Total-energy simulations of the energetics of the vacancy occupation of the γ-phase were made by using an empirical potential that permitted the ionic valence to vary according to the local environment, and included Coulombic electrostatic interactions among the anions and cations. The model predicted that, although the minimum enthalpy configuration had all of the Al vacancies of the spinel structure in octahedral sites, the energetic cost of a modest fraction of tetrahedral sites was small. The model was also used to explain differences, between previously reported simulations, in terms of their constraints on structural and charge relaxation.

Energetics of Aluminum Vacancies in Gamma Alumina. F.H.Streitz, J.W.Mintmire: Physical Review B, 1999, 60[2], 773-7