A STATISTICAL MECHANICAL STUDY OF THERMODYNAMIC PROPERTIES OF SOLID SODIUM UNDER PRESSURE BASED ON AN EFFECTIVE INTERIONIC POTENTIAL

Abstract

Basing on the Schiff effective interionic potential that has an oscillatory character and the correlative method of unsymmetrized self-consistent field (CUSF) that enables one to take into account the strong anharmonicity of the crystal lattice vibrations, we have calculated a complete set of equilibrium thermodynamic properties of solid sodium as functions of pressure and temperature: the lattice parameter, the elastic moduli, the thermal expansion coefficient, the Grüneisen parameter and the isochoric and isobaric heat capacities. Our results are compared with available experimental data. We also discuss the thermodynamic stability of the BCC lattice, the mechanism of its loss and its change under pressure.