Structural Analysis of a Molten (Li-Na-K) Cl Mixture of the Eutectic Composition by Means of X-Ray Diffraction and Molecular Dynamics Simulation

Abstract

X-Ray diffraction was performed for a molten (Li-Na-K)Cl mixture of, the eutecticcomposition (53.5-8.6-37.9 mol%) at (625±3) K. In order to separate the obtained structurefunction s·i(s) and the radial distribution function G(r) to individual atomic interactions, molecular dynamics (MD) simulation was applied. By modifying the Tosi-Fumi pair potentials, the s·i(s) and G(r) functions derived from the MD simulation could well reproduce those obtained from the X-ray diffraction method. With the 3-dimensional structure obtained from the MD simulation, the pair correlation functions g(r), the running coordination numbers n(r), the distribution of coordination numbers of Cl^- ions and the angular correlati on functions of Cl^- ions around cations were calculated. Based on these results, the change of the structure on mixing each component melt is discussed. The nearest neighbor distances between like-ions change on mixing, whereas those between unlike-ions in the mixtu r e are almost the same as those in the pure melts. On the other hand, the peak positions in t h e angular correlation functions of Cl^- ions around Li⁺ and K⁺ ions in the mixture are differen t from those in the pure melts, whereas the shape of the angular correlation function around Na⁺ ion is almost the same as that in the pure NaCl melt.