Abstract: The structure and infrared vibration of silica nanotubes with anhydrous structure(SiO2-NTs) and hydrogen-capped structure (SiO2-WNTs) have been investigated using the density-functional theory (DFT). It was found that the average binding energies were almost the same for SiO2-WNTs having same layer numbers or length. SiO2-WNTs are energetically more favorable than the SiO2-NTs and two-membered ring (2MR) molecular chains structure. IR spectrum of 4MR-WNTs was in well accord with the experimental data and the vibrations of oxygen atoms with directions parallel and normal to the axis of nanotubes show a strong size effect. The SiO2-WNTs would be considered as an appropriate structure model for one-dimensional silica nanotube.

Key words: Nanotube, Size effect, IR vibration, Stability