Department of Chemistry, Seoul National University, Seoul 151-747, Korea.
Phys Chem Chem Phys. 2010 Feb 28;12(8):2001-10. doi: 10.1039/b921725h. Epub 2010 Jan 22.
Dynamics of a coarse-grained model for the room-temperature ionic liquid, 1-ethyl-3-methylimidazolium hexafluorophosphate, couched in the united-atom site representation are studied via molecular dynamics simulations. The dynamically heterogeneous behavior of the model resembles that of fragile supercooled liquids. At or close to room temperature, the model ionic liquid exhibits slow dynamics, characterized by nonexponential structural relaxation and subdiffusive behavior. The structural relaxation time, closely related to the viscosity, shows a super-Arrhenius behavior. Local excitations, defined as the displacement of an ion exceeding a threshold distance, are found to be mainly responsible for structural relaxation in the alternating structure of cations and anions. As the temperature is lowered, excitations become progressively more correlated. This results in the decoupling of exchange and persistence times, reflecting a violation of the Stokes-Einstein relation.
通过分子动力学模拟研究了用统一原子位表示的室温离子液体 1-乙基-3-甲基咪唑六氟磷酸盐的粗粒模型的动力学。该模型的动态非均相行为类似于脆弱的过冷液体。在接近或接近室温的情况下，模型离子液体表现出缓慢的动力学，其特征是结构弛豫非指数和亚扩散行为。与粘度密切相关的结构弛豫时间表现出超 Arrhenius 行为。发现局部激发（定义为超过阈值距离的离子位移）主要负责阳离子和阴离子交替结构中的结构弛豫。随着温度的降低，激发变得越来越相关。这导致交换和持久性时间的解耦，反映了 Stokes-Einstein 关系的破坏。
