Accueil >
Production scientifique
![](plugins/kitcnrs-5.4.1/css/charte-2/img/boite-outils/icones/postdco.gif)
![](https://hal.archives-ouvertes.fr/img/tamponHal.png)
(307) Production(s) de KOB W.
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Relaxation dynamics of a linear molecule in a random static medium: A scaling analysis
Auteur(s): Moreno A. J., Kob W.
(Article) Publié:
The Journal Of Chemical Physics, vol. 121 p.380-386 (2004)
Résumé: We present extensive molecular dynamics simulations of the motion of a single linear rigid molecule in a two-dimensional random array of fixed overlapping disklike obstacles. The diffusion constants for the center of mass translation, D-CM, and for rotation, D-R, are calculated for a wide range of the molecular length, L, and the density of obstacles, rho. The obtained results follow a master curve Drho(mu)similar to(L(2)rho)(-nu) with an exponent mu=-3/4 and 1/4 for D-R and D-CM, respectively, that can be deduced from simple scaling and kinematic arguments. The nontrivial positive exponent nu shows an abrupt crossover at L(2)rho=zeta(1). For D-CM we find a second crossover at L(2)rho=zeta(2). The values of zeta(1) and zeta(2) correspond to the average minor and major axis of the elliptic holes that characterize the random configuration of the obstacles. A violation of the Stokes-Einstein-Debye relation is observed for L(2)rho>zeta(1), in analogy with the phenomenon of enhanced translational diffusion observed in supercooled liquids close to the glass transition temperature. (C) 2004 American Institute of Physics.
Commentaires: English Article 830HG
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Dynamics of a rod in a random static environment: non-Gaussian behaviour on large length scales
Auteur(s): Moreno A. J., Kob W.
(Article) Publié:
Philosophical Magazine Letters, vol. 84 p.1383-1388 (2004)
Résumé: We present molecular dynamics simulations of the motion of a single rod in a two-dimensional random static array of discs. For long rods the mean-squared displacement of the centre of mass shows a cage effect similar to that observed in supercooled liquids or dense colloidal systems. We have determined the time-dependence of the non-Gaussian parameter for different rod lengths. It is found that the long-time regime is strongly non-Gaussian even on length scales of the order of 10-15 times the rod length, thus showing the heterogeneity of the dynamics on such length scales.
Commentaires: English Article 821OC
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
![.](plugins/aigle//images/more_null_blue.png) |
Dynamics of a rigid rod in a glassy medium
Auteur(s): Moreno A. J., Kob W.
(Article) Publié:
Europhysics Letters (Epl), vol. 67 p.820-826 (2004)
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Channel formation and intermediate range order in sodium silicate melts and glasses
Auteur(s): Meyer A., Horbach J., Kob W., Kargl F., Schober H.
(Article) Publié:
Physical Review Letters, vol. 93 p.027801 (2004)
Résumé: We use inelastic neutron scattering and molecular dynamics simulation to investigate the interplay between the structure and the fast sodium ion diffusion in various sodium silicates. With increasing temperature and decreasing density the structure factors exhibit an emerging prepeak around 0.9 Angstrom(-1). We show that this prepeak has its origin in the formation of sodium rich channels in the static structure. The channels serve as preferential ion conducting pathways in the relative immobile Si-O matrix. On cooling below the glass transition this intermediate range order is frozen in.
Commentaires: English Article 836CF
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Virtual neutron scattering experiments
Auteur(s): Hugouvieux Virginie, Farhi E., Johnson M. R., Kob W.
(Article) Publié:
Physica B: Condensed Matter, vol. 350 p.151-154 (2004)
Résumé: In order to gain insight into the different contributions of the sample and instrument to the scattered intensity in neutron scattering experiments, the total simulation of such experiments is being developed. The method combines molecular dynamics sample simulations and Monte-Carlo instrument simulations. Virtual experiments currently allow absorption, multiple scattering and any kind of elastic/inelastic, coherent/incoherent scattering processes to be investigated. (C) 2004 Elsevier B.V. All rights reserved.
Commentaires: English Article 845ZZ
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Structural properties of a calcium aluminosilicate glass from molecular-dynamics simulations: A finite size effects study
Auteur(s): Ganster Patrick, Benoit Claude, Kob W., Delaye J.M.
(Article) Publié:
The Journal Of Chemical Physics, vol. 120 p.10172-10181 (2004)
Résumé: We study a calcium aluminosilicate glass of composition (SiO2)(0.67)-(Al2O3)(0.12)-(CaO)(0.21) by means of molecular-dynamics simulations, using a potential made of two-body and three-body interactions. In order to prepare small samples that can subsequently be studied by first principles, the finite size effects on the liquid dynamics and on the glass structural properties are investigated. We find that finite size effects affect the Si-O-Si and Si-O-Al angular distributions, the first peaks of the Si-O, Al-O, and Ca-O pair correlation functions, the Ca coordination, and the oxygen atoms' environment in the smallest system (100 atoms). We give evidence that these finite size effects can be directly attributed to the use of three-body interactions. (C) 2004 American Institute of Physics.
Commentaires: English Article 820QN
|
![--------------------](plugins/aigle//images/filet-couleur.gif)
|
|
Molecular dynamics simulations
Auteur(s): Binder K., Horbach J., Kob W., Paul W., Varnik F.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 16 p.S429-S453 (2004)
Résumé: A tutorial introduction to the technique of molecular dynamics (MD) is given, and some characteristic examples of applications are described. The purpose and scope of these simulations and the relation to other simulation methods is discussed, and the basic MD algorithms are described. The sampling of intensive variables (temperature T, pressure p) in runs carried out in the microcanonical (NVE) ensemble (N = particle number, V = volume, E = energy) is discussed, as well as the realization of other ensembles (e.g. the NVT ensemble). For a typical application example, molten SiO2, the estimation of various transport coefficients (self-diffusion constants, viscosity, thermal conductivity) is discussed. As an example of non-equilibrium molecular dynamics, a study of a glass-forming polymer melt under shear is mentioned.
Commentaires: English Article Sp. Iss. SI 800SU
|