In-depth explorations on the microstructural, thermodynamic and kinetic characteristics of MgCl2-KCl eutectic salt

First principle molecular dynamics (FPMD) simulations coupled with experimental measurements are used to investigate the thermophysical parameters, microstructures, and thermal transport properties of the MgCl2-KCl (32:68 mol%) eutectic salt. The phase transition behaviors are charactered by the thermal expansion coefficient, density, enthalpy of fusion, and specific heat capacity through FPMD simulations, and the simulated results cohesive well with those of our experiments. From the temperature dependences of radial distribution functions g(r) and coordination numbers, the mutations of peak heights of g(K)-(Cl)(r) and g(Mg)-(Cl)(r) near the melting point are related to the phase change, and the coordination structure of K-Cl is significantly changed from 6-fold to 5-fold with increasing temperature. Moreover, the prominent peaks in static structural factors are attributed to charge alternation structures of cation-Cl clusters, while pre-peaks are dominated by the Mg-Mg correlation. Based on ionic self-diffusion coefficients, the calculated thermal conductivity and shear viscosity of molten MgCl2-KCl are slightly lower than our experimental values. Nevertheless, the FPMD simulations provide an appropriate approach to evaluate the thermodynamic and kinetic properties of MgCl2-KCl eutectic, which contributes essential data for designing the heat transfer and storage system. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

In this study, first principle molecular dynamics (FPMD) simulations coupled with experimental measurements were used to investigate the thermophysical parameters, microstructures, and thermal transport properties of the MgCl2-KCl eutectic salt. The phase transition behaviors and coordination structure changes were characterized through FPMD simulations and compared with experimental results. The study also revealed the characteristics of peak heights in the static structural factors and the dominating effect of Mg-Mg correlation on pre-peaks. The calculated thermal conductivity and shear viscosity of the molten eutectic were slightly lower than the experimental values based on ionic self-diffusion coefficients.