Comparison of the single-crystal elastic constants of Th and a ThC0.063 alloy

The elastic constants of a single crystal of pure thorium have been measured over the temperature range 4.2–300 K. Measurements were repeated on the same crystal after sufficient carbon had been added to bring the composition to ThC0.063. The results show that carbon addition strengthens thorium with respect to dilational deformation and with respect to torsional deformation along 〈110〉 directions, but weakens thorium with respect to torsional deformation along 〈100〉 directions. The changes with respect to torsional resistance result in a reduced anisotropy ratio, 2C44/(C11−C12). Carbon addition raises the Debye temperature by only ∼3%. Magnetic susceptibility measurements were made on the crystal both before and after carbon addition. The overall results are in qualitative accord with a directional covalent character for the Th-C bonding interactions.