CHEM ECOL, V16, P1459
   STEVENS WJ, 1984, J CHEM PHYS, V81, P6026
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   SUSSMAN JL, 1973, ACTA CRYSTALLOGR B, V29, P2918
   TRIGO JR, 1993, ALCALOIDES PIRROLIZI
   TRIGO JR, 1993, J CHEM ECOL, V19, P669
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   VILKOV LV, 1983, DETERMINATION GEOMET
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NR 40
TC 7
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD JAN 30
PY 1996
VL 17
IS 2
BP 156
EP 166
PG 11
SC Chemistry, Multidisciplinary
GA TM791
UT ISI:A1996TM79100003
ER

PT J
AU DeAzevedo, ALMS
   Neto, BB
   Scarminio, IS
   DeOliveira, AE
   Bruns, RE
TI A chemometric analysis of ab initio vibrational frequencies and
   infrared intensities of methyl fluoride
SO JOURNAL OF COMPUTATIONAL CHEMISTRY
LA English
DT Article
ID DIPOLE-MOMENT DERIVATIVES; THEORETICAL THERMOCHEMISTRY; ANALYTIC
   EVALUATION; MOLECULES; SIGNS; HEATS; CH3F
AB Factorial design and principal component analyses are applied to CH3F
   infrared frequencies and intensities calculated from ab initio wave
   functions. In the factorial analysis, the quantitative effects of
   changing from a 6-31G to a 6-311G basis, of including polarization and
   diffuse orbitals, and of correcting for electron correlation using the
   second-order Moller-Plesset procedure are determined for all
   frequencies and intensities. The most significant main effect observed
   for the frequencies corresponds to the shift from Hartree-Fock to MP2
   calculations, which tends to lower all frequency values by
   approximately 100 cm(-1). For the intensities, the main effects are
   larger for the CF stretching and the CH3 asymmetric stretching modes.
   Interaction effects between two or more of the four factors are found
   to be of minor importance, except for the interaction between
   correlation and polarization. The principal component analysis
   indicates that wave functions with polarization and diffuse orbitals at
   the second-order Moller-Plesset level provide the best estimates for
   the harmonic frequencies, but not for the intensities. For the
   frequencies, the first principal component distinguishes between MP2
   and Hartree-Fock calculations, while the second component separates the
   wave functions with polarization orbitals from those without these
   orbitals. For the intensities, the separation is similar but less well
   defined. This analysis also shows that wave function optimization to
   calculate accurate intensities is more difficult than an optimization
   for frequencies. (C) 1996 by John Wiley & Sons, Inc.
C1 UNIV ESTADUAL CAMPINAS,INST QUIM,BR-13081970 CAMPINAS,SP,BRAZIL.
   UNIV FED PERNAMBUCO,DEPT QUIM FUNDAMENTAL,BR-50739 RECIFE,PE,BRAZIL.
   UNIV ESTADUAL LONDRINA,DEPT QUIM,LONDRINA,PARANA,BRAZIL.
CR BARROW GM, 1952, P ROY SOC LOND A MAT, V213, P27
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NR 22
TC 6
PU JOHN WILEY & SONS INC
PI NEW YORK
PA 605 THIRD AVE, NEW YORK, NY 10158-0012
SN 0192-8651
J9 J COMPUT CHEM
JI J. Comput. Chem.
PD JAN 30
PY 1996
VL 17
IS 2
BP 167
EP 177
PG 11
SC Chemistry, Multidisciplinary
GA TM791
UT ISI:A1996TM79100004
ER

EF