First-principles phase diagram calculations for the system NaCl-KCl: The role of excess vibrational entropy

First principles phase diagram calculations were performed for the system NaCl-KCl. Plane-wave pseudopotential calculations of formation energies were used as a basis for fitting cluster expansion Hamiltonians, both with and without an approximation for the excess vibrational entropy (S-VIB). including S-VIB dramatically improves the agreement between calculated and experimental phase diagrams: experimentally, the consolute point is {X-C = 0.348, T-C = 765 K}(Exp); without SVIB, it is {X-C = 0.46, Tc approximate to 1630 K}(Calc); with S-VIB, it is {X-C = 0.43, T-C = 930 K}(Calc). Published by Elsevier B.V.