Multiple-scattering approach to the electronic structure of amorphous and liquid metals

We demonstrate that the abstract multiple-scattering approach which has been used to derive Roth's effective-medium approximation (EMA) can be extended to the derivation of other proposed single-site theories such as the Schwartz-Ehrenreich, the Gyorffy-Korringa-Mills, the Ishida-Yonezawa theories, etc. The derivation of these theories involves assuming an integral-equation form for the scattering path operator. We shall also demonstrate that the EMA is the only single-site theory completely consistent with this assumption.