Theoretical investigation on structural evolution, energetic stability trend and electronic properties of Au n Cd(n=1–12)

Abstract

We systematically studied the geometrical structures, relative stabilities, electronic properties and chemical hardness of Au n Cd (n =1–12) clusters based on the framework of the density functional theory using relativistic all-electron methods. Low-lying energy structures include two-dimensional and three-dimensional geometries. Especially, all the lowest-energy structures of Au n Cd (n =1 −12) clusters are inclined to be planar geometries with slight distortion, in which the dopant Cd atom has higher coordination at n =2–6, but lower coordination at n =7–12. The fragmentation energies, second-order difference of energies, the highest occupied–lowest unoccupied molecular orbital gaps and chemical hardness of Au n Cd and Au n+1 exhibit a pronounced even–odd alternations phenomenon in the reverse order This result indicates that the geometrical, electronic and chemical stabilities of Au n Cd with even number of valence electrons are higher than those of the neighbouring Au n Cd with odd number of valence electrons and corresponding Au n+1 with odd number of valence electrons. Additionally, 4d valence electrons orbital of impurity Cd atom in Au n Cd hardly joins in the orbital interactions compared with 5d valence electrons of corresponding Au atom in Au n+1. Au–Cd bonds of Au n Cd clusters are weaker and have more obviously ionic-like characteristics than the corresponding Au–Au bonds of Au n+1. The impurity Cd atom can change the chemical stability pattern of pure gold clusters, namely the even-numbered Au n Cd are less reactive than the corresponding Au n+1 and neighbouring odd-numbered Au n Cd.