Work functions at facet edges.

We perform ab initio pseudopotential calculations for metal crystals with finite facets of different crystallographic orientation to investigate the work function profile near crystal edges. We examine local edge effects, and address the problem of the coexistence of different face-dependent local work functions at crystal edges. By modeling the electronic dipoles at the metal surface, we show how nonvanishing surface charges spontaneously appear on metals with inequivalent facets. Our studies of Al crystal nanowires with (100) and (111) facets are extended to derive the dependence of the work function on the crystal morphology in the macroscopic limit.