Crystallographic Analysis of TiO₂ Polymorphism (Brookite, Anatase, Rutile)

Crystallographic analysis of three TiO₂ structures shows that all of them have a rhombohedral anion sublattice close to their cubic closest packing. In brookite it competes with the hexagonal packing, and the packing of TiO₆ octahedra is less regular. High symmetry of anatase and rutile is initiated by the local (cubic) symmetry of TiO₆ octahedra. Cations occupy most symmetrical special positions and provide a coherent assembly of these “building units” by spreading the local symmetry over the entire structure.