Connecting microscopic and mesoscopic mechanics in model structural glasses.

Area of Science:

• Materials Science
• Condensed Matter Physics
• Computational Materials Science

Background:

• Amorphous solids exhibit complex elastic heterogeneities that are challenging to characterize.
• Understanding local mechanical responses is crucial for predicting material failure and macroscopic behavior.
• Existing methods for analyzing local stress and strain have limitations in capturing diverse material behaviors.

Purpose of the Study:

• To introduce a novel formalism for characterizing elastic heterogeneities in amorphous solids.
• To establish a link between microscopic structural properties and macroscopic mechanical responses.
• To develop a predictive framework for material behavior under stress, from ductile to brittle regimes.

Main Methods:

• Derivation of high-order strain-energy expansions for pairwise energies under athermal quasistatic dynamics.
• Statistical analysis of expansion coefficients and their correlation with soft, quasilocalized modes.
• Non-linear stress-strain expansion within a cavity to generate local yield stress maps ('bond micromechanics').
• Integration of local yield rules into a scalar elasto-plastic model (EPM).

Main Results:

• The 'bond micromechanics' method shows good agreement with the 'frozen matrix' method, with minor overestimation of large stress activations.
• The developed framework successfully predicts the stress response of materials across a ductile-to-brittle spectrum.
• Subdiffusive and diffusive shear band growths were observed in particle-based simulations and EPMs, respectively.

Conclusions:

• The novel formalism provides an effective tool for understanding elastic heterogeneities and their impact on material properties.
• The elasto-plastic model, informed by local yield rules, offers a promising approach for simulating material failure.
• Simple mesoscale models have limitations in capturing the aging dynamics of post-yielding amorphous systems.