Both samples exhibit 209 Bi CT that are greater than 1 MHz in breadth (Supplementary Figure Once again, DFT calculations provided a valuable basis for approaching the spectral fitting. As in the case of the In spectrum, the calculated shift anisotropy suggested that it would have no impact on the simulated 209 Bi linewidth at 9.4 T, and so the number of variable fitting parameters could be reduced. Note that a previous study of bismuth compounds (oxyhalides, nitrate pentahydrate, triflate, and acetate) observed chemical shift anisotropy values that were typically an order-of-magnitude larger than the calculated values for the bismuth oxides here. The quadrupolar tensor parameters were adjusted to match the discontinuities in the powder lineshape, and the quadrupolar coupling values from DFT were found to be within 5% of those determined experimentally (Table ). NMR spectra of the quadrupolar M-site cations in BiMTeO 6 were measured as further probes of the atomic structure models. Al MAS NMR of BiAlTeO 6 revealed a single pseudo-Voigt lineshape with a center of gravity at 18.5 ppm (Figure ). The calculated C Q of 2.0 MHz yields a narrower line (by about a factor of two) than the one observed; however, the calculated C Q is consistent with the breadth of the spinning sideband manifold (~670 kHz). Assuming this C Q magnitude, which equates to a quadrupolar shift of ca. 2.2 ppm, the isotropic shift is 20.7 ppm, but the estimated error in the shift is given at 3 ppm to account for uncertainty in the relatively featureless CT lineshape (Table ). A static Al NMR spectrum