Shear transformation distribution and activation in glasses at the atomic scale

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Amorphous silicon exhibits complex plastic deformation mechanisms at the atomic scale.
• Understanding shear transformations (STs) is crucial for modeling the mechanical behavior of amorphous materials.

Purpose of the Study:

• To characterize shear transformations (STs) at the atomic scale in amorphous silicon.
• To investigate the influence of pressure, glass relaxation, and damage on ST characteristics.
• To determine the energy barriers and activation volumes associated with STs.

Main Methods:

• Atomic-scale characterization of STs using a mapping on Eshelby inclusions.
• Investigation of pressure, glass relaxation, and damage effects.
• Nudged elastic band (NEB) calculations to measure energy barriers against ST activation.

Main Results:

• The ST effective volume (γ₀V₀) increases with plastic deformation, from ~10ų to ~60ų.
• Applied pressure does not significantly affect ST characteristics.
• The energy barrier for ST activation is controlled by the first ST, with an activation volume representing a fraction of the complete ST volume.
• Avalanches exhibit smaller activation volumes, likely due to accumulated local damage.

Conclusions:

• ST effective volume is a key parameter that evolves with plastic deformation in amorphous silicon.
• The energy barrier for ST activation is directly linked to the initial ST event.
• Findings provide critical data for developing accurate mesoscale models of plasticity in amorphous materials.