In contrast to that of the O V and O P environments, the O CT linewidths of the O V and O P environments. The O P1 and O P2 environments correspond to the peaks at ∼135 ppm and ∼145 ppm, respectively, and the O V1 environment corresponds to the peak at ∼620 ppm (the other O V2 site has a temperatureinvariant linewidth). The E A derived in this way corresponds to oxide-ion motion within the VO 4 and PO 4 polyhedral units, such as rotations or librations, on the spectral timescale (typically on the order of ∼1 kHz).