Abstract. The random-phase model (RPM) due to Mott (1967) and Cohen (1970), which is expected to be valid for a strongly disordered metallic system, is extended to derive an expression of the electrical conductivity for a case with off-diagonal or bond-type disorder where transfer integrals and hence current matrix elements (in the site representation) are random variables. The RPM expression of the electrical conductivity for such a system is not written simply in terms only of the density of states, in contrast to the Mott-Hindley-Friedman formula for the case with only diagonal disorder. Some simple model systems with the bond-type disorder are studied numerically by applying the RPM formula derived here.

Print publication: Issue 7 (14 April 1978)