Self-compressed inhomogeneous stabilized jellium model and surface relaxation of simple metal thin films

Abstract

The interlayer spacing near the surface of a crystal is different from that of the bulk. As a result, the value of the ionic density in the normal direction and near to the surface shows some variation from the bulk value, which is oscillatory in shape. To describe this behavior simply, we have formulated the self-compressed inhomogeneous stabilized jellium model and have applied it to simple metal thin films. In this model, for a ν-layered slab, each ionic layer is replaced by a jellium slice of constant density. The equilibrium densities of the slices are determined by minimizing the total energy per electron of the slab with respect to the slice densities. However, to avoid the complications that arise because of the increasing number of independent slice-density parameters for large-ν slabs, we consider a simplified version of the model that consists of only three jellium slices: one inner bulk slice with density [Formula: see text] and two similar surface slices, each of density [Formula: see text]. In this simplified model, each slice may contain more than one ionic layer. Application of this model to ν-layered slabs (3 ≤ ν ≤ 10) of Al, Na, and Cs shows that, in the equilibrium state, [Formula: see text] differs from [Formula: see text]. The difference is significant in the Al case, and the slab is more stable than that predicted by the homogeneous model with only one density parameter for the whole jellium background. In addition, we have calculated the overall relaxations, the work functions, and the surface energies and compared them with the results of earlier works.