Electronic Specific Heat of Vanadium Chromium Hydride

Abstract

Electronic specific-heat coefficients $\ensuremath{\gamma}$ have been measured for five samples of the ${\mathrm{V}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}{\mathrm{H}}_{y}$ system. Results on two samples with $y=0$ agree with known values of $\ensuremath{\gamma}$ for ${\mathrm{V}}_{1\ensuremath{-}x}{\mathrm{Cr}}_{x}$ alloys. All hydride samples $y\ensuremath{\ne}0$ have a decrease in $\ensuremath{\gamma}$ compared to nonhydride samples. The plotted points for hydride and nonhydride samples fall very close to a single curve of $\ensuremath{\gamma}$ versus $\mathfrak{z}$, the electron per atom ratio, when $\mathfrak{z}$ is determined by $\mathfrak{z}=5(1\ensuremath{-}x)+6x+y$. Results indicate that the rigid-band model is useful in qualitative interpretation of the effects of hydriding transition metals. The fact that $\ensuremath{\gamma}$ 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.