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Ref Arxiv: 0812.3559
Ref. & Cit.: NASA ADS
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Résumé:

Using molecular dynamics computer simulations we investigate the agingdynamics of a gel. We start from a fractal structure generated by the DLCA-DEFalgorithm, onto which we then impose an interaction potential consisting of ashort-range attraction as well as a long-range repulsion. After relaxing thesystem at T=0, we let it evolve at a fixed finite temperature. Depending on thetemperature T we find different scenarios for the aging behavior. For T>0.2 thefractal structure is unstable and breaks up into small clusters which relax toequilibrium. For T<0.2 the structure is stable and the dynamics slows down withincreasing waiting time. At intermediate and low T the mean squareddisplacement scales as t^{2/3} and we discuss several mechanisms for thisanomalous time dependence. For intermediate T, the self-intermediate scatteringfunction is given by a compressed exponential at small wave-vectors and by astretched exponential at large wave-vectors. In contrast, for low T it is astretched exponential for all wave-vectors. This behavior can be traced back toa subtle interplay between elastic rearrangements, fluctuations of chain-likefilaments, and heterogeneity.

Commentaires: 30 pages, 25 figures