Configuration-averaged Green’s function within the Korringa-Kohn-Rostoker cluster coherent-potential approximation

We derive an exact expression for the configuration-averaged Green's function within the Korringa-Kohn-Rostoker cluster coherent-potential approximation for a general cluster size. In an earlier publication [Phys. Rev. B 42, 9391 (1990)], the expression for the configuration-averaged Green's function was derived using the restricted-averaging method. Using these two expressions, we have calculated the density of states for a one-dimensional muffin-tin alloy, which shows a very small difference between the results of the two methods; the gross features remain the same, except for the height of some of the peaks. However, for the dilute alloy, there is a qualitative difference between the two results in the impurity band.