Structure and shape variations in intermediate-size copper clusters

摘要

Using extensive,unbiased searches based on density-functional theory,we explore the structural evolution of Cu_n clusters over the size range n = 8-20.For n = 8-16,the optimal structures are plateletlike,consisting of two layers,with the atoms in each layer forming a trigonal bonding network similar to that found in smaller,planar clusters (n <= 6).For n=17 and beyond,there is a transition to compact structures containing an icosahedral 13-atom core.The calculated ground-state structures are significantly different from those predicted earlier in studies based on empirical and semiempirical potentials.The evolution of the structure and shape of the preferred configuration of Cu_n,n <= 20,is shown to be nearly identical to that found for Na clusters,indicating a shell-model-type behavior in this size range.