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

Abstract

Adsorption of ${\mathrm{Au}}_N$ 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 $\mathrm{Mg}\mathrm{O}∕\mathrm{Mo}$ turn into singly charged cluster anions ${\mathrm{Au}}_N^{\delta }$, $\delta \approx -1$. Their structures and internal charging patterns are analogous to singly charged, planar, gas-phase cluster anions ${\mathrm{Au}}_N^{-}$. 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.