Energetic Minimum Structures of Imogolite Nanotubes: A First-Principles Prediction

We perform first-principles calculations to study the stable configurations and electronic structures of imogolite nanotubes. Two energetic minimum Structures (N-mu = 9, 12) are predicted and correlated to the natural and synthetic imogolite nanotubes. The electronic structures of both nanotubes are quite similar with a band gap of 5.2-5.3 eV. The Conduction band minimum (CBM) mainly arises from the states of the hydroxyls on the outer wall, whereas the valence band maximum (VBM) is contributed from the O(2p) states of the SiO4 tetrahedrons located on the inner wall. These features are consistent with the asymmetric charge distribution in the outer and inner regions of the tubes and responsible for electronic modifications in response to surface defects or decorations.