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The structure and infrared vibration of silica nanotubes with anhydrous structure (SiO₂-NTs) and hydrogen-capped structure (SiO₂-WNTs) were investigated using density-functional theory (DFT). It was found that the average binding energy was all the same for SiO₂-WNTs with the same layer number or length. SiO₂-WNTs were energetically more favorable than the SiO₂-NTs and two-membered ring (2MR) molecular chains structure. The IR spectrum of 4MR-WNTs was in well accord with the experimental data, and the vibrations of oxygen atoms, which were in directions parallel or normal to the axis of nanotubes, showed a strong size effect. The results indicated that SiO₂-WNTs is an appropriate structure model for one-dimensional silica nanotube.