Application of Statistical Moment Method to Thermodynamic Properties of Metals at High Pressures

Abstract

The moment method in statistical dynamics is used to study the thermodynamic properties of metals taking into account the anharmonicity effects of the lattice vibrations and hydrostatic pressures. The explicit expressions of the lattice constant, thermal expansion coefficient, and the specific heats Cv and Cp of cubic (fcc) metals are derived within the fourth order moment approximation. The thermodynamic quantities of Al, Au, Ag, Cu, and Pt metals are calculated as a function of the pressure, and they are in good agreement with the corresponding experimental results. The effective pair potentials work well for the calculations of transition and noble metals, compared to those of the sp-valence metals. For obtaining better agreement of the thermodynamic quantities of metals like Al, it is required at least to use the more sophisticated electronic many body potentials. In general, it has been shown that the anharmonicity effects of lattice vibration play a dominant role in determining the thermodynamic properties of metals under high pressures and at the finite (high) temperatures.