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Tuesday, 18. June 2013 |
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15:15 – 16:17 |
Abstract
The idea of
the sensitivity of dynamic properties of fluids on the liquid-like or gas-like
state of the system proposed in [1]
was a
breakthrough in understanding the dynamic dissimilarities of supercritical
fluids. For fluids a purely dynamic quantity
that was
suggested to discriminate between the liquid-like and solid-like states is the
so-called positive dispersion of collective
excitations
and inealstic X-ray scattering (IXS) experiments
proved this assumption [2]. The experiments revealed that the
positive
sound dispersion vanished at the thermodynamic point that could be treated as a
continuation of the Widom line
(maximum of the specific heat Cp(p) dependence) into the
supercritical region. Later on a theory of positive dispersion in
supercritical fluids [3] was constructed based on an analytical approach of
Generalized Collective Modes (GCM) [4,5].
This theory
revealed the leading role of non-hydrodynamic structural relaxation in positive
sound dispersion.
In this
talk recent results from simulations and theory of collective dynamics in
supercritical Argon [6] and soft-sphere fluids
will be
discussed and a comparison will be made with a recently proposed
“rigid”-”non-rigid” fluid dynamic crossover [7].
1. F.A.Gorelli, M. Santoro, T. Scopigno,
M. Krisch, and G. Ruocco,
Phys. Rev. Lett. v.97, 245702
(2006).
2. G. Simeoni, T. Bryk, F.A. Gorelli, M. Krisch, G. Ruocco, M. Santoro and T. Scopigno,
Nature Phys. v.6(7), 503 (2010).
3. T. Bryk,
4. I.M.Mryglod, I.P.Omelyan, and M.V.Tokarchuk, Mol. Phys. v.84 235 (1995).
5. T.Bryk, I.Mryglod, and G.Kahl, Phys.Rev.E, v.56, 2903
(1997).
6. F.A. Gorelli, T. Bryk, M. Krisch, G. Ruocco, M. Santoro and
T. Scopigno, Sci. Rep. v.3,
1203 (2013).
7. V.V. Brazhkin, Yu. D. Fomin, A. G. Lyapin, V. N. Ryzhov, and K. Trachenko, Phys.Rev. E v.85, 031203 (2012).