Adsorption of atomic oxygen on the MgO(100) surface

Ab initio calculations based on density functional theory and the pseudopotential method have been used to investigate the adsorption of neutral oxygen atoms on terraces and steps on the MgO (100) surface. The calculations include spin polarisation and gradient corrections, and are performed on periodically repeated systems large enough for the adsorbed atoms and the steps to be regarded as isolated. Full relaxation of all ions to equilibrium is included. Substantial binding energies of up to 2.0 eV for adsorption on terrace sites and of over 2.5 eV at step sites are found. An estimate is also reported for the energy barrier involved in migration of adsorbed oxygen across the (100) terrace. The relevance of our findings to an understanding of oxygen exchange between gas and crystal is discussed.