A Fragile-Strong Fluid Crossover and Universal Relaxation Times in a Confined Hard Disc Fluid

TL;DR

This study reveals a fragile-strong fluid crossover in confined hard disc systems, linked to jamming landscape properties, with universal relaxation behavior explained by facilitated dynamics, challenging traditional Adam-Gibbs predictions.

Contribution

It demonstrates the fragile-strong crossover in confined hard disc fluids and links it to jamming landscape features, introducing a facilitated dynamics perspective.

Findings

Crossover occurs at maximum isobaric heat capacity.

Relaxation times collapse onto a master curve when rescaled.

Facilitated dynamics effectively describe the crossover.

Abstract

We show that a system of hard discs confined to a narrow channel exhibits a fragile-strong fluid crossover located at the maximum of the isobaric heat capacity and that the relaxation times for different channel widths fall onto a single master curve when rescaled by the relaxation times and temperatures of the crossover. Calculations of the configurational entropy and the inherent structure equation of state find that the crossover is related to properties of the jamming landscape for the model but that the Adams-Gibbs relation does not predict the relaxation behavior. We also show that a facilitated dynamics description of the system, where kinetically excited regions are identified with local packing arrangements of the discs, successfully describes the fragile-strong crossover.