A novel algorithm was described that included the effect of host lattice flexibility into molecular dynamics simulations that used rigid lattices. It used a Lowe-Andersen thermostat for interface-fluid collisions to take the most important aspects of flexibility into account. The same diffusivities and other properties of the flexible framework system were reproduced at a small fraction of the computational cost of an explicit simulation. The influence of flexibility upon the self-diffusion of simple gases inside single walled carbon nanotubes was studied. Results were shown for different guest molecules (methane, helium, and sulfur hexafluoride), temperatures, and types of carbon nanotubes. It was shown that, at low loadings, flexibility was always relevant. Notably, it had a crucial influence upon the diffusive dynamics of the guest molecules.

A Novel Algorithm to Model the Influence of Host Lattice Flexibility in Molecular Dynamics Simulations: Loading Dependence of Self-Diffusion in Carbon Nanotubes. Jakobtorweihen, S., Lowe, C.P., Keil, F.J., Smit, B.: Journal of Chemical Physics, 2006, 124[15], 154706