(764e) Solid–Solid Phase Transitions in the NaCl–KCl System

We study the solid-to-solid phase transition in the NaCl–KCl system using molecular simulations. Below around 500°C, this system forms a solid solution with a pronounced miscibility gap between a sodium-rich and a potassium-rich phase [1]. We calculate the phase diagram in this region using the semi-grandcanonical Widom method, which averages over virtual particle transmutations at a fixed system composition [2]. By employing a newly modified version of a Fumi-Tosi style force field [3], we are able to get a remarkable degree of agreement with the experimental phase diagram. Furthermore, we calculate the thermodynamic driving force for nucleation and growth within the coexistence region and extrapolate the location of the critical point.

[1] D. Sergeev, D. Kobertz, and M. Müller, Thermochimica Acta 606, 25 (2015).

[2] P. Sindzingre, G. Ciccotti, C. Massobrio, and D. Frenkel, Chem. Phys. Lett. 136, 35 (1987).

[3] D. J. Adams and I. R. McDonald, J. Phys. Chem. C 7, 2761 (1974).