A quasi-crystalline model for a binary liquid, with 2 sub-lattices that contained randomly distributed vacancies, was developed on the basis of statistical thermodynamics. Relative partial molar quantities were then deduced. Constraints were identified which imposed adjustable parameters such that the Schottky constant increased with increasing temperature but never exceeded unity. Constraints were also identified for a system which formed a congruently melting narrow homogeneity-range compound. This model was an extension of an earlier version for liquids, and of similar models for narrow homogeneity-range compounds, in that the excess Gibbs energies for vacancy creation were cubic functions of the atomic fraction. The model was also an alternative to solution models which assumed the existence of a single equi-atomic associated species. The model was also applied to systems of varying polarity, all of which formed a narrow homogeneity-range crystalline compound whose stoichiometric composition was 50at%. Quantitatively good fits were obtained in the case of the Hg-Te, Cd-Te, Zn-Te and Pb-Te systems. With regard to the first 3 systems, the fits were comparable to those which were obtained by using the associated solution model and the same experimental data. Quantitatively good fits were also obtained in the case of the less-polar In-Sb and Ga-Sb systems, and these were comparable with those which had been obtained by using a Margules-type model in which the mixing enthalpy for the liquid was a quartic function of the atom fraction, and a quadratic function of temperature. The predicted mixing enthalpies at temperatures above the present range of experimental data were considered for the various systems and models.

R.F.Brebrick, T.C.Yu: Metallurgical and Materials Transactions A, 1995, 26[10], 2597-610