Solid-solid phase equilibria in the NaCl-KCl system

Anwar, J. and Leitold, C. and Peters, B. (2020) Solid-solid phase equilibria in the NaCl-KCl system. Journal of Chemical Physics, 152 (14): 144109. ISSN 0021-9606

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Solid solutions, structurally ordered but compositionally disordered mixtures, can form for salts, metals, and even organic compounds. The NaCl-KCl system forms a solid solution at all compositions between 657 °C and 505 °C. Below a critical temperature of 505 °C, the system exhibits a miscibility gap with coexisting Na-rich and K-rich rocksalt phases. We calculate the phase diagram in this region using the semi-grand canonical Widom method, which averages over virtual particle transmutations. We verify our results by comparison with free energies calculated from thermodynamic integration and extrapolate the location of the critical point. Our calculations reproduce the experimental phase diagram remarkably well and illustrate how solid-solid equilibria and chemical potentials, including those at metastable conditions, can be computed for materials that form solid solutions.

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Journal Article
Journal or Publication Title:
Journal of Chemical Physics
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Copyright 2020 American Institute of Physics. The following article appeared in The Journal of Chemical Physics, 152 (14), 2020 and may be found at This article may be downloaded for personal use only. Any other use requires prior permission of the author and the American Institute of Physics.
Uncontrolled Keywords:
?? phase diagramsphase equilibriapotassium compoundssodium chloridecritical temperaturesgrand canonicalmeta-stable conditionmiscibility gapsolid-solidthermodynamic integrationvirtual particleswidom methodssolid solutionsphysics and astronomy(all)physical and ??
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06 May 2020 10:35
Last Modified:
29 Nov 2023 00:28