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Theses

DYNAMIQUE DES SYSTÈMES DÉSORDONNES:
UNE ÉTUDE PAR DIFFUSION DE NEUTRONS

Abstract : The main task of this thesis is to perform a systematic investigation of the dynamics of glassy materials at temperatures T much smaller than Tg, the glass transition temperature. Both theoretical and experimental studies performed over the last two decades on different aspects of the glassy state, have established a number of peculiar properties that concern low energy dynamics and manifest themselves in low temperature specific heat, thermal conductivity, and inelastic scattering experiments. Some of the fundamental questions in this field, in particular about the microscopic nature of the dynamics and the origin of the “universal” features concerning the density of vibrational states in glasses, have not found a generally accepted answer. In order to explain some features of strong glasses, different systems have been investigated. Here we present new results on two strong glasses, vitreous silica (v-SiO2) and vitreous germania (v-GeO2). The technique employed was Inelastic Neutron Scattering (INS). The studies of these samples have been done in order to:
(i) develop a new procedure to extract the density of states from coherent systems extending the usual incoherent approximation;
(ii) study the QES of our samples at very low frequency range (in order to compare with Brillouin data and to asses a correlation with the mechanism causing the sound attenuation);
(iii) compare of the previous scattering data above-mentioned, in order to calculate the Raman coupling function C(omega) and its low frequency limit;
(iv) finally, investigate v-GeO2 to asses that both longitudinal and transverse acoustic branches are still somewhat defined also in glassy system.
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https://tel.archives-ouvertes.fr/tel-00011520
Contributor : Elisa Fabiani <>
Submitted on : Wednesday, February 1, 2006 - 2:46:31 PM
Last modification on : Tuesday, March 21, 2006 - 1:01:23 PM
Long-term archiving on: : Saturday, April 3, 2010 - 10:02:58 PM

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  • HAL Id : tel-00011520, version 1

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Elisa Fabiani. DYNAMIQUE DES SYSTÈMES DÉSORDONNES:
UNE ÉTUDE PAR DIFFUSION DE NEUTRONS. Analyse de données, Statistiques et Probabilités [physics.data-an]. Université Joseph-Fourier - Grenoble I, 2005. Français. ⟨tel-00011520⟩

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