What drives anion order in TiOF?

FeOF and TiOF both adopt the rutile structure, and exhibit anion ordering within 2D {110} planes. This anion order gives rise to diffuse scattering, caused by covalency-driven displacements of cations (M = Fe, Ti) within fac-MO3F3 octahedra. Surprisingly, the anion order is different in each case. Recent theoretical predictions have suggested that the TiOF ordering is caused by Ti-Ti (d1-d1) dimerization, but this would have to persist to extremely high temperatures. The aim of this experiment is therefore to investigate the Ti-Ti distance at high temperatures to (dis)prove this hypothesis.