Effects of surface charge on the electrostatic energy of an ionic crystal

Abstract
An earlier paper discussed the influence of the shape of a macroscopic piece of ionic crystal on the electrostatic energy of the whole piece of crystal. Some of the considerations of that paper are extended to include the effects on the bulk term in the energy of distributing excess charge on the surface of the piece of crystal. The bulk term in the electrostatic energy of the piece of crystal plus surface charges depends on the shape of the piece and the surface charge density. The minimum of this bulk term with respect to surface charge density occurs at a well defined surface charge density and is the usual (shape-independent) Madelung crystal energy.