Plastic response and correlations in athermally sheared amorphous solids

Abstract

The onset of irreversible deformation in low-temperature amorphous solids is due to the accumulation of elementary events, consisting of spacially and temporally localized atomic rearrangements involving only a few tens of atoms. Recently, numerical and experimental work addressed the issue of spatio-temporal correlations between these plastic events. Here, we provide further insight into these correlations by investigating, via molecular dynamics (MD) simulations, the plastic response of a two-dimensional amorphous solid to artificially triggered local shear transformations. We show that while the plastic response is virtually absent in as-quenched configurations, it becomes apparent if a shear strain was previously imposed on the system. Plastic response has a four-fold symmetry which is characteristic of the shear stress redistribution following the local transformation. At high shear rate we report evidence for a fluctuation-dissipation relation, connecting plastic response and correlation, which seems to break down if lower shear rates are considered.

Low-temperature anomalies of a vapor deposited glass

“…Localized defects of different nature have been discussed in the context of glasses, see e.g. [1][2][3][4][5][6][7][43][44][45][46], and our findings could be related to at least some of those theoretical proposals. Future work should clarify these connections, both by additional numerical simulations and analytical calculations.…”

“…Within this framework, defects such as vacancies and dislocations can be treated as small perturbations. This description breaks down for amorphous solids such as glasses, foams, emulsions, plastics, colloids, granular materials, bacterial colonies, and tissues [1][2][3][4][5][6][7]. In these systems, the identification of "defects" becomes challenging because the solid ground state is strongly disordered.…”

“…As a consequence, amorphous solids display many universal anomalies with respect to crystals. Examples are the so-called Boson Peak, an excess of low-energy vibrational modes [8]; the anomalous scaling of heat capacity and thermal conductivity with temperature [9,10]; the irreversible plastic response to arbitrarily small perturbations [1,3,4,11]; and highly cooperative relaxation dynamics, contributing to the socalled β-processes [12][13][14].…”

Mean-field avalanches in jammed spheres

“…Our next projects will follow mainly two directions: firstly, we want to run improved simulations, aimed to a finer characterization of the avalanches in finite dimensional systems. Secondly, in this article the maximum shear-strain was kept small in order to remain in the linear regime, but there is also much interest on the stationary elastoplastic regime that follows the yielding transition; we plan to study the distribution of avalanches in this setting, in order to be able to compare our results with all the works that have been published in the field, for example [36,37,38,39,40,41,42,43,44].…”

Contribution to viscosity from the structural relaxation via the atomic scale Green-Kubo stress correlation function

“…In particular, it has been shown that in deeply supercooled liquids (parent liquids) relaxation of the Green-Kubo stress correlation function at large times corresponds to the relaxation of the Green-Kubo stress correlation function calculated on the inherent structures (i.e., on the structures obtained through "an instant quench" from the parent liquid structures) [4][5][6]19]. Another direction in the considerations of the stress relaxation concerns the angular dependence of changes in the stress fields generated by local structural transformations [15,17,18,[20][21][22].…”