226 research outputs found
Effect of particle exchange on the glass transition of binary hard spheres
We investigate the replica theory of the liquid-glass transition for a binary
mixture of large and small additive hard spheres. We consider two different
ans\"atze for this problem: the frozen glass ansatz (FGA) in whichs the
exchange of large and small particles in a glass state is prohibited, and the
exchange glass ansatz (EGA), in which it is allowed. We calculate the dynamical
and thermodynamical glass transition points with the two ans\"atze. We show
that the dynamical transition density of the FGA is lower than that of the EGA,
while the thermodynamical transition density of the FGA is higher than that of
the EGA. We discuss the algorithmic implications of these results for the
density-dependence of the relaxation time of supercooled liquids. We
particularly emphasize the difference between the standard Monte Carlo and swap
Monte Carlo algorithms. Furthermore, we discuss the importance of particle
exchange for estimating the configurational entropy.Comment: 16 pages, 5 figure
Dynamically correlated regions and configurational entropy in supercooled liquids
When a liquid is cooled below its melting temperature, if crystallization is
avoided, it forms a glass. This phenomenon, called glass transition, is
characterized by a marked increase of viscosity, about 14 orders of magnitude,
in a narrow temperature interval. The microscopic mechanism behind the glass
transition is still poorly understood. However, recently, great advances have
been made in the identification of cooperative rearranging regions, or
dynamical heterogeneities, i.e. domains of the liquid whose relaxation is
highly correlated. The growth of the size of these domains is now believed to
be the driving mechanism for the increase of the viscosity. Recently a tool to
quantify the size of these domains has been proposed. We apply this tool to a
wide class of materials to investigate the correlation between the size of the
heterogeneities and their configurational entropy, i.e. the number of states
accessible to a correlated domain. We find that the relaxation time of a given
system, apart from a material dependent pre-factor, is a universal function of
the configurational entropy of a correlated domain. As a consequence, we find
that at the glass transition temperature, the size of the domains and the
configurational entropy per unit volume are anti-correlated, as originally
predicted by the Adam-Gibbs theory. Finally, we use our data to extract some
exponents defined in the framework of the Random First Order Theory, a recent
quantitative theory of the glass transition.Comment: 8 pages, 4 figures, 3 table
Comment to "Packing Hyperspheres in High-Dimensional Euclidean Space"
It is shown that the numerical data in cond-mat/0608362 are in very good
agreement with the predictions of cond-mat/0601573.Comment: comment to cond-mat/0608362; 3 pages, 1 figur
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