Abstract
Improved apparatus has been developed for measurement of the constant-volume heat capacity of condensed phases at low temperatures. The high-pressure calorimeter is closed by a remotely operated valve at the calorimeter and several problems associated with the usual blocked-capillary technique are thus eliminated. The heat capacity of hcp has been measured from approximately 0.35 K to the temperature of the transition to a mixed phase and for molar volumes between 20.5 and 21. 0 /mole. The data permit reliable extrapolations to 0 K to determine , the Debye characteristic temperature at 0 K, and the entropy. can be represented by the same function of for all molar volumes in the range studied. The data are in good agreement with Ahlers's recent measurements in the limited region of overlap, but the temperature dependence of at low temperatures and densities is different from that deduced by Ahlers by extrapolation from higher temperatures and densities. The values of obtained in this work and by Ahlers at higher densities can be represented by .
- Received 13 September 1972
DOI:https://doi.org/10.1103/PhysRevA.7.1029
©1973 American Physical Society