Ambiguities in Assigning Single‐Crystal NMR Data to Individual Atoms in the Crystal Structure: A Case Study of Hambergite, Be2₂BO3₃OH, by 9⁹Be and 11¹¹B NMR Spectroscopy, XRD Measurements and DFT Calculations

The NMR interaction tensors of Be and B of hambergite, BeBOOH, were derived from single‐crystal NMR experiments. In the orthorhombic crystal structure of hambergite (which we redetermined by single‐crystal XRD, confirming the results of previous studies), both beryllium and boron atoms occupy Wyckoff position , with atoms pairwise related by inversion symmetry. This leads to four magnetically independent Be and B atoms per site, which are observable in the NMR spectra. Unequivocal assignment of these resonances to atomic positions in the unit cell is generally impossible, as an analysis of the symmetry relations shows. For the hambergite system, this assignment ambiguity could be resolved with the help of DFT calculations using the VASP code, with the resulting eigenvectors compared with the experimental ones. Examination of Be–H dipolar coupling effects, which could be detected in some of the Be spectra, in combination with XRD experiments to confirm the goniometer axis orientation, provided further spatial information and confirmed the assignment. The thus determined numerical values for the quadrupolar coupling constants and isotropic chemical shifts are as follows: for Be[1] kHz and 1.6 ppm, for Be[2] kHz and 1.4 ppm and for B[1] MHz and 18.1 ppm.