A new, simple ab initio pseudopotential for use in floating spherical Gaussian orbital calculations. 2. Some results for hydrocarbons

1977 ◽  
Vol 99 (13) ◽  
pp. 4276-4278 ◽  
Author(s):  
S. Topiol ◽  
A. A. Frost ◽  
J. W. Moskowitz ◽  
M. A. Ratner
Keyword(s):  
Ab Initio ◽  
Gaussian Orbital

An ‘ ab initio ’ Gaussian orbital calculation of the (100) surface of crystalline lithium hydride

1972 ◽  
Vol 331 (1586) ◽  
pp. 347-359 ◽  
Keyword(s):  
Ab Initio ◽  
Lithium Hydride ◽  
Lithium Ions ◽  
Infinite Crystal ◽  
Gaussian Orbitals ◽  
Similar Computation ◽  
Alkali Halide Crystals ◽  
Hydride Ions ◽  
Semi Empirical ◽  
Gaussian Orbital

An ab initio computation has been performed for the (100) face of a lithium hydride ionic crystal. The computation follows a similar computation performed earlier for an infinite crystal of lithium hydride. A simple wavefunction of a type proposed by A. A. Frost was used in which pairs of electrons are assigned to orbitals described by simple spherical Gaussian functions, the positions and sizes of which are allowed to float to minimize the energy. In the surface computation the nuclei and the Gaussian orbitals in the ultimate and penultimate layers were allowed to float freely, those in the remaining layers being disposed as in the infinite crystal. It was found that, in the surface layer, the hydrogen nuclei were farther from the fixed (third) layer than the lithium nuclei. Also, while the orbitals of the lithium ions remained centred at the same place as the nuclei, corresponding to zero polarization of the lithium ions, the hydride ions showed considerable polarization, the centres of the orbitals being displaced considerably from the nuclei. The changes in the penultimate layer are also discussed. An estimate was made of the surface energy for this face of lithium hydride and the value found was reasonable when compared with semi-empirical values for the (100) surfaces of alkali halide crystals.

Structure of 6H–SiC(0001) Surfaces from AB-Initio Calculations

1998 ◽  
Vol 05 (01) ◽  
pp. 199-205 ◽  
Author(s):  
M. Sabisch ◽  
P. Krüger ◽  
A. Mazur ◽  
J. Pollmann
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Local Density ◽  
Substrate Surface ◽  
Basis Sets ◽  
Smooth Norm ◽  
Optimal Surface ◽  
Substrate Surfaces ◽  
Gaussian Orbital ◽  
Good Agreement

We report the results of ab-initio calculations of structural properties of hexagonal 6H–SiC(0001) surfaces. The calculations have been carried out self-consistently within local density approximation employing supercell geometries, smooth norm-conserving pseudopotentials in separable form and Gaussian orbital basis sets. We have investigated several structural models for adatom-induced [Formula: see text] reconstructions with adsorbed Si or C adatoms or trimers residing in threefold-symmetric T 4 or H 3 positions above Si- or C-terminated substrate surfaces, respectively. In the case of the Si-terminated substrate surface our results favor Si adatoms in T 4 sites as optimal configuration in very good agreement with experimental data. For the C-terminated substrate surface our results indicate that none of the investigated [Formula: see text] adatom or trimer configurations is the optimal surface structure.

Ab initio band theory approach to electron energy loss near edge structures

1988 ◽  
Vol 46 ◽  
pp. 506-507
Author(s):  
Xudong Weng ◽  
O.F. Sankey ◽  
Peter Rez
Keyword(s):  
Ab Initio ◽  
Local Density ◽  
Interpolation Method ◽  
Atomic Orbital ◽  
Plane Waves ◽  
Large Set ◽  
Theory Approach ◽  
Band Theory ◽  
Atomic Orbitals ◽  
Pseudopotential Calculations

Single electron band structure techniques have been applied successfully to the interpretation of the near edge structures of metals and other materials. Among various band theories, the linear combination of atomic orbital (LCAO) method is especially simple and interpretable. The commonly used empirical LCAO method is mainly an interpolation method, where the energies and wave functions of atomic orbitals are adjusted in order to fit experimental or more accurately determined electron states. To achieve better accuracy, the size of calculation has to be expanded, for example, to include excited states and more-distant-neighboring atoms. This tends to sacrifice the simplicity and interpretability of the method.In this paper. we adopt an ab initio scheme which incorporates the conceptual advantage of the LCAO method with the accuracy of ab initio pseudopotential calculations. The so called pscudo-atomic-orbitals (PAO's), computed from a free atom within the local-density approximation and the pseudopotential approximation, are used as the basis of expansion, replacing the usually very large set of plane waves in the conventional pseudopotential method. These PAO's however, do not consist of a rigorously complete set of orthonormal states.

An ab initio study of Se-reacted GaAs(0 0 1) surfaces

1998 ◽  
Vol 184-185 (1-2) ◽  
pp. 80-84 ◽  
Author(s):  
W Faschinger
Keyword(s):  
Ab Initio ◽  
Ab Initio Study
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