Structures of Liquid Metals and their Thermodynamic Properties

Abstract

Thermodynamic functions such as the total energy, the pressure or the equation of state of a liquid state have been represented formally in terms of the pair distribution function g(2)(r). However, so far as g(2)(r) is not expressed by an analytical function of pair potential, temperature and volume, it is not always useful for estimation of thermodynamic quantities of liquid.From the microscopic viewpoint it is considered that many of atoms in the liquid state of metals are in the oscillatory motion coherent with their neighbours in short life time, and some of atoms are in the translational motion through vacancies moving about freely among such oscillatory atoms. The partition function of simple liquid is constructed by introducing degrees of freedom of vibrational and translational motions. Using such a partition function the molar volume, the vapour pressure, the excess entropy and the specific heat of liquid Na are estimated as a function of temperature.There are many liquid alloys which show anomalous behaviours in thermodynamic and physical properties. It is considered that these anomalous behaviours originate mainly in the formation of the pseudo-molecules having a flexible structure different from the rigid molecules. A partition function of liquid alloy containing the formation of these pseudomolecules is estimated and the concentration of the pseudomolecule nR⁄N is derived as a function of the alloying composition. The heat of mixing of liquid alloys Cu–In and Cu–Sn, and the mixing entropy of liquid Cu–Sn alloy are evaluated.