Flow heterogeneities in supercooled liquids and glasses under shear

Abstract

Using extensive non-equilibrium molecular dynamics simulations, we investigate a glassforming binary Lennard-Jones mixture under shear. Both supercooled liquids and glasses are considered. Our focus is on the characterization of inhomogeneous flow patterns such as shear bands that appear as a transient response to the external shear. For the supercooled liquids, we analyze the crossover from Newtonian to non-Newtonian behavior with increasing shear rate $\dot{\gamma }$. Above a critical shear rate ${\dot{\gamma }}_c$ where a non-Newtonian response sets in, the transient dynamics are associated with the occurrence of short-lived vertical shear bands, i.e. bands of high mobility that form perpendicular to the flow direction. In the glass states, long-lived horizontal shear bands, i.e. bands of high mobility parallel to the flow direction, are observed in addition to vertical ones. The systems with shear bands are characterized in terms of mobility maps, stress-strain relations, mean-squared displacements, and (local) potential energies. The initial formation of a horizontal shear band provides an efficient stress release, corresponds to a local minimum of the potential energy, and is followed by a slow broadening of the band towards the homogeneously flowing fluid in the steady-state. Whether a horizontal or a vertical shear band forms cannot be predicted from the initial undeformed sample. Furthermore, we show that with increasing system size the probability for the occurrence of horizontal shear bands increases.

15 pages, 13 figures

References in corpus (5)

• Evaluation of the "disorder temperature" and "free volume" formalisms via simulations of shear banding in amorphous solids
• From Equilibrium to Steady State: The Transient Dynamics of Colloidal Liquids under Shear
• Brittle yielding of amorphous solids at finite shear rates
• Heterogeneous dynamics during yielding of glasses: effect of aging
• Shear Transformation Zones: State Determined or Protocol Dependent?

Cited by in corpus (1)

• On the yielding of a defect-rich model crystal under shear: insights from molecular dynamics simulations