Theoretical analysis of the structures of titanium dioxide crystals

This paper presents results of pseudopotential Hartree-Fock calculations on the titanium dioxide crystals. The optimized structures are in good agreement with experimental data. Both anatase and rutile structures have a large ionic character. The distortions from the undistorted crystals made of regular octahedra are discussed and qualitative trends for the distortions are justified by semiempirical calculations (extended H\"uckel theory). When correlation is taken into account, a large part of the binding energy is recovered and the rutile structure is found to be more stable than the anatase one.