Saric Denis, Kohns Maximilian, Vrabec Jadran
Thermodynamics and Energy Technology, University of Paderborn, 33098 Paderborn, Germany.
Laboratory of Engineering Thermodynamics, Technische Universität Kaiserslautern, 67633 Kaiserslautern, Germany.
J Chem Phys. 2020 Apr 30;152(16):164502. doi: 10.1063/1.5144991.
The concentration dependence of the dielectric constant and the density of 11 aqueous alkali halide solutions (LiCl, NaCl, KCl, RbCl, CsCl, LiI, NaI, KI, CsI, KF, and CsF) is investigated by molecular simulation. Predictions using eight non-polarizable ion force fields combined with the TIP4P/ε water model are compared to experimental data. The influence of the water model and the temperature on the results for the NaCl brine are also addressed. The TIP4P/ε water model improves the accuracy of dielectric constant predictions compared to the SPC/E water model. The solution density is predicted well by most ion models. Almost all ion force fields qualitatively capture the decline of the dielectric constant with the increase of concentration for all solutions and with the increase of temperature for NaCl brine. However, the sampled dielectric constant is mostly in poor quantitative agreement with experimental data. These results are related to the microscopic solution structure, ion pairing, and ultimately the force field parameters. Ion force fields with excessive contact ion pairing and precipitation below the experimental solubility limit generally yield higher dielectric constant values. An adequate reproduction of the experimental solubility limit should therefore be a prerequisite for further investigations of the dielectric constant of aqueous electrolyte solutions by molecular simulation.
通过分子模拟研究了11种碱金属卤化物水溶液（LiCl、NaCl、KCl、RbCl、CsCl、LiI、NaI、KI、CsI、KF和CsF）的介电常数和密度与浓度的关系。将使用八种非极化离子力场结合TIP4P/ε水模型的预测结果与实验数据进行了比较。还讨论了水模型和温度对NaCl盐水结果的影响。与SPC/E水模型相比，TIP4P/ε水模型提高了介电常数预测的准确性。大多数离子模型对溶液密度的预测效果良好。几乎所有离子力场在定性上都能捕捉到所有溶液介电常数随浓度增加以及NaCl盐水介电常数随温度增加而下降的趋势。然而，采样得到的介电常数在定量上大多与实验数据吻合较差。这些结果与微观溶液结构、离子对以及最终的力场参数有关。具有过多接触离子对且在实验溶解度极限以下出现沉淀的离子力场通常会产生较高的介电常数数值。因此，对于通过分子模拟进一步研究水电解质溶液的介电常数而言，充分再现实验溶解度极限应是一个先决条件。
