Using this GA procedure, we generated four 4×4×4 supercells, with each selected as the lowest energy structure after 100 GA generations. The resulting 4 × 4 × 4 structures feature no collinear O-Ti-O units and predominantly exhibit cis-TiO 2 F 4 coordination (93.0 %), with some fac-TiO 3 F 3 (3.5 %) and TiOF 5 (3.5 %) coordination (Fig. ). Additional analysis of the TiX 6 coordination geometries in these 4 × 4 × 4 models (see the Supporting Information) shows that the anions show small average deviations from ideal octahedra, while the mean Ti-O and Ti-F distances are significantly different, due to large off-centre displacements of the Ti cations (averaging 0.20 Å).