Anatase, crystal symmetry

In anatase, the arrangement of the aifions and cations is similar and the crystal is again tetragonal, but now each octahedron is somewhat distorted and shares four of its edges with other octahedra. In brookite, the structure is even more complicated with octahedra sharing both edges and corners. So the trend rutile-anatase-brookite is to ever decreasing symmetry. 

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