Thermally activated flow in models of amorphous solids

Area of Science:

• Materials Science
• Condensed Matter Physics
• Rheology

Background:

• Amorphous solids yield via a dynamical phase transition at a critical stress (Σc).
• Thermal fluctuations round this transition, enabling flow below Σc even in athermal systems.
• Understanding steady-state thermal flow in amorphous solids is crucial for predicting material behavior.

Purpose of the Study:

• To analytically solve thermally activated flow in amorphous solids at low temperatures using the Hébraud-Lequex (HL) model.
• To propose a general scaling law for transition rounding due to thermal fluctuations.
• To validate the proposed scaling law across different simulation models.

Main Methods:

• Mesoscopic elastoplastic modeling, specifically the Hébraud-Lequex (HL) model.
• Analytical solution for thermally activated flow at low temperatures.
• Numerical simulations including the HL model, a 2D elastoplastic model, and molecular dynamics of 2D Lennard-Jones glass.

Main Results:

• An analytical solution for thermally activated flow in the HL model at low temperatures was derived.
• A general scaling law was proposed, accurately describing the rounding of the yield transition.
• The scaling law demonstrated validity across various simulation approaches, confirming its broad applicability.

Conclusions:

• Thermal fluctuations significantly impact the yielding behavior of amorphous solids, leading to a rounded transition.
• The proposed general scaling law provides a unified framework for understanding this phenomenon.
• The findings are robust, confirmed by analytical solutions and diverse numerical simulations.