Ab Initio Molecular Dynamics Simulation of Microstructure and Transport Properties of K3AlF6-2.2NaF-AlF3 System

Abstract

Researching the aluminum molten salt system has always been challenging because of the high temperature and significant corrosion seen in the aluminum electrolysis industry. This paper employs ab initio molecular dynamics simulations to investigate the ionic structure and transport features of the K3AlF6-2.2NaF-AlF3 molten system. The findings indicate that the primary Al-F complex ion species present in K-rich molten salts are [AlF4]−, [AlF5]2−, and [AlF6]3−. The fluorine atom located at the bridge site constitutes around 3% of the overall composition, suggesting a rather modest degree of polymerization for the ionic structure. The relative diffusion rates of the ions in the system are as follows: sodium (Na) has the highest diffusion ability, followed by potassium (K), fluoride (F), and aluminum (Al). With the increase in K3AlF6 concentration, the distribution and diffusion coefficient of complex ions in the melt change, resulting in a decrease in the transport performance of the entire system. These fundamental research findings can contribute to the optimization of the aluminum electrolysis industry in the future.