The adsorption and diffusion of argon at 120K were examined in a (25,0) single-walled carbon nanotube bundle using a combination of grand canonical Monte Carlo and microcanonical molecular dynamics simulations. Interstices between the nanotubes provided the most energetically favorable adsorption sites, and filled completely at low relative pressures; followed by adsorption in the nanotubes. The self-diffusivities were calculated from the average mean squared displacements of argon atoms. In both flexible and rigid bundles, a bimodal diffusion mechanism was observed, with single-file diffusion occurring in the interstitial sites and Fickian diffusion in the nanotubes. Strong system-size effects were observed in the simulations. The largest system sizes revealed very little influence of the nanotube flexibility upon the diffusion of argon; even at the lowest pressures studied.

Dual Diffusion Mechanism of Argon Confined in Single-Walled Carbon Nanotube Bundles. Y.C.Liu, J.D.Moore, T.J.Roussel, K.E.Gubbins: Physical Chemistry Chemical Physics, 2010, 12[25], 6632-40