Ab initio modeling of TiO2 nanotubes

TiO2 nanotubes constructed from a lepidocrocite-like TiO2 layer were investigated with ab initio methods employing the periodic CRYSTAL code. The dependence of strain energies, structural and electronic properties on the tube diameter was investigated in the 18-57 angstrom range. Nanotubes constructed by a (0,n) rollup proved to be the most stable at all diameters. All three types of rollup undergo significant reconstruction at diameters <25 angstrom. All investigated structures possess a high (similar to 5.4 eV) band gap compared to bulk TiO2 phases (3.96 and 4.63 eV for rutile and anatase calculated with the same functional and basis set).