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Estimation of slow diffusion rates in confined systems: $CCl_4$ in zeolite NaA

Ghorai, Pradip KR and Yashonath, S and Lynden-Bell, RM (2002) Estimation of slow diffusion rates in confined systems: $CCl_4$ in zeolite NaA. In: Molecular Physics, 100 (5). pp. 641-647.

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Abstract

Often the rate of passage of gaseous molecules through model zeolites is too small to be computed directly. An estimate for the rate of passage of $CCl_4$ through the 8-ring window in a model of zeolite A has been obtained by combining a direct evaluation of the free energy pro®le and an adaptation of the rare events method. First the free energy pro®le is found from a direct evaluation of the canonical partition function at high dilution and the transition state theory rate constant obtained. The dynamic correction factor is then estimated from molecular dynamics runs and used to compute the actual rate $k_e_f_f$ . The method is used to estimate the rate of passage through the 8-ring window in a rigid model of zeolite A, and the results are compared with those obtained from rigid models with expanded windows and from the flexible model. Even a small expansion in the 8-ring window diameter increases the rate signi®cantly, but the changes associated with a flexible cage are small.

Item Type: Journal Article
Additional Information: Copyright of this article belongs to Taylor & Francis Group.
Department/Centre: Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited: 02 Jun 2006
Last Modified: 19 Sep 2010 04:28
URI: http://eprints.iisc.ernet.in/id/eprint/7465

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