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The high-frequency dynamics of liquids and supercritical fluids

Abstract : The thesis reports an experimental investigation of the microscopic dynamics in four prototype systems (i.e. Neon, Nitrogen, Ammonia and Water) in their respective liquid and supercritical phase, utilising inelastic X-ray scattering (IXS). The coherent dynamic structure factor, S(Q,w) was determined in the momentum transfer, Q (2 - 15 nm-1), and a frequency, w ( 1 - 60 THz), range corresponding to characteristic length and time scales of the microscopic dynamics in the nanometres and picoseconds regime. The experimental data have been interpreted in the framework of the generalized hydrodynamic theory. This formalism allows identifying the relaxation processes describing the intermolecular interactions, and provides quantitative values for the relaxation times and strengths, as well as related macroscopic quantities (sound speed and viscosity).
On going from the liquid into the supercritical phase, a qualitative common phenomenology has been observed. The main findings are the following: (i) A weakening of the positive sound dispersion associated to the structural relaxation. (ii) A change in the dominant microscopic mechanism responsible for intermolecular interactions that, in the liquid phase, are mainly represented by bonds while, in the supercritical phase, are dominated by intermolecular collisions.
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Contributor : Filippo Bencivenga <>
Submitted on : Wednesday, December 20, 2006 - 6:06:51 PM
Last modification on : Wednesday, December 20, 2006 - 6:34:11 PM
Long-term archiving on: : Tuesday, April 6, 2010 - 7:47:54 PM


  • HAL Id : tel-00121509, version 1




Filippo Bencivenga. The high-frequency dynamics of liquids and supercritical fluids. Fluid Dynamics [physics.flu-dyn]. Université Joseph-Fourier - Grenoble I, 2006. English. ⟨tel-00121509⟩



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