MOLECULAR-DYNAMICS STUDY OF NAF-ALF3 MELTS

Molecular dynamics simulations were used to develop ionic models of Na F-AlF3 melts at 1283 K. The thermodynamic properties of this system ex hibit slight deviations from ideality. Structural data suggest that al l of the melts have fairly loose structures. With increasing AlF3 cont ent, the Na-F coordination number rises from similar or equal to 4 to 9. The predominant AI-F coordination number is 6. The formation of a p olymeric network made up of anions such as AlF62- goes to completion b y similar to 50 mol % AlF3. The calculated 1283-K conductivity is in r easonable agreement with experimental data. In an applied electric fie ld, fluorine ions entrain aluminum ions toward the anode. With increas ing AlF3 content, the conductivity of the melts and the self-diffusion coefficients of the constituent ions decrease.