The geometrical structures and electronic properties as well as thermal stabilities of hydrogenated armchair (n,n) (n = 4 to 8) single-walled carbon nanotubes with Stone-Wales defects were investigated using density functional theory (DFT-B3LYP) in combination with the 6-31G basis set. It was found that the chemisorptions of two hydrogen atoms inside and outside the SW defective single-walled carbon nanotubes were exothermic processes. As the nanotube diameter increased, the reaction energy of exohedral addition decreased, whereas that of endohedral addition increased. Exohedral nanotube adsorption was energetically more favorable than endohedral adsorption for smaller diameter (4,4)-SW, (5,5)-SW single-walled carbon nanotubes, but not for larger diameter (7,7)-SW and (8,8)-SW single-walled carbon nanotubes. The result was different from hydrogen on perfect nanotubes. Significantly, compared with the adsorption on the exterior sidewalls of perfect single-walled carbon nanotubes, the reaction energies of the endo-hydrogenated (7,7)-SW and (8,8)-SW single-walled carbon nanotubes were more exothermic, meaning that the central CC bond of SW defect inside the armchair (7,7)-SW and (8,8)-SW single-walled carbon nanotube sidewalls was more reactive than that in perfect sites. This was different from the result reported on the sidewall reactivity of SW defects outside the armchair single-walled carbon nanotubes. The calculated energy gaps indicate that the hydrogen-chemisorbed SW defective armchair tubes were always wide energy gap structures. The energy gaps of endohedral hydrogen-chemisorbed tubes were higher than those of the corresponding perfect tubes.

Theoretical Study of Chemisorption of Hydrogen Atoms on the Sidewalls of Armchair Single-Walled Carbon Nanotubes with Stone-Wales Defect. A.D.Zhang, D.L.Wang, D.Y.Hou: Computational and Theoretical Chemistry, 2012, 999, 121-5