3,010 research outputs found
Phase separation and critical percolation in bidimensional spin-exchange models
Binary mixtures prepared in an homogeneous phase and quenched into a
two-phase region phase-separate via a coarsening process whereby domains of the
two phases grow in time. With a numerical study of a spin-exchange model we
show that this dynamics first takes a system with equal density of the two
species to a critical percolation state. We prove this claim and we determine
the time-dependence of the growing length associated to this process with the
scaling analysis of the statistical and morphological properties of the
clusters of the two phases.Comment: 6 pages, 9 figure
Critical percolation in the dynamics of the 2d ferromagnetic Ising model
We study the early time dynamics of the 2d ferromagnetic Ising model
instantaneously quenched from the disordered to the ordered, low temperature,
phase. We evolve the system with kinetic Monte Carlo rules that do not conserve
the order parameter. We confirm the rapid approach to random critical
percolation in a time-scale that diverges with the system size but is much
shorter than the equilibration time. We study the scaling properties of the
evolution towards critical percolation and we identify an associated growing
length, different from the curvature driven one. By working with the model
defined on square, triangular and honeycomb microscopic geometries we establish
the dependence of this growing length on the lattice coordination. We discuss
the interplay with the usual coarsening mechanism and the eventual fall into
and escape from metastability.Comment: 67 pages, 33 figure
Liquid stability in a model for ortho-terphenyl
We report an extensive study of the phase diagram of a simple model for
ortho-terphenyl, focusing on the limits of stability of the liquid state.
Reported data extend previous studies of the same model to both lower and
higher densities and to higher temperatures. We estimate the location of the
homogeneous liquid-gas nucleation line and of the spinodal locus. Within the
potential energy landscape formalism, we calculate the distributions of depth,
number, and shape of the potential energy minima and show that the statistical
properties of the landscape are consistent with a Gaussian distribution of
minima over a wide range of volumes. We report the volume dependence of the
parameters entering in the Gaussian distribution (amplitude, average energy,
variance). We finally evaluate the locus where the configurational entropy
vanishes, the so-called Kauzmann line, and discuss the relative location of the
spinodal and Kauzmann loci.Comment: RevTeX 4, 8 pages, 8 eps figure
Aging in short-ranged attractive colloids: A numerical study
We study the aging dynamics in a model for dense simple liquids, in which
particles interact through a hard-core repulsion complemented by a short-ranged
attractive potential, of the kind found in colloidal suspensions. In this
system, at large packing fractions, kinetically arrested disordered states can
be created both on cooling (attractive glass) and on heating (repulsive glass).
The possibility of having two distinct glasses, at the same packing fraction,
with two different dynamics offers the unique possibility of comparing --
within the same model -- the differences in aging dynamics. We find that, while
the aging dynamics of the repulsive glass is similar to the one observed in
atomic and molecular systems, the aging dynamics of the attractive glass shows
novel unexpected features.Comment: 8 pages, 11 figures, submited to Journal of Chemical Physic
Slow dynamics in a primitive tetrahedral network model
We report extensive Monte Carlo and event-driven molecular dynamics
simulations of the fluid and liquid phase of a primitive model for silica
recently introduced by Ford, Auerbach and Monson [J. Chem. Phys. 17, 8415
(2004)]. We evaluate the iso-diffusivity lines in the temperature-density plane
to provide an indication of the shape of the glass transition line. Except for
large densities, arrest is driven by the onset of the tetrahedral bonding
pattern and the resulting dynamics is strong in the Angell's classification
scheme. We compare structural and dynamic properties with corresponding results
of two recently studied primitive models of network forming liquids -- a
primitive model for water and a angular-constraint free model of
four-coordinated particles -- to pin down the role of the geometric constraints
associated to the bonding. Eventually we discuss the similarities between
"glass" formation in network forming liquids and "gel" formation in colloidal
dispersions of patchy particles.Comment: 9 pages, 10 figure
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