Factors determining crystal--liquid coexistence under shear.

Area of Science:

• Soft matter physics
• Materials science
• Non-equilibrium thermodynamics

Background:

• Shear flow interactions with order-disorder transitions are crucial in soft matter, influencing phenomena from liquid crystals to lubrication.
• While theories exist for continuous transitions, non-equilibrium phase coexistence under shear remains poorly understood.
• Understanding shear-induced phase behavior is vital for applications in materials processing and tribology.

Purpose of the Study:

• To investigate the principles governing non-equilibrium coexistence between phases of different symmetry under shear flow.
• To determine the mechanism behind the observed stationary coexistence between a strained crystal and a shearing liquid.
• To explore whether traditional thermodynamic concepts can explain this non-equilibrium phenomenon.

Main Methods:

• Non-equilibrium molecular dynamics simulations of spherical particles.
• Analysis of phase behavior under imposed shear flow.
• Comparison of simulation results with thermodynamic models.

Main Results:

• A stationary coexistence state was observed between a strained crystalline phase and the shearing liquid.
• This coexistence could not be explained by a non-equilibrium analogue of chemical potential.
• The findings suggest a balance between crystal growth and surface erosion by the melt governs the coexistence.

Conclusions:

• Non-equilibrium coexistence under shear flow is a distinct phenomenon not governed by equilibrium thermodynamic principles.
• A dynamic balance between crystal growth and melt erosion provides a mechanistic explanation for the observed stationary state.
• This research offers new insights into the behavior of materials under extreme flow conditions.