F. Angeli et al., Structural characterization of glass from the inversion of Na-23 and Al-273Q-MAS NMR spectra, J PHYS CH B, 103(47), 1999, pp. 10356-10364
A spectrum-inversion approach to extract information from MQ-MAS NMR spectr
a in glasses is presented. This allows the reconstruction of the underlying
two-dimensional distribution of the isotropic chemical shift correlated to
the quadrupolar interaction. The dependency upon the quadrupolar interacti
on and the RF field strength of coherence transfers involved in the MQ-MAS
experiment are taken into account in the present approach. The performance
of the inversion procedure is examined. Thereafter, we attempt to correlate
the distributions of each interaction to structural local information. Two
complex glasses (a borosilicate and a basaltic-like glass) have been studi
ed using Al-17 and Na-23 3Q-MAS NMR. These two nuclei allowed us to investi
gate their local environment. The interpretation of the different site dist
ributions is discussed in terms of topological disorder, i.e., the distribu
tion of specific geometrical parameters such as bond distances and angles.
Using the semiempirical relationships previously established with crystalli
ne silicate compounds, the distributions of the Na-O distance and the Al-O-
Si bond angle have been determined from the extracted distributions of the
isotropic chemical shift. The limits of the interpretation of quadrupolar i
nteraction distributions are also discussed.