ELECTRONIC-STRUCTURE OF RANDOM BINARY-ALLOYS BEYOND THE SINGLE-SITE APPROXIMATION

We study the influence of short-range order (SRO) and correlated scatt ering by pairs of atoms on the electronic structure of random binary a lloys. Our approach is based on the gamma expansion method (GEM) propo sed by Tokar, and implemented within a tight-binding linear-muffin-tin orbital (TB-LMTO) formulation of the (single-site) coherent potential approximation (SCPA) which approximately accounts for geometric relax ation. Results are presented for Ag0.87Al0.13, in which the SRO has re cently been measured, and Cu0.715Pd0.285 for which older data exist, a nd where lattice relaxation effects play an important role. In both ca ses we find that the density of states (DOS) of the system is only wea kly affected by the SRO. The applicability of the GEM to a first princ iples determination of the degree of SRO is briefly discussed.