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(307) Production(s) de BERTHIER L.


Yield Stress Materials in Soft Condensed Matter
Auteur(s): Bonn Daniel, Denn Morton m., Berthier L., Divoux Thibaut, Manneville Sébastien
(Article) Publié:
Reviews Of Modern Physics, vol. 89 p.035005 (2017)
Texte intégral en Openaccess :
Ref HAL: hal01589027_v1
Ref Arxiv: 1502.05281
DOI: 10.1103/RevModPhys.89.035005
WoS: 000407999000001
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
193 Citations
Résumé: We present a comprehensive review of the physical behavior of yield stress materials in soft condensed matter, which encompass a broad range of materials from colloidal assemblies and gels to emulsions and nonBrownian suspensions. All these disordered materials display a nonlinear flow behavior in response to external mechanical forces, due to the existence of a finite force threshold for flow to occur: the yield stress. We discuss both the physical origin and rheological consequences associated with this nonlinear behavior, and give an overview of experimental techniques available to measure the yield stress. We discuss recent progress concerning a microscopic theoretical description of the flow dynamics of yield stress materials, emphasizing in particular the role played by relaxation time scales, the interplay between shear flow and aging behavior, the existence of inhomogeneous shear flows and shear bands, wall slip, and nonlocal effects in confined geometries.
Commentaires: Review article: V1: 58 pages, 38 figs, 487 refs. V2: Final version 44 pages, 27 figs, 449 refs. Accepted for publication in Rev. Mod. Phys. Réf Journal: Rev. Mod. Phys. 89, 035005 (2017)



Ultralongrange dynamic correlations in a microscopic model for aging gels
Auteur(s): Chaudhuri Pinaki, Berthier L.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 95 p.060601 (2017)
Texte intégral en Openaccess :
Ref HAL: hal01585104_v1
Ref Arxiv: 1605.09770
DOI: 10.1103/PhysRevE.95.060601
WoS: 000403358400001
Ref. & Cit.: NASA ADS
Exporter : BibTex  endNote
11 Citations
Résumé: We use largescale computer simulations to explore the nonequilibrium aging dynamics in a microscopic model for colloidal gels. We find that gelation resulting from a kineticallyarrested phase separation is accompanied by `anomalous' particle dynamics revealed by superdiffusive particle motion and compressed exponential relaxation of time correlation functions. Spatiotemporal analysis of the dynamics reveals intermittent heterogeneities producing spatial correlations over extremely large length scales. Our study is the first microscopicallyresolved model reproducing all features of the spontaneous aging dynamics observed experimentally in soft materials.
Commentaires: Réf Journal: Phys. Rev. E 95, 060601 (2017)



Catching up with experiments: Equilibrium simulations of supercooled liquids beyond laboratory time scales
Auteur(s): Coslovich D., Berthier L., Ninarello A. S., Ozawa M.
Conference: 10th Liquid Matter Conference (Ljubljana, SI, 20170717)
Ref HAL: hal01576120_v1
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Résumé: Computer simulations give precious insight into the microscopic behavior of disordered and amorphous materials, but their typical time scales are orders of magnitude shorter than the experimentally relevant ones. In particular, simulations of supercooled liquids cover at most 45 decades of viscous slowing down, which falls far short of the 13 decades commonly accessible in experimental studies. We close this enormous gap for a class of realistic models of liquids, which we successfully equilibrate beyond laboratory time scales by means of the swap Monte Carlo algorithm. We show that combined optimization of selected features of the interaction potential, such as particle softness, polydispersity and nonadditivity, leads to computer models with excellent glassforming ability. For such models, we achieve over 10 orders of magnitude speedup in equilibration time scale. This numerical advance allows us to address some outstanding questions concerning glass formation, such as the role of local structure and the relevance of an entropy crisis, in a dynamical range that remains inaccessible in experiments. Our results support the view that nontrivial static correlations continue to build up steadily in supercooled liquids even below the laboratory glass temperature.



