Charged and neutral O vacancies in the bulk and on perfect and defective surfaces of MgO were characterized as quantum-mechanical sub-systems chemically bonded to the host lattice and containing most of the charge left by the removed oxygen atoms. Attractors of the electron density appeared inside the vacancy, a necessary condition for the existence of a subsystem according to the atoms in molecules theory. The analysis of the electron localization function also showed attractors at the vacancy sites, which were associated to a localization basin shared with the valence domain of the nearest O atoms. This polyatomic super-anion exhibited chemical trends guided by the formal charge and the coordination of the vacancy. The topological approach was shown to be essential to understand and predict the nature and chemical reactivity of these objects. There was not a vacancy but a coreless pseudo-anion that behaved as an activated host O.

Rigorous Characterization of Oxygen Vacancies in Ionic Oxides. P.Mori-Sánchez, J.M.Recio, B.Silvi, C.Sousa, A.M.Pendás, V.Luaña, F.Illas: Physical Review B, 2002, 66[7], 075103 (6pp)