Computer simulations of critical dynamics in
fluids
CSIC Building (#406),
Seminar Room 4122.
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Computer simulations of critical dynamics in fluids
Professor
Jan V. Sengers
University of Maryland

Abstract:
The static and dynamic behavior of systems is known
to become singular near critical points. As
explained by the renormalizationgroup theory of
critical phenomena, this singular behavior finds its
origin in the presence of fluctuations at all length
scales, from microscopic to mesoscopic. During the
past decade considerable progress has been made in
simulating critical fluctuations in fluids and fluid
mixtures with computers. Thus accurate numerical
data have been obtained for the thermodynamic
behavior of fluids near critical points
Computer simulations of critical dynamics, however,
appear to be more challenging for two reasons.
First, the fluctuations exhibit an anomalous
critical slowing down that is intimately related to
the socalled longtimetail behavior of the dynamic
correlation functions. As a consequence, finitesize
effects are even more significant than in computer
simulations of equilibrium critical properties and
turn out to be more pronounced. Second, one needs to
carefully distinguish between the decay of
shortrange fluctuations versus the decay of
longrange fluctuations.
We shall present computer simulations of critical
dynamics in a mixture of LennardJones liquids. It
will be shown how a proper finitesize analysis of
the simulation data can account for the phenomena
mentioned above, leading to physically reliable
results completely consistent with the theoretical
predictions from modecoupling theory and with
experimental evidence, thus validating
moleculardynamics simulations as a new procedure
for studying critical dynamics.
*Research performed in collaboration with S.K. Das
and M.E. Fisher at the University of Maryland and
with J. Horbach and K. Binder at the Johannes
Gutenberg Universität Mainz, Germany.
References:
S.K. Das, M.E. Fisher, J.V. Sengers, J. Horbach. and
K. Binder, Phys. Rev. Lett. 97, 025702 (2006).
S.K. Das, J. Horbach, K. Binder, M.E. Fisher, and
J.V. Sengers, J. Chem. Phys. 125, 024506 (2006).
[slides] 