Largescale structure of randomly jammed particles
Auteur(s): Ikeda A., Berthier L., Parisi Giorgio
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 95 p.052125 (2017)
Texte intégral en Openaccess :
Ref HAL: hal01541319_v1
Ref Arxiv: 1701.00936
DOI: 10.1103/PhysRevE.95.052125
WoS: 000401455100001
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12 Citations
Résumé: We numerically analyse the density field of threedimensional randomly jammed packings of monodisperse soft frictionles spherical particles, paying special attention to fluctuations occurring at large lengthscales. We study in detail the twopoint static structure factor at low wavevectors in Fourier space. We also analyse the nature of the density field in real space by studying the largedistance behavior of the twopoint pair correlation function, of density fluctuations in subsystems of increasing sizes, and of the direct correlation function. We show that such real space analysis can be greatly improved by introducing a coarsegrained density field to disentangle genuine largescale correlations from purely local effects. Our results confirm that both Fourier and real space signatures of vanishing density fluctuations at large scale are absent, indicating that randomly jammed packings are not hyperuniform. In addition, we establish that the pair correlation function displays a surprisingly complex structure at large distances, which is however not compatible with the longrange negative correlation of hyperuniform systems but fully compatible with an analytic form for the structure factor. This implies that the direct correlation function is shortranged, as we also demonstrate directly. Our results reveal that density fluctuations in jammed packings do not follow the behavior expected for random hyperuniform materials, but display instead a more complex behavior.
Commentaires: 11 pages, 9 figs. Réf Journal: Phys. Rev. E 95, 052125 (2017)



Models and algorithms for the next generation of glass transition studies
Auteur(s): Ninarello A. S., Berthier L., Coslovich D.
(Article) Publié:
Physical Review X, vol. 7 p.021039 (2017)
Texte intégral en Openaccess :
Ref HAL: hal01539636_v1
Ref Arxiv: 1704.08864
DOI: 10.1103/PhysRevX.7.021039
WoS: 000402816600002
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102 Citations
Résumé: Successful computer studies of glassforming materials need to overcome both the natural tendency to structural ordering and the dramatic increase of relaxation times at low temperatures. We present a comprehensive analysis of eleven glassforming models to demonstrate that both challenges can be efficiently tackled using carefully designed models of size polydisperse supercooled liquids together with an efficient Monte Carlo algorithm where translational particle displacements are complemented by swaps of particle pairs. We study a broad range of size polydispersities, using both discrete and continuous mixtures, and we systematically investigate the role of particle softness, attractivity and nonadditivity of the interactions. Each system is characterized by its robustness against structural ordering and by the efficiency of the swap Monte Carlo algorithm. We show that the combined optimisation of the potential's softness, polydispersity and nonadditivity leads to novel computer models with excellent glassforming ability. For such models, we achieve over ten orders of magnitude gain in the equilibration timescale using the swap Monte Carlo algorithm, thus paving the way to computational studies of static and thermodynamic properties under experimental conditions. In addition, we provide microscopic insights into the performance of the swap algorithm which should help optimizing models and algorithms even further.



Does the configurational entropy of polydisperse particles exist?
Auteur(s): Ozawa M., Berthier L.
(Article) Publié:
The Journal Of Chemical Physics, vol. 146 p.014502 (2017)
Texte intégral en Openaccess :
Ref HAL: hal01435941_v1
Ref Arxiv: 1609.07979
DOI: 10.1063/1.4972525
WoS: 000393431000021
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16 Citations
Résumé: Classical particle systems characterized by continuous size polydispersity, such as colloidal materials, are not straightforwardly described using statistical mechanics, since fundamental issues may arise from particle distinguishability. Because the mixing entropy in such systems is divergent in the thermodynamic limit we show that the configurational entropy estimated from standard computational approaches to characterize glassy states also diverges. This reasoning would suggest that polydisperse materials cannot undergo a glass transition, in contradiction to experiments. We explain that this argument stems from the confusion between configurations in phase space and states defined by free energy minima, and propose a simple method to compute a finite and physically meaningful configurational entropy in continuously polydisperse systems. Physically, the proposed approach relies on an effective description of the system as an $M^*$component system with a finite $M^*$, for which finite mixing and configurational entropies are obtained. We show how to directly determine $M^*$ from computer simulations in a range of glassforming models with different size polydispersities, characterized by hard and soft interparticle interactions, and by additive and nonadditive interactions. Our approach provides consistent results in all cases and demonstrates that the configurational entropy of polydisperse system exists, is finite, and can be quantitatively estimated.
Commentaires: 13 pages, 4 figures. v2: Published version. Réf Journal: J. Chem. Phys. 146, 014502 (2017)



Collective motion in dense activematerials
Auteur(s): Berthier L.
Conférence invité: 4th international soft matter conference (Grenoble, FR, 20160912)
