New formulation of the coherent potential approximation for the electrical conductivity of random binary alloys

Abstract

The coherent potential approximation for the electrical conductivity of disordered binary alloys is formulated on the basis of the quantum kinetic equations. The configuration average is denoted by a projection operator. The qualitative properties in the coherent potential approximation for the average density operator ( rho (z)) are examined and compared with those of its exact counterpart. Finally, for the case of a general one-band model of a random binary alloy, the DC electrical conductivity tensor is calculated. This new formulation constitutes a generalisation of a method used for the study of equilibrium properties of random binary alloys without additional assumptions, in contrast to Velicky's work where an additional decoupling approximation is assumed in generalising the CPA idea for the equilibrium properties to that of the transport properties. Furthermore, the new formulation has already been shown to be capable of accommodating the average t-matrix approximation (ATA) scheme.