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(306) Production(s) de KOB W.
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Fracture of Sodium-Silicate Glasses: Insights from computer simulations
Auteur(s): Kob W.
Conférence invité: 7th International Congress on Ceramics (Iguacu Falls, BR, 2018-06-17)
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Translational and Rotational Dynamical Heterogeneities in Granular Systems
Auteur(s): Kou Binquan, Cao Yixin, Li Jindong, Xia Chengjie, Li Zhifeng, Dong Haipeng, Zhang Ang, Zhang Jie, Kob W., Wang Yujie
(Article) Publié:
Physical Review Letters, vol. 121 p.018002-1 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01833984_v1
DOI: 10.1103/PhysRevLett.121.018002
WoS: 000437746100006
Exporter : BibTex | endNote
8 Citations
Résumé: We use X-ray tomography to investigate the translational and rotational dynamical heterogeneitiesof a three dimensional hard ellipsoids granular packing driven by oscillatory shear. We find thatparticles which translate quickly form clusters with a size distribution given by a power-law withan exponent that is independent of the strain amplitude. Identical behavior is found for particles that are translating slowly, rotating quickly, or rotating slowly. The geometrical properties of these four different types of clusters are the same as those of random clusters. Different cluster types are considerably correlated/anticorrelated, indicating a significant coupling between translational androtational degrees of freedom. Surprisingly these clusters are formed already at time scales that aremuch shorter than theα−relaxation time, in stark contrast to the behavior found in glass-forming systems.
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Dynamic and thermodynamic crossover scenarios in the Kob-Andersen mixture: Insights from multi-CPU and multi-GPU simulations
Auteur(s): Coslovich D., Ozawa M., Kob W.
(Article) Publié:
European Physical Journal E, vol. 41 p.62 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01818216_v1
DOI: 10.1140/epje/i2018-11671-2
WoS: WOS:000432624100001
Exporter : BibTex | endNote
11 Citations
Résumé: The physical behavior of glass-forming liquids presents complex features of both dynamic and thermodynamic nature. Some studies indicate the presence of thermodynamic anomalies and of crossovers in the dynamic properties, but their origin and degree of universality is difficult to assess. Moreover, conventional simulations are barely able to cover the range of temperatures at which these crossovers usually occur. To address these issues, we simulate the Kob-Andersen Lennard-Jones mixture using efficient protocols based on multi-CPU and multi-GPU parallel tempering. Our setup enables us to probe the thermodynamics and dynamics of the liquid at equilibrium well below the critical temperature of mode-coupling theory, TMCT=0.435. We find that below T=0.4 the analysis is hampered by partial crystallization of the metastable liquid, which nucleates extended regions populated by large particles arranged in an fcc structure. By filtering out crystalline samples, we reveal that the specific heat grows in a regular manner down to T=0.38. Possible thermodynamic anomalies suggested by previous studies can thus occur only in a region of the phase diagram where the system is highly metastable. Using the equilibrium configurations obtained from the parallel tempering simulations, we perform molecular dynamics and Monte Carlo simulations to probe the equilibrium dynamics down to T=0.4. A temperature-derivative analysis of the relaxation time and diffusion data allows us to assess different dynamic scenarios around TMCT. Hints of a dynamic crossover come from analysis of the four-point dynamic susceptibility. Finally, we discuss possible future numerical strategies to clarify the nature of crossover phenomena in glass-forming liquids.
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New optimization scheme to obtain interaction potentials for oxide glasses
Auteur(s): Sundararaman Siddharth, Huang Liping, Ispas S., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 148 p.194504 (2018)
Texte intégral en Openaccess :
Ref HAL: hal-01806569_v1
DOI: 10.1063/1.5023707
WoS: 000432853800077
Exporter : BibTex | endNote
18 Citations
Résumé: We propose a new scheme to parameterize effective potentials that can be used to simulate atomic systems such as oxide glasses. As input data for the optimization, we use the radial distribution functions of the liquid and the vibrational density of state of the glass, both obtained from ab initio simulations, as well as experimental data on the pressure dependence of the density of the glass. For the case of silica, we find that this new scheme facilitates finding pair potentials that are significantly more accurate than the previous ones even if the functional form is the same, thus demonstrating that even simple two-body potentials can be superior to more complex three-body potentials. We have tested the new potential by calculating the pressure dependence of the elastic moduli and found a good agreement with the corresponding experimental data.
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On the structure of liquids and glasses: More order than expected
Auteur(s): Kob W.
Conférence invité: APS March meeting (Los Angeles, US, 2018-03-05)
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Structure and Dynamics of a Polymer Nanocomposite
Auteur(s): Sorichetti V., Hugouvieux Virginie, Kob W.
(Affiches/Poster)
Gordon Research Conference on Soft Condensed Matter Physics (Boston, US), 2017-08-13
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