Molecular dynamics simulations of the local structure and physicochemical properties of CaCl2 molten salt

Abstract

CaCl2 molten salt, as a common electrolyte in the process of molten salt electrolysis, has a high decomposition potential and a strong ability to bind O2−. So the study of the structure and properties of CaCl2 is significant for the molten salt electrolysis. In this paper, molecular dynamics simulations (MD) method was used to investigate the variation rule of the local structure and physicochemical properties of CaCl2 molten salt with temperature. The results show that the temperature has less effect on the heterozygous ion pairs and more effect on the homozygous ion pair. With the increase of temperature, the interaction between ion pairs is weakened, the coordination number decreases, the local structure changes a little, and the structural configuration tends to be an irregular octahedral structure with vacancies. The calculated self-diffusion coefficients, viscosities, and ionic conductivities are consistent well with the reality, but there is a significant error in densities due to the strong polarization effect of Ca2+ compared to the reality. The local structure directly determines the thermodynamic properties of the molten salts. This study promotes the basic theoretical research on alkaline earth metal-containing molten salts and is an important reference for the study of molten salt electrolysis process.