The O-deficient (100) surface was studied by means of total-energy calculations, within the density functional theory. Selected surface configurations were considered, which presented increasing densities of neutral O vacancies; ranging from 12.5 to 100%. The missing O was periodically distributed, in the surface layer, either homogeneously or in a close-packed fashion. It was shown that the electronic structure was characterized by occupied states in the gap which resulted either from hybridization of atomic-like orbitals that were localized on vacancy sites, or which involved surface Mg orbitals. The latter case occurred at high vacancy concentrations, and the conditions for the appearance of metallicity in the surface layer were derived. The formation energy of O vacancies was calculated as a function of the vacancy concentration and the particular configuration. A 2-body model potential was proposed in order to account for their interaction. The activation energy for vacancy diffusion at the surface was also calculated, and provided a complete set of parameters for describing the thermodynamics as well as the kinetics of O vacancies on a MgO(100) surface.

Interaction between Oxygen Vacancies on MgO(100). F.Finocchi, J.Goniakowski, C.Noguera: Physical Review B, 1999, 59[7], 5178-88