Monte Carlo simulations of dielectric relaxation in Na-mordenites
- Resource Type
- Authors
- V. E. Van Doren; Jean-Charles Giuntini; Patrick Senet; François Henn; S. Devautour; Guillaume Maurin
- Source
- Computational materials science
- Subject
- Arrhenius equation
General Computer Science
Chemistry
Physics
Monte Carlo method
General Physics and Astronomy
Interatomic potential
General Chemistry
Activation energy
Dielectric
Molecular physics
Mordenite
Computational Mathematics
symbols.namesake
Mechanics of Materials
Atom
symbols
Physical chemistry
Rectangular potential barrier
General Materials Science
- Language
- English
- ISSN
- 0927-0256
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.