ELECTRONIC-STRUCTURE OF DISORDERED NB-MO ALLOYS STUDIED USING THE CHARGE-SELF-CONSISTENT KORRINGA-KOHN-ROSTOKER COHERENT-POTENTIAL APPROXIMATION

We present an all-electron fully charge-self-consistent Korringa-Kohn- Rostoker coherent potential approximation (KKR-CPA) study of the elect ronic structures of disordered bcc Nb1-xMox alloys over the entire com position range. Specific computations are reported for x = 0.0, 0.25, 0.50, 0.75, and 1.0. Extensive comparisons with the predictions of the Nb-based rigid-band model (RBM) and other theoretical results, as wel l as with the relevant experimental results insofar as they are availa ble are made. The particular issues that we focus on concern the evolu tion of the Fermi surface (FS), and the changes in the density of stat es and the superconducting transition temperature (T-c) of Nb with inc reasing Mo content. The N- and H-centred FS sheets of Nb are found to shrink essentially rigidly, but the Gamma-centred sheets evolve in a h ighly non-rigid-band manner. The x = 0.25 Mo alloy displays an especia lly large disorder-induced smearing of the Gamma-centred FS sheets. Di rect experimental information concerning the FS is available only for the N-centred sheet via positron annihilation and in this regard our r esults are in accord with the measurements. Concerning superconductivi ty, we have computed the Hopfield parameters eta(Nb) and eta(Mo) for t he Nb and Mo sites, and used the results to obtain T-c for Nb1-xMox vi a the McMillan formula. We find that this simple scheme describes the observed composition dependence of T-c in Nb1-xMox reasonably well.