Atomic Positional Parameters
Ti 4a 0.0000 0.0000 0.0000
O  8e 0.0000 0.0000 0.2081

Reference
CJ Howard, TM Sabine and F Dickson (1991) Acta Crystallographica, B47, 462-468

Mineral Chemistry
Anatase is one of three TiO₂ polymorphs, the others being brookite and rutile. Each titanium ion in anatase is coordinated by six oxygens, and each oxygen ion by three titaniums. The TiO₆ octahedra share edges with four adjacent octahedra - see the central octahedron in the figure which shows this arrangement.

Anatase may be found in schist and gneiss, where it occurs in low temperature hydrothermal veins associated with quartz, brookite, adularia, rutile, hematite, titanite and chlorite. It is also a common constituent of sediments and placer deposits, and is an alteration product of titanite (sphene) and ilmenite.

The CHIME figure shows titanium ions as grey spheres, and oxygens as red spheres. Note the central titanium in the figure which gives the 'tI' body centred tetragonal lattice - see Bravais Lattices on this web-site.