Structure of molten alkali chlorides

Abstract

We use the hypernetted chain (HNC) approximation to calculate the thermodynamic and structural properties of the five molten alkali chlorides studied by simulation methods in the preceding paper. Solutions are obtained by the Newton–Raphson method recently developed by Abernethy and Gillan (1980). We show that the internal energies are in excellent agreement with simulation, and the pressures are in fair agreement, but the compressibilities are too large by a factor of about 2. The radial distribution functions and partial structure factors are in most respects in good agreement with those produced by the rigid-ion simulations. We also compare the structural results obtained from the HNC theory with those given by a recent semi-empirical theory due to Abramo et al. (1978), which is based on the mean spherical approximation. We show that the latter is considerably inferior to the HNC theory and, in particular, greatly overemphasizes the effects of ionic size difference.