Structural Computer Simulation On Molten Rare Earth Halide With Molecular Dynamics Method

Rare earth was called the "treasury" of new materials. Commonly the molten salt electrolysis and metallothermic reduction process were introduced to manufacture rare earth metal. In the manufacturing the rare earth metal or the alloy with the molten salt electrolysis process, it is most important to choose the proper molten salts. Researching the structure of molten salts is the base of grasping the physical chemical properties and correctly understanding the polarization process. With the development and spreading of computer simulation technology has great success been obtained in studying the structure of molten salts.In this paper, the principles and methods of molecular dynamics (MD) method in the computer simulation technology are introduced briefly. The molten rare earth halide systems such as molten rare earth chloride and rare earth fluoride, involved in the molten salt electrolysis process that is used to manufacture rare earth metal and alloy, are simulated with MD method. Some important information on the structure of the melts, such as the radical distribution functions, the coordination for particles in the melts and the bond angle distributions, and the dynamic properties such as self-diffusion constant of the ions were obtained.In the system of rare earth chloride, the systems of REC13, KCl-LaCl3 and RECl3-KCl-NaCl (KCl/NaCl=l:l mol ratio) are simulated. Six rare earth chlorides in REC13 system, such as LaCl3, PrCl3, NdCl3, GdCl3, DyCl3 and YC13, are simulated. The information on the structure of the melts and the dynamics property were obtained, sequentially the influence of the radius of rare earth metal ions on melt structure were found. The melt structure of KCl-LaCl3 was simulated at the four constituents respectively, the information of structure and dynamic property were obtained, sequentially the effect of the melt constituents on melt structure were found. In the systemof RECl3-KCl-NaCl (KCl/NaCl=l:l mol ratio), the melt structure of the molten salt mixture of three rare earth metal chlorides at the three constituents were simulated respectively, and information of melt structure and the dynamic property were obtained, sequentially the effect of the melt constituents on melt structure were found.In the system of rare earth fluoride mainly, the melt structure of LiF-LaFs were simulated at three kinds of constituents, three different temperatures respectively. The information on structure of melts and dynamic property were obtained, sequentially the influence of the melt constituent and temperature on the structure of melts were obtained.The information on structure of molten salts and dynamic properties in the rare earth halide system were Summarized. The influence of rare earth metal ionic radius and rare earth halide concentration on melt structure is great, and proper choice to rare earth halide concentration in the molten salts has great benefits to manufacturing rare earth metal and alloy.