Structural refinement of the RT LaOF phases by coupling powder X-Ray diffraction, 19F and 139La solid state NMR and DFT calculations of the NMR parameters

The structures of the beta- and t-LaOF phases have been refined from XRPD patterns. For both phases, F-19 and La-139 solid-state NMR spectra recorded at high magnetic fields show the presence of a single F and a single La local environment, indicating a full anionic ordering in these oxyfluoride compounds. DFT calculations of the F-19 and La-139 chemical shielding tensors and of the La-139 EFG tensor have been performed for the proposed structural models. The observed good agreement between experimental and calculated NMR parameters for both phases highlights the accuracy of the structural data.