Comparison between some properties of small clusters and the (1 1 1) surface of palladium: a density-functional approach

We report a density-functional study of some electronic properties as well as the adsorption energy of atomic hydrogen and atomic oxygen on small palladium clusters (n=3–13). Concerning the bare clusters, we report the ionization potential and the estimated corresponding work function for the metallic surface, as well as the cohesive energies and the mean Pd–Pd binding energy. The adsorption energies of H and O atoms are calculated, together with their influence on the work function and ionization potential. These theoretical results are compared with those from the literature; the calculated surface properties (work function, adsorption energy, geometrical conformation of the adsorbate), are in good agreement with available experimental data. On the other hand, cohesive energies of the clusters or Pd–Pd binding energies do not compare with available data for the bulk metal, showing that the cluster approach is not valid in this case.