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Title
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Monte Carlo simulations of dielectric relaxation in Na-mordenites
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Author
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Abstract
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| The chemical composition of zeolites is defined by the average ratio between the number of 4-coordinated Si and Al atoms of the lattice (ratio Si/Al). Each Al atom adds a net negative charge to the otherwise SiO2 lattice which is counterbalanced by an extra-framework mobile cation. These counter-ions are responsible for the major polarization of the material at low frequencies (10(6) Hz). The nature, localization and diffusion of these cations depend on the Si/Al ratio and influence the catalytic properties of the material. Here, we present a joint theory-experiment study of these properties at the atomic level. The thermally stimulated depolarization current (TSDC) of Na-mordenites is measured for increasing Si/Al ratios. The analysis of these dielectric relaxation data leads to activation energy barriers for the Na+ "jumps" responsible for the polarization change. Using semi-empirical inter-atomic potentials and Monte Carlo algorithms we propose a possible mechanism for the cation motions occurring in TSDC experiments. (C) 2001 Elsevier Science B.V. All rights reserved. |
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Language
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English
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Source (journal)
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Computational materials science
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Publication
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2001
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ISSN
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0927-0256
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DOI
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10.1016/S0927-0256(01)00175-6
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Volume/pages
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22
:1-2
(2001)
, p. 106-111
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ISI
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000171255400019
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Full text (Publisher's DOI)
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Full text (publisher's version - intranet only)
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