Molecular simulations corroborated the existence of the so-called window effect: an increase in diffusion rate by orders of magnitude when the alkane chain length increased so that the shape of the alkane was no longer commensurate with that of a zeolite cage. This effect was shown to be characteristic of molecular sieves with pore openings that approached the diameter of the adsorbate. Moreover, the physical compatibility between the adsorbate and the adsorbent had a direct effect upon the heat of adsorption, the Henry coefficients, the activation energy and the frequency factors.

Incommensurate Diffusion in Confined Systems. D.Dubbeldam, S.Calero, T.L.M.Maesen, B.Smit: Physical Review Letters, 2003, 90[24], 245901 (4pp)