The adsorption of atomic hydrogen on (5,5) armchair carbon nanotube has been studied by using density functional theory, and the geometries and adsorption energies for the 5% and 10% coverage of H atoms have been investigated. The calculated results indicate that, the adsorption of H at the exterior is energetically favorable than that at the interior, and the second H atom prefers to be adsorbed at the carbon sites near the first one. By analyzing the band structures, it is known that after the adsorption of the first H atom, the armchair nanotube will become semiconductor. When the second H atom is adsorbed at the even site, the tube keeps its conductive characteristic, while the transfer ability of this tube is weaker for the case at odd site. The change of the transport property can be explained by examining the arrangement of the ( conjugation of the carbon nanotube.

Key words: carbon nanotube, band structure, transport property, density functional theory