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Diffusion and vibrational relaxation of a diatomic molecule in the pore network of a pure silica zeolite: a molecular dynamics study

Demontis, Pierfranco and Suffritti, Giuseppe Baldovino and Tilocca, Antonio (1996) Diffusion and vibrational relaxation of a diatomic molecule in the pore network of a pure silica zeolite: a molecular dynamics study. The Journal of Chemical Physics, Vol. 105 (13), p. 5586-5594. eISSN 1089-7690. Article.

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DOI: 10.1063/1.472398


The vibrational relaxation and the diffusion of diatomic molecules in the zeolite silicalite have been studied through molecular dynamics simulations in the microcanonical statistical ensemble. The adopted model accounts for the vibrations of the framework and sorbed atoms using a harmonic potential for the silicalite and a Morse potential for the diatomic molecule. The results show that the framework favors the relaxation of diatomics oscillating at frequencies near to its characteristic vibrational frequencies, leading in such cases to lower relaxation times and to an increasing in the energy exchanged per collision. The diffusion of a two-site oscillating molecule representing ethane has been also investigated; the diffusion coefficient and the heat of adsorption agree very well with the experimental data. Arrhenius parameters for the diffusion have been calculated, and some insights into the diffusion mechanism have been obtained from log–log plots and by inspection of the distribution of the ethane molecules in the silicalite channels. Therefore the simplified model adopted seems to adequately describe the diffusive motion and the guest–host energy exchanges, and it could be useful in order to study simple bimolecular reactions in zeolites.

Item Type:Article
ID Code:309
Uncontrolled Keywords:Zeolites, diatomic molecules, molecular dynamics calculations, simulation, statistics, microcanonical ensemble, vibrational states, morse potential
Subjects:Area 03 - Scienze chimiche > CHIM/02 Chimica fisica
Divisions:001 Università di Sassari > 01 Dipartimenti > Chimica
Publisher:American Institute of Physics
Publisher Policy:Depositato in conformità con la politica di copyright dell'Editore
Deposited On:18 Aug 2009 10:02

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