A SIMPLE LATTICE MODEL FOR THE MIXING PROPERTIES OF MOLTEN K(X)(KCL)(1-X) SOLUTIONS

A very simple lattice model is presented for mixtures of alkali metals and alkali halides, like Kx(KCl)1-x. The valence electrons are assume d to be excluded from the Wigner-Seitz spheres associated with the ani ons, while they are uniformly distributed over the cation Wigner-Seitz spheres. The calculated excess volume of mixing turns out to be posit ive over most of the concentration range, in qualitative agreement wit h experiment, provided the surface energy of the electrons, associated with the boundary of the anion Wigner-Seitz spheres, is taken into ac count. The results of this model differ considerably from earlier pred ictions based on linear electron screening theory.