Accession Number : AD0657433

Title :   THE COVALENT BOND IN CRYSTALS. II. PARTIALLY IONIC BINDING,

Corporate Author : CHICAGO UNIV ILL

Personal Author(s) : Phillips,J. C.

Report Date : 1967

Pagination or Media Count : 38

Abstract : The general theory of covalent bonding developed in AD-657 432 is extended to heteropolar crystals. In diatomic crystals the theory depends on two parameters, an energy gap for each atom, or an energy gap for the medium and a polarizability parameter eta. The latter can be determined by comparison with empirical pseudopotential form factors; the value obtained for GaAs and ZnSe which brings the form factors of the latter into agreement with the ion core form factors of Animalu and Heine, is eta = -0.05 + 0.05 or - 0.05. This polarizability parameter can be used to estimate the effective charge ec* defined by Callen, which describes the splitting of longitudinal and transverse optic modes of vibration at q = 0. The result in GaAs is ec*/e = 0.14 + 0.04 or - 0.04, in rough agreement with the experimental value of 0.20 + 0.03 or - 0.03. The experimental values for ec* may be used to estimate the gap parameters for each atom when complete data are available. (Author)

Descriptors :   (*CRYSTALS, *CHEMICAL BONDS), (*SEMICONDUCTORS, CHEMICAL BONDS), CRYSTAL STRUCTURE, THEORY, BAND THEORY OF SOLIDS, GALLIUM ARSENIDES, ZINC COMPOUNDS, SELENIDES, POLARIZATION, CRYSTAL LATTICES, ELECTROSTATICS

Subject Categories : Physical Chemistry
      Crystallography
      Solid State Physics

Distribution Statement : APPROVED FOR PUBLIC RELEASE