Specific Heat of Diamond at Low Temperatures

Abstract

Specific heat data on diamond at temperatures between 20° and 300°K are reported. Comparisons of the data have been made with the predictions of the Debye theory. The deviation of the specific heat from the value given by the three‐dimensional continuum theory in the low temperature region can be qualitatively described in terms of a superposition of a simple Einstein frequency. It has been found that variations that occur in expressing reduced characteristic temperatures as a function of reduced temperatures for diamond are qualitatively similar to those of the face‐centered cubic metals Al, Cu, and Ag. The values of entropy, enthalpy, and free energy have been determined and tabulated at integral values of temperature from 25° to 300°K. The entropy of diamond at 298.16°K is 0.568±0.005 cal/g‐atom/deg.