Accueil >
Production scientifique
(305) Production(s) de KOB W.
 |
Computational Material Science
Auteur(s): Kob W.
Conférence invité: ModSysC2020 (Montpellier, FR, 2012-03-07)
|
|
|
Non-monotonic temperature evolution of dynamic correlations in glass-forming liquids 
Auteur(s): Kob W., Roldan-Vargas Sandalo, Berthier L.
(Article) Publié:
Nature Physics, vol. 8 p.164-167 (2012)
Texte intégral en Openaccess : 
Ref HAL: hal-00667220_v1
DOI: 10.1038/NPHYS2133
WoS: 000300403700023
Exporter : BibTex | endNote
183 Citations
Résumé: The viscosity of glass-forming liquids increases by many orders of magnitude if their temperature is lowered by a mere factor of 2-3. Recent studies suggest that this widespread phenomenon is accompanied by spatially heterogeneous dynamics, and a growing dynamic correlation length quantifying the extent of correlated particle motion. Here we use a novel numerical method to detect and quantify spatial correlations that reveal a surprising non-monotonic temperature evolution of spatial dynamical correlations, accompanied by a second length scale that grows monotonically and has a very different nature. Our results directly unveil a dramatic qualitative change in atomic motions near the mode-coupling crossover temperature, which involves no fitting or indirect theoretical interpretation. These findings impose severe new constraints on the theoretical description of the glass transition, and open several research perspectives, in particular for experiments, to confirm and quantify our observations in real materials.
|
|
Static and Dynamic Length Scales in Glass-forming Liquids
Auteur(s): Kob W.
Conférence invité: Workshop on Computer Simulation Studies in Condensed Matter Physics (Athens, US, 2012-02-20)
|
|
|
|
Structural, And Vibrational Properties Of Borosilicate Glasses From First Principles Studies
Auteur(s): Pedesseau L., Ispas S., Kob W.
Conference: Journée 2011 du Pôle Ouest du Réseau Français de Chimie Théorique (RFCT) (NANTES, FR, 2011-06-06)
Ref HAL: hal-00663461_v1
Exporter : BibTex | endNote
Résumé: We have carried out first-principles molecular dynamics simulations of a sodium borosilicate (NBS) glass within the framework of DFT. The composition is 6SiO2-3Na2O-B2O3 and the density was fixed to 2.51g.cm-3. The system size is 320 atoms (i.e. 60 silicon, 180 oxygen, 60 sodium and 20 boron atoms) which is rather demanding for ab initio simulations and has been chosen to obtain a good statistics, in particular for quantities associated to the lowest concentrated element (boron). The simulations have been started at 4500K in the canonical ensemble (NVT) and followed by a simulation in the microcanonical ensemble (NVE). Subsequently, the system is progressively cooled to 300K within 60ps. In order to characterized the structure of the system we have calculated the pair correlation functions, the angular distributions, the Qn distributions, the non bridging oxygen's concentration as well as the partial structure factors. Moreover, we have studied the environment of 3- and 4-fold (BIII and BIV) coordinated boron atoms. Furthermore, the vibrational density of states has been studied in details. Indeed, both BIII and BIV atoms have specific frequencies, and the partial vibrational density of the 3-fold coordinated B atoms has been found to be a weighted sum of two specific contributions: 3-fold symmetric coordinated B (B ) atoms and asymmetric coordinated B (B ) atoms. Identically, the partial vibrational density of the 4-fold coordinated B atoms has been found to depend on the nature of their second neighbor respectively with 4 Si and 0 B atoms as second neighbor and so on. The infrared spectra of our glassy models is also presented.
|
|
Static and Dynamic Properties of Telechelic Gels
Auteur(s): Kob W.
Conférence invité: Modeling and Simulation of Materials in Soft Matter Science (Oak Ridge National Laboratory, US, 2011-11-09)
|
|
The vibrational density of states of a disordered gel model
Auteur(s): Rovigatti Lorenzo, Kob W., Sciortino Francesco
(Article) Publié:
The Journal Of Chemical Physics, vol. 135 p.104502 (2011)
|
|
Computer simulation study of the phase behavior and structural relaxation in a
gel-former modeled by three-body interactions
Auteur(s): Saw Shibu, Ellegaard Niels, Kob W., Sastry Srikanth
(Article) Publié:
The Journal Of Chemical Physics, vol. 134 p.164506 (2011)
|
1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29 30 31 32 33 34 35 36 37 38 39 40 41 42 43 44 
