Seeding Method for Ice Nucleation under Shear

TL;DR

This paper develops a formalism extending Classical Nucleation Theory to include shear effects, enabling prediction of ice nucleation rates under shear flow using seeded molecular dynamics, and identifies optimal shear conditions for ice formation.

Contribution

The authors introduce a novel theoretical framework incorporating shear rate into nucleation rate calculations, validated by molecular dynamics simulations, applicable at moderate supercoolings.

Findings

Optimal shear rates for ice nucleation are around 10^6-10^7 s^{-1}.

Nucleation rate exhibits non-monotonic dependence on temperature under shear.

High shear rates (>10^8 s^{-1}) inhibit ice nucleation.

Abstract

Hydrodynamic flow can have complex and far-reaching consequences on the rate of homogenous nucleation. We present a general formalism for calculating the nucleation rates of simply sheared systems. We have derived an extension to the conventional Classical Nucleation Theory, explicitly embodying the shear rate. Seeded Molecular Dynamics simulations form the backbone of our approach. The framework can be used for moderate supercoolings, at which temperatures brute-force methods are practically infeasible. The competing energetic and kinetic effects of shear arise naturally from the equations. We show how the theory can be used to identify shear regimes of ice nucleation behaviour for the mW water model, unifying disparate trends reported in the literature. At each temperature, we define a crossover shear rate in the limit of $1000-10,000 \ s^{-1}$, beyond which the nucleation rate increases steadily upto a maximum, at the optimal shear rate. For $235$, $240$, $255$ and $260 \ K$, the optimal shear rates are in the range of $\approx 10^6-10^7 \ s^{-1}$. For very high shear rates beyond $10^8 \ s^{-1}$, nucleation is strongly inhibited. Our results indicate that the shear-dependent nucleation rate curves have a non-monotonic dependence on temperature.