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(305) Production(s) de KOB W.
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Computer Simulations of Glassy Systems with pinned Particles
Auteur(s): Kob W.
Conférence invité: Spin glasses: An old tool for new problems (Cargese, FR, 2014-08-25)
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Current Status of Computer Simulation of Glass. Will DFT replace force-field methods?
Auteur(s): Kob W.
Conférence invité: Expert Panel on Computer Simulation of Glass (Mainz, DE, 2014-11-14)
Résumé: In the first part of this talk I will give a very brief overview on what
questions on glasses can be addressed by means of computer simulations.
As a result I will argue why the response to the above question is "No".
In the second part of the talk I will discuss a method, called "parallel
tempering", that allows to overcome one of the big issues encountered in
the simulation of glasses, the equilibration at low fictive temperatures.
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Hunting for static and dynamical length scales in glassy systems
Auteur(s): Kob W.
(Séminaires)
University of Pennsilvania (Philadelphia, US), 2014-10-07 |
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Nonlinear dynamic response of glass-forming liquids to random pinning
Auteur(s): Kob W., Coslovich D.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 90 p.052305 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-01101053_v1
PMID 25493794
Ref Arxiv: 1403.3519
DOI: 10.1103/PhysRevE.90.052305
WoS: 000345539100004
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
26 Citations
Résumé: We use large scale computer simulations of a glass-forming liquid in which a fraction c of the particles has been permanently pinned. We find that the relaxation dynamics shows an exponential dependence on c. This result can be rationalized by assuming that the configurational entropy of the pinned liquid decreases linearly upon increasing of c. This behavior is discussed in the context of thermodynamic theories for the glass transition, notably the Adam-Gibbs picture and the random first order transition theory. For intermediate and low temperatures we find that the slowing down of the dynamics due to the pinning saturates and that the cooperativity decreases with increasing c, results which indicate that in glass-forming liquids there is a dynamic crossover at which the shape of the relaxing entities changes.
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On the structure of sodium-borosilicate glasses: Insight from ab initio
simulations
Auteur(s): Kob W.
Conférence invité: 1st Joint Meeting of DGG – ACerS GOMD (Aachen, DE, 2014-05-25)
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Crossovers in the dynamics of supercooled liquids probed by an amorphous wall
Auteur(s): Hocky Glen M, Berthier L., Kob W., Reichman David R.
(Article) Publié:
Physical Review E: Statistical, Nonlinear, And Soft Matter Physics, vol. 89 p.052311 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-00998409_v1
PMID 25353804
Ref Arxiv: 1402.5974
DOI: 10.1103/PhysRevE.89.052311
WoS: 000336765000003
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
37 Citations
Résumé: We study the relaxation dynamics of a binary Lennard-Jones liquid in the presence of an amorphous wall generated from equilibrium particle configurations. In qualitative agreement with the results presented in Nature Phys. {\bf 8}, 164 (2012) for a liquid of harmonic spheres, we find that our binary mixture shows a saturation of the dynamical length scale close to the mode-coupling temperature $T_c$. Furthermore we show that, due to the broken symmetry imposed by the wall, signatures of an additional change in dynamics become apparent at a temperature well above $T_c$. We provide evidence that this modification in the relaxation dynamics occurs at a recently proposed dynamical crossover temperature $T_s > T_c$, which is related to the breakdown of the Stokes-Einstein relation. We find that this dynamical crossover at $T_s$ is also observed for a system of harmonic spheres as well as a WCA liquid, showing that it may be a general feature of glass-forming systems.
Commentaires: 9 pages, 7 figures
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Intermittent dynamics and logarithmic domain growth during the spinodal decomposition of a glass-forming liquid
Auteur(s): Testard V., Berthier L., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 140 p.164502 (2014)
Texte intégral en Openaccess :
Ref HAL: hal-00991464_v1
Ref Arxiv: 1309.1587
DOI: 10.1063/1.4871624
WoS: 000336047700043
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
57 Citations
Résumé: We use large-scale molecular dynamics simulations of a simple glass-forming system to investigate how its liquid-gas phase separation kinetics depends on temperature. A shallow quench leads to a fully demixed liquid-gas system whereas a deep quench makes the dense phase undergo a glass transition and become an amorphous solid. This glass has a gel-like bicontinuous structure that evolves very slowly with time and becomes fully arrested in the limit where thermal fluctuations become negligible. We show that the phase separation kinetics changes qualitatively with temperature, the microscopic dynamics evolving from a surface tension-driven diffusive motion at high temperature to a strongly intermittent, heterogeneous and thermally activated dynamics at low temperature, with a logarithmically slow growth of the typical domain size. These results shed light on recent experimental observations of various porous materials produced by arrested spinodal decomposition, such as nonequilibrium colloidal gels and bicontinuous polymeric structures, and they elucidate the microscopic mechanisms underlying a specific class of viscoelastic phase separation.
Commentaires: 18 pages
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