On the thermal expansion of solids

Abstract

The thermal expansion of alkali halides has been investigated at very low temperatures and at high temperatures. Attention has been concentrated on the isotropic cases, for which a formal expression for the Gruneisen constant has been obtained. It is shown that the Gruneisen constant is expected to increase somewhat as the temperature is increased. It is further shown that the contributions from the individual vibrations to the Gruneisen constant at low temperatures vary over a very wide range. The Gruneisen rule, however, is shown to require only that a certain average value of these contributions should not vary with frequency.