Application of the Korringa-Kohn-Rostoker cluster coherent-potential approximation to an s phase shift semicircular model

An s phase shift semicircular model of a random substitutional binary alloy has been used as a test case for studying the self-consistent Korringa-Kohn-Rostoker cluster coherent-potential approximation (KKR-CCPA). In addition to being computationally simpler, the model has the advantage that a corresponding model exists in the well known tight-binding framework. A one-to-one correspondence has been shown between the KKR-CCPA equations and the tight-binding CCPA equations. In the tight-binding framework, it has been shown that certain quantities, which were hitherto calculated approximately, can be obtained exactly by the partitioning technique. Results for density of states in the CCPA show rich structure in the impurity band, which arises due to correlated scattering from clusters of atoms.