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2012
ACL
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L.Martel, S.Cadars, E.Véron, D.Massiot, M.Deschamps, 'Effects of the orientation of the 23Na-29Si dipolar vector on the dipolar mediated heteronuclear solid state NMR correlation spectrum of crystalline sodium silicates', Solid State NMR 45-46 1-10 (2012) doi:10.1016/j.ssnmr.2012.04.001
Dipolar-Heteronuclear Multiple Quantum Correlation (D-HMQC) experiment based on SR421 recoupling was shown as a very efficient probe of spatial proximities in ordered or disordered materials. As crystalline sodium silicates have been extensively studied using 1D and 2D MAS NMR experiments and DFT calculations, they have been used as candidate model systems to perform this D-HMQC experiment. In this work, we demonstrate that the combination of 29Si and 23Na NMR at high magnetic field and DFT calculations makes it possible to revisit the assignment of the NMR signature of δ-Na2Si2O5 polymorph. Then, after performing the D-HMQC experiment on this crystalline sample, we identified lineshape distortions on the 23Na spectra extracted from this 2D map. Numerical simulations showed that these distortions results to an effect of the relative orientation between the 23Na quadrupolar tensor and the 23Na-29Si dipolar vector at the origin of the magnetization transfer.
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