Departamento de Química Fundamental, Instituto de Química, Universidade de São Paulo, Avenida Professor Lineu Prestes 748, São Paulo 05508-070, Brazil.
Department of Chemistry, The University of Western Ontario, 1151 Richmond Street, London, Ontario N6A 5B7, Canada.
J Chem Inf Model. 2021 Dec 27;61(12):5938-5947. doi: 10.1021/acs.jcim.1c01181. Epub 2021 Nov 19.
Polarizable force fields are gradually becoming a common choice for ionic soft matter, in particular, for molecular dynamics (MD) simulations of ionic liquids (ILs) and deep eutectic solvents (DESs). The CL&Pol force field introduced in 2019 is the first general, transferable, and polarizable force field for MD simulations of different types of DESs. The original formulation contains, however, some problems that appear in simulations of ethaline and may also have a broader impact. First, the originally proposed atomic diameter parameters are unbalanced, resulting in too weak interactions between the chlorides and the hydroxyl groups of the ethylene glycol molecules. This, in turn, causes an artificial phase separation in long simulations. Second, there is an overpolarization of chlorides due to strong induced dipoles that give rise to the presence of peaks and antipeaks at very low -vector values (2.4 nm) in the partial components of the structure factors. In physical terms, this is equivalent to overestimated spatial nanoscale heterogeneity. To correct these problems, we adjusted the chloride-hydroxyl radial distribution functions against ab initio data and then extended the use of the Tang-Toennis damping function for the chlorides' induced dipoles. These adjustments correct the problems without losing the robustness of the CL&Pol force field. The results were also compared with the nonpolarizable version, the CL&P force field. We expect that the corrections will facilitate reliable use of the CL&Pol force field for other types of DESs.
可极化力场逐渐成为离子软物质的常用选择，特别是对于离子液体 (ILs) 和深共晶溶剂 (DESs) 的分子动力学 (MD) 模拟。2019 年引入的 CL&Pol 力场是第一个用于不同类型 DESs 的 MD 模拟的通用、可转移和可极化力场。然而，原始公式存在一些在乙腈模拟中出现的问题，也可能具有更广泛的影响。首先，最初提出的原子直径参数不平衡，导致氯化物与乙二醇分子的羟基之间的相互作用太弱。这反过来又导致在长时间模拟中出现人为的相分离。其次，由于强诱导偶极子，氯化物过度极化，导致结构因子的部分分量中在非常低的矢量值 (2.4nm) 处出现峰和反峰。从物理角度来看，这相当于高估了空间纳米级异质性。为了解决这些问题，我们根据从头算数据调整了氯化物-羟基的径向分布函数，然后扩展了 Tang-Toennis 阻尼函数用于氯化物的诱导偶极子。这些调整在不失 CL&Pol 力场稳健性的情况下纠正了这些问题。结果还与非极化版本的 CL&P 力场进行了比较。我们期望这些修正将有助于可靠地使用 CL&Pol 力场进行其他类型的 DESs 的模拟。
