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(307) Production(s) de KOB W.
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Crossovers in the dynamics of supercooled liquids probed by an amorphous wall ![doi link](plugins/aigle//images/ext_link.jpg)
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 : ![arxiv](plugins/aigle//images/logo-arxiv.png)
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 ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Testard V., Berthier L., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 140 p.164502 (2014)
Texte intégral en Openaccess : ![arxiv](plugins/aigle//images/logo-arxiv.png)
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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Equilibrating Complex and Disordered Materials
Auteur(s): Kob W.![Auteur correspondant (Corresp.)](plugins/aigle//images/corresponding.gif)
Conférence invité: 38th International Conference and Expo on Advanced Ceramics and Composites (Daytona Beach, US, 2014-01-26)
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Comment on "Residual entropy and structural disorder in glass: A two level model and a review of spatial and ensemble vs. temporal sampling" by A. Takada, R. Conradt, and P. Richet [J. Non-Cryst. Solids, 360, 13 (2013)] ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Gupta Prabhat K., Kob W.![Auteur correspondant (Corresp.)](plugins/aigle//images/corresponding.gif)
(Article) Publié:
Journal Of Non-Crystalline Solids, vol. 387 p.28 (2014)
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Phase Diagram of a Reentrant Gel of Patchy Particles ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Roldan-Vargas Sandalo, Smallenburg Frank, Kob W. , Sciortino Francesco
(Article) Publié:
The Journal Of Chemical Physics, vol. 139 p.244910 (2013)
Texte intégral en Openaccess : ![arxiv](plugins/aigle//images/logo-arxiv.png)
Ref HAL: hal-00923977_v1
DOI: 10.1063/1.4849115
WoS: 000329191800050
Exporter : BibTex | endNote
16 Citations
Résumé: We study the phase diagram of a binary mixture of patchy particles which has been designed to form a reversible gel. For this we perform Monte Carlo and molecular dynamics simulations to investigate the thermodynamics of such a system and compare our numerical results with predictions based on the analytical parameter-free Wertheim theory. We explore a wide range of the temperature-density-composition space that defines the three-dimensional phase diagram of the system. As a result, we delimit the region of thermodynamic stability of the fluid. We find that for a large region of the phase diagram the Wertheim theory is able to give a quantitative description of the system. For higher densities, our simulations show that the system is crystallizing into a BCC structure. Finally, we study the relaxation dynamics of the system by means of the density and temperature dependences of the diffusion coefficient. We show that there exists a density range where the system passes reversibly from a gel to a fluid upon both heating and cooling, encountering neither demixing nor phase separation.
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Computer Simulations of Glassy Systems
Auteur(s): Kob W.![Auteur correspondant (Corresp.)](plugins/aigle//images/corresponding.gif)
Conférence invité: School on Computer SImulations (Wildbad Kreuth, DE, 2013-09-16)
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Gelling by Heating ![doi link](plugins/aigle//images/ext_link.jpg)
Auteur(s): Roldan-Vargas Sandalo, Smallenburg Frank, Kob W., Sciortino Francesco
(Article) Publié:
Scientific Reports, vol. 3 p.2451 (2013)
Texte intégral en Openaccess : ![openaccess](plugins/aigle//images/logo-openaccess.png)
Ref HAL: hal-00858675_v1
PMID 23948858
DOI: 10.1038/srep02451
WoS: 000323147500001
Exporter : BibTex | endNote
25 Citations
Résumé: We exploit the concept of competing interactions to design a binary mixture of patchy particles that forms a reversible gel upon heating. Our molecular dynamics computer simulation of such a system shows that with increasing temperature the relaxation dynamics slows down by more than four orders of magnitude and then speeds up again. The system is thus a fluid both at high and at low temperatures and a solid-like disordered open network structure at intermediate temperature. We further discuss the feasibility of realizing a real material with this reversible behavior.
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