Monte Carlo and HNC calculations for molten potassium chloride

Abstract

Monte Carlo calculations of the equilibrium properties of particles interacting with the Huggins–Mayer potential for potassium chloride have been made at the single temperature of 1700 K over the volume range 80 cm³ mol^–1 to 13 cm³ mol^–1(at which density the pressure is 2.1 × 10¹¹ Pa). Results are presented for the pressure, internal energy and elastic moduli as functions of density. The Madelung constant is found to vary linearly with volume over the entire range. It is found that under increasing pressure the structure of the liquid gradually alters from an open, charge-ordered arrangement to one more nearly resembling that of an simple non-ionic mixture. The g_+– distribution is not greatly affected by increasing the density but the g₊₊ and g_–– distributions are considerably altered, with the emergence of a second peak at about 33 cm³ mol^–1. Only at a molar volume below about 15 cm³ mol^–1 is there any significant difference between the g₊₊ and g_–– distributions.

The HNC theory has been solved using the same potential over the same density range. The agreement with the Monte Carlo results for pressure and electrostatic energy is very good throughout. The radial distributions are in qualitative agreement throughout, with good agreement at low densities. The HNC static structure factors and direct correlation functions have also been calculated.