Ab initio modeling of trititanate nanotubes

Nanotubes with H2Ti3O7 stoichiometry have been studied by ab initio methods in the diameter range of similar to 20-60 angstrom. The distribution of the protons on the unit cell surface and its effect on the structure and electronic properties of the titanium dioxide backbone has been investigated. The preferred protonation pattern was found to be the function of the diameter of the nanotube and the convexity of the surface. Trititanate tubes have been found to be more stable than lepidocrocite nanotubes at all diameters. At diameters < 50 angstrom the dissociation of water from the internal surface and the emergence of a new tube wall structure was observed. Band gaps were found to change only slightly with the curvature, the maximum difference from the flat slab values was +/- 0.5 eV.