DFT Study of CH4 Adsorption on the (5,0), (4,4), (5,5) and (6,6) Single-Walled Carbon Nanotubes. Calculated Binding Energies, NMR and NQR Parameters

Behavior of a single CH4 molecule adsorbed on external surface of H-capped (4,4) (5,5), (6,6) and (5,0) single-walled carbon nanotubes (SWCNTs) is studied via B97D hybrid density functional and 6-31G* basis set. Binding energies clearly exhibit adsorption dependence on tube diameter. 13C and 1H chemical shielding tensors are calculated at the B971 level using GIAO method. The 1H and 13C(CH4) NMR results reveal that chemical shielding due to CH4 molecule adsorption are also dependent upon the nanotube electronic structure, and radius. 2H nuclear quadrupole coupling constants, CQ, and asymmetry parameter, ·, reveal the remarkable effect of CH4 adsorption on electronic structure of the SWCNTs.