From Equilibrium to Steady State: The Transient Dynamics of Colloidal Liquids under Shear

TL;DR

This paper combines simulations, theory, and experiments to analyze the transient stress and particle motion in colloidal liquids under shear, revealing the microscopic origins of stress overshoot and super-diffusive behavior near the glass transition.

Contribution

It introduces a comprehensive approach linking macroscopic stress responses to microscopic particle dynamics during shear startup in colloidal glasses.

Findings

Identification of negative correlations causing stress overshoot

Observation of super-diffusive particle motion in transient dynamics

Establishment of a link between stress curves and particle motion

Abstract

We investigate stresses and particle motion during the start up of flow in a colloidal dispersion close to arrest into a glassy state. A combination of molecular dynamics simulation, mode coupling theory and confocal microscopy experiment is used to investigate the origins of the widely observed stress overshoot and (previously not reported) super-diffusive motion in the transient dynamics. A link between the macro-rheological stress versus strain curves and the microscopic particle motion is established. Negative correlations in the transient auto-correlation function of the potential stresses are found responsible for both phenomena, and arise even for homogeneous flows and almost Gaussian particle displacements.