ON THE STABILITY OF DITITANATE NANOTUBES: A DENSITY FUNCTIONAL THEORY STUDY

Nanotubes having the H 2Ti 2O 5 stoichiometry have been studied by DFT methods in the diameter of ∼20-60 Å. Dititanate nanotubes have been found to be more stable than the dry lepidocrocite nanotubes and the tubes based on trititanate (H 2Ti 3O 7) structures at all diameters investigated. At diameters <40 Å, expulsion of water from the inner wall of the tube reduces the strain and stabilizes the structure. Band gaps were found to change only slightly with the curvature (±0.5 eV from the flat slab values) and are about 1 eV higher than the TiO 2 bulk value. The hydration of the nanotubes induce tails in the density of the states of the valence band that push the edge of the band up. © 2010 American Chemical Society.