Surface and size effects on the electronic states of small metallic clusters: a model calculation

Abstract

The authors compute exactly the eigenvalues of atomic clusters of arbitrary size with a simple cubic structure in the tight-binding approach (LCAO), including surface effects. To represent the electronic structure of the hypothetical metallic clusters they consider well separated and p states. They find strong deviations from the corresponding states of the bulk cubium where the number of particles is of the order of 104 or less (R<or approximately=50 AA): new states appear near the top of the bands and states disappear near the bottom of the bands. This produces an upward shift of the Fermi level and of the mean energy with decreasing size and an asymmetric and deformed shape of the density of states. Effects of the geometrical shape of the cluster and of the environment are also considered. They discuss the relevance of their results on the interpretation of recent photoemission experiments on small metallic clusters.