Department of Chemical and Biomolecular Engineering, Tulane University, New Orleans, Louisiana 70118, USA.
Sandia National Laboratories, Center for Biological and Engineering Sciences, Albuquerque, New Mexico 87185, USA.
J Chem Phys. 2018 Jun 14;148(22):222821. doi: 10.1063/1.5023121.
Laying a basis for molecularly specific theory for the mobilities of ions in solutions of practical interest, we report a broad survey of velocity autocorrelation functions (VACFs) of Li and PF ions in water, ethylene carbonate, propylene carbonate, and acetonitrile solutions. We extract the memory function, γ(t), which characterizes the random forces governing the mobilities of ions. We provide comparisons controlling for the effects of electrolyte concentration and ion-pairing, van der Waals attractive interactions, and solvent molecular characteristics. For the heavier ion (PF), velocity relaxations are all similar: negative tail relaxations for the VACF and a clear second relaxation for γt, observed previously also for other molecular ions and with n-pentanol as the solvent. For the light Li ion, short time-scale oscillatory behavior masks simple, longer time-scale relaxation of γt. But the corresponding analysis of the solventberg LiHO does conform to the standard picture set by all the PF results.
为分子特异性理论奠定基础，我们报告了广泛的研究，涉及在实际感兴趣的溶液中锂离子和 PF 离子的速度自相关函数 (VACF)。我们提取了记忆函数 γ(t)，它描述了控制离子迁移率的随机力。我们提供了比较，控制了电解质浓度和离子对、范德华吸引力以及溶剂分子特性的影响。对于较重的离子 (PF)，速度弛豫都是相似的：VACF 的负尾部弛豫和 γt 的明显第二次弛豫，以前也观察到其他分子离子和以正戊醇作为溶剂的情况。对于轻的 Li 离子，短时间尺度的振荡行为掩盖了 γt 的简单、长时间尺度的弛豫。但是对溶剂伯格 LiHO 的相应分析符合所有 PF 结果所设定的标准图像。
