Heat Capacity of Copper-Germanium Alloys below 4.2°K

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Abstract
Heat capacity measurements below 4.2°K have been made on a series of alloys in the primary phase of the copper-germanium system. When corrected for lattice expansion, the resulting change in the electronic specific heat for low electron/atom ratios is found to be the same as that for the copper-zinc system. In neither case is the variation consistent with that expected for a parabolic valence band, thereby lending support to the previously advanced hypothesis that the Fermi surface in copper departs appreciably from sphericity. Both systems exhibit the same variation of Debye temperature with electron concentration, when appropriate corrections are made for the differences in the atomic mass and volume of the two alloy series. This supports the idea that the variation of the elastic constants in these alloys is influenced principally by the proximity of the Fermi surface to the boundaries of the first Brillouin zone. The variation of elastic constants with solute concentration, as deduced from the present work, is compared with that obtained from ultrasonic pulse measurements at room temperature.

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