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(305) Production(s) de KOB W.
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Numeric simulations of the dynamics of liquids and glasses
Auteur(s): Kob W.
(Article) Publié:
Journal De Physique Iv (Proceedings), vol. 111 p.395-395 (2003)
Commentaires: French Article 723VR
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The dynamics of melts containing mobile ions: computer simulations of sodium silicates
Auteur(s): Horbach J., Kob W., Binder K.
(Article) Publié:
Journal Of Physics: Condensed Matter, vol. 15 p.S903-S908 (2003)
Résumé: We present the results of large-scale computer simulations in order to discuss the structural and dynamic properties of sodium silicate melts with the compositions (Na2O)2(SiO2) (NS2) and (Na2O)20(SiO2) (NS20). We show that, compared to silica (SiO2), these systems exhibit additional intermediate range order on intermediate length scales that stem from the tetrahedral network structure. By means of intermediate-scattering functions, we characterize the dynamics of sodium in the system under consideration. Whereas in NS2 the incoherent scattering functions for Na decay much faster to zero than the coherent ones for Na-Na, in NS20 this different behaviour of the incoherent and coherent functions is not very pronounced. On the other hand, the incoherent functions of the two systems share a very peculiar feature: their long-time decay can be described by a Kohlrausch law with a constant exponent beta for q > q(th) where q(th) is significantly below the location of the main peak in the static structure factor for the Na-Na correlations.
Commentaires: English Article Sp. Iss. SI 665YD
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Statics and dynamics of the ten-state nearest-neighbour Potts glass on the simple-cubic lattice
Auteur(s): Brangian C., Kob W., Binder K.
(Article) Publié:
Journal Of Physics A: Mathematical And General, vol. 36 p.10847-10866 (2003)
Résumé: We present the results of Monte Carlo simulations of two different three-dimensional-Potts glass models with short-range random interactions. In the first model, a +/-J-distribution of the bonds is chosen, in the second model a Gaussian distribution. In both cases, the first two moments of the distribution are chosen to be J(0) = -1, DeltaJ = +1, so that no ferromagnetic ordering of the Potts spins can occur. We find that for all temperatures investigated the spin glass susceptibility remains finite, that the spin glass order parameter remains zero, and that the specific heat has only a smooth Schottky-like peak. These results can be understood quantitatively by considering small but independent clusters of spins. Hence, we have evidence that there is no static phase transition at any nonzero temperature. Consistent with these findings, only very minor size effects are observed, which implies that all correlation lengths of the models remain very short. We also compute for both models the time autocorrelation function C(t) of the Potts spins. While in the Gaussian model C(t) shows a smooth uniform decay, the correlator for the +/-J model has several distinct steps. These steps correspond to the breaking of bonds in small clusters of ferromagnetically coupled spins (dimers, trimers, etc). The relaxation times follow simple Arrhenius laws, with activation energies that are readily interpreted within the cluster picture, giving evidence that the system does not have a dynamic transition at a finite temperature. Hence we find that for the present models, all the transitions known for the mean-field version of the model are completely wiped out. Finally, we also determine the time auto-correlation functions of individual spins, and show that the system is dynamically very heterogeneous.
Commentaires: English Article 747BX
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The interplay between structure and ionic motions in glasses
Auteur(s): Binder K., Horbach J., Kob W., Winkler A.
(Article) Publié:
Computing In Science And Engineering, vol. 5 p.60-66 (2003)
Commentaires: English Editorial Material 653MR
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Computer Simulations of Supercooled Liquids and Glasses
Auteur(s): Kob W.
Conference: Lecture series at the Departament de fisica i Enginyeria Nuclear (Barcelone, ES, 2003-07-09)
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Vibrational properties of alkali silicate glasses : ab initio versus classical force fields
Auteur(s): Ispas S., Zotov N., De wispelaere S., Kob W.
Conference: CONCIM Conference on Non-Crystalline Inorganic Materials (Bonn, DE, 2003)
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Introduction to the physics of glasses
Auteur(s): Kob W.
Conference: Statistical Physics of Glasses, Spin Glasses, Information Processing and Combinatorial Optimization (Les Houches, France, FR, 2003-03-03)
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