Tight-binding coherent-potential-approximation study of the electronic states of palladium-noble-metal alloys

Calculations of the electronic states of Pd--noble-metal disordered alloys were performed using an improved version of the tight-binding coherent-potential-approximation (TB-CPA) formalism. The results for Pd--Ag are in excellent agreement with both experiment and the Korringa--Kohn--Rostoker (KKR) CPA. For Pd--Au, good agreement was obtained with specific-heat measurements. For Pd--Cu, probably due to charge-transfer effects, satisfactory agreement was not obtained with experiment at the Cu-rich end. The calculations indicate that if (a) highly accurate Slater--Koster parameters are used and (b) all the orbitals are included in the CPA conditions (i.e. not using a one-level TB model), the TB-CPA gives results that are equivalent to those of the KKR-CPA, except in cases where off-diagonal disorder might be important. 17 ref.--AA