Lattice Defects in Zincblende Part I. Phenomenological Expressions of Interionic Potentials

Abstract

As the basis of the calculation on formation energies of lattice defects, phenomenological expressions of interionic potentials are derived. In zincblende crystal which is partly ionic and partly covalent, the effective charge on the constituent ions is reduced to a certain amount Ze (Z=1.66, e: magnitude of the electronic charge), whereas covalent attraction between two ions adjacent to each other is generated, which is assumed to be exponential form −b_cexp (−r⁄ρc) such as the usual expression of exchange repulsion. As a preliminary calculation to Part II, the lattice energy variation when one anion or cation is displaced from its regular position in a perfect crystal is calculated on taking account of the Madelung, Van der Waals, exchange repulsion, covalency attraction energies and the polarization energies of the displaced ion and all other surrounding ions. All the physical constants already known in references and derived in our calculation are tabulated in Table III.