The role of shear in crystallization kinetics: From suppression to enhancement

TL;DR

This study uses molecular dynamics simulations to explore how shear flow influences crystallization in hard sphere liquids, revealing that shear can both suppress and enhance crystallization depending on the regime and strain rate.

Contribution

It uncovers the dual role of shear in crystallization kinetics, showing suppression in activated regimes and enhancement in diffusion-limited regimes, with effects varying by strain rate.

Findings

Shear can both suppress and enhance crystallization.

Shear effects depend on the quiescent mechanism and strain rate.

Crystallization becomes activated again at high strain rates near the glass transition.

Abstract

In many technical applications, but also in natural processes like ice nucleation in clouds, crystallization proceeds in the presence of stresses and flows, hence the importance to understand the crystallization mechanism in simple situations. We employ molecular dynamics simulations to study the crystallization kinetics of a nearly hard sphere liquid that is weakly sheared. We demonstrate that shear flow both enhances and suppresses the crystallization kinetics of hard spheres. The effect of shear depends on the quiescent mechanism: suppression in the activated regime and enhancement in the diffusion-limited regime for small strain rates. At higher strain rates crystallization again becomes an activated process even at densities close to the glass transition.