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arXiv 2102.02761cond-mat.soft
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离子液体不同粗粒模型的动力学性质

Dynamical properties across different coarse-grained models for ionic liquids

Joseph F. Rudzinski, Sebastian Kloth, Svenja Wörner, Tamisra Pal, Kurt Kremer, Tristan Bereau, Michael Vogel

摘要:

室温离子液体(RTILs)因其丰富的物理化学性质(包括结构和动力学的不均一性)而在分子液体中脱颖而出。RTIL中静电相互作用的重要性导致了长的特征长度和时间尺度,并促使了一些粗粒度(CG)模拟模型的发展。在这项研究中,我们的目标是更好地了解某些CG参数化策略和动力学性质和所产生的模型的可转移性之间的联系。我们系统地比较了五个CG模型:一个模型主要参数化的实验热力学观测值;这个模型的改进,以增加其结构的准确性;和三个模型,再现一组给定的结构分布函数的建设,不同的分子内参数化和参考温度。所有五个CG模型显示有限的结构可转移性随温度的变化,也导致各种有效的动力学加速因子,相对于一个参考原子模型。另一方面,结构为基础的CG模型往往会导致更一致的阳离子-阴离子相对扩散比基于的模型,为一个单一的热力学状态点。通过连接短时间尺度和长时间尺度的动力学行为,我们证明了不同的粗粒度模型的不同的动力学性质可以在很大程度上崩溃到一个单一的曲线,这提供了证据的路线,以构建动态一致的CG模型的RTIL。

英文摘要:

Room-temperature ionic liquids (RTILs) stand out among molecular liquids for their rich physicochemical characteristics, including structural and dynamic heterogeneity. The significance of electrostatic interactions in RTILs results in long characteristic length- and timescales, and has motivated the development of a number of coarse-grained (CG) simulation models. In this study, we aim to better understand the connection between certain CG parametrization strategies and the dynamical properties and transferability of the resulting models. We systematically compare five CG models: a model largely parametrized from experimental thermodynamic observables; a refinement of this model to increase its structural accuracy; and three models that reproduce a given set of structural distribution functions by construction, with varying intramolecular parametrizations and reference temperatures. All five CG models display limited structural transferability over temperature, and also result in various effective dynamical speedup factors, relative to a reference atomistic model. On the other hand, the structure-based CG models tend to result in more consistent cation-anion relative diffusion than the thermodynamic-based models, for a single thermodynamic state point. By linking short- and long-timescale dynamical behaviors, we demonstrate that the varying dynamical properties of the different coarse-grained models can be largely collapsed onto a single curve, which provides evidence for a route to constructing dynamically-consistent CG models of RTILs.

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