A density functional study on the AunAg (n = 1–12) alloy clusters

• The AunAg clusters are generated by substituting Ag atom for one Au atom.
• The chemical reactivity can be enhanced to some extent after doping Ag atom.
• The odd-numbered AunAg cluster is relatively more stable.
• The influence of impurity Ag is mainly determined by the Ag5s electrons.

An all-electron scalar relativistic calculation on AunAg (n = 1–12) clusters has been performed by using density functional theory with the generalized gradient approximation at PW91 level. The lowest energy geometries of AunAg clusters are distorted slightly and still keep the planar structures due to the strong scalar relativistic effect in gold cluster. They may be generated by substituting Ag atom for one gold atom of the Aun+1 cluster at the relatively lower coordinated site. All these substitution sites are at the edge of plane and believed to be the reactive site for substitution and adsorption. Compared with corresponding Au–Au bond in pure Aun+1 clusters, the Au–Ag bonds and most Au–Au bonds near Ag atom are weakened, and only a few Au–Au bonds far from Ag atom are strengthened slightly. The chemical reactivity can be enhanced to some extent after doping Ag atom. The odd-numbered AunAg cluster is relatively more stable than the neighboring even-numbered AunAg cluster. The influence of impurity Ag is mainly determined by the half-filled bands of nearly free Ag5s electrons. The odd–even alterations of magnetic moments and electronic configurations for AunAg clusters can be observed clearly and may be simply understood in terms of the electron pairing effect.