Kuang et al. also found from AIMD simulations at 1373 K that the coordination number of V sites varied between 4.0 and 4.3 for both V-substituted phases, with the larger average coordination number observed for the lower V-substituted material, in excellent agreement with the present results. For Bi 0.852 P 0.148 O 1.648 , the temperature-dependent behaviour of the O spectra differs significantly from that of the V-substituted samples. With increasing temperature, both the O P and O Bi resonances exhibit linewidth narrowing that is indicative of increased rates of local oxide-ionic motion, and this narrowing allows for observation of an additional resonance for each environment above ∼473 K. However, even at 873 K, the two groups of resonances remain distinct, showing no sign of the coalescence that is seen in Bi 0.913 V 0.087 O 1.587 and Bi 0.852 V 0.148 O 1.648 . This result is indicative of ionic motion that remains local (e.g., PO 4 rotations or librations) or is confined to distinct sublattices, with minimal long-range exchange between the Bi-O and P-O sublattices on the NMR timescale. Moreover, the appearance of spinning sideband intensity arising from the O P environment (but not from O Bi ) above 673 K is suggestive of increasing rates of local ionic motion, and further supports the idea that the motion remains distinct between the two sublattices.