Argon adsorption in open-ended single-wall carbon nanotubes

• Published in: Physical review. B, Condensed matter and materials physics Condensed matter and materials physics, 2005-04, Vol.71 (15)
• Main Authors: Rols, S., Johnson, M.R., Zeppenfeld, P., Bienfait, M., Vilches, O.E., Schneble, J.
• Format: Article
• Language: English
• Subjects: ADSORPTION; ARGON; CARBON; CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND SUPERFLUIDITY; INTERSTITIALS; MOLECULAR DYNAMICS METHOD; NANOTUBES; NEUTRON DIFFRACTION; SIMULATION
• ISSN: 1098-0121; 1550-235X
• DOI: 10.1103/PhysRevB.71.155411

Thermodynamic and neutron-diffraction measurements combined with molecular dynamics simulation are used to determine the adsorption energies and the structure of argon condensed in the various adsorption sites of purified open-ended single-wall nanotube bundles. On the basis of these experiments and the simulation results, a consistent adsorption scenario has been derived. The adsorption proceeds first by the population of the walls inside the open nanotubes and the formation of one-dimensional Ar chains in the grooves at the outer surface of the bundles, followed by the filling of the remaining axial sites inside the nanotubes and the completion of a quasihexagonal monolayer on the outer surface of the bundle. The measurements also provide an estimate of the relative abundance of the various adsorption sites revealing that a major part of the adsorbed Ar is stored inside the open-ended nanotubes. Nanotube bundles generally show a certain degree of heterogeneity and some interstitial sites should be populated over a range of Ar chemical potential. However, for the sample used here, diffraction data and simulations suggest that heterogeneity is not a key feature of the bundles and there is little direct evidence of interstitial sites being populated.