Single-particle fluctuations and directional correlations in driven hard-sphere glasses

Mandal, Suvendu; Chikkadi, Vijayakumar; Nienhuis, Bernard; Raabe, Dierk; Schall, Peter; Varnik, Fathollah

doi:10.1103/physreve.88.022129

Cited by 30 publications

(39 citation statements)

References 31 publications

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“…[19], which evaluates deviations from an affine deformation on a local scale. This quantity has been used with noted success to characterize plasticity [19,20,7,21,8,9,22]; in particular, it was shown to yield results consistent with other measures of nonaffinity in Ref. [21].…”

Section: Indicator Of Plastic Activitymentioning

confidence: 91%

“…By investigating the transverse particle diffusivity, Lemaître and colleagues then showed that these correlations persist at finite shear rates [28] and at finite temperatures [29,30]. The spatial structure of these correlations was revealed by Chikkadi, Mandal, Varnik, et al [7,8]; these researchers provided convincing experimental and numerical evidence that the correlations between flow heterogeneities, quantified by D 2 min , are longranged and all the more anisotropic as shear prevails over thermal effects, i.e., at larger Peclet numbers. To do so, they monitored particle displacements in a driven "hard sphere" colloidal glass with confocal microscopy and were able to reproduce their experimental observations qualitatively with MD simulations.…”

Section: Plastic Correlatormentioning

confidence: 99%

“…But, even when sheared amorphous solids do not exhibit permanent shear localisation, there is growing evidence of the existence of correlations between the localised rearranging regions (referred to as plastic events in the following), that is, of a spatial organisation of the flow at intermediate time scales: In Ref. [7], Chikkadi and co-workers observed Send offprint requests to: a colloidal glass with confocal microscopy and demonstrated that the non-affine displacements in the material were spatially correlated, prior to any shear-banding instability, while Mandal, Varnik, and colleagues [8,9] supported such experimental findings with numerical simulations. The observed correlations are interpreted as the effect of the long-range elastic deformation field induced by a plastic event in the material, at the origin of avalanches of plastic events.…”

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids

2014

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Abstract. The slow flow of amorphous solids exhibits striking heterogeneities: swift localised particle rearrangements take place in the midst of a more or less homogeneously deforming medium. Recently, experimental as well as numerical work has revealed spatial correlations between these flow heterogeneities. Here, we use molecular dynamics (MD) simulations to characterise the rearrangements and systematically probe their correlations both in time and in space. In particular, these correlations display a four-fold azimuthal symmetry characteristic of shear stress redistribution in an elastic medium and we unambiguously detect their increase in range with time. With increasing shear rate, correlations become shorter-ranged and more isotropic. In addition, we study a coarse-grained model motivated by the observed flow characteristics and challenge its predictions directly with the MD simulations. While the model captures both macroscopic and local properties rather satisfactorily, the agreement with respect to the spatiotemporal correlations is at most qualitative. The discrepancies provide important insight into relevant physics that is missing in all related coarse-grained models that have been developed for the flow of amorphous materials so far, namely the finite shear wave velocity and the impact of elastic heterogeneities on stress redistribution.

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Section: Indicator Of Plastic Activitymentioning

confidence: 91%

Section: Plastic Correlatormentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

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Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids

2014

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“…Some of us recently addressed this issue for a hard-sphere glass both via computer simulations and experiments with a focus on the direction dependence of correlations and the crossover from the thermal regime of supercooled liquids to the athermal limit of strongly driven glasses [10,11]. Qualitative agreement was found between simulations and experiments regarding both the behavior of single particle fluctuations (found to be isotropic) and the anisotropy of their spatial correlations.…”

Section: Introductionmentioning

confidence: 90%

Correlations of plasticity in sheared glasses

et al. 2014

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In a recent paper [Mandal et al., Phys. Rev. E 88, 022129 (2013)], the nature of spatial correlations of plasticity in hard-sphere glasses was addressed both via computer simulations and in experiments. It was found that the experimentally obtained correlations obey a power law, whereas the correlations from simulations are better fitted by an exponential decay. We here provide direct evidence-via simulations of a hard-sphere glass in two dimensions (2D)-that this discrepancy is a consequence of the finite system size in the 3D simulations. By extending the study to a 2D soft disk model at zero temperature [Durian, Phys. Rev. Lett. 75, 4780 (1995)], the robustness of the power-law decay in sheared amorphous solids is underlined. Deviations from a power law occur when either reducing the packing fraction towards the supercooled regime in the case of hard spheres or changing the dissipation mechanism from contact dissipation to a mean-field-type drag in the case of soft disks.

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“…In athermal quasi-static simulations, Maloney and Lemaître showed that elementary events tend to organize into correlated avalanches [13]. Later, evidence for a correlation in the non-affine displacements of a colloidal glass was first reported by Chikkadi and co-workers in experiments [14] and then confirmed by Mandal and Varnik [15,16] in numerical simulations. In Ref.…”

Section: Introductionmentioning

confidence: 90%

Plastic response and correlations in athermally sheared amorphous solids

2016

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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.

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Single-particle fluctuations and directional correlations in driven hard-sphere glasses

Cited by 30 publications

References 31 publications

Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids

Spatiotemporal correlations between plastic events in the shear flow of athermal amorphous solids

Correlations of plasticity in sheared glasses

Plastic response and correlations in athermally sheared amorphous solids

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