Étude par dynamique moléculaire ab-initio des verres de chalcogénures GeS2 et (M2S)0.33(GeS2)0.66 M=Na, Ag

Abstract : Ab-initio molecular dynamics simulations are used to study GeS2 and (M2S)0.33(GeS2)0.66 M=Na,Ag chalcogenide glasses. A new theoretical method which uses ring statistics is proposed in order to analyse the connectivity of amorphous materials. The cooling rate effect on the physical properties of the GeS2 glasses is analysed. The medium and short range order analysis reveals the existence of a maximum cooling rate above which the structure of the material is too similar to the one of the liquid. This is confirmed by the ring statistics analysis which also highlights major differences between the connectivity of the liquid and the glassy GeS2 structures. Finally the existence of extended charged regions in the glassy GeS2 matrix is confirmed even for the lowest cooling rates. The conditions needed to observe the diffusion of the sodium atoms in the glassy (Na2S)0.33(GeS2)0.66 matrix are studied. When the diffusion process occurs the displacement of the sodium atoms seems to become cooperative. Parametrisation attempts are done in order to model (Ag2S)0.33(GeS2)0.66 and GeS2 chalcogenide glasses using the SIESTA code.
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Submitted on : Tuesday, April 17, 2012 - 3:16:39 PM
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Sébastien Le Roux. Étude par dynamique moléculaire ab-initio des verres de chalcogénures GeS2 et (M2S)0.33(GeS2)0.66 M=Na, Ag. Matériaux. Université Montpellier II - Sciences et Techniques du Languedoc, 2008. Français. ⟨tel-00688343⟩

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