First-principles methods were used to study the vacancy formation energy and its variation with depth, the energetics of the interaction of 2 point defects or of adsorbed O atom and vacancy, as well as substitutional O adsorption at the (111) surface. The stability of various configurations of vacancies and O atoms was examined. The vacancy formation energy decreased with the depth of the vacancy. Vacancies in sub-surface layers increased the binding of O adatoms in on-surface hollow sites. The surface and sub-surface substitutional sites appeared to be unstable to O adsorption, and were not stabilized by simultaneous on-surface adsorption.

Vacancy Formation and O Adsorption at the Al(111) Surface. A.Kiejna: Physical Review B, 2003, 68[23], 235405 (6pp)