Multiple scattering by non-muffin-tin potentials: general formulation

Multiple scattering theory (MST) is developed for arbitrary local potentials. The resulting method is exact and differs from the usual muffin-tin formalism only in requiring an improved treatment of single centre scattering; propagation between scattering events is described by the same free-particle Green function (structure constants) which arises in the muffin-tin formalism. Detailed numerical tests are presented which demonstrate the effectiveness of the method for a model of crystalline silicon for which exact numerical solutions are available. The results indicate that earlier approximate generalizations of the theory, while helpful, remove only about 2/3 of the error introduced by the muffin-tin approximation.