Arrest of flow and emergence of activated processes at the glass transition of a suspension of particles with hard sphere-like interactions

TL;DR

This study investigates the glass transition in a hard sphere-like particle suspension, revealing how density fluctuation arrest and momentum response impairment lead to increased viscosity and activated processes that prevent a perfect glass formation.

Contribution

It combines scattering functions and velocity correlations to elucidate the mechanisms behind the glass transition and the role of thermal energy in activated processes.

Findings

Density fluctuations arrest from the main structure factor peak.

Viscosity increases as momentum response is impaired.

Thermal energy stretching indicates ergodicity-restoring processes.

Abstract

By combining aspects of the coherent and self intermediate scattering functions, measured by dynamical light scattering on a suspension of hard sphere-like particles, we show that the arrest of particle number density fluctuations spreads from the position of the main structure factor peak. Taking the velocity auto-correlation function into account we propose that as density fluctuations are arrested the system's ability to respond to diffusing momentum currents is impaired and, accordingly, the viscosity increases. From the stretching of the coherent intermediate scattering function we read a quantitative manifestation of the undissipated thermal energy, the source of those, ergodicity restoring, processes that short-circuit the sharp transition to a perfect glass.