A. G. Davydov, N. K. Tkachev.
ABSTRACT
The developed model of thermodynamic perturbation theory to take into account the extra charge-induced dipole contribution to the free energy of molten alkali-halide systems was applied to describe equilibria between a liquid and solid in binary mixtures of salts that have the same anions. Calculations of the liquidus in the binary phase diagrams of the LiF‒NaF, LiF‒KF, NaF‒KF, NaF‒CsF and KF‒CsF eutectic systems have been carried out. The errors in determining the liquidus positions of the considered fluoride mixtures did not exceed 15 percent in relation to the available FactSage data when using tabular ionic radii and polarizabilities. The deviations between calculated and literature data become more noticeable when considering systems that contain larger and more polarizable cations. Moreover, a shift in the position of eutectic equilibria towards less infusible components by up to 5‒10 percent and a slight overestimation in the eutectic temperatures as compared to the experiment and FactSage data are observed.
KEY WORDS:
charge-dipole interaction, charged hard spheres, thermodynamic perturbation theory, mean spherical approximation, alkali fluoride, melting point, liquidus, phase diagram, eutectic equilibrium.
DOI: 10.31857/S0235010621030038