To validate against the experimental PDF data, each GA-predicted structure was used as an initial structural model that was fitted to the experimental PDF data, with the atomic positions left unrefined to limit the number of fitting parameters. All four GA-predicted structures give a better fit for the experimental data than the average cubic P m 3m model (R w = 31.2 %), with the best fit obtained for GA structure 4 (R w = 16.4 %) (Fig. ). The improved fit to the experimental PDF data is particularly evident in the split peak at 1.82 Å and 1.99 Å, which we previously assigned to nearest-neighbour Ti-O and Ti-F distances, respectively, and in the region between 3.5 Å and 4.0 Å, which we assigned to Ti-X-Ti pairs, and which is consistent with the observation from our 2 × 2 × 2 supercell DFT dataset that ReO 3 -type TiOF 2 preferentially adopts anion configurations that allow the Ti-O and Ti-F bond-lengths to be shorter and longer, respectively, than the average Ti-X bond-length of 1.90 Å. Our assignment of these peaks in the experimental PDF spectrum is also validated by direct analysis of the GA-predicted structures (Supporting Information), which gives mean Ti-O and Ti-F distances of 1.81 Å and 1.99 Å, respectively, and a clear splitting in Ti-X-Ti distances.