Simple electrolyte solutions: Comparison of DRISM and molecular dynamics results for alkali halide solutions
Simple electrolyte solutions: Comparison of DRISM and molecular dynamics results for alkali halide solutions
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DOI：
10.1063/1.4775743
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发表时间：
2013-01-28
影响因子：
4.4
通讯作者：
Case, David A.
中科院分区：
文献类型：
--
作者：
Joung, In Suk;Luchko, Tyler;Case, David A.
利用分子溶剂化的介电一致参考相互作用位点模型（DRISM），我们计算了碱化盐在水溶液中的结构和热力学信息，它们是盐浓度的函数。利用n阶闭包族（包括常用的超网状链方程（HNC）和kovalko - hirata闭包）的偏级数展开，研究了与DRISM相关的闭包关系变化的影响。结果与使用相同力场的显式分子动力学（MD）模拟进行了比较，并进行了实验。在浓度低于0.5 m时，DRISM预测的离子平均活度系数与实验值吻合较好，特别是在使用HNC闭合时。由于实验中不知道单个离子的活度（以及相应的溶剂化自由能），所以只直接比较了DRISM和MD的结果，发现它们有相当好的一致性。由DRISM直接估算的水活度与由DRISM离子活度和Gibbs-Duhem方程得出的值几乎一致，但计算压力作为盐浓度函数的变化主导了这些比较。在忽略这些压力变化的情况下，与实验结果吻合较好。比较了DRISM和MD模拟下三种浓度NaCl溶液的径向分布函数。DRISM在阳离子周围显示出类似的水分布，但阴离子周围的水结构偏离了MD的结果；这也可能与系统的高压有关。尽管存在一些问题，但DRISM-PSE-n是研究简单电解质热力学性质的有效工具。(C) 2013年美国物理研究所。[http://dx.doi.org/10.1063/1.4775743]
Using the dielectrically consistent reference interaction site model (DRISM) of molecular solvation, we have calculated structural and thermodynamic information of alkali-halide salts in aqueous solution, as a function of salt concentration. The impact of varying the closure relation used with DRISM is investigated using the partial series expansion of order-n (PSE-n) family of closures, which includes the commonly used hypernetted-chain equation (HNC) and Kovalenko-Hirata closures. Results are compared to explicit molecular dynamics (MD) simulations, using the same force fields, and to experiment. The mean activity coefficients of ions predicted by DRISM agree well with experimental values at concentrations below 0.5 m, especially when using the HNC closure. As individual ion activities (and the corresponding solvation free energies) are not known from experiment, only DRISM and MD results are directly compared and found to have reasonably good agreement. The activity of water directly estimated from DRISM is nearly consistent with values derived from the DRISM ion activities and the Gibbs-Duhem equation, but the changes in the computed pressure as a function of salt concentration dominate these comparisons. Good agreement with experiment is obtained if these pressure changes are ignored. Radial distribution functions of NaCl solution at three concentrations were compared between DRISM and MD simulations. DRISM shows comparable water distribution around the cation, but water structures around the anion deviate from the MD results; this may also be related to the high pressure of the system. Despite some problems, DRISM-PSE-n is an effective tool for investigating thermodynamic properties of simple electrolytes. (C) 2013 American Institute of Physics. [http://dx.doi.org/10.1063/1.4775743]