Berlin 2018 – scientific programme
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DY: Fachverband Dynamik und Statistische Physik
DY 53: Complex Fluids and Soft Matter (joint session DY/ CPP / BP)
DY 53.12: Talk
Wednesday, March 14, 2018, 18:30–18:45, BH-N 334
Charge-Scaling Effect on the Dynamics of an Ionic Liquid: A Molecular Dynamics Simulation Study — •Tamisra Pal and Michael Vogel — Institut für Festkörperphysik, Technische Universität Darmstadt , Hochschulstraße 6, 64289 Darmstadt, Germany
We investigate the structural and dynamical relaxation processes in several charge-scaled 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF6]) room temperature ionic liquids (ILs) using molecular dynamics simulation, to quantify the relevance of the ionic charges on the temperature-dependent structural relaxation, including its dynamic heterogeneity. Charge-scaling provides an innovative way to systematically alter the dynamics of liquids by variation of a single control parameter. The rationale behind the use of reduced partial charges between ±0.48 to 0.72 e is mainly governed by the charge-transfer mechanism taking place in the hydrogen bond between the imidazolium ring and the anion, along with the polarizability effects that invoked huge interest to better describe the dynamics in ILs. We perform extensive simulations from low temperatures in the viscous regime to high temperature far above the melting point to analyze the dependence of the dynamics on the ionic charges in a detailed manner. To characterize dynamics in terms of activation energies over the whole temperature range, recent studies on molecular glass formers have shown that E(T) can be split into low temperature cooperative energy Ec(T) and high temperature constant activation energy E∞. We extend these studies to relate the Ec(T) associated with the collective molecular motion to the dynamical heterogeneity, e.g., to the size of clusters of mobile ions.