Inhomogeneous fluid approach to solvation thermodynamics. 2. Applications to simple fluids
Inhomogeneous fluid approach to solvation thermodynamics. 2. Applications to simple fluids
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DOI：
10.1021/jp972358w
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发表时间：
1998-04-30
影响因子：
3.3
通讯作者：
Lazaridis, T
中科院分区：
文献类型：
--
作者：
Lazaridis, T
在前面的文章中，基于能量方程的非齐次形式和熵的相关展开，推导出了无限稀释时的偏摩尔能和熵的表达式。这些表达式在这里适用于密集硬球和伦纳德-琼斯溶剂中一系列不同大小的溶质，其中一些作为与水比较的参考体系。在假设混合物中的非均质溶剂-溶剂对相关函数等于公牛的情况下，得到了数值结果；溶剂径向分布函数（Kirkwood叠加近似）。通过积分方程理论（percusyevick近似）和蒙特卡罗模拟得到了所需的相关函数。将热力学结果与同一系统的状态方程、积分方程和自由能模拟结果进行了比较。对于硬球系统，超额熵与状态方程结果很好地吻合，但在许多Lennard-Jones系统中；计算得到的偏摩尔能和偏摩尔熵低于期望值。这是由于用叠加近似法过高估计了体三重态相关函数的结构。化学势的分解表明，相似的溶剂化自由能可以有完全不同的物理来源。具体地说，在高内聚能密度的溶剂中，化学势是由溶质周围局部溶剂-溶剂相互作用的破裂所主导的。在低内聚能密度的溶剂中，压力-体积项占主导地位。溶剂-溶剂相互作用强度的增加导致溶质化学势的增加，这是由于更高的溶剂重组能，溶剂重组熵的增加不足以补偿。
In the previous paper expressions for the partial molar energy and entropy at infinite dilution have been derived based on the inhomogeneous forms of the energy equation and the correlation expansion for the entropy. These expressions are here applied to a series of solutes of varying size in dense hard-sphere and Lennard-Jones solvents, some of which serve as reference systems for comparison with water. Numerical results are obtained under the assumption that the inhomogeneous solvent-solvent pair correlation function in the mixture is equal to the bull; solvent radial distribution function (Kirkwood superposition approximation). The correlation functions required are obtained by both integral equation theory (Percus-Yevick approximation) and Monte Carlo simulations. The thermodynamic results are compared with equation of state, integral equation, and free energy simulation results for the same systems. For hard-sphere systems the excess entropies are in good agreement with equation-of-state results but in many Lennard-Jones systems the; calculated partial molar energies and entropies are lower than the expected values. This is attributable to overestimation of-the structure of the bulk triplet correlation function by the superposition approximation. The decomposition of the chemical potential shows that similar solvation free energies can have entirely different physical origins. Specifically, in solvents of high cohesive energy density the chemical potential is dominated by the breakup of solvent-solvent interactions locally around the solute. In solvents of low cohesive energy density it is dominated by the pressure-volume term. Increase in solvent-solvent interaction strength leads to increase in the chemical potential of the solute due to the higher solvent reorganization energy, which is insufficiently compensated by an increase in solvent reorganization entropy.