Transition metals supported on oxides: density functional cluster studies of palladium deposition on MgO(001)

The interaction of isolated Pd atoms and of a square Pd-4 cluster with the (001) surface of MgO is investigated by means of density functional (DF) ca lculations. The oxide surface is represented by various model clusters and the effect of the surrounding is taken into account by embedding the cluste r in point charges and total ion model potentials. The calculations are per formed at the relativistic level using the Becke-Perdew exchange-correlatio n functional. The adsorption properties determined with this computational scheme are compared with other DF results. The bonding of the Pd atoms and clusters with the surface is analyzed in terms of charge density difference plots. It is found that the polarization of the metal adsorbate due to the surface electric field provides an important contribution to the metal-oxi de adhesion energy.