Electronic structure calculations on alloys using the polymorphous coherent-potential approximation

We present self-consistent calculations of the electronic density of states of disordered copper-palladium and silver-palladium alloys using the polymorphous coherent-potential approximation and the Korringa-Kohn-Rostoker coherent-potential approximation. We find that the agreement between the theoretical partial density of states of palladium $d$ bands in copper-rich copper-palladium alloys and experiment is significantly improved when the polymorphous coherent-potential approximation is used. The densities of states of silver-palladium alloys calculated with the two versions of the coherent-potential approximation are identical and agree with experiment. This indicates that the improved treatment of Coulomb effects in the polymorphous coherent-potential approximation is necessary only for alloys such as copper palladium that have considerable charge transfer.