Applicability of the coherent-potential approximation in the theory of random alloys

The applicability of the coherent-potential approximation (CPA) for the description of electronic properties of completely random alloys is investigated. This is done by calculating the density of states and the total energy for different systems and by comparing the results with those obtained for large supercells consisting of up to 320 atoms in the framework of the order-N locally self-consistent Green's function method. Thereby it is found that in the framework of the CPA one obtains a reliable description of the electronic structure of random alloys. The total energy of a completely disordered alloy can also be reliably estimated provided an appropriate account is given for the electrostatic contribution to the one-electron potential and energy. Therefore, we conclude that the CPA can be safely applied to study the influence of disorder on various properties of metallic alloys for which the muffin-tin or atomic sphere approximation is sufficient and the chemical contribution to the total energy dominates.