物理化学学报 >> 2016, Vol. 32 >> Issue (3): 647-655.doi: 10.3866/PKU.WHXB201601042

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LiCl-KCl-CeCl3熔盐结构与热力学的分子动力学模拟

姜涛1,王宁1,程长明1,彭述明1,*(),严六明2   

  1. 1 中国工程物理研究院核物理与化学研究所, 四川绵阳 621999
    2 上海大学理学院化学系, 上海 200444
  • 收稿日期:2015-10-28 发布日期:2016-03-04
  • 通讯作者: 彭述明 E-mail:pengshuming@caep.cn
  • 基金资助:
    国家自然科学基金重大研究计划-集成项目(91426302);国家自然科学基金(21301163)

Molecular Dynamics Simulation on the Structure and Thermodynamics of Molten LiCl-KCl-CeCl3

Tao JIANG1,Ning WANG1,Chang-Ming CHENG1,Shu-Ming PENG1,*(),Liu-Ming YAN2   

  1. 1 Institute of Nuclear Physics and Chemistry, China Academy of Engineering Physics, Mianyang 621999, Sichuan Province, P. R. China
    2 Department of Chemistry, College of Sciences, Shanghai University, Shanghai 200444, P. R. China
  • Received:2015-10-28 Published:2016-03-04
  • Contact: Shu-Ming PENG E-mail:pengshuming@caep.cn
  • Supported by:
    the Major Research Plan of the National Natural Science Foundation of China(91426302);National Natural Science Foundation of China(21301163)

摘要:

采用分子动力学模拟的方法,研究了LiCl-KCl-CeCl3熔盐中CeCl3的结构性质和热力学,获得了LiCl-KCl-CeCl3熔盐中密度与组成、密度与温度的关系数据;径向分布函数gCe-Cl(r)的第一个峰位置为0.259nm, Ce3+对应的第一个配位数约为6.9;混合熔盐中计算数据与纯熔盐中数据的差异可以解释为混合熔盐中Ce3+和Cl-的相互作用比纯的CeCl3更强; LiCl-KCl熔盐中Ce3+的自扩散活化能为22.5 kJ·mol-1,从活化能的本质来说, Ce3+自扩散所需要克服的能垒要略低于U3+(25.8 kJ·mol-1)。当Ce3+的摩尔分数从0.005增加到0.05时,其指前因子从31.9×10-5 cm2·s-1减少到21.8×10-5 cm2·s-1;随着Ce3+摩尔分数从0.005增长到0.05,单位体积内(忽略总体积的变化)Ce3+的增加意味着其扩散阻力增加,而自扩散的能力降低,导致了指前因子的减小。

关键词: LiCl-KCl-CeCl3, 结构, 热力学, 分子动力学, 扩散系数

Abstract:

The structure and thermodynamics of CeCl3 in molten LiCl-KCl-CeCl3 mixtures were studied by molecular dynamics simulation. The relationship formulas of temperature and density, and composition and density were obtained. The first peak for the gCe-Cl(r) radial distribution function was located at 0.259 nm and the corresponding first coordination number of Ce3+ was ~6.9. This inconsistency between molecular dynamics and experimental data could be attributed to the fact that our values were obtained for molten LiCl-KCl-CeCl3 mixtures, in which the interaction between Ce3+ and Cl- was more powerful than that in pure molten CeCl3. Regarding self-diffusion coefficients, the activation energy of Ce3+ was 22.5 kJ·mol-1, which is smaller than that of U3+ (25.8 kJ·mol-1). Furthermore, the pre-exponential factors for Ce3+ decreased from 31.9×10-5 to 21.8×10-5 cm2·s-1 as the molar fraction of Ce3+ increased from 0.005 to 0.05. This means that in the unit volume (ignoring the change of total volume), the diffusion resistance of Ce3+ increased, and the self-diffusion ability decreased, which resulted in a decrease of pre-exponential factors.

Key words: LiCl-KCl-CeCl3, Structure, Thermodynamics, Molecular dynamics, Diffusion coefficient

MSC2000: 

  • O641