A molecular dynamics simulation study towards understanding the effects of diameter and chirality on hydrogen adsorption in singlewalled carbon nanotubes

A force field methodology has been developed for the description of carbon-carbon and carbon-molecular hydrogen interactions that is ideally suited to modeling hydrogen adsorption on single-walled carbon nanotubes (SWNT). The method makes use of existing parameters of potential functions developed for sp² and sp³ hybridized carbon atoms and allows accurate representation of molecular forces on curved carbon surfaces. This approach has been used in molecular dynamics (MD) simulations for hydrogen adsorption in SWNT. The results reveal significant nanotube deformations, consistent with ab initio MD simulations, and the calculated energies of adsorption at room temperature are comparable to the reported experimental heats of adsorption for H₂ in SWNT. The efficiency of this new method has permitted the MD simulation of hydrogen adsorption on a wide range of SWNT types, varying such parameters as nanotube diameter and chirality. The results show that these SWNT physical parameters have a substantial effect on the energies of adsorption and hydrogen capacities.