Adsorption of gold clusters on metal-supported MgO:: Correlation to electron affinity of gold

Adsorption of Au-N clusters (N=1-6) on a bulk MgO(001) surface and on an ultrathin (3 ML) MgO(001) film supported by Mo metal is investigated via density-functional theory calculations. Comparison of the two substrates unambiguously shows that the gold clusters adsorbed on MgO/Mo turn into singly charged cluster anions Au-N(delta), delta approximate to-1. Their structures and internal charging patterns are analogous to singly charged, planar, gas-phase cluster anions Au-N(-). The adsorption energy has prominent size-dependent odd-even oscillations, correlating fully with the known electron affinity of gas-phase Au clusters in this size range.