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Développement d'une nouvelle approche pour la modélisation structurale de verres boratés : combiner Résonance Magnétique Nucléaire (RMN) et Dynamique Moléculaire

Abstract : Glasses are materials used in many fields. However, their structures still not well known because of the lack of long range order, making it difficult to extract the structural information of these materials. It is accepted that the glassy network is made of many elementary unit chains, being boron triangles and tetrahedron in the case of borate glasses. Nuclear magnetic resonance (NMR) has proven to be a vital characterization technique for the glasses study. It allows the measurement of proportion of each unit. The determination of the structural resolution of glasses remains a major scientific challenge for understanding of the relationship between the glass properties and it elemental compositions. This thesis aims to develop new NMR approach combining 1D, 2D and oxygen-17 NMR with DFT-GIPAW calculations on numerical models in order to characterize the intermediate ranger order NMR fingerprint. The first study is on sodium borate glasses. It highlighted that only ab-initio molecular dynamics (MD) can reproduce the boron rings, which have been confirmed by the NMR data, taking into account of the fine NMR parameters distributions effects. The second study is on aluminoborate glasses. Unlike the previous, the computed MD structures are not in agreement with NMR data. Thereby, a diferente stuctural simulation is applied. Refined models have been determined by Reverse Monte Carlo by constraining few experimental NMR data. This method allows to significantly improve the agreement between sumulated models and the experiment.
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Submitted on : Friday, January 17, 2020 - 12:13:07 PM
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Erwan Chesneau. Développement d'une nouvelle approche pour la modélisation structurale de verres boratés : combiner Résonance Magnétique Nucléaire (RMN) et Dynamique Moléculaire. Matière Condensée [cond-mat]. Université Paris Saclay (COmUE), 2019. Français. ⟨NNT : 2019SACLV058⟩. ⟨tel-02443654⟩

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