Abinitio calculations on the Al2O3(0001) surface

Abstract

We calculate using a density functional pseudopotential method the atomic and electronic structure of the (0001) surface of α-alumina (Al₂O₃). The material is studied in the form of a slab with periodic boundary conditions, containing up to eight layers of the stoichiometric Al₂O₃ units. Five different terminations of the surface are calculated, representing different surface excesses of oxygen, and their free energies are estimated as a function of oxygen partial pressure. Internal relaxations of the atomic positions are obtained. The aluminium terminated surface, which is stoichiometric, has the lowest surface energy for a wide range of oxygen pressures.