Are there stable ion-pairs in room-temperature ionic liquids? Molecular dynamics simulations of 1-n-butyl-3-methylimidazolium hexafluorophosphate.
Are there stable ion-pairs in room-temperature ionic liquids? Molecular dynamics simulations of 1-n-butyl-3-methylimidazolium hexafluorophosphate.
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DOI：
10.1021/ja906337p
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发表时间：
2009-10
影响因子：
15
通讯作者：
Wei Zhao;F. Leroy;B. Heggen;Stefan Zahn;B. Kirchner;S. Balasubramanian;F. Müller-Plathe
中科院分区：
文献类型：
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作者：
Wei Zhao;F. Leroy;B. Heggen;Stefan Zahn;B. Kirchner;S. Balasubramanian;F. Müller-Plathe
采用全原子模型对离子液体1-正丁基-3-甲基咪唑六氟磷酸[bmim][PF(6)]进行了分子动力学模拟。对一些结构和动力特性进行了分析。发现氢键比预期的要弱，因为它们的寿命短，这是由于阴离子的快速旋转运动。基于长轨迹测量了离子扩散系数和离子电导率等输运特性，与实验结果吻合较好。离子液体的电导率偏离能斯特-爱因斯坦关系的现象在我们的工作中得到了很好的再现。根据我们的分析，我们认为这种偏差是由于阳离子和阴离子随时间尺度上升到纳秒的相关运动造成的。相比之下，我们没有发现长期离子对一起迁移的证据。
Molecular dynamics simulations with an all-atom model were carried out to study the ionic liquid 1-n-butyl-3-methylimidazolium hexafluorophosphate, [bmim][PF(6)]. Analysis was carried out to characterize a number of structural and dynamic properties. It is found that the hydrogen bonds are weaker than expected, as indicated by their short lifetimes, which is due to the fast rotational motion of anions. Transport properties such as ion diffusion coefficients and ionic conductivity were also measured on the basis of long trajectories, and good agreement was obtained with experimental results. The phenomenon that electrical conductivity of ionic liquids deviates from the Nernst-Einstein relation was well reproduced in our work. On the basis of our analysis, we suggest that this deviation results from the correlated motion of cations and anions over time scales up to nanoseconds. In contrast, we find no evidence for long-lived ion-pairs migrating together.