Application of the complex model to liquid metal-salt systems

The complex model developed by Hoch and Arpshofen is used to describe the phase diagram of several alkali halide-alkali metal systems. In the first approximation, Δ_m^ex = ΔH_m = n(x ? xⁿ)w where n is the size of the complex (number of atoms), W is the interaction parameter, and x is the atom fraction of the compoennt with the lower binding capcacity. In several systems the complete form of the above equation is applied, including deviation from ramdomness and vibrational entropy contributions.If the liquid is single-phase, the data are calculated from the liquidus line. If a miscibility gap exists in the liquid, it is used to calculate the parameters.The model requires only two constants (n and W), and thus can be used to calculate phase diagrams, where relatively little information is available. As an example, the calculation of the U-UO₂, Th-ThO₂ phase diagram is outlined.