Figure 6: H− ions in apatites.
(a) Local structure around the channel in apatite, showing the coordinating ions with OH− and H− ions. (b) 1H−magic-angle-spinning nuclear magnetic resonance (NMR) spectra collected in apatite samples annealed in wet N2 (indicated by blue lines), in dry O2 (orange) and with TiH2 (brown and red). Filled areas highlight the signals assigned to H− ions. (c) Infrared transmission spectra measured for the same set of samples. (d) Correlation between chemical shifts (δiso) in the NMR spectra and wavenumbers in the infrared spectra. Blue and red shaded areas indicate chemical shift ranges predicted using the dM–H and dO–H…O correlations with δiso (H−) and δiso (H+), respectively, given in Fig. 4 and equation 1.
