Impact of pressure on plastic yield in amorphous solids with open structure

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Amorphous silica displays anomalous plasticity, with yield stress decreasing under hydrostatic pressure, contrary to typical materials.
• Understanding this behavior is crucial for predicting the mechanical response of glasses.

Purpose of the Study:

• To investigate the unusual plastic response of amorphous silica under varying hydrostatic pressure.
• To elucidate the role of structure and free volume in the deformation mechanisms of amorphous silica.

Main Methods:

• Molecular dynamics simulations were employed to model the plastic response of an open-structured amorphous silica model.
• Analysis focused on yield stress dependence on pressure, yield surface shape, and rearrangement event correlations.

Main Results:

• Simulations reproduced the anomalous decrease in yield stress with pressure in open silica structures.
• Plastic response normalized upon material compaction, consistent with local buckling and quadratic yield surface predictions.
• Free volume was confirmed as a key internal variable for continuum descriptions.
• Rearrangement event analysis showed strong intermittency in open structures, becoming homogeneous upon compaction.

Conclusions:

• The study confirms the anomalous pressure dependence of plasticity in amorphous silica and its normalization upon compaction.
• Local buckling and free volume are critical factors in understanding amorphous silica's plastic deformation.
• Compaction influences the nature of atomic rearrangements, impacting the material's aging properties.