Electronic structure of substitutionally disordered metal alloys: Single-site approximation for canonicaldbands

The semirealistic theory of the electronic structure of substitutionally disordered transition-metal alloys, based on the Harrison scaling rules for the universal linear combination of atomic orbitals parametrization, is developed within the single-site approximation. The theory allows one to treat different band structures of the alloy species and naturally leads to the multiplicative off-diagonal randomness in the interatomic blocks of the Hamiltonian matrix. The central result is the novel expression for the full averaged Green’s function, which is then used for the evaluation of both the site-diagonal quantities (like the density of states) and the k→-dependent properties (like the Bloch spectral density). The theory is illustrated on the model of the canonical d bands applied to the alloys ${\mathrm{Cu}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Ni}}_{\mathrm{x}}$, ${\mathrm{Ag}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Pd}}_{\mathrm{x}}$ and ${\mathrm{Cu}}_{1\mathrm{-}\mathrm{x}}$ ${\mathrm{Pd}}_{\mathrm{x}}$. The results of numerical calculations agree reasonably with the recent Korringa-Kohn-Rostoker coherent-potential approximation data on these alloys.