Töpfer Kai, Boittier Eric, Devereux Mike, Pasti Andrea, Hamm Peter, Meuwly Markus
Department of Chemistry, University of Basel, Klingelbergstrasse 80, CH-4056 Basel, Switzerland.
Department of Chemistry, University of Zürich, CH-8000 Zürich, Switzerland.
J Phys Chem B. 2024 Nov 7;128(44):10937-10949. doi: 10.1021/acs.jpcb.4c05480. Epub 2024 Oct 24.
Parametrizing energy functions for ionic systems can be challenging. Here, the total energy function for an eutectic system consisting of water, SCN, K and acetamide is improved vis-a-vis experimentally measured properties. Given the importance of electrostatic interactions, two different types of models are considered: the first (model ) uses atom-centered multipole whereas the other two (models and ) are based on fluctuating minimal distributed charges (fMDCM) that respond to geometrical changes of SCN. The Lennard-Jones parameters of the anion are adjusted to best reproduce experimentally known hydration free energies and densities, which are matched to within a few percent for the final models irrespective of the electrostatic model. Molecular dynamics simulations of the eutectic mixtures with varying water content (between 0 and 100%) yield radial distribution functions and frequency correlation functions for the CN-stretch vibration. Comparison with experiments indicates that models based on fMDCM are considerably more consistent than those using multipoles. Computed viscosities from models and are within 30% of measured values and their change with increasing water content is consistent with experiments. This is not the case for model .
为离子系统的能量函数设定参数可能具有挑战性。在此，针对由水、硫氰根、钾和乙酰胺组成的共晶体系，相对于实验测量性质，其总能量函数得到了改进。鉴于静电相互作用的重要性，考虑了两种不同类型的模型：第一种（模型 ）使用以原子为中心的多极子，而另外两种（模型 和 ）基于对硫氰根几何变化做出响应的波动最小分布电荷（fMDCM）。调整阴离子的 Lennard-Jones 参数，以最佳地重现实验已知的水化自由能和密度，最终模型的这些量在几个百分点内匹配，而与静电模型无关。对不同含水量（0%至100%）的共晶混合物进行分子动力学模拟，得出了用于CN伸缩振动的径向分布函数和频率相关函数。与实验的比较表明，基于fMDCM的模型比使用多极子的模型更加一致。模型 和 计算得到的粘度在测量值的30%以内，并且它们随含水量增加的变化与实验一致。模型 则并非如此。
