Madelung effects at crystal surfaces: Implications for photoemission

Abstract

An equation originally derived by Lennard-Jones and Dent for the estimation of Madelung potentials is utilized to study the properties of these potentials within the bulk and at the surfaces of crystals. It is clear from the equation that potentials at atomic sites only one lattice constant distant from the surface are, in general, indistinguishable from those in the bulk. The equation indicates also that Madelung sums in real space can be so organized as to make them more tractable computationally than they are usually considered to be. Madelung potentials for atomic sites at and near surfaces are obtained for NaCl(100), NaCl(110), CsCl(110), zinc blende (110), wurtzite ($11\overline{2}0$), and rutile (001).