Dr. Tamisra Pal

Post Doctoral Research Fellow
Technische Universitat Darmstadt
Email : tamisra.pal[at]gmail.com

 

 

 

Brief bio:

Tamisra Pal received her M. Sc. in Chemistry from University of Calcutta in 2008. She obtained her Ph.D. in Chemistry under the supervision of Prof. Ranjit Biswas, at S. N. Bose National Centre for Basic Sciences, Kolkata. She has been post-doctoral researcher in the group of Prof. Dr. Michael Vogel at Technische Universitat Darmstadt, Germany, since 2015. Her research interests include understanding complex structural and dynamical behavior of room temperature ionic liquid which form self-assemblies in bulk and under confinement, handling new tools and techniques in molecular dynamics simulation (All-Atom and Coarse-Graining) to investigate several other properties in complex fluids.

 

EFFECT OF ELECTROSTATIC INTERACTIONS ON THE STRUCTURAL RELAXATION OF IONIC LIQUIDS: A MOLECULAR DYNAMICS SIMULATION STUDY

 

Ionic liquids (ILs) are known as good glass formers. These liquids close to the glass transition temperature in bulk or inside nanoscopic confinements exhibit a slowdown of dynamics of several orders of magnitude. Particularly, we tried to elucidate the microscopic mechanism of the slowdown in structural relaxation to the energy associated with the growth of the length scale upon cooling. In this work, we investigate the structural and dynamical relaxation processes in several charge-scaled 1-butyl-3-methylimidazolium hexafluorophosphate ([Bmim][PF₆]) room temperature ionic liquids 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 can be split into low temperature cooperative energy and high temperature constant activation energy . We extend these studies to relate the associated with the collective molecular motion to the dynamical heterogeneity of the structural relaxation, e.g., to the size of clusters of mobile ions.