Electronic states in amorphous metals: comparison of effective medium theories with 'exact' calculations

The authors have investigated the electronic structure of an amorphous metal within a s band tight-binding framework. Their investigations were based on a number of effective medium theories proposed in recent years. These theories purport to describe the electronic structure of systems with short-range order. The aim of these investigations was to compare the theories with an 'exact' calculation performed recently by Fujiwara and Tanabe (1979) on the same model. They establish that the effective medium approximation (EMA) proposed by Roth (1974) provides the most satisfactory description of the electronic structure. Useful insight into the applicability and range of validity of the various theories for the three-dimensional case is obtained.