A novel algorithm for modelling the influence of the host lattice flexibility in molecular dynamics simulations was extended to chain-like molecules and mixtures. This technique, based upon a Lowe-Andersen thermostat, conserved the advantages of both simplicity and efficiency. The same diffusivities and other properties of the flexible framework system were reproduced. Computationally demanding flexible host lattice simulations could be avoided. Using this methodology the influence of flexibility upon diffusion of n -alkanes inside single-walled carbon nanotubes was studied. Furthermore, results were shown for diffusion of two mixtures (methane-helium and ethane-butane). Using these results the accuracy of theories describing diffusion in the Knudsen regime was investigated. For the dynamics in carbon nanotubes the Knudsen diffusivities were much too low. The Smoluchowski model gives better results. Interestingly, the extended Smoluchowski model could reproduce the simulation results obtained for a rigid host lattice. This model was modified so as also to treat collisions with a flexible interface correctly. As the tangential momentum accommodation coefficient was needed for the theoretical models, a simple concept for calculating it was introduced.

Diffusion of Chain Molecules and Mixtures in Carbon Nanotubes: the Effect of Host Lattice Flexibility and Theory of Diffusion in the Knudsen Regime. Jakobtorweihen, S., Lowe, C.P., Keil, F.J., Smit, B.: Journal of Chemical Physics, 2007, 127[2], 024904