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Yan, Tianying; Wang, Yanting; Knox, Craig; Yan, TY , Nankai Univ, Inst New Energy Mat Chem, Tianjin 300071, Peoples R China
On the Dynamics of Ionic Liquids: Comparisons between Electronically Polarizable and Nonpolarizable Models II
Source PublicationJOURNAL OF PHYSICAL CHEMISTRY B
KeywordKerr-effect Spectroscopy Molecular-force Field 1-butyl-3-methyl Imidazolium Hexafluorophosphate Alkyl Chain-length Transport-properties Physicochemical Properties Intermolecular Dynamics Dielectric Response Relaxation Processes Computer-simulation
AbstractAn electronically polarizable model has been developed for the ionic liquid (IL) 1-ethyl-3-methyl-imidazolium nitrate (EMIM(+)/NO(3)(-)) (Yan et al. J. Phys. Chem. B DOI:10.1021/jp9089112). Molecular dynamics simulations were then performed with both the polarizable and nonpolarizable models. Both models exhibited certain properties that are similar to a supercooled liquid behavior even though the simulations were run at 400 K (89 K above the melting point of EMIM(+)/NO(3)(-)). The ionic mean-squared displacement and transverse current correlation function of both models were well represented by a memory function with a fast Gaussian initial relaxation followed by the two-step exponential functions for beta- and alpha-structural relaxations. Another feature shared by both models is the dynamic heterogeneity, which highlights the complex dynamic behavior of ILs. Apart from the overall slow dynamics, the relaxation of the H-atoms attached to the methyl group demonstrates a "free rotor" type of motion. Also, the ethyl group shows the fastest overall relaxation, due to the weak electrostatic interactions on it Such flexibility enhances the entropic effect and thus favors the liquid state at room temperature. For the dynamical properties reported in this paper, the polarizable model consistently exhibited faster relaxations (including translational and reorientational motions), higher self-diffusion and ionic conductivity, and lower shear viscosity than the nonpolarizable model. The faster relaxations of the polarizable model result from attenuated long-range electrostatic interactions caused by enhanced screening from the. polarization effect. Therefore, simulations based on the polarizable model may be analogous to simulations with the nonpolarizable model at higher temperatures. On the other hand, the enhanced intermolecular interactions for the polarizable model at short-range due to the additional charge-dipole and dipole dipole interactions result in a red shift of the intramolecular C H stretch spectrum and a higher degree Of ion association, leading to a spectrum with enhanced conductivity across the whole frequency range. The vibrational motion associated with the intermolecular hydrogen bonding is highly IR active, highlighting the importance of hydrogen bond dynamics in ILs.
2010
ISSN1520-6106
Volume114Issue:20Pages:6886-6904
Subject AreaPhysics
Indexed BySCI
Citation statistics
Cited Times:46[WOS]   [WOS Record]     [Related Records in WOS]
Document Type期刊论文
Identifierhttp://ir.itp.ac.cn/handle/311006/5102
Collection理论物理所科研产出_SCI论文
Corresponding AuthorYan, TY , Nankai Univ, Inst New Energy Mat Chem, Tianjin 300071, Peoples R China
Recommended Citation
GB/T 7714
Yan, Tianying,Wang, Yanting,Knox, Craig,et al. On the Dynamics of Ionic Liquids: Comparisons between Electronically Polarizable and Nonpolarizable Models II[J]. JOURNAL OF PHYSICAL CHEMISTRY B,2010,114(20):6886-6904.
APA Yan, Tianying,Wang, Yanting,Knox, Craig,&Yan, TY , Nankai Univ, Inst New Energy Mat Chem, Tianjin 300071, Peoples R China.(2010).On the Dynamics of Ionic Liquids: Comparisons between Electronically Polarizable and Nonpolarizable Models II.JOURNAL OF PHYSICAL CHEMISTRY B,114(20),6886-6904.
MLA Yan, Tianying,et al."On the Dynamics of Ionic Liquids: Comparisons between Electronically Polarizable and Nonpolarizable Models II".JOURNAL OF PHYSICAL CHEMISTRY B 114.20(2010):6886-6904.
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