Adsorption of Pd atoms and Pd₄ clusters on the MgO(001) surface: A density functional study

We performed gradient-corrected density functional calculations on the adsorption of Pd atoms and Pd₄ clusters on the MgO(001) surface. The surface was represented by clusters embedded in point charge arrays and total ion model potentials. Pd atoms adsorb on top of the O ions with a binding energy of 0.9 ± 0.1 eV and a distance of 2.2 Å. A Pd₄ square cluster is almost perfectly accommodated to the MgO substrate, suggesting a preference for pseudomorphic growth of large Pd particles. Pd-Pd distances are substantially elongated compared to the bulk metal, in agreement with observations on small supported Pd clusters.