Department of Chemical and Biomolecular Engineering, University of Tennessee, Knoxville, Tennessee 37996, United States.
J Phys Chem B. 2012 Jan 12;116(1):305-13. doi: 10.1021/jp207089e. Epub 2011 Dec 28.
Molecular dynamics (MD) simulations were conducted to compare the performance of four force fields in predicting thermophysical properties of tri-n-butyl-phosphate (TBP) in the liquid phase. The intramolecular force parameters used were from the Assisted Model Building with Energy Refinement (AMBER) force field model. The van der Waals parameters were based on either the AMBER or the Optimized Potential for Liquid Simulation (OPLS) force fields. The atomic partial charges were either assigned by performing quantum chemistry calculations or utilized previously published data, and were scaled to approximate the average experimental value of the electric dipole moment. Canonical ensemble computations based on the aforementioned parameters were performed near atmospheric pressure and temperature to obtain the electric dipole moment, mass density, and self-diffusion coefficient. In addition, the microscopic structure of the liquid was characterized via pair correlation functions between selected atoms. It has been demonstrated that the electric dipole moment can be approximated within 1% of the average experimental value by virtue of scaled atomic partial charges. The liquid mass density can be predicted within 0.5-1% of its experimentally determined value when using the corresponding charge scaling. However, in all cases, the predicted self-diffusion coefficient is significantly smaller than a commonly quoted experimental measurement; this result is qualified by the fact that the uncertainty of the experimental value was not available.
采用分子动力学（MD）模拟方法比较了四种力场在预测液态三正丁基磷酸酯（TBP）热力学性质方面的性能。所使用的分子内力参数来自于辅助模型构建与能量精修（AMBER）力场模型。范德华参数基于 AMBER 或优化的液体模拟势能（OPLS）力场。原子部分电荷要么通过进行量子化学计算来分配，要么利用先前发表的数据，并进行缩放以近似平均实验电偶极矩值。基于上述参数的正则系综计算在接近常压和温度的条件下进行，以获得电偶极矩、质量密度和自扩散系数。此外，通过选定原子之间的对关联函数来表征液体的微观结构。结果表明，通过缩放原子部分电荷可以将电偶极矩近似到实验平均值的 1%以内。当使用相应的电荷缩放时，可以将液体质量密度预测到实验确定值的 0.5-1%以内。然而，在所有情况下，预测的自扩散系数都明显小于通常引用的实验测量值；这一结果的原因是实验值的不确定度不可用。
