A C102H30 graphene sheet has been rolled up to construct Single-Walled Carbon NanoTube Fragments (SWCNTFs) as parts of armchair carbon nanotubes by computational quantum chemistry methods. Non-covalent cation-π interactions of the Na+ cation on the central rings of SWCNTFs have investigated. The binding energies of the Na+-SWCNTF complexes versus true strain parameter (R) change in three brands. Structural parameters, electron charge density values, and also effects of aromaticity on the binding energies were gauged. Results show that partially localization of the π electron clouds of SWCNTFs enhances strength of the cation-π interactions in some cases. Thus, changing the π electron clouds of SWCNTs may help to improve surface modification of these materials through the cation-π interactions, which has important applications such as storage of electric energy by transportation of cations through the walls of SWCNTs and enhancement of the hydrogen adsorption compared to pure SWCNTs.
 Thess A., Lee R., Nikolaev P., Dai H., Petit P., Robert J., Xu C., Lee Y.H., Kim S.G., Rinzler A.G., Colbert D.T., Scuseria G., Tomanek D., Fischer J.E., Smalley R.E., Crystalline Ropes of Metallic Carbon Nanotubes, Science, 273: 483-487 (1996).