Wang Ning, Maginn Edward J
Department of Chemical and Biomolecular Engineering, University of Notre Dame, Notre Dame, Indiana 46556, United States.
J Phys Chem B. 2024 Jan 25;128(3):871-881. doi: 10.1021/acs.jpcb.3c07238. Epub 2024 Jan 16.
Ionic liquids (ILs) have been used in many applications, including gas separations, electrochemistry, lubrication, and catalysis. Understanding how the different properties of ILs are related to their chemical structure and composition is crucial for these applications. Experimental investigations often provide limited insights and can be tedious in exploring a range of state points. Therefore, molecular simulations have emerged as a powerful tool that not only offers a microscopic perspective but also enables rapid screening and prediction of physical properties. The accuracy of these predictions, however, depends on the quality of the intermolecular potentials (force fields) used. The widely used classical fixed charge models, such as GAFF, OPLS, and CL&P, are popular due to their simplicity and computational efficiency. However, it has been shown that the use of integer charges with these classical models leads to sluggish dynamics. The use of scaled charge models can improve the dynamics, but these mean-field approaches are unable to account for polarization effects explicitly. Several different approaches have been proposed to include polarizability in IL force fields. In this work, we follow the protocol of the CL&Pol model to develop a Drude oscillator model based on the GAFF force field (Goloviznina, K., et al. , , 5858). We compare the performance of the model for eight imidazolium- and pyrrolidinium-based ILs against that of other models. We find that the new model provides reasonable estimations of density, self-diffusivity, and structural properties for these ILs and suggests a relatively simple way of extending the general GAFF model to more ILs.
离子液体（ILs）已被应用于许多领域，包括气体分离、电化学、润滑和催化。了解离子液体的不同性质如何与其化学结构和组成相关，对于这些应用至关重要。实验研究往往提供的见解有限，并且在探索一系列状态点时可能很繁琐。因此，分子模拟已成为一种强大的工具，它不仅提供微观视角，还能快速筛选和预测物理性质。然而，这些预测的准确性取决于所使用的分子间势（力场）的质量。广泛使用的经典固定电荷模型，如GAFF、OPLS和CL&P，因其简单性和计算效率而受到欢迎。然而，已经表明，在这些经典模型中使用整数电荷会导致动力学迟缓。使用缩放电荷模型可以改善动力学，但这些平均场方法无法明确考虑极化效应。已经提出了几种不同的方法来将极化率纳入离子液体力场。在这项工作中，我们遵循CL&Pol模型的方案，基于GAFF力场开发了一种德鲁德振子模型（Goloviznina, K.,等人， ， ，5858）。我们将该模型对八种基于咪唑鎓和吡咯烷鎓的离子液体的性能与其他模型进行了比较。我们发现，新模型为这些离子液体的密度、自扩散系数和结构性质提供了合理的估计，并提出了一种将通用GAFF模型扩展到更多离子液体的相对简单的方法。
