A quantum mechanical study of proton exchange in sulfoxides with retention and inversion of configuration

1969 ◽  
Vol 47 (1) ◽  
pp. 113-135 ◽  
Author(s):  
Arvi Rauk ◽  
Saul Wolfe ◽  
I. G. Csizmadia
Keyword(s):  
Proton Exchange ◽  
Basis Sets ◽  
Significant Finding ◽  
Gaussian Basis Sets ◽  
Mechanical Study ◽  
Self Consistent Field ◽  
Quantum Mechanical Study ◽  
Sulfinyl Group ◽  
And Inversion ◽  
Detailed Work

A survey of the experimental data on the structures of α-sulfonyl and α-sulfinyl carbanions is presented as an introduction to the present work, a theoretical study of hydrogen methyl sulfoxide (HMSO) and hydrogen methylsulfinyl anion (HMSO−) by nonempirical self consistent field (s.c.f.) calculations using Gaussian basis sets. Calculations on dimethyl sulfoxide (DMSO) and its conjugate base (DMSO−) are also presented and fully justify the choice of HMSO and HMSO− for the detailed work. A conformational energy surface (total energy as a function of rotation about the C—S bond and inversion of the carbanion angle) for HMSO− is presented and used to determine the stereochemical fate of a carbanion generated next to a sulfinyl group. Predictions are made concerning the probable course of proton exchange next to S—O and an explanation is offered for the experimental facts concerning exchange in sulfoxides. A very significant finding is that postulation of d-orbital conjugation is not essential to explain the asymmetry of α-sulfinyl carbanions.

scholarly journals Quantum Mechanical Study of YTiO3 to the Investigation of Piezoelectricity

2011 ◽  
Vol 2011 ◽  
pp. 1-5
Author(s):  
Raimundo Dirceu de Paula Ferreira ◽  
Marcos Antonio Barros dos Santos ◽  
Maycon da Silva Lobato ◽  
Jardel Pinto Barbosa ◽  
Marcio de Souza Farias ◽  
...  
Keyword(s):  
Total Energy ◽  
Piezoelectric Properties ◽  
Piezoelectric Effect ◽  
Basis Set ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Mechanical Study ◽  
Quantum Mechanical Study

In previous articles we reported through theoretical studies the piezoelectric effect in BaTiO3, SmTiO3, and YFeO3. In this paper, we used the Douglas-Kroll-Hess (DKH) second-order scalar relativistic method to investigate the piezoelectricity in YTiO3. In the calculations we used the [6s4p] and [10s5p4d] Gaussian basis sets for the O (3P) and Ti (5S) atoms, respectively, from the literature in combination with the (30s21p16d)/[15s9p6d] basis set for the Y (3D) atom, obtained by generator coordinate Hartree-Fock (GCHF) method, and they had their quality evaluated using calculations of total energy and orbital energies (HOMO and HOMO-1) of the 2TiO+1 and 1YO+1 fragments. The dipole moment, the total energy, and the total atomic charges in YTiO3 in Cs space group were calculated. When we analyze those properties we verify that it is reasonable to believe that YTiO3 does not present piezoelectric properties.

Universal Gaussian basis functions in relativistic quantum chemistry: atomic Dirac–Fock–Coulomb and Dirac–Fock–Breit calculations

1992 ◽  
Vol 70 (6) ◽  
pp. 1822-1826 ◽  
Author(s):  
G. L. Malli ◽  
A. B. F. Da Silva ◽  
Yasuyuki Ishikawa
Keyword(s):  
Relativistic Quantum ◽  
Basis Set ◽  
Basis Sets ◽  
Interaction Energies ◽  
Gaussian Basis Sets ◽  
Consistent Field ◽  
Self Consistent ◽  
Self Consistent Field ◽  
Gaussian Basis Set ◽  
Good Agreement

Matrix Dirac–Fock–Coulomb and Dirac–Fock–Breit self-consistent field calculations are performed for a number of neutral atoms. He (Z = 2) through Xe (Z = 54), using the universal Gaussian basis set (18s, 12p, 11d) reported recently by Da Silva etal. The total Dirac–Fock–Coulomb, the Dirac–Fock–Breit, and the Breit interaction energies calculated with this universal Gaussian basis set are in good agreement with the corresponding values obtained by using an extensive well-tempered Gaussian basis set for the He through Ca (Z = 20) atoms. Although this universal Gaussian basis set is inadequate for the calculation of total Dirac–Fock–Coulomb and Dirac–Fock–Breit energies for the Kr, Sr, and Xe atoms, the Breit interaction energies calculated with this basis for these three atoms are in very good agreement with the corresponding Breit interaction energies obtained by using the extensive well-tempered Gaussian basis sets. Work is in progress to generate a more extensive and energetically better universal Gaussian basis set for He through Xe for its use in non-relativistic Hartree–Fock as well as Dirac–Fock self-consistent field calculations on polyatomics involving heavy atoms.

