Atomic-scale origin of dynamic viscoelastic response and creep in disordered solids

Abstract

Viscoelasticity has been described since the time of Maxwell as an interpolation of purely viscous and purely elastic response, but its microscopic atomic-level mechanism in solids has remained elusive. We studied three model disordered solids: a random lattice, the bond-depleted fcc lattice, and the fcc lattice with vacancies. Within the harmonic approximation for central-force lattices, we applied sum-rules for viscoelastic response derived on the basis of non-affine atomic motions. The latter motions are a direct result of local structural disorder, and in particular, of the lack of inversion-symmetry in disordered lattices. By defining a suitable quantitative and general atomic-level measure of nonaffinity and inversion-symmetry, we show that the viscoelastic responses of all three systems collapse onto a master curve upon normalizing by the overall strength of inversion-symmetry breaking in each system. Close to the isostatic point for central-force lattices, power-law creep $G(t)\sim t^{-1/2}$ emerges as a consequence of the interplay between soft vibrational modes and non-affine dynamics, and various analytical scalings, supported by numerical calculations, are predicted by the theory.

References in corpus (6)

• Jamming at Zero Temperature and Zero Applied Stress: the Epitome of Disorder
• Irreversible reorganization in a supercooled liquid originates from localised soft modes
• Non-affine response: jammed packings versus spring networks
• Rigidity Loss in Disordered Systems: Three Scenarios
• Floppiness, cutting, and freezing: Dynamic critical scaling near isostaticity
• Dynamical behavior of disordered spring networks

Cited by in corpus (2)

• Equilibrium and non-equilibrium molecular dynamics approaches for the linear viscoelasticity of polymer melts
• Scaling up the lattice dynamics of amorphous materials by orders of magnitude