Dual control-volume grand canonical molecular dynamics simulations were made of CH4-CF4 mixtures in carbon nanotubes. Composition-dependent transport diffusivities and fluxes were calculated for varying driving forces in order to investigate the influence of the very large driving force in simulations; which was about four orders of magnitude larger than in real experimental systems. As the flux depended upon the driving force, the transport diffusivity was independent of it, so that the simulation could be used to model transport under experimental conditions. The results of composition-dependent diffusivities at four different temperatures were presented. A linear function described the composition dependence and reproduced the simulated concentration profiles very well. Analysis of the temperature dependence indicated that transport in the investigated system was due to liquid-like molecular diffusion and not to activated diffusion.

Composition Dependent Transport Diffusion Coefficients of CH4/CF4 Mixtures in Carbon Nanotubes by Non-Equilibrium Molecular Dynamics Simulations. Düren, T., Keil, F.J., Seaton, N.A.: Chemical Engineering Science, 2002, 57[8], 1343-54