Developing the multipolar-polarizable AMOEBA force field for large molecules presents its own set of complexities. However, by segmenting the molecules into smaller fragments and ensuring that each fragment is transferable to other systems, the process of parameterizing large molecules such as fatty acids can be simplified without compromising accuracy. In this study, we present a fragment-based AMOEBA FF development for long-chain fatty acid ionic liquids (LCFA-ILs). AMOEBA enables us to incorporate polarization to measurably enhance the precision in modeling these large highly charged systems. This is of significant importance since the computational investigation of ILs needs accurate modeling. Additionally, to leverage the tunability of ILs, it is essential to test numerous anion and cation combinations to identify the most suitable formulation for each application. However, conducting such experiments can be resource-intensive and time-consuming, but accurate molecular modeling can expedite the exploration process. Here, the newly developed parameters were evaluated by comparing the decomposed intermolecular interaction energies for ion pairs with energies determined by quantum mechanics calculations as a reference. By employing this FF in molecular dynamics simulations, we predicted bulk and structural properties including density, enthalpy of vaporization, diffusion coefficient, and radial distribution function of diverse LCFA-ILs. Notably, the good agreement between the experimental data and those calculated using our parameters validates the accuracy of our methodology. Therefore, this new procedure provides an accurate approach to parameterizing large systems, paving the way for studying more complicated systems such as lipids, polymers, micelles and membrane proteins.

中文翻译：

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研究脂肪酸基离子液体的特性：AMOEBA 力场的进步


为大分子开发多极化可极化 AMOEBA 力场具有自身的复杂性。然而，通过将分子分割成更小的片段并确保每个片段都可以转移到其他系统，可以在不影响准确性的情况下简化大分子（如脂肪酸）的参数化过程。在这项研究中，我们提出了一种基于片段的长链脂肪酸离子液体 （LCFA-ILs） 的 AMOEBA FF 开发。AMOEBA 使我们能够整合极化，以显著提高这些大型高电荷系统建模的精度。这一点非常重要，因为 IL 的计算研究需要精确的建模。此外，为了利用 IL 的可调性，必须测试多种阴离子和阳离子组合，以确定最适合每种应用的配方。然而，进行此类实验可能既耗费资源又耗时，但准确的分子建模可以加快探索过程。在这里，通过将离子对的分解分子间相互作用能量与量子力学计算确定的能量进行比较作为参考来评估新开发的参数。通过在分子动力学模拟中使用该 FF，我们预测了不同 LCFA-ILs 的体积和结构特性，包括密度、汽化焓、扩散系数和径向分布函数。值得注意的是，实验数据与使用我们的参数计算的数据之间的良好一致性验证了我们方法的准确性。 因此，这种新程序提供了一种参数化大型系统的准确方法，为研究更复杂的系统（如脂质、聚合物、胶束和膜蛋白）铺平了道路。