MD Simulations of the Formation of Stable Clusters in Mixtures of Alkaline Salts and Imidazolium-Based Ionic Liquids

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• 作者：Trinidad M茅ndez-Morales ; Jes煤s Carrete ; Silvia Bouz贸n-Capelo ; Mart铆n P茅rez-Rodr铆guez ; 脫scar Cabeza ; Luis J. Gallego ; Luis M. Varela
• 刊名：The Journal of Physical Chemistry B
• 出版年：2013
• 出版时间：March 21, 2013
• 年：2013
• 卷：117
• 期：11
• 页码：3207-3220
• 全文大小：518K
• 年卷期：v.117,no.11(March 21, 2013)
• ISSN：1520-5207

文摘

Structural and dynamical properties of room-temperature ionic liquids containing the cation 1-butyl-3-methylimidazolium ([BMIM]⁺) and three different anions (hexafluorophosphate, [PF₆]^{鈭?/sup>, tetrafluoroborate, [BF₄]鈭?/sup>, and bis(trifluoromethylsulfonyl)imide, [NTf₂]鈭?/sup>) doped with several molar fractions of lithium salts with a common anion at 298.15 K and 1 atm were investigated by means of molecular dynamics simulations. The effect of the size of the salt cation was also analyzed by comparing these results with those for mixtures of [BMIM][PF₆] with NaPF₆. Lithium/sodium solvation and ionic mobilities were analyzed via the study of radial distribution functions, coordination numbers, cage autocorrelation functions, mean-square displacements (including the analysis of both ballistic and diffusive regimes), self-diffusion coefficients of all the ionic species, velocity and current autocorrelation functions, and ionic conductivity in all the ionic liquid/salt systems. We found that lithium and sodium cations are strongly coordinated in two different positions with the anion present in the mixture. Moreover, [Li]+ and [Na]+ cations were found to form bonded-like, long-lived aggregates with the anions in their first solvation shell, which act as very stable kinetic entities within which a marked rattling motion of salt ions takes place. With very long MD simulation runs, this phenomenon is proved to be on the basis of the decrease of self-diffusion coefficients and ionic conductivities previously reported in experimental and computational results.}