Surface Energies of Smalln Metal Clusters

Abstract

Publisher Summary The research of clusters is closely related to surface physics. As clusters have a high surface-to-volume ratio such clusters may be viewed as three-dimensional surfaces. For this reason, investigations on clusters are of current interest. In the present chapter, the cohesive properties of small sodium and copper clusters are discussed on the base of LCAO–LDA calculations. The chapter represents the binding energy (EB) in terms of orbital energies in the cluster, orbital energies in the isolated atoms, and occupation numbers of the orbitals. This rough estimation of binding energy provides reasonable results in comparison with experimental and other theoretical data. The chapter explains that the binding energy per atom (EB/N) increases with increasing cluster size toward the bulk cohesive energy in the case of Cu N . The difference between the binding energy of a cluster and the energy of N atoms in the bulk phase can be used for definition of a surface tension for the cluster. The surface tensions calculated in this way are comparable with the corresponding surface tensions of bulk material. Especially for Cu N clusters σ tends downwards to the bulk surface tension with increasing cluster size. This is quite similar to the classical relation for size dependence of microparticles. This size dependence was confirmed excellently for argon clusters (H≤100). The results presented in the chapter show strong oscillations for N clusters, their source is the electronic shell filling effect in the case of Na N clusters.