Crystal Growth in Fluid Flow: Nonlinear Response Effects

TL;DR

This study uses molecular dynamics simulations to explore how strong shear flow influences crystal growth kinetics in a binary alloy, revealing suppression near melting point and non-monotonic velocity dependence at lower temperatures due to nonlinear fluid responses.

Contribution

It demonstrates the nonlinear effects of shear flow on crystal growth, highlighting conditions where flow enhances or suppresses growth, which was not previously understood.

Findings

Shear flow suppresses crystal growth near melting point.

At lower temperatures, growth velocity varies non-monotonically with shear rate.

Flow-induced enhancement of growth is due to increased particle mobility.

Abstract

We investigate crystal-growth kinetics in the presence of strong shear flow in the liquid, using molecular-dynamics simulations of a binary-alloy model. Close to the equilibrium melting point, shear flow always suppresses the growth of the crystal-liquid interface. For lower temperatures, we find that the growth velocity of the crystal depends non-monotonically on the shear rate. Slow enough flow enhances the crystal growth, due to an increased particle mobility in the liquid. Stronger flow causes a growth regime that is nearly temperature-independent, in striking contrast to what one expects from the thermodynamic and equilibrium kinetic properties of the system, which both depend strongly on temperature. We rationalize these effects of flow on crystal growth as resulting from the nonlinear response of the fluid to strong shearing forces.