Compressing nearly hard sphere fluids increases glass fragility

We use molecular dynamics to investigate the glass transition occurring at large volume fraction, φ, and low temperature, T , in assemblies of soft repulsive particles. We find that equilibrium dynamics in the (φ, T )-plane obey a form of dynamic scaling in the proximity of a critical point at T =0 and φ=φ 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 φ passes smoothly from that of a strong glass to that of a very fragile glass as φ increases beyond φ 0 . Correlations between fragility and various physical properties are explored.