Simulation of Isovalent Impurities in Magnesium Oxide Using Hartree-Fock Clusters

Abstract

An unrestricted Hartree-Fock (UHF) approach has been developed by Kunz and his coworkers^1,2,3 to study the optical excitation properties of atomic, molecular, and solid-state systems and the results have been sufficiently satisfactory⁴. In the present study, three computational models are used to simulate the sulphur-doped magnesium oxide (MgO). The first model is the seven-ion cluster (S-6Mg): one sulphur ion at the center with six nearest magnesium ions. The second one is the same cluster plus some surrounding ions considered as point charges at the sites of the nuclei. The third is the one used in “Ionic Crystal with Electronic Cluster, Automatic Program” (ICECAP)⁵. In this model, the (S-6Mg) cluster is embedded in a shell-model lattice. The ions in this lattice are taken as dipole polarizable point charges coupled harmonically to uniformly charged massless spherical shells. The interactions among the ions are in terms of the Coulomb and short-range potentials. In fact, ICECAP is developed especially for determining the defect properties of crystalline materials arising from excess electrons, holes, or impurities in the crystal. A detailed description of this program package will be given by A.B. Kunz at this conference.