Ab initio study of Mg adatom and MgO molecule adsorption and diffusion on the MgO (0 0 1) surface

First-principles calculations based on the density functional theory of the adsorption and migration energies of Mg atom and MgO molecule on a flat MgO (0 0 1) surface are reported and discussed. The isolated neutral Mg adatom binds quite loosely to the surface (Eads≃0.46 eV) and has to overcome a barrier of about 0.30 eV in between two stable O adsorption sites. The MgO molecule forms iono-covalent bonds with the surface, with an adsorption energy of 2.5±0.1 eV. At variance with the isolated Mg adatom, the surface diffusion of the MgO molecule may imply a sequence of elementary rotation step around its ends. The computed barriers for molecule, 90° rotation around its O and Mg atoms are 0.35 and 0.46 eV, respectively.