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.

scholarly journals Adapted Gaussian basis sets for atoms from Li through Xe generated with the generator coordinate Hartree-Fock method

2001 ◽  
Vol 73 (4) ◽  
pp. 511-517 ◽  
Author(s):  
EUSTÁQUIO V. R. DE CASTRO ◽  
FRANCISCO E. JORGE
Keyword(s):  
Total Energy ◽  
Wave Functions ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Discretization Technique

The generator coordinate Hartree-Fock method is used to generate adapted Gaussian basis sets for the atoms from Li (Z=3) through Xe (Z=54). In this method the Griffin-Hill-Wheeler-Hartree-Fock equations are integrated through the integral discretization technique. The wave functions generated in this work are compared with the widely used Roothaan-Hartree-Fock wave functions of Clementi and Roetti (1974), and with other basis sets reported in the literature. For all atoms studied, the errors in our total energy values relatively to the numerical Hartree-Fock limits are always less than 7.426 mhartree.

Gaussian basis sets for the atoms from K through Xe

2001 ◽  
Vol 79 (2) ◽  
pp. 121-123 ◽  
Author(s):  
R Centoducatte ◽  
E VR de Castro ◽  
F E Jorge
Keyword(s):  
Key Words ◽  
Ground State ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Discretization Technique ◽  
Total Energies

An improved generator coordinate Hartree-Fock (IGCHF) method is used to generate Gaussian basis sets for the atoms from K (Z = 19) through Xe (Z = 54). The Griffin-Hill-Wheeler-HF equations are integrated using the integral discretization technique. The ground state HF total energies obtained by us are compared with those calculated with the original GCHF method and with other approaches reported in the literature. The largest difference between our energy values and the corresponding ones computed with a numerical HF method is equal to 6.003 mhartree for Kr (Z = 36).Key words: improved generator coordinate Hartree-Fock method, Gaussian basis sets, total energies.

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.

Generation, contraction, and polarisation of Gaussian basis sets for atomic and molecular calculations using the generator coordinate method with polynomial discretisation: atoms from Na through Cl

2021 ◽  
Author(s):  
Amanda Ribeiro Guimaraes ◽  
Rugles César Barbosa ◽  
Ana Cristina Tello Mora ◽  
Aldineia Pereira da Silva ◽  
Júlia Maria Aragon Alves ◽  
...  
Keyword(s):  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Generator Coordinate Method ◽  
Coordinate Method ◽  
Hartree Fock ◽  
Generator Coordinate ◽  
Molecular Calculations

The polynomial Generator Coordinate Hartree-Fock Gaussian basis sets, pGCHF, for the atoms Na, Mg, Al, Si, P, S, and Cl were generated using the generator coordinate method based on polynomial...

Hartree-Fock Stability and Broken Symmetry Solutions of O2- and S2- Anions in External Confinement

2007 ◽  
Vol 72 (2) ◽  
pp. 197-222 ◽  
Author(s):  
Filip Holka ◽  
Pavel Neogrády ◽  
Miroslav Urban ◽  
Josef Paldus
Keyword(s):  
Model Systems ◽  
Basis Set ◽  
Broken Symmetry ◽  
Basis Sets ◽  
Gaussian Basis Sets ◽  
Hartree Fock ◽  
Harmonic Confinement ◽  
Electron Correlation Effects ◽  
Doubly Charged

We study the effect of a confining potential on systems that exhibit Hartree-Fock (HF) instabilities, and thus admit broken symmetry (BS) HF solutions, by relying on the O2- and S2- doubly-charged anions as model systems. We find that with the increasing strength of the external harmonic confinement potential, W(r) = 1/2(ωr)2 (with 0.0 ≤ ω < 0.2), the BS solutions are systematically eliminated. We use extended, diffuse, doubly-augmented Gaussian basis sets up to and including d-aug-cc-pV6Z, and find that the number and the character of BS solutions exhibit significant basis set effects. These basis sets were further extended by additional ghost basis functions, located away from the atomic center. The role of the electron correlation effects for the BS HF solutions was examined by the CCSD(T) method. In addition to modelling the confinement by the harmonic-like potential W(r), we also examined a more realistic "confinement", realized by a grid of point charges modelling the crystal structure of MgO. Again, we find that the HF instabilities and the implied BS solutions disappear with the increasing magnitude of the model charges simulating the crystal environment. At the same time, the O2- anion is energetically stabilized with respect to both the O- anion and the neutral oxygen atom.

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