Institute of Theoretical Chemistry, State Key Laboratory of Theoretical and Computational Chemistry, Jilin University, Changchun 130023, China.
Phys Chem Chem Phys. 2013 May 28;15(20):7701-12. doi: 10.1039/c3cp44108c. Epub 2013 Apr 17.
A coarse-grained model, with three sets of effective pair potentials for 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) ionic liquid, is introduced and used to study the structural and dynamical properties over extended length and time scales. Three sets of effective pair potentials between coarse-grained beads are obtained using the Newton Inversion and the Iterative Boltzmann Inversion methods, respectively, with different treatment of electrostatic interactions. The coarse-grained simulation results are compared systematically with corresponding atomistic simulation results on several thermodynamical and structural quantities together with charge density distributions. In addition, the scattering and dynamical properties are also calculated and compared to both atomistic simulation results and experimental measurements. While all three sets of the effective potentials provide perfect agreement with the atomistic simulation for radial distribution functions, our analysis shows that in coarse-grained simulations, the long-range electrostatic interactions between ionic groups are important and should be treated explicitly to improve the reliability of other simulation results. With explicit incorporation of electrostatic interactions derived from the Newton Inversion, the coarse-grained potentials provide the most consistent description of thermodynamical, scattering and dynamical properties including their temperature dependence as compared to atomistic simulations. We conclude also that the current atomistic force field should be further improved to meet specific requirements for studying the dynamical properties of the [Bmim][PF6] system over a large temperature range.
介绍并使用了一种粗粒化模型，该模型具有针对 1-丁基-3-甲基咪唑六氟磷酸盐([Bmim][PF6])离子液体的三组有效对势能，以在较大的长度和时间尺度上研究结构和动力学性质。使用牛顿反演和迭代玻尔兹曼反演方法，分别用不同的静电相互作用处理方法获得了三组粗粒化珠子之间的有效对势能。将粗粒化模拟结果与几个热力学和结构量以及电荷密度分布的相应原子模拟结果进行了系统比较。此外，还计算并比较了散射和动力学性质，以与原子模拟结果和实验测量结果进行比较。虽然三组有效势能都为径向分布函数提供了与原子模拟完全一致的结果，但我们的分析表明，在粗粒化模拟中，离子基团之间的长程静电相互作用很重要，应该明确处理以提高其他模拟结果的可靠性。与牛顿反演得出的静电相互作用明确结合使用，与原子模拟相比，粗粒化势提供了对热力学、散射和动力学性质（包括其温度依赖性）的最一致描述。我们还得出结论，目前的原子力场应进一步改进，以满足在较大温度范围内研究[Bmim][PF6]系统动力学性质的特定要求。
