HEAT-CAPACITIES BETWEEN 1.5 AND 16-K AND SUPERCONDUCTIVITY OF V-H AND NB-H ALLOYS

Molar heat capacities have been measured for VHn and NbHn with n up to 1.93 at temperatures between 1.5 and 16 K. The height of the peak in plots of the electronic specific heat, indicating superconductivity, diminishes with increasing hydrogen content in the α + β two-phase region, and can be taken as a measure of the fractional amount of α-phase present (lever-rule). In NbHn, accordingly, the two-phase region presumably extends up to n ≈ 0.9 at helium temperatures. No hydride phase, including VH2 and NbH2, showed superconductivity above 1.5 K. The measured γ-coefficients of the V/H-alloys agree with APW band-structure calculations for V metal in the range 5 ≤ ne, ≤ 7 of band electron concentration. They coincide with the γ-coefficients of V/Cr-alloys reported in the literature. Hence VHn represents another example of the shifting bands" concept developed recently for PdHn. © 1979."