Structure and stability of oxygen vacancies on sub-surface, terraces, and low-coordinated surface sites of MgO:: an ab initio study

Abstract

We have performed ab initio Hartree–Fock cluster model calculations on the electronic structure and properties of neutral and charged oxygen vacancies, the F color centers, at various sites of the MgO(001) surface. Sub-surface, surface, step, and corner sites have been considered. For each site we have determined the optimal structure, the relative stability of neutral versus charged vacancies, the formation energy, and, for the paramagnetic F + centers, the spin distribution as given by the isotropic hyperfine coupling constants of the unpaired electron with the surrounding Mg 2+ nuclear spin. The barrier for diffusion of oxygen ions in the presence of F 2+ centers has been estimated for the migration from the sub-surface to the surface, from a terrace site to another terrace site, and from a step to a terrace site.