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Transition vitreuse, hétérogénéité dynamique et vieillissement dans les systèmes a dynamique lente
(37) Production(s) de l'année 2023

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The two faces of friction in the relaxation dynamics of granular systems
Auteur(s): Kob W.
Conférence invité: Komaba Mini-Workshop (Tokyo, JP, 2023-08-22)
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Granular materials under cyclic shear: No elastic regime and they always flow
Auteur(s): Kob W.
Conférence invité: 9th International Discussion Meeting on Relaxation in Complex Systems (Chiba, JP, 2023-08-12)
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Surface properties of alkali silicate glasses: Influence of the modifiers 
Auteur(s): Zhang Z., Ispas S., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 158 p.244504 (2023)
Texte intégral en Openaccess : 
Ref HAL: hal-04856797_v1
Ref Arxiv: 2205.02461
DOI: 10.1063/5.0155497
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: Using large-scale molecular dynamics simulations, we investigate the surface properties of lithium, sodium, and potassium silicate glasses containing 25 mol % of alkali oxide. The comparison of two types of surfaces, a melt-formed surface (MS) and a fracture surface (FS), demonstrates that the influence of the alkali modifier on the surface properties depends strongly on the nature of the surface. The FS exhibits a monotonic increase of modifier concentration with increasing alkali size while the MS shows a saturation of alkali concentration when going from Na to K glasses, indicating the presence of competing mechanisms that influence the properties of a MS. For the FS, we find that larger alkali ions reduce the concentration of under-coordinated Si atoms and increase the fraction of two-membered rings, implying an enhanced chemical reactivity of the surface. For both types of surfaces, the roughness is found to increase with alkali size, with the effect being more pronounced for the FS than for the MS. The height–height correlation functions of the surfaces show a scaling behavior that is independent of the alkali species considered: The ones for the MS are compatible with the prediction of the frozen capillary wave theory while the ones for the FS show a logarithmic growth, i.e., on the nanoscale these surfaces are not self-affine fractals. The influence of the modifier on the surface properties are rationalized in terms of the interplay between multiple factors involving the size of the ions, bond strength, and charge balance on the surface.
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On the medium-range order in silicate glass-formers: From standard two-body correlations to many-body correlations
Auteur(s): Kob W.
Conférence invité: 4th International Workshop on Challenges of MD simulations of Glasses and Amorphous Materials (Corning, US, 2023-07-13)
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Deformation and fracture of silicate glasses: New insights from atomistic simulations
Auteur(s): Kob W.
Conférence invité: GOMD 2023 (New Orleans, US, 2023-06-04)
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A unified state diagram for the yielding transition of soft colloids 
Auteur(s): Aime S., Truzzolillo D., Pine David, Ramos L., Cipelletti L.
(Article) Publié:
Nature Physics, vol. p.1-7 (2023)
Ref HAL: hal-04194500_v1
DOI: 10.1038/s41567-023-02153-w
Exporter : BibTex | endNote
Résumé: Concentrated colloidal suspensions and emulsions are amorphous soft solids, widespread in technological and industrial applications and studied as model systems in physics and materials sciences. They are easily fluidized by applying mechanical stress, undergoing a yielding transition that still lacks a unified description. Here we investigate yielding in three classes of repulsive soft solids and find that at the microscopic level, yielding consists of a transition between two distinct dynamical states. We rationalize this by proposing a lattice model with dynamical coupling between neighbouring sites, leading to a unified state diagram for yielding. Employing the analogy with van der Waals phase diagram for real gases, we show that distance from a critical point plays a major role in the emergence of first-order-like versus second-order-like features in yielding, thereby reconciling previously contrasting observations on the nature of the transition.
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Two-Dimensional Crystals far from Equilibrium 
Auteur(s): Galliano Leonardo, Cates Michael, Berthier L.
(Article) Publié:
Physical Review Letters, vol. 131 p.047101 (2023)
Ref HAL: hal-04184847_v1
DOI: 10.1103/PhysRevLett.131.047101
Exporter : BibTex | endNote
Résumé: When driven by nonequilibrium fluctuations, particle systems may display phase transitions and physical behaviour with no equilibrium counterpart. We study a two-dimensional particle model initially proposed to describe driven non-Brownian suspensions undergoing nonequilibrium absorbing phase transitions. We show that when the transition occurs at large density, the dynamics produces long-range crystalline order. In the ordered phase, long-range translational order is observed because equipartition of energy is lacking, phonons are suppressed, and density fluctuations are hyperuniform. Our study offers an explicit microscopic model where nonequilibrium violations of the Mermin-Wagner theorem stabilize crystalline order in two dimensions.
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