Part 1: Operational characteristics of a low temperature adiabatic calorimeter at the University of Tennessee. Part 2: Contributions to the heat capacity of solid Molybdenum (20-2890 K.)

Part 1 of this thesis deals with the operational characteristics of the low temperature adiabatic calorimeter in this Department. The principles of operation are discussed and a detailed description is given of the calorimeter. Operational procedures are outlined and problems faced during operation and their remedies are discussed in detail. This should prove to be of great help to future operators of this equipment. Finally, some data on the heat capacity of the empty cell as obtained by the author are given. These are compared to the data obtained by the fabricator of the equipment, Dr. Y. Higashigaki.

Part 2 of the thesis deals with the heat capacity of solid Molybdenum in the temperature range 20 - 2890 K. Heat capacity data for Mo in this range have been taken from the literature and a best fit to these data obtained. A rigorous calculation of the dilation correction has been carried out for the entire temperature range under consideration. This is possible only because of recent measurements of high temperature velocity of sound which allow the calculation of adiabatic compressibility values. The heat capcity at constant volume thus obtained by the rigorous dilation correction is compared to the values yielded by various approximating techniques.

A detailed analysis has been made of the various physical contributions to the heat capacity of Mo; in particular the electronic and vacancy contributions are dealt with in detail. It is surmised:

a) that the Electron-Phonon enhancement model is the best model for the electronic heat capacity of Mo;

b) that there is a real, positive enharmonic contribution to the heat capacity of Mo;

c) that the energy of vacancy formation is not very large and hence the contribution to the heat capacity of Mo from the formation of vacancies is indeed quite significant near the melting point.

The last point mentioned is quite controversial and the relevant points in the debate have been discussed.