Predicting plasticity of amorphous solids from instantaneous normal modes

Abstract

We present a mathematical description of amorphous solid deformation and plasticity by extending the concept of instantaneous normal modes (INMs) to deformed systems, which allows us to retain the effect of strain on the vibrational density of states (VDOS). Starting from the nonaffine lattice dynamics (NALD) description of elasticity and viscoelasticity of glasses, we formulate the linear response theory up to large deformations by considering the strain-dependent tangent modulus at finite values of shear strain. The (nonaffine) tangent shear modulus is computed from the vibrational density of states (VDOS) of affinely strained configurations at varying strain values. The affine strain, found analytically on the static (undeformed) snapshot of the glass, leads to configurations that are rich of soft low-energy modes as well as unstable modes (negative eigenvalues) that are otherwise completely "washed out" and lost, if one lets the system relax after strain. This procedure is fully consistent with the structure of NALD. The INM spectrum of deformed states allows for the analytical prediction of the stress-strain curve of a model glass, including the prediction of the yield point. Good parameter-free quantitative agreement is shown between the prediction and simulations of athermal quasi-static shear of a coarse-grained polymer glass.

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Cited by in corpus (5)

• Clustering of negative topological charge precedes plastic failure in 3D glasses
• Eigenvalue analysis of stress-strain curve of two-dimensional amorphous solids of dispersed frictional grains with finite shear strain
• Timescale bridging in atomistic simulations of epoxy polymer mechanics using non-affine deformation theory
• Enhanced Vibrational Stability in Glass Droplets
• Revisiting the question of what instantaneous normal modes tell us about liquid dynamics