Work

Heterogeneous dynamics and its length scale in simple ionic liquid models: a computational study

Year: 2016

Type: article

Abstract: We numerically investigate the dynamic heterogeneity and its length scale found in coarse-grained ionic liquid model systems. In our ionic liquid model systems, cations are modeled as dimers with a positive charge, while anions are modeled as monomers with a negative charge, respectively. To study the effect of the charge distributions on the cations, two ionic liquid models with different charge distributions are used and the model with a neutral charge is also considered as a counterpart. To reveal the heterogeneous dynamics in the model systems, we examine spatial distributions of displacement and time distributions of exchange and persistence times. All the models show a significant increase of the dynamic heterogeneity as the temperature is lowered. The dynamic heterogeneity is quantified via the well-known four-point susceptibility, χ4(t), which measures the fluctuations of a time correlation function. The dynamic correlation length is calculated by fitting the dynamic structure factor, S4(k,t), with the Ornstein-Zernike form at the time scale at which the dynamic heterogeneity reaches the maximum value. The obtained time and length scales exhibit a power law relation at the low temperatures, similar to various supercooled liquid models. In particular, the charged model systems show unusual crossover behaviors which are not observed in the uncharged model system. We ascribe the crossover behavior to the enhanced cage effect caused by charges on the particles.

Source: Physical Chemistry Chemical Physics

DOI: 10.1039/c5cp07368e

Authors: Soree Kim, Sang-Won Park, YounJoon Jung

Institution: Seoul National University

Language: English

Topic: Material Dynamics and Properties

Subfield: Materials Chemistry

Field: Materials Science

Domain: Physical Sciences

Open Access status: green

Funder: Korea Institute of Science and Technology Information

Award: G8321253091