Ab-initio molecular dynamics calculation on microstructures and thermophysical properties of NaCl–CaCl2–MgCl2 for concentrating solar power

NaCl–CaCl2–MgCl2 ternary molten salt is a potential material for thermal transfer and storage applications at high temperatures. In the present work, its microstructures and thermophysical properties over a wide operating temperature range were investigated by using ab-initio molecular dynamics simulations. An approach-to-equilibrium molecular dynamics method was used to calculate the thermal conductivity of molten salts. The local coordination structures and mechanisms of their temperature dependence were investigated. It can be found that the dominant bonding interactions are between cation-chlorine ion pairs, which can be considered as bridges connecting the local structures in liquids. The interaction between ions decreases with the increase of temperature as distances of ion clusters get larger. The thermophysical properties were evaluated in detail from 703 to 1173 K, showing a good accordance with the experimental data. A detailed relationship between operating temperature, microstructure, and thermophysical properties has been studied. The results suggest that the changes in thermodynamic properties with increasing temperature are caused by the variations of microstructures, in terms of the distances and bonding characteristics of ions. •Ab-initio molecular dynamics simulations are applied for NaCl–CaCl2–MgCl2.•Approach-to-equilibrium molecular dynamics method is used for thermal conductivity.•The relationship between operating temperature and properties has been studied.•Properties of molten salt are determined by the distances and interactions of ions.