Electronic structure of alloy surfaces: Coherent-potential approximation

The electronic structure of alloy surfaces is investigated within the framework of the coherent-potential approximation, a scheme originally derived for infinite alloy systems and here generalized to the case of the semi-infinite cleaved alloy crystal. The theory is applied to substitutional binary alloys, described by a single-band Wannier model one-electron Hamiltonian. Numerical results for the configurationally averaged surface density of states are discussed for a variety of system parameters. Among the cases considered are alloys of uniform composition and alloys in which the surface composition differs from that of the interior.