Examination of reference potentials for the molten K_x(KCl)_1-x system by the Percus-Yevick approximation

Abstract

The structure of the molten K _x (KCl)^1-x system at the metal rich side has been investigated by using three kinds of reference potential, which are the simplified versions of the model pair potentials proposed previously, within the framework of the Percus-Yevick (PY) approximation. It is shown that the sharp rise of the total structure factor at low momentum transfers, which is characteristic of the neutron diffraction experiment, and the very long range correlation between anions are due to the relatively weak attraction between anions. The similarity of the results for the screened and the unscreened Coulomb potentials is pointed out. The existence of the same similarity has been tested in the case of pure molten KCl. The four kinds of screened potentials, which were obtained for K_0·8(KCl)_0·2, have been used to mimic the pair distribution functions of the molten KCl system. The results are compared with those of the simulation calculation and of the mean spherical approximation (MSA) calculations for the Yukawa and the Coulomb potentials with hard cores. The entropy values for the latter two potentials are calculated. A good agreement with experiment is obtained by the use of the electronic dielectric constant ϵ = 2·112 in the case of the Coulomb potentials.