Adsorption of transition-metal atoms on MgO(001) surfaces: Atomic structures, diffusion and electronic structures

The adsorption structures and diffusion of transition-metal (TM) adatoms on defect-free MgO(001) surfaces were investigated in this study by using ab initio electronic structure calculations based on the density functional theory. The preferential adsorption of TM on top of a surface oxygen atom was found, which coincides with the results of previous works. The surface diffusion occurred along the channel that passed through a hollow site and the energy barriers ranged from 0.12 to 0.83 eV. We also found that whereas Ni adatoms effectively switched on the spin polarization to reduce the diffusion barrier on the surface, all the other TM adatoms kept their spin state during the surface diffusion. Also examined were the electronic properties of the TM adatoms on MgO(001). We found that the energy levels of the TM adatoms in the gap region of MgO(001) depended on the adsorption sites and that the shapes of the electronic structures significantly varied with the adsorption sites.