Relation structure-luminescence dans les verres dopés terre rare

Les matériaux inorganiques dopés terre rare sont à l’origine de nombreuses applications dans le domaine de la photonique (lasers, guides d’onde actifs, amplificateurs à fibre…). Les propriétés de luminescence des ions terre rare étant essentiellement liées à la structure locale qui les entoure, il s’avère nécessaire de caractériser et de comprendre ce lien pour pouvoir optimiser les matériaux synthétisés aujourd’hui et envisager les matériaux de demain. C’est tout l’objet des travaux présentés à l’occasion de cette HDR qui résume l’ensemble de mes activités de recherche menées dans le cadre du laboratoire LPhiA. Au sein de l’équipe « couches minces et verres dopés », j’ai ainsi pu développer des techniques d’investigation originales, s’appuyant sur la modélisation de structures vitreuses par dynamique moléculaire et le calcul de leurs propriétés de luminescence. En étroite collaboration avec des équipes réalisant la synthèse et la caractérisation expérimentales, ces activités de modélisation ont ainsi permis de comprendre les spécificités de ce lien entre structure et luminescence, essentiellement dans des verres silicatés, mais aussi dans des matrices fluorées et plus récemment dans des vitrocéramiques

Simulation of ultrashort heat pulses on vitreous thin plates-application to the determination of dynamic constants

Date du colloque : 09/2010International audienc

Cutoff effect in molecular dynamics simulations of interaction induced light scattering spectra

International audienceA strong dependence of the interaction induced light scattering integrated intensity with the cutoff radius was previously reported in noble liquids molecular dynamics simulations (A.J.C. Ladd, T.A. Litovitz, J.H.R. Clarke, L.V. Woodcock, J. Chem. Phys. 72 (1980) 1759; and J.H.R. Clarke, L.V. Woodcock, Chem. Phys. Lett. 78 (1981) 121). It was concluded that the uncertainties arising from this effect were much larger than can be tolerated in any evaluation of the light scattering mechanism. No real explanation or solution ever appeared in the literature on this problem. Here we report a very strong dependence of the interaction induced spectra calculated by molecular dynamics simulations on the number of atoms used in a liquid argon simulation. We show that this effect is proportional to the square of the density involved in the simulation-4 and that it obeys to a Rcutoff power law with the cutoff radius Rcutoff. To obtain accurate spectra up to high frequency shifts, large cutoff radii have then to be used corresponding to thousands of atoms in the simulation. The time of the simulation is then prohibited. An explanation for both effects is proposed and two different methods to solve this problem are tested. @ 1997 Elsevier Science B.V

Molecular dynamics simulation of Eu3+ in aqueous solution comparison with experimental luminescence spectra

Using molecular dynamics simulations, we have studied the environment of Eu3+ salts in aqueous solution. In the case of hydration number of 8, the symmetry of the first hydration shell is found to be very close to the D4d. We have therefrom calculated the ligand field parameters according to the point charge model. The luminescence spectra were reconstructed from this set of computed Bkq, and finally compared with experimental spectra

Molecular dynamics simulations of rare-earth-doped glasses

In the recent years the use of the molecular dynamics technique has become very common in the study of glass. The purpose of the present paper is to focus on recent advancements on the use of this method to investigate rare-earth-doped glasses. We report an overview of the use of simulations to study their specific structural features and luminescence properties

Numerical Simulations of the Structure and Spectroscopic Properties of Rare-Earth Doped Glasses

A review of the research that has been devoted to the simulation of the structure and spectroscopic properties of rare-earth doped glasses is presented. Since the seminal papers of Brawer and Weber who have applied Monte-Carlo or molecular dynamics techniques, some other very important results have been reported concerning the local structure of the dopants. As a result, crystal field models have been applied and several pecularities of the optical spectra of rare earth ions in glasses have been understood

Molecular dynamics simulation of phase transitions in crystalline lead (II) fluoride

Using classical molecular dynamics applied to crystalline PbF2, we have simulated transitions between cubic and orthorhombic phases and reciprocally. These transitions were induced by pressure and temperature treatments. The orthorhombic phase was evidenced by analysis of different distribution functions and XRD spectra drawn from the ions positions in the simulated samples. (C) 2014 Elsevier B.V. All rights reserved

Molecular dynamics simulation of trivalent europium in aqueous solution: A study on the hydration shell structure

As a prelude to a spectroscopic investigation of doped wet gels, we have made molecular dynamics simulations of a very dilute EuCl3 solution. The symmetry properties of the first hydration shell of Eu3+ have been determined. The 8 water molecules of this shell are roughly arranged according to the square antiprism D 4d pseudo‐symmetry. Though the arrangement of oxygens is little distorted from regular positions, the orientation of the water molecules themselves is found to be not so well organized at room temperature