Structural, electronic and magnetic properties of small gold clusters with a copper impurity

A set of all-electron scalar relativistic calculations on AunCu (n = 1–12) clusters has been performed using density functional theory with the generalized gradient approximation at PW91 level. The lowest energy geometries of AunCu clusters may be considered as assemblies of triangular Au3 moieties substituted with one Cu atom at the highest coordinated site. All these lowest energy geometries of the AunCu clusters are slightly distorted but retain the planar structures of the Aun+1 clusters due to the strong scalar relativistic effects. The Au–Cu bonds are stronger, and a few Au–Au bonds far from the Cu atom are weaker, than the corresponding Au–Au bonds in pure Aun+1 clusters. After doping with a Cu atom, the thermodynamic stability and chemical reactivity are enhanced to some extent. The odd-numbered AunCu clusters with even numbers of valence electrons are more stable than the neighboring even-numbered AunCu clusters with odd numbers of valence electrons. Odd–even alternations of magnetic moments and electronic configurations for the AunCu clusters can be observed clearly and may be understood in terms of the electron pairing effect.