Theoretical Studies of Structure and Dynamics of Molten Salts: The LiF鈥揟hF4 System

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• 作者：Jian-Biao Liu ; Xin Chen ; Yi-Heng Qiu ; Chao-Fei Xu ; W. H. Eugen Schwarz ; Jun Li
• 刊名：Journal of Physical Chemistry B
• 出版年：2014
• 出版时间：December 4, 2014
• 年：2014
• 卷：118
• 期：48
• 页码：13954-13962
• 全文大小：446K
• ISSN：1520-5207

文摘

LiF鈥揟hF₄ molten salt (MS) is the fuel for advanced MS reactors. Knowledge of the microscopic MS structure and dynamics is required for an understanding of the macroscopic physical and chemical properties of the MS phases. We have performed molecular dynamics simulations on LiF鈥揟hF₄ MS at different molar percentages (LiF/ThF₄ = 20.0 to 0.5) and temperatures (1100 to 1400 K). Experimental deductions and recent theoretical results on the coordination structures and transport properties of the MS are well reproduced. The density of states of the [ThF₈]^{4鈥?/sup> species and the character of the Th鈥揊 bonding are investigated. The interplay between the microscopic structures and the dynamical properties is elucidated. Corresponding to the smaller effective radius of Zr, the activation barrier of the M4+鈥揊鈥?/sup> dissociation and the lifetime of the first coordination shell of M4+ are both smaller for M = Th than for M = Zr in the respective LiF鈥揗F₄ systems. The shorter Zr鈥揊 bond is stronger than the longer Th鈥揊 bond, while the coordination number of the predominant [ZrF₇]3鈥?/sup> species is smaller than that of the dominant [ThF₈]4鈥?/sup> species. An approximate formula is proposed for the lifetime of F鈥?/sup> ions in the first solvation shell of molten MF_n (M = Y, Zr, Th) in terms of the radial distribution function.}