27Al NMR experiments and quadrupolar parameter ab initio calculations: Crystallographic structure refinement of β-Ba3AlF9

27Al quadrupolar parameters are determined for the three aluminium sites in β-Ba3AlF9 from the reconstruction of experimental SATRAS and MQ-MAS NMR spectra. These quadrupolar parameters are then computed using the DFT linearized augmented plane wave method implemented in the WIEN2k code.A fine agreement between experimental and calculated values is obtained only after optimizing the β-Ba3AlF9 structure. The optimized structure is more satisfactory than the previously published one from a crystallographic point of view (bond lengths and angles).This approach which allows to refine crystallographic structures especially when they lack accuracy may be extendable to other compounds containing quadrupolar nuclei.

The β-Ba3AlF9 structure has been refined coupling the experimental determination of the three 27Al quadrupolar parameters and their ab initio calculations using the DFT Wien2k code. This method which is extendable to other compounds containing other quadrupolar nuclei, allows to refine crystallographic structures of low accuracy as well as assignments of NMR lines to specific atomic sites.