Anomalies in the sheared nucleation behaviour of glass-forming supercooled liquids

Crystal nucleation of flowing supercooled liquids is notoriously challenging to study using molecular dynamics (MD) computer simulations and experiments. Our understanding of the microscopic effects of shear on nucleating sytems is fragmented, but over the past decade, the general consensus is that the nucleation rate is non-monotonic with shear.

We have formulated a modified Classical Nucleation Theory (called shear-CNT), which is a cost-effective methodology pairing seeded MD simulations with extended CNT equations, explicitly incorporating the shear rate as a dependent variable. Shear-CNT enables us to examine the sheared nucleation behaviour of several systems---water, Lennard-Jones and hard-spheres over a wide range of supercoolings and shear rates inaccessible to brute-force MD. Our results reveal that the non-monotonic variation of the nucleation rate with shear is universal. We also show that the temperature-dependent nucleation behaviour of water exhibits a novel anomaly, which originates from the “Stokes-Einstein (SE) violation”; a well-known decoupling of the zero-shear diffusion coefficient and viscosity in supercooled liquids and glasses. This dependence on the SE violation indicates that this anomaly is a general property of glass-forming liquids, or of 'simple' systems near the glass transition temperature.