Density functional study of structural and electronic properties of small binary Be(n)Cu(m) (n + m = 2~7) clusters.

The geometrical structures, electronic properties and relative stabilities of small bimetallic Be n Cu m (n + m = 2-7) clusters have been systematically investigated by using a density functional method at the B3PW91 level. In the most stable structures of Be n Cu m , the Be atoms tend to gather together and construct similar configurations to those of pure Be n clusters. Meanwhile, there is a tendency for Cu atoms to segregate toward the Be n cluster surface. The successive binding energies, cohesive energies, second difference of energies, the highest occupied-lowest unoccupied molecular orbital energy gaps and chemical hardness of Be n Cu m are also investigated. All of them demonstrate that the clusters with even number of copper atoms present relatively higher stabilities. The natural population analyses on the Be n Cu m clusters reveal that, the charge transfers from Be to Cu when the average coordination numbers (Nc) of Be atom is less than 3, whereas the charge-transferring direction reverses when Nc(Be) increases.