Thermodynamic properties of solid Ar, Kr and Xe based upon a short range central force and the improved self-consistent phonon scheme

Abstract

The thermodynamic properties of solid Ar, Kr and Xe are investigated within the framework of the self-consistent phonon method. We have used a central two-body potential of the MieLennard-Jones type. The lowest order self-consistent scheme, the so-called self-consistent phonon harmonic approximation (SC), is shown to be inadequate. The effect of including, in the Helmholtz free energy, the leading terms omitted by the sca is examined in detail and a comparison is also made with our earlier work based on the Born-von Kármán approximation. We find substantial differences between the results based on different approximations to the free energy.