Molecular dynamics simulations in zeolites : from deterministic to random motion

Molecular dynamics (MD) simulations of argon in silicalite were performed in order to study the transition from the deterministic motion at short times to the random motion at long times. A characteristic length λ (time τ) is associated with this change in dynamics. At a temperature T=229(14) K, we...

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Bibliographic Details
Published in:The Journal of chemical physics 1993-01, Vol.98 (2), p.1509-1513
Main Authors: EL AMRANI, S, KOLB, M
Format: Article
Language:English
Subjects:
Catalysis
Chemical Sciences
Chemistry
Exact sciences and technology
General and physical chemistry
Ion-exchange
Surface physical chemistry
Zeolites: preparations and properties
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Summary:Molecular dynamics (MD) simulations of argon in silicalite were performed in order to study the transition from the deterministic motion at short times to the random motion at long times. A characteristic length λ (time τ) is associated with this change in dynamics. At a temperature T=229(14) K, we find λ=0.45(8) Å [τ=0.21(6) ps]. A detailed analysis of the trajectories shows that the optimal choice for the elementary time step Δt in MD is slightly below τ. Little is gained by decreasing Δt as two trajectories with almost identical initial conditions diverge exponentially fast with time. A MD algorithm with variable Δt is proposed and used to show that the size of the zeolite channels and cavities influences how the asymptotic Gaussian random process is reached.
ISSN:0021-9606
1089-7690
DOI:10.1063/1.464315