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Lignes de percolation dans un fluide supercritique

Abstract : The aim of this thesis is to establish the correspondence between the phase diagram of a simple fluid and its microscopic structure in terms of clusters of particles. Large scale Monte-Carlo and molecular dynamics calculations suggest that self-bound clusters are present in the supercritical phase, that is for temperatures above the critical one. These clusters, that are cooler than the system, generate a percolation line, characterized by the universal exponents of random percolation in three dimensions. This line, which starts at the thermodynamical critical point, is almost iso-energetic. Moreover, a non percolating macroscopic cluster appears as soon as one penetrates into the two-phase region for densities below the critical one. This clean correspondence between thermodynamics and morphologic changes is a natural consequence of the definition of clusters on physical grounds. Various experiments, within the reach of present day experimental techniques, are suggested to show the presence of these self-bound clusters and the existence of the critical percolation line. We have also studied the case of small systems, in order to discuss experiments of atomic aggregates and atomic nuclei fragmentation. Indeed, by simulations of the expansion of a liquid droplet, we have showed that self-bound clusters are the precursors of the observed fragments at the end of the fragmentation process. In small systems, critical behaviours are less pronounced, but the properties of the self-bound clusters remain qualitatively valid. In addition to its relevance in fundamental research, this work may allow a better understanding of the solubility of supercritical fluids used in many industrial processes.
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Contributor : Nicolas Sator <>
Submitted on : Wednesday, October 16, 2002 - 3:26:59 PM
Last modification on : Wednesday, December 9, 2020 - 3:09:21 PM
Long-term archiving on: : Tuesday, September 11, 2012 - 6:05:47 PM


  • HAL Id : tel-00001823, version 1


Nicolas Sator. Lignes de percolation dans un fluide supercritique. Analyse de données, Statistiques et Probabilités []. Université Paris Sud - Paris XI, 2000. Français. ⟨tel-00001823⟩



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