Thermal Diffusivity of H2O Near the Critical Point

Sengers, J. V.; Perkins, Robert L.; Huber, Marcia L.; Neindre, B. Le

doi:10.1007/s10765-009-0643-x

Cited by 10 publications

(14 citation statements)

References 48 publications

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“…8. Note that here, for the case of soft-sphere fluids, we observed similar D T (n) dependence as it was known for real supercritical fluids [42] and were reported in studies of critical behavior of thermal diffusivity D T of CO 2 , C 2 H 6 [43], and H 2 O [44]. Interestingly, both density dependencies D T (n) and D L (n) for soft-sphere fluids have minima right in the region of the smallest PSD, at the density n * ∼ 0.37 (see Fig.…”

Section: Crossover In Collective Dynamics Of Soft-sphere Fluidssupporting

confidence: 88%

“…For realistic fluids, the critical behavior of thermal diffusivity D T = λ nC P depends on the divergence of thermal conductivity λ and specific heat at constant pressure C P at the critical point [45]. The experiments [43,44] give evidence of a rapid decay of D T on approaching the critical point, i.e., leading contribution from the C P and, consequently, the line of the minimum of D T (n) for realistic fluids should be very close to their Widom line. This makes a strong argument in connecting the dynamic crossover in systems with and without coexistence gas-liquid binodal.…”

Section: Crossover In Collective Dynamics Of Soft-sphere Fluidsmentioning

confidence: 99%

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Collective excitations in soft-sphere fluids

et al. 2014

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Despite that the thermodynamic distinction between a liquid and the corresponding gas ceases to exist at the critical point, it has been recently shown that reminiscence of gaslike and liquidlike behavior can be identified in the supercritical fluid region, encoded in the behavior of hypersonic waves dispersion. By using a combination of molecular dynamics simulations and calculations within the approach of generalized collective modes, we provide an accurate determination of the dispersion of longitudinal and transverse collective excitations in soft-sphere fluids. Specifically, we address the decreasing rigidity upon density reduction along an isothermal line, showing that the positive sound dispersion, an excess of sound velocity over the hydrodynamic limit typical for dense liquids, displays a nonmonotonic density dependence strictly correlated to that of thermal diffusivity and kinematic viscosity. This allows rationalizing recent observation parting the supercritical state based on the Widom line, i.e., the extension of the coexistence line. Remarkably, we show here that the extremals of transport properties such as thermal diffusivity and kinematic viscosity provide a robust definition for the boundary between liquidlike and gaslike regions, even in those systems without a liquid-gas binodal line. Finally, we discuss these findings in comparison with recent results for Lennard-Jones model fluid and with the notion of the "rigid-nonrigid" fluid separation lines.

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Section: Crossover In Collective Dynamics Of Soft-sphere Fluidssupporting

confidence: 88%

Section: Crossover In Collective Dynamics Of Soft-sphere Fluidsmentioning

confidence: 99%

Collective excitations in soft-sphere fluids

et al. 2014

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“…Their density dependences were obtained qualitatively similar with a minimum right at the density where the vanishing PSD was observed. For the soft sphere fluids was obtained similar density dependence of D T as it was known for real supercritical fluids [51] and were reported in studies of critical behaviour of thermal diffusivity D T of CO 2 , C 2 H 6 [60] and H 2 O [61]. Both quantities D T and D L define the behaviour of the PSD as it follows from the analytical expression reported in 4.25.…”

Section: Crossover In Collective Dynamics Of Supercritical Fluidssupporting

confidence: 67%

“…The experiments [60,61] give evidence of a rapid decay of D T on approaching the critical point, i.e. leading contribution from the C P , and consequently, the line of the minimum of D T ðnÞ for realistic fluids should be very close to their Widom line.…”

Section: Crossover In Collective Dynamics Of Supercritical Fluidsmentioning

confidence: 95%

“…It seems that namely these two quantities are responsible for the dynamic crossover for all fluids: supercritical ones and soft-sphere systems. It is necessary to stress, that the experimental studies [60,61] were performed for fluids near the critical point. Therefore for temperatures far away from the critical region new simulation studies for Lennard-Jones fluids are required in order to check the behaviour of positive sound dispersion in a wide range of temperatures: from critical region up to very high temperatures.…”

Section: Crossover In Collective Dynamics Of Supercritical Fluidsmentioning

confidence: 99%

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Collective Excitations in Supercritical Fluids

Bryk

Gorelli

Ruocco

et al. 2015

Springer Proceedings in Physics

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Recent progress in theoretical and simulation studies of collective excitations in supercritical fluids is reviewed. We discuss a methodology of fit-free estimation of dispersion of longitudinal and transverse excitations in simple fluids. The issue of vanishing positive sound dispersion-a viscoelastic increase of the speed of sound from adiabatic one to its high-frequency (elastic) value-with reduction of density, as it was observed in inelastic X-ray scattering experiments on supercritical Ar, is discussed from the point of view of finding distinctions in collective dynamics of low-and high-density supercritical fluids. On the basis of several theoretical models within the extended hydrodynamic description of density-density correlations in liquids analytical expressions for positive sound dispersion are obtained and applied for analysis of time correlation functions obtained from molecular dynamics simulations. A location of a crossover from the liquid-like to gas-like types of collective dynamics is discussed based on general findings for spectra of collective excitations in supercritical Ar and soft sphere fluids.

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