Abstract: The growth mechanism of armchair single-walled carbon nanotube has been studied theoretically by AM1 method as implemented in Gaussian03 program. The following results were obtained. (1) Let C2 radicals be the carbon source for the growth of the carbon nanotube, then the most likely growth mechanism would be as follows. An intermediate is formed firstly by the direct addition of C2 radical to the open end of the carbon nanotube without an energy barrier, then via a transition state the reaction produces the product, i.e., C2 becomes the component of the hexagon of the nanotube. (2) From (3,3) to (6,6), the activation energy decreases (from 66.8 to 46.1 kJ•mol−1), whereas the conjugation of the nanotube increases. (3) The distribution of the frontier molecular orbitals indicates that the two edges of the newly formed hexagon maybe grow easily.

Key words: Armchair single-walled carbon nanotubes (ASWCNT), Growth mechanism, C2 radical, Transition state, AM1