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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, I. Mryglod, T. Scopigno, G. Ruocco, F. Gorelli and M. Santoro, J.Chem.Phys. v.133, 024502 (2010).

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).

 

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