 |
 |
|
Paris, M. (2014) The two aluminum sites in the Al-27 MAS NMR spectrum of kaolinite: Accurate determination of isotropic chemical shifts and quadrupolar interaction parameters. Am. Miner. 99 393–400.
Added by: Florent Boucher (2016-04-29 09:26:45) |
| Type de référence: Article DOI: 10.2138/am.2014.4607 Numéro d'identification (ISBN etc.): 0003-004X Clé BibTeX: Paris2014a Voir tous les détails bibliographiques  |
Catégories: IMN Mots-clés: 1st-principles, al-27 mas nmr, aluminosilicates, augmented wave method, crystal-structure, EFG calculations, gibbsite, isotropic chemical shift, Kaolinite, nuclei, quadrupolar parameters, quantum, satellite transitions, si-29, spectroscopy Créateurs: Paris Collection: Am. Miner. |
Consultations : 1/518
Indice de consultation : 4% Indice de popularité : 1% |
| Résumé |
|
{The problem of resolving the two aluminum sites in the Al-27 NMR spectrum of kaolinite has been unsuccessfully addressed for 30 years. A few years ago, it was shown that the two sites cannot be spectrally separated even by the use of high magnetic fields. Nevertheless, it is still possible to determine the NMR parameters of both sites. In this article, we present an alternative approach. We show that, at low magnetic field (7 T), the individual spinning sideband lineshapes of the outer satellite transitions are sensitive enough to differentiate information coming from the two aluminum sites. Thus, the isotropic chemical shift delta, the quadrupolar constant C-Q, and asymmetry parameter eta(Q) of each site can be obtained by accurately fitting the full Al-27 MAS spectrum acquired at low magnetic field. In return, this approach requires a carefully acquired and post-treated Al-27 spectrum. It is concluded that the two sets of parameters (delta = 7.5 ppm
Added by: Florent Boucher |