Etude structurale du verre de TeO₂ et de la variété désordonnée TeO₂-δ par dynamique moléculaire.

Abstract : This work aims to improve the structural description of the pure TeO2 glass and to give a deep insight into the structure of the disordered δ-TeO2 phase by means of molecular dynamics (MD) simulations.We derived simple but nontrivial interatomic potentials (IAPs), which take into account the polarisability of tellurium and oxygen atoms using the core-shell model. We demonstrated the important role of the electronic lone pair of the tellurium atoms in the formation of asymmetrical TeOx units. The accurate IAPs is able to reproduce 17 crystalline TeO2-based structures and are appropriate for MD simulations of disordered systems.The MD simulations of the pure glass and δ-TeO2 phase structures were carried out. It was demonstrated that the TeO2-glass consists of mainly TeO3 and TeO4 structural units and a large number of non-bridging oxygen (NBO) atoms is observed. The coordination number of the tellurium atoms in the glass is less than in the pure crystalline structures.In the δ-TeO2 phase, the tellurium atoms form a well-defined crystalline (FCC) lattice and the oxygen atoms exhibit a large positional disorder. This phase has a structural units distribution and a tellurium coordination number and a proportion of NBO atoms similar to those of the glass. Hence, the structure of δ-TeO2 is closer to that of glass than to the structures of other pure TeO2 crystalline polymorphs.
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Anastasia Gulenko. Etude structurale du verre de TeO₂ et de la variété désordonnée TeO₂-δ par dynamique moléculaire.. Mécanique des matériaux [physics.class-ph]. Université de Limoges, 2014. Français. ⟨NNT : 2014LIMO0013⟩. ⟨tel-01127133⟩

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