Electronic structure of Nb-Mo alloys

Thermoreflectance measurements on Nb/sub x/Mo/sub 1hyphenx/ alloys (x=0.2, 0.5, 0.8) have been carried out in the 0.5--5.0 eV energy region. Augmented-plane-wave (APW) calculations for Nb at two different lattice parameters and for Mo, as well as coherent-potential-approximation calculations (CPA), have been carried out and have been used in the interpretation of the experimental results. Several optical transitions (..sigma../sub 1/(E/sub F/) ..-->.. ..sigma../sub 3/, G/sub 4/(E/sub F/) ..-->.. G/sub 1/, N/sub 2/ ..-->.. N'/sub 1/), have been identified, and their concentration dependence followed. These results contribute significantly toward putting the interpretation of the optical properties of Nb, Mo, and their alloys on a much more secure footing. In particular, it has been confirmed that while the lower conduction bands behave roughly as predicted by the rigid-band model, the higher-lying conduction bands show distinctly non-rigid-band-like behavior.