A study of bimetallic Cu–Ag, Au–Ag and Pd–Ag clusters adsorbed on a double-vacancy-defected MgO(100) terrace

Abstract

Binary M₂Ag₆, M₂Ag₇, M₁Ag₇ and M₁Ag₈clusters (M = Cu, Au, Pd) adsorbed on an MgO(100) terrace presenting a double vacancy (DV) neutral defect are investigated through a combination of density-functional (DF) biased searches and global optimizations. Alloying allows one to probe the adsorption characteristics of the DV-defected surface. It is found that Au₁Ag₇ and Au₂Ag₆ are core-shell magic clusters, in analogy with the pure silver case. The magic character is reduced for Cu₁Ag₇ and Cu₂Ag₆, because the shortening of Cu–Ag distances is counteracted by a double-frustration effect due to the DV, and is practically absent for Pd₁Ag₇ and Pd₂Ag₆, because the requirements of the metallic bond conduction electron count are in conflict with the metal–surface interaction. However, fluxionality is enhanced for Pd–Ag clusters with respect to the pure silver case, which could influence their catalytic properties.