Molecular dynamics simulation on local structure and thermodynamic properties of molten ternary chlorides systems for thermal energy storage

摘要

Molten alkali chlorides mixtures are potential thermal energy storage materials. The structure and thermodynamic properties of LiCl-NaCl-KCl systems with different KCl concentrations were investigated by molecular dynamics simulation. The force field was verified by experimental data for the density and viscosity, and its precision was compared with the first-principle-based molecular dynamics simulation results. The densities obtained from rigid ion model were in satisfactory agreement with experimental values with a minimum error of 4.9% underestimation. The discrepancy in the structural information obtained by the two methods was no more than 1%. The local structure and thermodynamic properties were simulated across a full range of KCl concentration from 900 to 1200 K. The stability of cations coordination was analyzed by cage-out correlation function. The calculated self-diffusion coefficients, shear viscosity, heat capacity, and thermal conductivity were in good agreements with the available experimental data. The results showed that addition of KCl strengthened the correlation between unlike charged ions pairs, which was verified by the stability analysis. The stability of the first coordination shell determined the shear viscosities. Change in the structure affected the thermodynamic properties.