EARLY OXIDATION STAGES OF MG(0001) - A DENSITY-FUNCTIONAL STUDY

We determine the geometry of the ground state and of several low energ y metastable configurations of oxygen adsorbed on Mg(0001) for coverag e 1/16 less than or equal to Theta less than or equal to 1. In agreeme nt with experiments, we find that oxygen is adsorbed below the Mg surf ace, forming ionic islands commensurate with the metal lattice. Molecu lar dynamics simulations show how O-2/Mg(0001) spontaneously dissociat es and incorporates below the Mg top layer. The collision and the prog ression towards the most stable configuration involve complex, many-at om processes.