Electronic Specific Heat of Vanadium Chromium Hydride

Electronic specific-heat coefficients $\gamma$ have been measured for five samples of the ${\mathrm{V}}_{1-x}{\mathrm{Cr}}_x{\mathrm{H}}_y$ system. Results on two samples with $y=0\mathrm{}$ agree with known values of $\gamma$ for ${\mathrm{V}}_{1-x}{\mathrm{Cr}}_x$ alloys. All hydride samples $y\ne 0$ have a decrease in $\gamma$ compared to nonhydride samples. The plotted points for hydride and nonhydride samples fall very close to a single curve of $\gamma$ versus $\mathfrak{z}$, the electron per atom ratio, when $\mathfrak{z}$ is determined by $\mathfrak{z}=5\mathrm{}(1-x)+6x+y$. Results indicate that the rigid-band model is useful in qualitative interpretation of the effects of hydriding transition metals. The fact that $\gamma$ depends upon $\mathfrak{z}$ and not upon relative amounts of Cr or H supports the concept that the hydrogen atom contributes its electron to the host-metal conduction band.