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Modélisation de verres intervenant dans le conditionnement des déchets radioactifs par dynamiques moléculaires classique et ab initio

Abstract : A calcium aluminosilicate glass of molar composition 67 % SiO_2 - 12 % Al_2O_3 - 21 % CaO was modelled by classical and ab initio molecular dynamics.
The size effect study in classical MD shows that the systems of 100 atoms are more ordered than the larger ones. These effects are mainly due to the 3-body terms in the empirical potentials. Nevertheless, these effects are smalls and the structures generated are in agreement with experimental data. In such kind of glass, we denote an aluminium avoidance and an excess of non bridging oxygens which can be compensated by tricoordinated oxygens.

When the dynamics of systems of 100 and 200 atoms is followed by ab initio MD, some local arrangements occurs (bond length, angular distributions). Thus, more realistic vibrational properties are obtained in ab initio MD.

The modelling of thin films shows that aluminum atoms extend to the most external part of the surface and they are all tri-coordinated. Calcium atoms are set in the sub layer part of the surface and they produce a depolymerization of the network. In classical MD, tri-coordinated aluminium atoms produce an important electric field above the surface. With non bridging oxygens, they constitue attractive sites for single water molecules.
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Contributor : Patrick Ganster <>
Submitted on : Monday, January 3, 2005 - 5:52:33 PM
Last modification on : Friday, April 12, 2019 - 1:15:08 AM
Long-term archiving on: : Thursday, September 13, 2012 - 1:55:41 PM

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  • HAL Id : tel-00007894, version 1

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Patrick Ganster. Modélisation de verres intervenant dans le conditionnement des déchets radioactifs par dynamiques moléculaires classique et ab initio. Matière Condensée [cond-mat]. Université Montpellier II - Sciences et Techniques du Languedoc, 2004. Français. ⟨tel-00007894⟩

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