1,721,038 research outputs found
SEMIEMPIRICAL SELF-ENERGY CORRECTIONS TO LDA BANDS OF SEMICONDUCTORS, AND A SCALING LAW FOR THE SCISSOR OPERATOR
No full textA semiempirical approach to the evaluation of corrections to LDA electronic states and effective masses in semiconductors is described. Applications to GaAs, AlAs, Ge, Ga1-xAlxAs VCA alloys are presented, and a scaling law for the scissor operator is discussed
On the compressed-ion model of cohesion in alkali halides
No full textFirst-principle local-density calculations of the total energy of ions confined within a sphere were performed The results for positive alkali and negative halogen ions are used to test the validity of the compressed-ion model for the cohesion of alkali halides recently proposed by Narayan and Ramaseshan It was found that the model is not realistic since the calculated ionic compression energies are by far too large to account for the observed equilibrium lattice constants and bulk moduli of alkali halides
Density-functional perturbation theory for lattice dynamics with ultrasoft pseudopotentials
No full textWe generalize density-functional perturbation theory for lattice dynamics to Vanderbilt's ultrasoft pseudopotential scheme. This formulation accounts for the nonorthogonality of the orbitals, the augmentation of the electron density, and the dependence of the generalized orthogonality constraint on the atomic positions. Both insulating and metallic systems are considered. Application of the theory to the vibrations of small molecules (CO, CO2, CH4, and H2O) and to the phonon dispersion of the noble metals (Cu, Ag, Au) shows overall agreement with experiment. [SO163-1829(97)51742-5]
Influence of electronic relaxation on core and valence excited states of alkaline-earth atoms
No full textThe dependence on the hole quantum numbers of single-particle excited states of the alkaline-earth atoms Be, Mg, and Ca is studied within the Hartree-Fock frozen-core method. For a given orbital state of the outer electron, we find that the term values of all core excitations are nearly the same but they differ from that of the valence excitation. The similarity of the core Rydberg series is explained in terms of the electron-density relaxation. The first term of a Rydberg series is anomalous when the excited electron penetrates appreciably into the atomic core. Our findings are compatible with all available experimental data. The latter, however, are not accurate enough to confirm the predicted similarity among the core Rydberg series
Ab initio study of the dielectric properties of silicon and gallium arsenide using polarized Wannier functions
No full textWe present a first-principles calculation of the electronic properties of crystalline silicon and gallium arsenide in a uniform electric field. Polarized Wannier-like functions which are confined in a finite region are obtained by minimizing a total-energy functional which depends explicitly on the macroscopic polarization of the solid. The polarization charge density and the electronic dielectric constant are computed via finite differences. The results coincide with those of the linear response approach in the Limit of vanishing electric field and infinite localization region. [S0163-1829(98)50340-2]
Ryderberg series of valence and core excited rare-gas atoms- effects of electron relaxtion
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