Molecular Dynamics Simulation of the Effect of Zr and b on Cryolite Molten Salt System 78%Na₃AlF₆-9.5%AlF₃-5.0%CaF₂-7.5%Al₂O₃

Abstract

The analysis of high temperature physical and chemical properties of molten salt system of aluminum electrolysis has guiding significance for practical production In this paper, the molecular dynamics calculation method was used to simulate the physical and chemical properties of 78%Na3AlF6-9.5%AlF3-5.0%CaF2-7.5%Al2O3 molten salt electrolyte system with Zr and B as additives at 1200K and standard atmospheric pressure. The effects of Zr and B elements on the radial distribution function, coordination number, diffusion coefficient, viscosity, and conductivity of electrolyte system were discussed in detail. The simulation results showed that Zr4+ weakened the connection between Al3+, while the addition of B3+ enhanced the interaction between Al3+, Na+, and F-. In the electrolyte system without impurities, the order of self-diffusion coefficient is Na+ > O2- > F- > Ca2+ > Al3+. And the addition of Zr4+ is conducive to the diffusion of ions in the system, while the addition of B3+ is not conducive to the diffusion of ions in the system. What’s more, the addition of Zr improves the conductivity of the system, while the addition of B reduces the conductivity of the system.