The quasi-harmonic approximation and a generalized Grneisen equation of state

Abstract

The validity of the Grüneisen equation of state for a solid having a continuous distribution of frequencies is investigated. It is shown that one cannot generally replace <i>∂S</i>/<i>∂V</i> with the heat capacity multiplied by appropriate Grüneisen constants. A model frequency distribution is used to show the difference that can arise.