The timescale for lone-pair reorientation is similar to the timescale of fluoride-ion site-site transitions, which suggests possible coupling between these two kinds of dynamics. To examine whether the fluoride ion dynamics and lone pair dynamics are, in fact, coupled, we performed an additional AIMD simulation with all fluoride ions fixed at their ideal fluorite positions, and calculated the corresponding Sn-dipole orientational autocorrelation function. With the fluoride ions fixed, the lonepair orientational autocorrelation function decorrelates on a sub-picosecond timescale (Fig. ), decaying to a rotationally symmetric (unbiased) value of zero.