Homogeneous nucleation of colloidal melts under the influence of shearing fields

TL;DR

This study investigates how shear flow influences homogeneous crystal nucleation in colloidal melts, revealing suppression of nucleation, increased critical nucleus size, and anisotropic nucleus orientation using simulations and theoretical modeling.

Contribution

It introduces a phenomenological extension of classical nucleation theory to account for shear effects and characterizes the anisotropic orientation of nuclei under shear flow.

Findings

Shear flow suppresses crystal nucleation.

Critical nucleus size increases with shear rate.

Nuclei tend to align with the vorticity direction.

Abstract

We study the effect of shear flow on homogeneous crystal nucleation, using Brownian Dynamics simulations in combination with an umbrella sampling like technique. The symmetry breaking due to shear results in anisotropic radial distribution functions. The homogeneous shear rate suppresses crystal nucleation and leads to an increase of the size of the critical nucleus. These observations can be described by a simple, phenomenological extension of classical nucleation theory. In addition, we find that nuclei have a preferential orientation with respect to the direction of shear. On average the longest dimension of a nucleus is along the vorticity direction, while the shortest dimension is preferably perpendicular to that and slightly tilted with respect to the gradient direction.