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(306) Production(s) de KOB W.
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Surface of a calcium aluminosilicate glass by classical and ab initio molecular dynamics simulations
Auteur(s): Ganster Patrick, Benoit Magali, Delaye J. M., Kob W.
(Article) Publié:
Surface Science, vol. 602 p.114-125 (2008)
Texte intégral en Openaccess :
Ref HAL: hal-00368331_v1
DOI: 10.1016/j.susc.2007.09.047
WoS: 000252904700018
Exporter : BibTex | endNote
14 Citations
Résumé: We present the structural properties of thin films of a calcium alummosilicate glass generated by classical molecular dynamics (MD). The films are generated by two methods: in the first, the films are created in the liquid state and quenched to 300 K; in the second, the films are generated at room temperature. Depending on the method, film thickness and surface roughness are different but the main structural characteristics of the films are similar. The atomic concentration appears to be inhomogeneous from the center of the films to the surface and new structural entities are present at the film surfaces. The surfaces are depleted in calcium atoms and are enriched in aluminum atoms. This atomic arrangement induces a de-polymerized area under the surface. At the surface, all structural properties are modified in comparison with those of the bulk: interatomic distances, angular distributions, ring size, coordinations. In order to confirm the surface properties, we relaxed a surface using ab initio molecular dynamics. Some modifications appear but they do not significantly change the results obtained by classical MD, validating the use of interatomic potentials for the study of such films. (C) 2007 Elsevier B.V. All rights reserved.
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Coupling decoupling between translational and rotational dynamics in a supercooled molecular liquid
Auteur(s): Chong S.h., Kob W.
(Article) Publié:
Physical Review Letters, vol. 102 p.025702 (2009)
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Tracking heterogeneous dynamics during the alpha-relaxation of a simple glass-former
Auteur(s): Chaudhuri Pinaki, Sastry S., Kob W.
(Article) Publié:
Physical Review Letters, vol. submitted p. (2008)
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A random walk description of the heterogeneous dynamics of colloidal gels
Auteur(s): Chaudhuri Pinaki, Gao G., Berthier L., Kilfoil M., Kob W.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 20 p.244126 (2008)
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New fitting scheme to obtain effective potential from Car-Parrinello molecular dynamics simulations: Application to silica
Auteur(s): Carre Antoine, Horbach Juergen, Ispas S., Kob W.
(Article) Publié:
Europhysics Letters (Epl), vol. 82 p.17001 (2008)
Texte intégral en Openaccess :
Ref HAL: hal-00364973_v1
Ref Arxiv: 0802.2421
DOI: 10.1209/0295-5075/82/17001
WoS: 000255369300018
Ref. & Cit.: NASA ADS
Exporter : BibTex | endNote
91 Citations
Résumé: A fitting scheme is proposed to obtain effective potentials fromCar-Parrinello molecular dynamics (CPMD) simulations. It is used toparameterize a new pair potential for silica. MD simulations with this newpotential are done to determine structural and dynamic properties and tocompare these properties to those obtained from CPMD and a MD simulation usingthe so-called BKS potential. The new potential reproduces accurately the liquidstructure generated by the CPMD trajectories, the experimental activationenergies for the self-diffusion constants and the experimental density ofamorphous silica. Also lattice parameters and elastic constants of alpha-quartzare well-reproduced, showing the transferability of the new potential.
Commentaires: 6 pages, 5 figures
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On the nature of native defects in high OH-content silica glasses: A first-principles study
Auteur(s): Benoit Magali, Poehlmann Marcus, Kob W.
(Article) Publié:
Europhysics Letters (Epl), vol. 82 p.57004 (2008)
DOI: 10.1209/0295-5075/82/57004
WoS: 000256301100022
9 Citations
Résumé: First-principles simulations based on the density functional theory are used in order to generate silica glasses containing 3.84wt% water molecules employing different quench protocols. Using the Kohn-Sham density of states we find localized states in the band gap that can be associated with doubly occupied Si-O dangling bond (DB) which are negatively charged and are compensated by positively charged threefold coordinated oxygens. The position of these states above the O 2p valence band depends on the local environment of the dangling bonds, in particular on the presence of other defects in their neighborhood, and on the hydrogen bond length. These native defects, which could exist in optical fibers for instance, are compatible with the optical absorption and photoluminescence bands observed in amorphous silica and their dependence in the OH content. If present, these pre-existing defects would play a significant role as precursors in the laser-induced defect formation process. Copyright (c) EPLA, 2008.
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Anomalous transport in glassforming liquids
Auteur(s): Kob W., Appignanesi G.A., Rodriguez Fris J.A., Montani R. A.
Chapître d'ouvrage: Anomalous Transport Foundations And Applications, vol. p.347-366 (2008)
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