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 (001) surface were reported. The isolated neutral Mg adatom binds quite loosely to the surface, with an adsorption energy of about 0.46eV, and had to overcome a barrier of about 0.30eV between 2 stable O adsorption sites. The MgO molecule formed iono-covalent bonds with the surface, with an adsorption energy of 2.5eV. 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 were 0.35 and 0.46eV, respectively.
Ab Initio Study of Mg Adatom and MgO Molecule Adsorption and Diffusion on the MgO(001) Surface. G.Geneste, J.Morillo, F.Finocchi: Applied Surface Science, 2002, 188[1-2], 122-7