Ref HAL: hal-01689194_v1
DOI: 10.1039/C7NJ03922K
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10 Citations

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Ref Arxiv: 1705.10156
DOI: 10.21468/SciPostPhys.3.4.027
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15 Citations
Résumé:

We numerically study the jamming transition of frictionless polydisperse spheres in three dimensions. We use an efficient thermalisation algorithm for the equilibrium hard sphere fluid and generate amorphous jammed packings over a range of critical jamming densities that is about three times broader than in previous studies. This allows us to reexamine a wide range of structural properties characterizing the jamming transition. Both isostaticity and the critical behavior of the pair correlation function hold over the entire range of jamming densities. At intermediate length scales, we find a weak, smooth increase of bond orientational order. By contrast, distorted icosahedral structures grow rapidly with increasing the volume fraction in both fluid and jammed states. Surprisingly, at large scale we observe that denser jammed states show stronger deviations from hyperuniformity, suggesting that the enhanced amorphous ordering inherited from the equilibrium fluid competes with, rather than enhances, hyperuniformity. Finally, finite size fluctuations of the critical jamming density are considerably suppressed in the denser jammed states, indicating an important change in the topography of the potential energy landscape. By considerably stretching the amplitude of the critical "J-line", our work disentangles physical properties at the contact scale that are associated with jamming criticality, from those occurring at larger length scales, which have a different nature.

Ref HAL: hal-01667079_v1
Ref Arxiv: 1708.04259
DOI: 10.1088/1367-2630/aa914e
WoS: 000424893800001
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14 Citations
Résumé:

Dense assemblies of self-propelled particles undergo a nonequilibrium form of glassy dynamics. Physical intuition suggests that increasing departure from equilibrium due to active forces fluidifies a glassy system. We falsify this belief by devising a model of self-propelled particles where increasing departure from equilibrium can both enhance or depress glassy dynamics, depending on the chosen state point. We analyze a number of static and dynamic observables and suggest that the location of the nonequilibrium glass transition is primarily controlled by the evolution of two-point static density correlations due to active forces. The dependence of the density correlations on the active forces varies non-trivially with the details of the system, and is difficult to predict theoretically. Our results emphasize the need to develop an accurate liquid state theory for nonequilibrium systems.

Commentaires: . Réf Journal: New J. Phys. 19, 125006 (2017)

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DOI: 10.1038/nature24062
WoS: WOS:000415365500038
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40 Citations

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Ref Arxiv: 1706.10081
DOI: 10.1209/0295-5075/119/36003
WoS: 000415019400017
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14 Citations
Résumé:

We use a swap Monte Carlo algorithm to numerically prepare bulk glasses with kinetic stability comparable to that of glass films produced experimentally by physical vapor deposition. By melting these systems into the liquid state, we show that some of our glasses retain their amorphous structures longer than 10^5 times the equilibrium structural relaxation time. This exceptional kinetic stability cannot be achieved experimentally for bulk materials. We perform simulations at both constant volume and constant pressure to demonstrate that the density mismatch between the ultrastable glass and the equilibrium liquid accounts for a major part of the observed kinetic stability.

Commentaires: 7 Pages, 6 Figures. Figures 4b) and 5b) updated, revisions to text to improve discussion, missing page numbers added to references, typos corrected. Réf Journal: EPL 119, 36003 (2017)

Ref HAL: hal-01656760_v1
DOI: 10.1063/1.5012271
WoS: 000416842200006
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4 Citations
Résumé:

.We present a class of simple algorithms that allows to find the reaction path in systems with a complexpotential energy landscape. The approach does not need any knowledge on the product state and doesnot require the calculation of any second derivatives. The underlying idea is to use two nearby points inconfiguration space to locate the path of slowest ascent. By introducing a weak noise term, the algorithmis able to find even low-lying saddle points that are not reachable by means of a slowest ascent path. Sincethe algorithm makes only use of the value of the potential and its gradient, the computational effort to findsaddles is linear in the number of degrees of freedom, if the potential is short-ranged. We test the performanceof the algorithm for two potential energy landscapes. For the M¨uller-Brown surface we find that the algorithmalways finds the correct saddle point. For the modified M¨uller-Brown surface, which has a saddle point thatis not reachable by means of a slowest ascent path, the algorithm is still able to find this saddle point withhigh probability

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Ref Arxiv: 1706.02738
DOI: 10.1103/PhysRevLett.119.188002
WoS: 000414137900014
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48 Citations
Résumé:

Glass films created by vapor-depositing molecules onto a substrate can exhibit properties similar to those of ordinary glasses aged for thousands of years. It is believed that enhanced surface mobility is the mechanism that allows vapor deposition to create such exceptional glasses, but it is unclear how this effect is related to the final state of the film. Here we use molecular dynamics simulations to model vapor deposition and an efficient Monte Carlo algorithm to determine the deposition rate needed to create ultra-stable glassy films. We obtain a scaling relation that quantitatively captures the efficiency gain of vapor deposition over bulk annealing, and demonstrates that surface relaxation plays the same role in the formation of vapor-deposited glasses as bulk relaxation does in ordinary glass formation.

Commentaires: Five pages and five figures. Data relevant to this work have been archived and can be accessed at https://doi.org/10.7924/G8P26W5G. Réf Journal: Phys. Rev. Lett. 119, 188002 (2017)