Structure of amorphous Fe80-P13-C7 alloy by X-ray diffraction

In the frame of a semiclassical picture a systematic approximation scheme for the hopping-conductivity is derived which provides a classification in terms of the length of correlated hopping-chains. With the aid of an integral equation for the propagation probability of carriers and a decoupling procedure for configuration averages, conductivity is expressed by the zeroth and second moments of independently averaged contributions of paths containing less than a fixed number of hops. A sum rule allows to carry out the static limit explicitly. The lowest order conductivity reduces to a simple form which is presented for later evaluations.