Strain-rate and temperature-driven transition in the shear transformation zone for two-dimensional amorphous solids

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Amorphous solids deform via shear transformation zones (STZs).
• Understanding STZ characteristics is crucial for predicting material behavior under stress.
• Previous studies often focused on athermal or quasistatic conditions.

Purpose of the Study:

• To investigate the effects of strain rate and temperature on STZ characteristics in 2D amorphous solids.
• To couple a self-learning metabasin escape algorithm with shear deformation for enhanced potential energy surface exploration.
• To elucidate the transition in STZ behavior under varying thermomechanical conditions.

Main Methods:

• Coupling a self-learning metabasin escape algorithm with shear deformation.
• Exploring the potential energy surface (PES) of 2D amorphous solids.
• Atomistic calculations under varying strain rates and temperatures.

Main Results:

• A transition in STZ characteristics was observed with changes in temperature and strain rate.
• At high temperatures/strain rates, STZs resemble those from athermal quasistatic calculations.
• At lower temperatures/experimentally relevant strain rates, STZs exhibit thermally activated behavior.
• Key changes include increased STZ size, altered deformation mechanisms (shear to tension), and reduced nucleation stress.

Conclusions:

• The study identifies two distinct regimes of STZ characteristics based on temperature and strain rate.
• The findings bridge the gap between athermal quasistatic simulations and thermally activated processes in amorphous solids.
• This work provides new insights into the fundamental mechanisms governing the mechanical response of amorphous materials.