Atomic Heat of Diamond from 11° to 200°K

The atomic heat of 8.3 moles of clear diamond chips has been measured between 11° and 200°K in a vacuum calorimeter. The capsule correction has been made a much smaller fraction of the total heat capacity in this work than in earlier investigations resulting in improved accuracy at the lowest temperatures. Comparison is made with the theoretical values of Marcus. The observations are consistent with the calculated $\theta$ variation and with a ${\theta }_D\mathrm{}\left(0\right)=2240\mathrm{}°\pm 5°$K calculated from the elastic constants. Small discrepancies with the theory at the lowest temperatures are attributed to causes other than the vibrational heat capacity of the bulk lattice.