Early oxidation stages of Mg(0001): A density functional study

We determine the geometry of the ground state and of several low energy metastable configurations of oxygen adsorbed on Mg(0001) for coverage 1/16 less than or equal to Theta less than or equal to 1. In agreement with experiments, we find that oxygen is adsorbed below the Mg surface, forming ionic islands commensurate with the metal lattice. Molecular dynamics simulations show how O-2/Mg(0001) spontaneously dissociates and incorporates below the Mg top layer. The collision and the progression towards the most stable configuration involve complex, many-atom processes.