University of Rochester, Rochester, New York 14627-0216, USA.
Phys Chem Chem Phys. 2011 Sep 21;13(35):16055-62. doi: 10.1039/c1cp21379b. Epub 2011 Aug 9.
Based on classical molecular dynamics simulations, we discuss the impact of Coulombic interactions on a comprehensive set of properties of room temperature ionic liquids (RTILs) containing 1,3-dimethylimidazolium (MMIM(+)), N-butylpyridinium (BPY(+)), and bis(trifluoromethane sulfonyl)imide (TFSI(-)) ions. Ionic transport is found to be noticeably hindered by the excessive Coulombic energy, originating from the neglect of electronic polarization in the condensed phase of these RTILs. Starting from the models, recently suggested by Lopes and Padua, we show that realistic ionic dynamics can be achieved by the uniform scaling of electrostatic charges on all interaction sites. The original model systematically overestimates density and heat of vaporization of RTILs. Since density linearly depends on charge scaling, it is possible to use it as a convenient beacon to promptly derive a correct scaling factor. Based on the simulations of [BPY][TFSI] and [MMIM][TFSI] over a wide temperature range, we conclude that the suggested technique is feasible to greatly improve quality of the already existing non-polarizable FFs for RTILs.
基于经典分子动力学模拟，我们讨论了库仑相互作用对包含 1,3-二甲基咪唑鎓（MMIM(+)）、N-丁基吡啶鎓（BPY(+)）和双（三氟甲烷磺酰基）亚胺（TFSI(-)）离子的室温离子液体（RTILs）的一系列性质的影响。发现离子输运受到来自于这些 RTILs 凝聚相电子极化忽略的大量库仑能的明显阻碍。从 Lopes 和 Padua 最近提出的模型出发，我们展示了通过对所有相互作用位点的静电电荷进行均匀缩放，可以实现真实的离子动力学。原始模型系统地高估了 RTILs 的密度和蒸发热。由于密度与电荷缩放呈线性关系，因此可以将其用作快速得出正确缩放因子的便利基准。基于对 [BPY][TFSI]和 [MMIM][TFSI]在很宽温度范围内的模拟，我们得出结论，所提出的技术可行，可大大提高现有的非极化力场对 RTILs 的质量。
