Cui Shengting, de Almeida Valmor F, Khomami Bamin
Materials Research and Innovation Laboratory Department of Chemical and Biomolecular Engineering, University of Tennessee , Knoxville, Tennessee 37996, United States.
J Phys Chem B. 2014 Sep 11;118(36):10750-60. doi: 10.1021/jp5040135. Epub 2014 Aug 27.
Molecular dynamics simulations of tri-n-butyl-phosphate (TBP)/n-dodecane mixture in the liquid phase have been carried out using two recently developed TBP force field models (J. Phys. Chem. B 2012, 116, 305) in combination with the all-atom optimized potentials for liquid simulations (OPLS-AA) force field model for n-dodecane. Specifically, the electric dipole moment of TBP, mass density of the mixture, and the excess volume of mixing were computed with TBP mole fraction ranging from 0 to 1. It is found that the aforementioned force field models accurately predict the mass density of the mixture in the entire mole fraction range. Commensurate with experimental measurements, the electric dipole moment of the TBP was found to slightly increase with the mole fraction of TBP in the mixture. Also, in accord with experimental data, the excess volume of mixing is positive in the entire mole fraction range, peaking at TBP mole fraction range 0.3-0.5. Finally, a close examination of the spatial pair correlation functions between TBP molecules, and between TBP and n-dodecane molecules, revealed formation of TBP dimers through self-association at close distance, a phenomenon with ample experimental evidence.
利用最近开发的两种磷酸三正丁酯（TBP）力场模型（《物理化学杂志B》2012年，第116卷，第305页），结合正十二烷的全原子液体模拟优化势（OPLS - AA）力场模型，对液相中的磷酸三正丁酯（TBP）/正十二烷混合物进行了分子动力学模拟。具体而言，计算了TBP的电偶极矩、混合物的质量密度以及混合过量体积，TBP的摩尔分数范围为0至1。结果发现，上述力场模型能准确预测整个摩尔分数范围内混合物的质量密度。与实验测量结果一致，发现TBP的电偶极矩随混合物中TBP的摩尔分数略有增加。此外，与实验数据相符，混合过量体积在整个摩尔分数范围内均为正值，在TBP摩尔分数范围0.3 - 0.5时达到峰值。最后，对TBP分子之间以及TBP与正十二烷分子之间的空间对关联函数进行仔细研究，发现TBP分子通过近距离自缔合形成了二聚体，这一现象有充分的实验证据。
