Effect of total and pair configurational entropy in determining dynamics of supercooled liquids over a range of densities

TL;DR

This study investigates how total and pair configurational entropy influence the dynamics of supercooled liquids with Lennard-Jones and WCA potentials across various densities, revealing thermodynamic origins of their differences.

Contribution

It demonstrates that differences in dynamics between LJ and WCA systems can be explained thermodynamically using configurational entropy, and explores how these differences vary with density.

Findings

Thermodynamic differences decrease at higher densities.

Pair entropy differences originate mainly from A-A and A-B particle pairs.

Dynamics differences are explained by configurational entropy variations.

Abstract

In this paper, we present a study of supercooled liquids interacting with the Lennard Jones (LJ) potential and the corresponding purely repulsive (Weeks-Chandler-Andersen or WCA) potential, over a range of densities and temperatures, in order to understand the origin of their different dynamics in spite of their structures being similar. Using the configurational entropy as the thermodynamic marker via the Adam Gibbs (AG) relation, we show that the difference in the dynamics of these two systems at low temperatures can be explained from thermodynamics. At higher densities both the thermodynamical and dynamical difference between these model systems decrease, which is quantitatively demonstrated in this paper by calculating different parameters. The study also reveals the origin of the difference in pair entropy despite the similarity in the structure. Although the maximum difference in structure is obtained in the partial radial distribution function (rdf) of the B type of particles, the rdf of AA pairs and AB pairs give rise to the differences in the entropy and dynamics. This work supports the observation made in an earlier study (Phys. Rev. Lett.,\textbf {113}, 225701, 2014) and shows that they are generic in nature, independent of density.