Abstract
The enthalpy of gem diamonds has been measured from 273° to 1073°K using a ``drop'' method and a Bunsen ice calorimeter. The derived heat‐capacity values, which are believed to be accurate to ±0.5%, are used to calculate the thermal functions of diamond above 298.15°K. Values of Cv0 (harmonic) derived from the present investigation and recent measurements of the thermal expansion and the elastic constants of diamond are compared with theoretical treatments. Reasonably good agreement in the temperature range of this study can be obtained with a single Debye function (ΘD=1860) obtained from the measured elastic constants. Extrapolation of the data gives Θ=1880±10.

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