Vibrational relaxation and diffusion of diatomic molecules in silicalite were studied via molecular dynamics simulations of a microcanonical statistical ensemble. The model accounted for vibrations of the framework and sorbed atoms, using an harmonic potential for the silicalite and a Morse potential for the diatomic molecule. The results showed that the framework favored the relaxation of diatomics oscillating at frequencies near to its characteristic vibrational frequencies leading, in such cases, to lower relaxation times and to an increase in the energy exchanged per collision. The diffusion of a two-site oscillating molecule, representing ethane, was also investigated and the diffusion coefficient and heat of adsorption agreed very well with experimental data. Diffusion and Vibrational Relaxation of a Diatomic Molecule in the Pore Network of a Pure Silica Zeolite: a Molecular Dynamics Study. P.Demontis, G.B.Suffritti, A.Tilocca: Journal of Chemical Physics, 1996, 105[13], 5586-94

Table 40

Diffusion of Light Hydrocarbons

in Silicalite-1 at 292K