MAS NMR spectra of quadrupolar nuclei in disordered solids: The Czjzek model

Structural disorder at the scale of two to three atomic positions around the probe nucleus results in variations of the EFG and thus in a distribution of the quadrupolar interaction. This distribution is at the origin of the lineshape tailing toward high fields which is often observed in the MAS NMR...

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Bibliographic Details
Published in:Journal of magnetic resonance (1997) 2008-06, Vol.192 (2), p.244-251
Main Authors: d’Espinose de Lacaillerie, Jean-Baptiste, Fretigny, Christian, Massiot, Dominique
Format: Article
Language:English
Subjects:
Aluminum-27
Amorphous materials
Chemical Sciences
Disorder
Electrical field gradient
Gel
Glass
Lineshape
Material chemistry
Quadrupolar nuclei
Solid-state NMR
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Summary:Structural disorder at the scale of two to three atomic positions around the probe nucleus results in variations of the EFG and thus in a distribution of the quadrupolar interaction. This distribution is at the origin of the lineshape tailing toward high fields which is often observed in the MAS NMR spectra of quadrupolar nuclei in disordered solids. The Czjzek model provides an analytical expression for the joint distribution of the NMR quadrupolar parameters υ Q and η from which a lineshape can be predicted. This model is derived from the Central Limit Theorem and the statistical isotropy inherent to disorder. It is thus applicable to a wide range of materials as we have illustrated for 27Al spectra on selected examples of glasses (slag), spinels (alumina), and hydrates (cement aluminum hydrates). In particular, when relevant, the use of the Czjzek model allows a quantitative decomposition of the spectra and an accurate extraction of the second moment of the quadrupolar product. In this respect, it is important to realize that only rotational invariants such as the quadrupolar product can make sense to describe the quadrupolar interaction in disordered solids.
ISSN:1090-7807
1096-0856
DOI:10.1016/j.jmr.2008.03.001