Compressing nearly hard sphere fluids increases glass fragility

TL;DR

This study uses molecular dynamics to explore how compressing soft sphere fluids near a critical point affects their glass transition and fragility, revealing a smooth transition from strong to fragile glass behavior.

Contribution

It identifies a dynamic scaling near a critical point that links the glass transition in soft spheres to hard sphere behavior, highlighting a continuous change in fragility.

Findings

Dynamics obey a scaling law near the critical point

Fragility increases smoothly with volume fraction beyond the critical point

Correlations between fragility and physical properties are established

Abstract

We use molecular dynamics to investigate the glass transition occurring at large volume fraction, phi, and low temperature, T, in assemblies of soft repulsive particles. We find that equilibrium dynamics in the (phi, T) plane obey a form of dynamic scaling in the proximity of a critical point at T=0 and phi=phi_0, which should correspond to the ideal glass transition of hard spheres. This glass point, `point G', is distinct from athermal jamming thresholds. A remarkable consequence of scaling behaviour is that the dynamics at fixed phi passes smoothly from that of a strong glass to that of a very fragile glass as phi increases beyond phi_0. Correlations between fragility and various physical properties are explored.