Static and dynamic ionic structure of molten CaCl2 via first-principles molecular dynamics simulations

Abstract

Molten CaCl2 could further broaden and open up new solar power applications due to its high melting point and chemical stability. However, few studies have focused on the ionic structure of molten CaCl2 with the experimental limitations such as extremely high temperature, high corrosiveness, and water absorbency, so that static and dynamic structure of molten CaCl2 has not been well understood. In this work, the static and dynamic ionic structure of molten salts was investigated by conducting first-principles molecular dynamics simulations. Structural features like short-range order and intermediate-range order are observed in molten CaCl2. The 6-coordinated structure stays dominant in the CaCl2 melt among the temperature range of 1100–1500 K. The network structure is filled with distorted octahedron which tends to be rutile structure, and these octahedrons are linked via corner-sharing and edge-sharing models. Among the temperature range of 1100–1500 K, the increase of temperature can accelerate the movement of ions, but there is no obvious effect on the local ionic structure of molten CaCl2. Analysis in this paper may be supportive to fill the gap in understanding the ion behavior of molten CaCl2 and other divalent chlorides.