Ferreira Elisabete S C, Voroshylova Iuliia V, Pereira Carlos M, D S Cordeiro M Natália
Departamento de Química e Bioquímica, LAQV@REQUIMTE, Faculdade de Ciências, Universidade do Porto , Rua do Campo Alegre, 4169-007 Porto, Portugal.
Departamento de Química e Bioquímica, CIQ(UP), Faculdade de Ciências, Universidade do Porto , Rua do Campo Alegre, 4169-007 Porto, Portugal.
J Phys Chem B. 2016 Sep 29;120(38):10124-10137. doi: 10.1021/acs.jpcb.6b07233. Epub 2016 Sep 13.
In this work, we combined various parameters found in the literature for the choline cation, chloride anion, and ethylene glycol to set up force field models (FFMs) for a eutectic mixture, namely, ethaline (1:2 choline chloride/ethylene glycol (ChCl:2EG)). The validation of these models was carried out on the basis of physical and chemical properties, such as the density, expansion coefficient, enthalpy of vaporization, self-diffusion coefficients, isothermal compressibility, surface tension, and shear viscosity. After the initial evaluation of the FFMs, a refinement was found necessary and accomplished by taking into account polarization effects in a mean-field manner. This was achieved by rescaling the electrostatic charges of the ions based on partial charges derived from ab initio molecular dynamics (MD) simulations of the bulk system. Classical all-atom MD simulations performed over a large range of temperatures (298.15-373.15 K) using the refined FFMs clearly showed improved results, allowing a better prediction of experimental properties. Specific structural properties (radial distribution functions and hydrogen bonding) were then analyzed in order to support the adequacy of the proposed refinement. The final selected FFM leads to excellent agreement between simulated and experimental data on dynamic and structural properties. Moreover, compared to the previously reported force field model (Perkins, S. L.; Painter, P.; Colina, C. M. Experimental and Computational Studies of Choline Chloride-Based Deep Eutectic Solvents. J. Chem. Eng. Data 2014, 59, 3652-3662), a 10% improvement in simulated transport properties, i.e., self-diffusion coefficients, was achieved. The isothermal compressibility, surface tension, and shear viscosity for ethaline are accessed in MD simulations for the first time.
在本研究中，我们综合了文献中发现的胆碱阳离子、氯离子和乙二醇的各种参数，建立了一种低共熔混合物即乙盐（1:2氯化胆碱/乙二醇（ChCl:2EG））的力场模型（FFM）。这些模型的验证是基于密度、膨胀系数、汽化焓、自扩散系数、等温压缩率、表面张力和剪切粘度等物理和化学性质进行的。在对力场模型进行初步评估后，发现有必要进行改进，并通过以平均场方式考虑极化效应来实现。这是通过根据从本体系统的从头算分子动力学（MD）模拟得出的部分电荷重新缩放离子的静电荷来实现的。使用改进后的力场模型在大范围温度（298.15 - 373.15 K）下进行的经典全原子MD模拟清楚地显示出结果得到了改善，能够更好地预测实验性质。然后分析了特定的结构性质（径向分布函数和氢键），以支持所提出的改进的充分性。最终选定的力场模型在动态和结构性质的模拟数据与实验数据之间达成了极好的一致性。此外，与先前报道的力场模型（Perkins, S. L.; Painter, P.; Colina, C. M. Experimental and Computational Studies of Choline Chloride-Based Deep Eutectic Solvents. J. Chem. Eng. Data 2014, 59, 3652 - 3662）相比，模拟的传输性质即自扩散系数提高了10%。首次在MD模拟中获得了乙盐的等温压缩率、表面张力和剪切粘度。
