Adsorption of Late Transition Metal Atoms on MgO/Mo(100) and MgO/Ag(100) Ultrathin Films: A Comparative DFT Study

The adsorption properties of Ni, Pd, Pt, Cu, Ag, and Au atoms on MgO ultrathin films deposited on Mo(100) or Ag(100) substrates are determined from first principle DFT calculations and compared with the corresponding adsorption characteristics on the bare MgO(100) surface. The three supports exhibit different behaviors. On MgO/Mo(100) thin films there is an electron transfer from the metal/oxide interface to all considered adatoms. In some cases, like for Pd, the charge transfer is small and the species remains atomic-like, while for other atoms like Cu, Ag, Au or Pt there is a net transfer of one electron with formation of full anions. This has dramatic consequences on the preferred adsorption sites, on the bond strength, and on the magnetic state of the adatoms: all these quantities are totally different from what is found for the same atoms on the bare MgO(100) surface. MgO/Ag(100) films have an intermediate behavior between that of MgO/Mo(100) thin films and of the MgO(100) surface: the charge transfer is found only for Au and, to a smaller extent, for Pt atoms. All other atoms considered keep essentially the same electronic structure and preferred adsorption site shown on MgO(100). The reasons for the different behavior are rationalized in terms of global properties of the metal/oxide interface, and in particular of its work function.