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Unified study of glass and jamming rheology in soft particle systems

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DOI: 10.1038/nphys2435
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In their Correspondence, Flenner and Szamel compare the temperature dependence of an alternative dynamic length scale, ξ_4, with that of ξ^dyn, which we studied. Using computer simulations of the same system, they conclude that these two length scales have a different temperature dependence. In particular, ξ_4 does...

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Ref Arxiv: 1203.4423
DOI: 10.1016/j.phpro.2012.05.012
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11 Citations

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Ref Arxiv: 1203.0825
DOI: 10.1103/PhysRevLett.109.018301
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192 Citations
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We explore numerically the shear rheology of soft repulsive particles at large volume fraction. The interplay between viscous dissipation and thermal motion results in multiple rheological regimes encompassing Newtonian, shear-thinning and yield stress regimes near the 'colloidal' glass transition when thermal fluctuations are important, crossing over to qualitatively similar regimes near the 'jamming' transition when dissipation dominates. In the crossover regime, glass and jamming sectors coexist and give complex flow curves. Although glass and jamming limits are characterized by similar macroscopic flow curves, we show that they occur over distinct time and stress scales and correspond to distinct microscopic dynamics. We propose a simple rheological model describing the glass to jamming crossover in the flow curves, and discuss the experimental implications of our results.

Commentaires: 5 pages, 3 figs

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Ref Arxiv: 1203.3392
DOI: 10.1103/PhysRevE.86.031502
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68 Citations
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We present a comprehensive theoretical study of finite size effects in the relaxation dynamics of glass-forming liquids. Our analysis is motivated by recent theoretical progress regarding the understanding of relevant correlation length scales in liquids approaching the glass transition. We obtain predictions both from general theoretical arguments and from a variety of specific perspectives: mode-coupling theory, kinetically constrained and defect models, and random first order transition theory. In the latter approach, we predict in particular a non-monotonic evolution of finite size effects across the mode-coupling crossover due to the competition between mode-coupling and activated relaxation. We study the role of competing relaxation mechanisms in giving rise to non-monotonic finite size effects by devising a kinetically constrained model where the proximity to the mode-coupling singularity can be continuously tuned by changing the lattice topology. We use our theoretical findings to interpret the results of extensive molecular dynamics studies of four model liquids with distinct structures and kinetic fragilities. While the less fragile model only displays modest finite size effects, we find a more significant size dependence evolving with temperature for more fragile models, such as Lennard-Jones particles and soft spheres. Finally, for a binary mixture of harmonic spheres we observe the predicted non-monotonic temperature evolution of finite size effects near the fitted mode-coupling singularity, suggesting that the crossover from mode-coupling to activated dynamics is more pronounced for this model. Finally, we discuss the close connection between our results and the recent report of a non-monotonic temperature evolution of a dynamic length scale near the mode-coupling crossover in harmonic spheres.

Commentaires: 19 pages, 10 figures

PMID 22400507
DOI: 10.1103/PhysRevE.85.011102
WoS: 000299120300003
148 Citations

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PMID 22463166
Ref Arxiv: 1112.1536
DOI: 10.1103/PhysRevE.85.021120
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34 Citations
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We use a random pinning procedure to study amorphous order in two glassy spin models. On increasing the concentration of pinned spins at constant temperature, we find a sharp crossover (but no thermodynamic phase transition) from bulk relaxation to localisation in a single state. At low temperatures, both models exhibit scaling behaviour. We discuss the growing length and time scales associated with amorphous order, and the fraction of pinned spins required to localize the system in a single state. These results, obtained for finite dimensional interacting models, provide a theoretical scenario for the effect of random pinning that differs qualitatively from previous approaches based either on mean-field, mode-coupling, or renormalization group reatments.

Commentaires: 15 pages, 9 figs Journal: Phys. Rev. E 85, 021120 (2012)