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- Many-body static correlations and fragility of viscous liquids

Auteur(s): Coslovich D.

Conference: Unifying concepts in glass physics V (Paris, FR, 2011-12-12)


Résumé:

We discuss the relationship between many-body static correlations and fragility in model viscous liquids. To probe static correlations beyond the pair level we analyze the spatial extension of clusters of interconnected locally preferred structures [1]. We also extract the point-to-set correlation lengths by randomly pinning the positions of finite fractions of particles. As a general rule, we find that many-body static correlations of LJ mixtures starts growing markedly upon cooling below the onset temperature T_O. Deep in the slow dynamics regime, the thermal rate of growth of static correlations is higher the more fragile the liquid. These two observations allow us to rationalize the large discrepancies of dynamic behavior between LJ and WCA liquids reported in [2]. Eventually, we compare our results for close-packed liquids to those for a model of strong, tetrahedral liquid. In this latter case, the growth of point-to-set correlation lengths by decreasing temperature appears weaker than in the LJ liquids. Our results thus indicate that inclusion of many-body static correlations in theories of the glass transition should be most crucial for the description of fragile glass-formers. [1] D. Coslovich, PRE 83, 051505 (2011) [2] L. Berthier and G. Tarjus PRL 103, 170601 (2009)