Title
Monte Carlo simulations of dielectric relaxation in Na-mordenites Monte Carlo simulations of dielectric relaxation in Na-mordenites
Author
Faculty/Department
Faculty of Sciences. Physics
Publication type
article
Publication
Subject
Physics
Source (journal)
Computational materials science
Volume/pages
22(2001) :1-2 , p. 106-111
ISSN
0927-0256
ISI
000171255400019
Carrier
E
Target language
English (eng)
Full text (Publishers DOI)
Affiliation
University of Antwerp
Abstract
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.
E-info
https://repository.uantwerpen.be/docman/iruaauth/a71132/8c01998.pdf
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