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9 results on '"Castets, Aurore"'

1. Simulation of NMR Fermi contact shifts for Lithium battery materials: the need of an efficient hybrid functional approach

Author

Zhang, Yuesheng, Castets, Aurore, Carlier, Dany, Ménétrier, Michel, and Boucher, Florent

Subjects
Condensed Matter - Materials Science
Abstract

In the context of the development of NMR Fermi contact shift calculations for assisting structural characterization of battery materials, we propose an accurate, efficient, and robust approach based on the use of an all electron method. The full-potential linearized augmented plane wave method, as implemented in the WIEN2k code, is coupled with the use of hybrid functionals for the evaluation of hyperfine field quantities. The WIEN2k code is able to fully relax relativistic core states and uses an autoadaptive basis set that is highly accurate for the determination of the hyperfine field. Furthermore, the way hybrid functional approaches are implemented offers the possibility to use them at no additional computational cost. In this paper, NMR Fermi contact shifts for lithium are studied in different classes of paramagnetic materials that present an interest in the field of Li-ion batteries: olivine LiMPO4 (M = Mn, Fe, Co, Ni), anti-NASICON type Li3M2(PO4)3 (M = Fe, V), and antifluorite-type Li6CoO4. Making use of the possibility to apply partial hybrid functionals either only on the magnetic atom or also on the anionic species, we evidence the role played by oxygen atoms on polarisation mechanisms. Our method is quite general for an application on various types of materials., Comment: 39 pages

Published
2012

4. Multinuclear NMR of paramagnetic compounds: Measurements and modelling

Author

Castets, Aurore, Toulin, Stéphane, Institut de Chimie de la Matière Condensée de Bordeaux (ICMCB), Institut de Chimie du CNRS (INC)-Centre National de la Recherche Scientifique (CNRS)-Institut Polytechnique de Bordeaux-Université de Bordeaux (UB), Université Sciences et Technologies - Bordeaux I, Michel Ménétrier, and Dany Carlier

Subjects
Calculs ab initio, [CHIM.MATE] Chemical Sciences/Material chemistry, Transition metal phosphates, MAS NMR 7Li, RMN MAS 7Li, 1H, Batteries au lithium, [CHIM.MATE]Chemical Sciences/Material chemistry, Lithium battery, Phosphates de métal de transition, 31P, Contact de Fermi, Fermi contact, GGA+U, First principles calculations
Abstract

Paramagnetic materials for positive electrodes for Li batteries have been studied by multinuclear NMR. The local environment of the probed nucleus can be characterized by solid state NMR making use of hyperfine interactions due to transfer of some electron spin density (Fermi contact shift) on this nucleus, via more or less complex mechanisms. We studied a series of transition metal phosphates as Li3M2(PO4)3 (M = Fe, V) with anti-NASICON structure, LiMPO4X (M = Fe, Mn; X = OH, F) belonging to the tavorite family and the homeotypic phases MPO4.H2O (M = Fe, Mn, V). All these materials have been characterized by 7Li, 31P and 1H NMR, and the local environments of these nuclei have been analyzed to propose possible spin transfer mechanisms. First principles DFT calculations have been carried out to, first of all, reproduce the experimental NMR shifts, and then to confirm or complement the understanding of these mechanisms, in particular by plotting spin density maps., Ce travail consiste en l'étude par RMN multinoyaux de matériaux paramagnétiques d'électrodes positives pour batteries au Li. La RMN du solide permet une caractérisation de l'environnement local du noyau sondé grâce à l'exploitation des interactions hyperfines dues à la présence d'une certaine densité d'électrons célibataires (déplacement de contact de Fermi) ou de conduction (déplacement de Knight) sur ce noyau (densité transférée selon des mécanismes plus ou moins complexes). Les matériaux étudiés sont des phosphates de métaux de transition tels que Li3M2(PO4)3 (M = Fe, V), la famille des tavorites LiMPO4X (M = Fe, Mn; X = OH, F) ou encore les phases homéotypiques MPO4.H2O (M = Fe, Mn, V). Pour tous ces matériaux, caractérisés par RMN du 7Li, 31P et 1H, l'environnement local de ces noyaux a été étudié afin d'envisager les mécanismes de transfert de spin possibles. Des calculs ab initio ont été effectués pour reproduir les déplacements de RMN, puis établir des cartes de densité de spin afin d'étayer ou compléter la compréhension de ces mécanismes.

Published
2011

8. Red Wine Tannins Fluidify and Precipitate Lipid Liposomesand Bicelles. A Role for Lipids in Wine Tasting?

Author

Furlan, Aurélien L., Castets, Aurore, Nallet, Frédéric, Pianet, Isabelle, Grélard, Axelle, Dufourc, Erick J., and Géan, Julie

Subjects
*RED wines, *TANNINS, *FLUIDICS, *PRECIPITATION (Chemistry), *LIPOSOMES, *LIPID analysis
Abstract

Sensory properties of red wine tanninsare bound to complex interactionsbetween saliva proteins, membranes taste receptors of the oral cavity,and lipids or proteins from the human diet. Whereas astringency hasbeen widely studied in terms of tannin–saliva protein colloidalcomplexes, little is known about interactions between tannins andlipids and their implications in the taste of wine. This study dealswith tannin–lipid interactions, by mimicking both oral cavitymembranes by micrometric size liposomes and lipid droplets in foodby nanometric isotropic bicelles. Deuterium and phosphorus solid-stateNMR demonstrated the membrane hydrophobic core disordering promotedby catechin (C), epicatechin (EC), and epigallocatechin gallate (EGCG),the latter appearing more efficient. C and EGCG destabilize isotropicbicelles and convert them into an inverted hexagonal phase. Tanninsare shown to be located at the membrane interface and stabilize thelamellar phases. These newly found properties point out the importanceof lipids in the complex interactions that happen in the mouth duringorganoleptic feeling when ingesting tannins. [ABSTRACT FROM AUTHOR]

Published
2014
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9. RMN de matériaux paramagnétiques : mesures et modélisation

Author

CASTETS, Aurore, Carlier-Larregaray, Dany, Ménétrier, Michel, Gautier, Régis, Masquelier, Christian, Deschamps, Michaël, Boucher, Florent, Delmas, Claude, Michel Ménétrier, and Dany Carlier

Subjects
Calculs ab initio, RMN MAS 7Li, 31P, 1H, RMN MAS 7Li, 1H, Batteries au lithium, GGA+U, Phosphates de métal de transition, 31P, Contact de Fermi

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