A structural jellium model of cluster electronic structure

Abstract

A structural jellium model has been developed which accounts for the electronic structures of clusters using a crystal-field perturbation. Although it is related to previous models proposed by Knight et al., this model allows predictions to be made concerning the gross stuctural features of metal clusters; something the original jellium model is incapable of doing. The zero-order potential we derive is of central-field form, depends on the geometry of the cluster, and has a general form that can produce an energy-level ordering similar to that of Knight's rounded well, but can also accommodate other orderings. In particular, qualitative arguments suggest that this potential produces different energy level orderings for clusters with a nucleus with large positive charge at the centre of the cluster, enabling the spherical jellium model to be applied to alkali metal clusters seeded with magnesium and zinc. Analysis of the effects of the non-spherical perturbation on the spherical jellium shell structures leads to the conclusion that for a cluster with a closed-shell electronic structure a high symmetry arrangement which is approximately or precisely close packed will be preferred and provides a basis for rationalising those structures, which have been predicted using ab initio calculations, of clusters with incomplete shell electronic configurations.