arXivDaily arXiv每日学术速递 周一至周五更新
北美退伍军人节(Veterans Day),12 日无更新
arXiv 1805.00697cond-mat.soft
收藏

离子液体中离子输运动力学:两种动力学扩散态

Kinetics of Ion Transport in Ionic Liquids: Two Dynamical Diffusion States

Guang Feng, Ming Chen, Sheng Bi, Zachary A. H. Goodwin, Eugene B. Postnikov, Michael Urbakh, Alexei A. Kornyshev

摘要:

采用经典的分子动力学模拟,研究了室温离子液体[Bmim][TFSI]中离子的迁移率.分析单个阳离子和阴离子的轨迹,我们估计离子在束缚、聚集状态以及离子准自由移动时所花费的时间。使用这些信息,我们评估占主导地位的电导率的自由离子的平均部分。由此限定的自由离子的量包括15- 25%,在300-600 K的范围内随着温度单调增加,其余的离子被暂时束缚,而不是在局部电势中移动。从电流自相关函数计算的电导率作为温度的函数,再现报道的实验数据。有趣的是,对于自由离子,迁移率和扩散系数之间的能斯特-爱因斯坦关系保持得相当好。与电子半导体类似,可以谈论离子液体的离子半导体模型,其具有由能隙分开的离子的价(或激子)和导带态。然而,所获得的离子液体的带隙是非常小的,约0.026 eV,允许两个动态状态之间的容易的互换。

英文摘要:

Using classical molecular dynamics simulations, we investigate the mobility of ions in [Bmim][TFSI], a typical room temperature ionic liquid. Analyzing the trajectories of individual cations and anions, we estimate the time that ions spend in bound, clustered states, and when the ions move quasi-freely. Using this information, we evaluate the average portion of free ions that dominate conductivity. The amount of thus defined free ions comprises 15-25%, monotonically increasing with temperature in the range of 300-600 K, with the rest of the ions being temporarily bound, moving rather in local potentials. The conductivities as a function of temperature, calculated from electric current autocorrelation functions, reproduce reported experimental data well. Interestingly, for free ions the Nernst-Einstein relationship between the mobility and diffusion coefficient holds fairly well. In analogy with electronic semiconductors, one can speak about an ionic semiconductor model for ionic liquids with valence (or excitonic) and conduction band states for ions, separated by an energy gap. The obtained band gap for the ionic liquid is, however, very small, about 0.026 eV, allowing for easy interchanges between the two dynamic states.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

↑