Crystallization in a sheared colloidal suspension

Abstract

We study numerically the crystallization process in a supersaturated suspension of repulsive colloidal particles driven by simple shear flow. The effect of the shear flow on crystallization is two-fold: while it suppresses the initial nucleation, once a large enough critical nucleus has formed its growth is enhanced by the shear flow. Combining both effects implies an optimal strain rate at which the overall crystallization rate has a maximum. To gain insight into the underlying mechanisms, we employ a discrete state model describing the transitions between the local structural configurations around single particles. We observe a time-scale separation between these transitions and the overall progress of the crystallization allowing for an effective Markovian description. By using this model, we demonstrate that the suppression of nucleation is due to the inhibition of a pre-structured liquid.

Crystal nucleation as the ordering of multiple order parameters

“…The effects of external fields on precursor regions were also considered [37,139,157]. External walls were considered experimentally and numerically in vertically vibrated quasi-two-dimensional granular liquids and two-and three-dimensional colloidal systems respectively [157], showing that the walls enhance structural order in the fluid, in a manner that is consistent with the bulk behavior, under an influence of wall-induced short-range translational ordering (i.e., layering).…”

“…[37] instead considered the effect of rough walls on colloidal suspensions under the effects of gravity, where the suppression of bond orientational order and layering next to the walls results in a strong suppression of nucleation. Also shear was shown to suppress precursor regions [139], while at the same time increasing the rate of growth of crystals. The interplay between these two effects is at the origin of the non-monotonous crystallization rate as a function of the shear rate [139].…”

“…Also shear was shown to suppress precursor regions [139], while at the same time increasing the rate of growth of crystals. The interplay between these two effects is at the origin of the non-monotonous crystallization rate as a function of the shear rate [139].…”

“…The idea of studying crystallization under external fields by studying the effects of the field on the bond orientational order is also a new direction for future research, which has been considered for example in Ref. [139] for the case of crystallization in sheared suspensions.…”

Shear-induced laning transition in a confined colloidal film

“…Specifically, we consider the case of n = 3 layers. The system is studied on the basis of overdamped Brownian dynamics (BD) simulation without hydrodynamic interactions (following various earlier studies on dense systems under flow [21][22][23][24]). The particles interact via screened Coloumb interactions (matched to a real, silica system [25,26]), and the confining walls are considered as smooth on the particle scale.…”