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Dynamique et rhéologie des fluides complexes (gels, polymères, mousses, colloïdes)
(24) Production(s) de l'année 2020
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How to "measure" a structural relaxation time that is too long to be measured?
Auteur(s): Berthier L., Ediger Mark d.
(Article) Publié:
The Journal Of Chemical Physics, vol. p.044501 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02986282_v1
Ref Arxiv: 2005.06520
DOI: 10.1063/5.0015227
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: It has recently become possible to prepare ultrastable glassy materials characterised by structural relaxation times which vastly exceed the duration of any feasible experiment. Similarly, new algorithms have led to the production of ultrastable computer glasses. Is it possible to obtain a reliable estimate of a structural relaxation time that is too long to be measured? We review, organise, and critically discuss various methods to estimate very long relaxation times. We also perform computer simulations of three dimensional ultrastable hard spheres glasses to test and quantitatively compare some of these methods for a single model system. The various estimation methods disagree significantly and it is not yet clear how to accurately estimate extremely long relaxation times.
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Ultrastable metallic glasses in silico
Auteur(s): Parmar A. D. S., Ozawa M., Berthier L.
(Article) Publié:
Physical Review Letters, vol. p.085505 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02986302_v1
PMID 32909772
Ref Arxiv: 2002.01317
DOI: 10.1103/PhysRevLett.125.085505
WoS: 000561724800007
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
2 Citations
Résumé: We devise a generic strategy and simple numerical models for multi-component metallic glasses for which the swap Monte Carlo algorithm can produce highly stable equilibrium configurations equivalent to experimental systems cooled more than $10^7$ times slower than in conventional simulations. This paves the way for a deeper understanding of thermodynamic, dynamic, and mechanical properties of metallic glasses. As a first application, we extend configurational entropy measurements down to the experimental glass temperature, and demonstrate a qualitative evolution of the mechanical response of metallic glasses of increasing stability towards brittleness.
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Finite-dimensional vestige of spinodal criticality above the dynamical glass transition
Auteur(s): Berthier L., Charbonneau Patrick, Kundu Joyjit
(Article) Publié:
Physical Review Letters, vol. p.108001 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02986305_v1
PMID 32955295
Ref Arxiv: 1912.11510
DOI: 10.1103/PhysRevLett.125.108001
WoS: 000564051900012
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
15 Citations
Résumé: Finite-dimensional signatures of spinodal criticality are notoriously difficult to come by. The dynamical transition of glass-forming liquids, first described by mode-coupling theory, is a spinodal instability preempted by thermally activated processes that also limit how close the instability can be approached. We combine numerical tools to directly observe vestiges of the spinodal criticality in finite-dimensional glass formers. We use the swap Monte Carlo algorithm to efficiently thermalise configurations beyond the mode-coupling crossover, and analyze their dynamics using a scheme to screen out activated processes, in spatial dimensions ranging from $d=3$ to $d=9$. We observe a strong softening of the mean-field square-root singularity in $d=3$ that is progressively restored as $d$ increases above $d=8$, in surprisingly good agreement with perturbation theory.
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Random-field Ising model criticality in a glass-forming liquid
Auteur(s): Guiselin B., Berthier L., Tarjus Gilles
(Article) Publié:
Physical Review E, vol. 102 p.042129 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02925447_v1
Ref Arxiv: 2004.10555
DOI: 10.1103/PhysRevE.102.042129
WoS: WOS:000582805100002
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: We use computer simulations to investigate the extended phase diagram of a supercooled liquid linearly coupled to a quenched reference configuration. An extensive finite-size scaling analysis demonstrates the existence of a random-field Ising model (RFIM) critical point and of a first-order transition line, in agreement with field-theoretical approaches. The dynamics in the vicinity of this critical point resembles the peculiar activated scaling of RFIM-like systems, and the overlap autocorrelation displays a logarithmic stretching. Our study firmly establishes the RFIM criticality in three-dimensional supercooled liquids at equilibrium.
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On the overlap between configurations in glassy liquids
Auteur(s): Guiselin B., Tarjus Gilles, Berthier L.
(Article) Publié:
The Journal Of Chemical Physics, vol. 153 p.224502 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02925446_v1
Ref Arxiv: 2007.07625
DOI: 10.1063/5.0022614
WoS: WOS:000600047800001
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
Résumé: The overlap, or similarity, between liquid configurations is at the core of the mean-field description of the glass transition, and remains a useful concept when studying three-dimensional glass-forming liquids. In liquids, however, the overlap involves a tolerance, typically of a fraction $a/\sigma$ of the inter-particle distance, associated with how precisely similar two configurations must be for belonging to the same physically relevant "state". Here, we systematically investigate the dependence of the overlap fluctuations and of the resulting phase diagram when the tolerance is varied over a large range. We show that while the location of the dynamical and thermodynamic glass transition (if present) are independent of $a/\sigma$, that of the critical point associated with a transition between a low- and a high-overlap phases in the presence of an applied source nontrivially depends on the value of $a/\sigma$. We rationalize our findings by using liquid-state theory and the hypernetted chain (HNC) approximation for correlation functions. In addition, we confirm the theoretical trends by studying a three-dimensional glass-former by computer simulations. We show in particular that a specific choice of $a/\sigma$ maximizes the temperature of the critical point, pushing it up in a liquid region where viscosity is low and computer investigations are easier due to a significantly faster equilibration.
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Ultralow effective interfacial tension between miscible molecular fluids
Auteur(s): Carbonaro A., Cipelletti L., Truzzolillo D.
(Article) Publié:
Physical Review Fluids, vol. 5 p.074001 (2020)
Texte intégral en Openaccess :
Ref HAL: hal-02912991_v1
DOI: 10.1103/PhysRevFluids.5.074001
WoS: WOS:000547338700003
Exporter : BibTex | endNote
Résumé: We exploit the deformation of drops spinning in a denser background fluid to investigate the effective interfacial tension (EIT) between miscible molecular fluids. We find that, for sufficiently low interfacial tension, spinning drops develop dumbbell shapes, with two large heads connected by a thinner central body. We show that this shape depends not only on the density and viscosity contrast between the drop and background fluids, but also on the fluid molecular structure, and hence on the stresses developing at their interface due to a different molecular interaction. We systematically investigate the dynamics of dumbbell-shaped drops of water-glycerol mixtures spinning in a pure glycerol reservoir. By developing a model for the deformation based on the balance of the shear stress opposing the deformation, the imposed normal stress on the drop, and an effective interfacial tension, we exploit the time evolution of the drop shape to measure the EIT. Our results showthat the EIT in water-glycerol systems is orders of magnitude lower than that reported in previous experimental measurements, and in excellent agreement with values calculated via the phase field model proposed by Truzzolillo et al. [Phys. Rev. X 6, 041057 (2016)].
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