Dynamic crossover in [VIO^(2+)][Tf_(2)N-]_(2) ionic liquid

作     者：任淦 Gan Ren

作者机构：Departments of Physics&Key Laboratory of Photonic and Optical Detection in Civil AviationCivil Aviation Flight University of ChinaGuanghan 618307China 

出 版 物：《Chinese Physics B》 (中国物理B（英文版）)

年 卷 期：2021年第30卷第1期

页      面：374-379页

核心收录：

学科分类：07[理学] 0702[理学-物理学] 

基　　金：Project supported by the Science Foundation of Civil Aviation Flight University of China(Grant Nos.J2019-059 and JG2019-19)。 

主　　题：ionic liquids dynamic crossover heterogeneity order parameter fractal dimension fragile 

摘      要：Ionic liquids usually behave as fragile liquids,and the temperature dependence of their dynamic properties obeys supper-Arrhenius law.In this work,a dynamic crossover is observed in([VIO^(2+)][Tf_(2)N-]_(2)) ionic liquid at the temperature of 240-800 K.The diffusion coefficient does not obey a single Arrhenius law or a Vogel-Fulcher-Tammann(VFT) relation,but can be well fitted by three Arrhenius laws or a combination of a VFT relation and an Arrhenius law.The origin of the dynamic crossover is analyzed from correlation,structure,and thermodynamics.Ion gets a stronger backward correlation at a lower temperature,as shown by the fractal dimension of the random walk.The temperature dependence function of fractal dimension,heterogeneity order parameter,and thermodynamic data can be separated into three regions similar to that observed in the diffusion coefficient.The two crossover temperatures observed in the three types of data are almost the same as that in diffusion coefficient fitted by three Arrhenius laws.The results indicate that the dynamic crossover of[VIO2+][Tf2 N-]2 is attributed to the heterogeneous structure when it undergoes cooling.