The properties of isolated neutral O vacancies and divacancies of metal oxides of increasing complexity (MgO, CaO, α-Al2O3 and ZnO) were studied by means of density-functional theory within a super-cell periodic approach. Vacancy formation energies, vacancy-vacancy interactions, and geometry rearrangements around these point defects were investigated in detail. The characterization of the electronic structure of these point defects was established by analysis of the density of states and of the topology of the electron density and of electron localization function. It was found that the chemical character of the oxide determined the properties of the O vacancies. For covalent ZnO, a more complex scheme arose in which the relaxation around the O vacancy was much larger leading to the formation of Zn4-like almost metallic particles in the crystal. The relationship of these structures with the crystal shear planes was considered. The present study showed that super-cells containing approximately 200-300 atoms provided convergent values for the geometrical and electronic structure of O vacancies of these metal oxides in the point defect low concentration limit.

On the Convergence of Isolated Neutral Oxygen Vacancy and Divacancy Properties in Metal Oxides using Super-Cell Models. J.Carrasco, N.Lopez, F.Illas: Journal of Chemical Physics, 2005, 122[22], 224705