A similar Arrhenius relationship can also be applied to the temperature-dependent O CT linewidth(s) for the O V and O P environments plotted in Figure , under the assumption that this variation is related to changes in the rate of oxide-ion motion. In this analysis, the logarithm of the inverse CT linewidth is plotted against inverse temperature, which gives a linear relationship when the relevant motional rate is on the order of the MAS rate, i.e., typically when the rate is between 100 Hz and 10 kHz. The results of the linewidth fitting are shown in Figure and Table .