A Quantum Mechanical Study of the Thermal Conduction Across a ZrB2-SiC Interface as a Function of Temperature and Strain

2011 ◽  
Author(s):  
Vikas Samvedi ◽  
Vikas Tomar
Keyword(s):  
Thermal Conduction ◽  
Function Theory ◽  
Phase Changes ◽  
Basis Sets ◽  
Second Phase ◽  
Triple Junctions ◽  
Mechanical Study ◽  
Conduction Behavior ◽  
Quantum Mechanical Study ◽  
Property Changes

Studies on nanocomposites have proven them to be a promising option for various applications based on their excellent thermal and mechanical properties, especially at high temperatures. Such materials consist of heterogeneities in the form of interfaces, grain boundaries, triple junctions, and second phase dispersion. It is, therefore, important to understand the effect of heat transfer across a nanocomposite interface on its thermal conduction behavior. Analyses need to take into account possible phase changes as a function of changes in temperature and thermal stress levels. In the present research, atomistic analyses of thermal conduction across a nanocomposite interface are performed using quantum simulations based on plane-wave basis sets combined with the density function theory (DFT). Analyses of the effect of straining on the nanocomposite property changes are performed to study it as a promising means to obtain nanocomposites with tailored properties.

scholarly journals Theoretical study of structure, vibrational and electronic spectra of isomers of methyl-3-methoxy-2-propenoate

2004 ◽  
Vol 2 (3) ◽  
pp. 456-479 ◽  
Author(s):  
Ajit Virdi ◽  
V. Gupta ◽  
Archna Sharma
Keyword(s):  
Electronic Spectra ◽  
Density Functional ◽  
Substantial Reduction ◽  
Basis Sets ◽  
Potential Energy Distribution ◽  
Functional Theory ◽  
Symmetry Coordinates ◽  
Mechanical Study ◽  
Quantum Mechanical Study ◽  
Vibrational Bands

AbstractA systematic quantum mechanical study of the possible conformations, their relative stabilities, vibrational and electronic spectra and thermodynamic parameters of methyl-3-methoxy-2-propenoate has been reported for the electronic ground (S0) and first excited (S1) states using time-dependent and time-independent Density Functional Theory (DFT) and RHF methods in extended basis sets. Detailed studies have been restricted to the E-isomer, which is found to be substantially more stable than the Z-isomer. Four possible conformers c′Cc, c′Tc, t′Cc, t′Tc, of which the first two are most stable, have been identified in the S0 and S1 states. Electronic excitation to S1 state is accompanied with a reversal in the relative stability of the c′Cc and c′Tc conformers and a substantial reduction in the rotational barrier between them, as compared with the S0 state. Optimized geometries of these conformers in the S0 and S1 states are being reported. Based on suitably scaled RHF/6-31G** and DFT/6-311G** calculations, assignments have been provided to the fundamental vibrational bands of both these conformers in terms of frequency, form and intensity of vibrations and potential energy distribution across the symmetry coordinates in the S0 state. A complete interpretation of the electronic spectra of the conformers has been provided.

Nonempirical s.c.f. calculations on sulfur atom, hydrogen sulfide, and dihydrogen sulfoxide

1968 ◽  
Vol 46 (8) ◽  
pp. 1205-1214 ◽  
Author(s):  
A. Rauk ◽  
I. G. Csizmadia
Keyword(s):  
Multiple Bond ◽  
Optimization Procedure ◽  
Basis Set ◽  
Basis Sets ◽  
Minimal Basis ◽  
Gaussian Basis Sets ◽  
Chemical Systems ◽  
A Value ◽  
Self Consistent Field ◽  
Sulfur Containing

This paper reports the first attempt to use Gaussian basis sets in nonempirical self-consistent field (s.c.f.) calculations on sulfur-containing chemical systems. Exponents for Gaussian-type functions (G.t.f.) on S atom are given for the minimal basis set. The optimization procedure is described and the optimized exponents utilized on calculations on S atom, H2S, and the hypothetical dihydrogen sulfoxide (H2SO). Calculations by the minimal basis set of (G.t.f.), using these exponents, gave a value for the HSH angle of H2S that agrees well with the experimentally determined value. Calculations of H2SO support a "multiple bond" picture of the S—O bond.

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