Institute for Computational Physics, University Stuttgart, Pfaffenwaldring 27, 70569 Stuttgart, Germany.
Chemphyschem. 2012 May 14;13(7):1625-37. doi: 10.1002/cphc.201100997. Epub 2012 Feb 17.
Classical molecular dynamics simulations are a valuable tool to study the mechanisms that dominate the properties of ionic liquids (ILs) on the atomistic and molecular level. However, the basis for any molecular dynamics simulation is an accurate force field describing the effective interactions between all atoms in the IL. Normally this is done by empirical potentials which can be partially derived from quantum mechanical calculations on simple subunits or have been fitted to experimental data. Unfortunately, the number of accurate classical non-polarizable models for ILs that allow a reasonable description of both dynamical and statical properties is still low. However, the strongly increasing computational power allows one to apply computationally more expensive methods, and even polarizable-force-field-based models on time and length scales long enough to ensure a proper sampling of the phase space. This review attempts to summarize recent achievements and methods in the development of classical force fields for ionic liquids. As this class of salts covers a large number of compounds, we focus our review on imidazolium-based ionic liquids, but show that the main conclusions are valid for non-imidazolium salts, too. Insight obtained from recent electronic density functional results into the parametrization of partial charges and on the influence of polarization effects in bulk ILs is highlighted. An overview is given of different available force fields, ranging from the atomistic to the coarse-grained level, covering implicit as well as explicit modeling of polarization. We show that the recently popular usage of the ion charge as fit parameter can looked upon as treating polarization effects in a mean-field matter.
经典分子动力学模拟是研究离子液体（ILs）在原子和分子水平上性质的主要机制的一种有价值的工具。然而，任何分子动力学模拟的基础都是一个准确的力场，该力场描述了 IL 中所有原子之间的有效相互作用。通常这是通过经验势来完成的，经验势可以部分从简单的亚基的量子力学计算中推导出来，也可以拟合实验数据。不幸的是，允许对动力学和静态性质进行合理描述的 IL 准确的经典非极化模型的数量仍然很少。然而，计算能力的大幅提高使得人们可以在足够长的时间和长度尺度上应用更昂贵的计算方法，甚至是基于极化力场的模型，以确保对相空间进行适当的采样。本文综述试图总结离子液体经典力场开发的最新成果和方法。由于这类盐涵盖了大量的化合物，我们的综述重点是基于咪唑鎓的离子液体，但也表明主要结论对非咪唑鎓盐也是有效的。突出显示了从最近的电子密度泛函结果中获得的关于部分电荷参数化和在大块 IL 中极化影响的见解。综述了从原子到粗粒级别的不同可用力场，涵盖了对极化的隐式和显式建模。我们表明，最近流行的将离子电荷用作拟合参数的方法可以看作是在平均场物质中处理极化效应。
