Calculation of phase diagrams for the FeCl 2 , PbCl 2 , and ZnCl 2 binary systems by using molecular dynamics simulation
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INTRODUCTION
THE recycling of heavy-metal halide waste generated in industrial processes must consider phase equilibria for the prevention of environmental pollution and the recovery of resources. Recently, the efficient and economic recycling methods, and the separation and recovery of impurity materials such as heavy-metal halides and oxyhalide compounds in the recycling processes, were investigated by various researchers.[1–7] Especially, the importance of physicochemical properties such as formation behavior and phase equilibrium of heavy-metal halides, oxides, and oxyhalide compounds containing Fe, Pb, and Zn generated by treatment of waste such as metal refining dusts and incineration ash has been increased. However, the structural and thermodynamic properties and phase diagrams for these systems are not yet accurately known, because the high evaporation and condensation rates of these systems alter the experimental results. In this study, the structural, transport, and thermodynamic properties for heavy-metal chloride systems are calculated by using the molecular dynamics (MD) method. The MD simulation determines physicochemical properties based on the dynamic quantities of individual species in the solid and fluid simulating cells. The thermodynamic properties can be
calculated by using some basic potential parameters in the MD simulation, which differs from the computer-based software packages such as FactSage and Thermo-Calc calculating based on measured thermodynamic properties. Therefore, MD simulations can effectively estimate the structural, transport, and thermodynamic properties of high melting temperature and high vapor pressure materials. In the previous work, we successfully assessed the structural, transport, and thermodynamic properties for the BaO, CaO, and CaF2 binary systems,[8] and the CaO-SiO2 and FeO-SiO2 systems,[9,10] by the MD calculation to determine the respectful phase diagrams. These results of calculation show that the MD simulation is a useful method for the calculation of phase diagrams for the oxide and halide systems. The purpose of the present research is to determine the optimum potential for the calculation of FeCl2, PbCl2, and ZnCl2 systems and to calculate the structural, transport, and thermodynamic properties for pure FeCl2, PbCl2, and ZnCl2, and each binary system, by MD simulation. Finally, the phase diagrams for the ZnCl2-PbCl2, FeCl2-PbCl2, and FeCl2-ZnCl2 binary systems are estimated based on the structural and thermodynamic parameters obtained by MD calculation. II. MD CALCULATION A. Interatomic Potential
WON-GAP SEO, formerly Graduate Student, Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, is with the Technical Research and Development Center, Hyundai Hysco, Suncheon, Jeollanam, Korea. HIROYUKI MATSUURA, Graduate Student, and FUMITAKA TSUKIHASHI, Professor, are with the Department of Advanced Materials Science, Graduate School of Frontier Sciences, The University of Tokyo, Chiba, 277-8561, Japan. Contact
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