Structure of substituted hydroxyapatite: The solid state nmr (nuclear magnetic resonance) point of view.

We have shown that the combination of advanced solid state NMR experiments [7] and ab initio calculations of NMR parameters can lead to a novel description of substituted HAp structures. In the case of silicate substitution, the anions located within the structure are unambiguously characterized by selective 1H → 29Si CP transfer and 31P → 29Si experiments can edit the 29Si MAS spectra in terms of 31P/29Si dipolar interaction. 2D heteronuclear interactions will be performed in a near future. In the case of carbonate substituted HAp, the study of the 1H → 13C dynamics allowed to fully characterize the various 13C sites. By combining NMR calculations starting from DFT models and experiments, distributions of A-, B- and A/B sites were clearly characterized.