Duignan Timothy T, Baer Marcel D, Schenter Gregory K, Mundy Christopher J
Physical Science Division , Pacific Northwest National Laboratory , P.O. Box 999 , Richland , Washington 99352 , USA . Email:
Chem Sci. 2017 Sep 1;8(9):6131-6140. doi: 10.1039/c7sc02138k. Epub 2017 Jul 4.
Single ion solvation free energies are one of the most important properties of electrolyte solutions and yet there is ongoing debate about what these values are. Only the values for neutral ion pairs are known. Here, we use DFT interaction potentials with molecular dynamics simulation (DFT-MD) combined with a modified version of the quasi-chemical theory (QCT) to calculate these energies for the lithium and fluoride ions. A method to correct for the error in the DFT functional is developed and very good agreement with the experimental value for the lithium fluoride pair is obtained. Moreover, this method partitions the energies into physically intuitive terms such as surface potential, cavity and charging energies which are amenable to descriptions with reduced models. Our research suggests that lithium's solvation free energy is dominated by the free energetics of a charged hard sphere, whereas fluoride exhibits significant quantum mechanical behavior that cannot be simply described with a reduced model.
单离子溶剂化自由能是电解质溶液最重要的性质之一，但关于这些数值究竟是多少仍存在争议。目前仅知道中性离子对的数值。在此，我们使用密度泛函理论相互作用势结合分子动力学模拟（DFT-MD），并结合准化学理论（QCT）的修正版本来计算锂离子和氟离子的这些能量。我们开发了一种校正DFT泛函中误差的方法，并与氟化锂对的实验值取得了很好的一致性。此外，该方法将能量划分为表面势、空穴和充电能等具有物理直观意义的项，这些项适合用简化模型来描述。我们的研究表明，锂的溶剂化自由能主要由带电硬球的自由能主导，而氟则表现出显著的量子力学行为，无法用简化模型简单描述。
