Theoretical Comparative Study of Oxygen Adsorption on Neutral and Anionic Agn and Aun Clusters (n=2-25)

Using density functional theory, we performed a theoretical comparative study of oxygen adsorption on neutral and anionic Ag-n and Au-n clusters in a large size range of n = 2-25. Ionization potentials (IPs) and electron affinities (EAs) of the pure clusters and the M-n(q)-O-2 binding energies E-bind(M-n(q)-O-2) in the (MnO2)(q) complexes (M = Ag, Au; q = 0, -1) were determined. Three density fiinctionals, namely, BP86, revPBE, and B3LYP, were used in the calculations, among which the BP86 functional gave the best results for IPs and EAs, while B3LYP gave the best results for Ebind(M-n(q)-O-2) A number of differences between the silver and gold dusters and their reactivities toward O-2 adsorption are accounted for by the calculations. One interesting result is that the calculated Au-n(-)-O-2 binding energies are in good, quantitative agreement with the measured relative reactivities of the Au-n(-) cluster anions toward O-2 adsorption.