Ordered distribution of aluminum atoms in analcime |
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Authors: | M Kato T Hattori |
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Institution: | (1) Research Center for Chemometrics, Toyohashi University of Technology, Toyohashi, 441 Japan FAX: +81-532-44-6610 e-mail: mkato@tut3c.tut.ac.jp, JP |
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Abstract: | Based on the connectivity relations among tetrahedron sites and the NMR spectra, we propose an ordered distribution of aluminum
atoms in the framework of analcime with space groups of Pbcb and Pcaa. The symmetries of the ordered distributions are formally
the same as Pcca. These symmetries are much lower than those reported by others such as Ia3d, I41/acd, Ibca, and I2/a. The lowering of symmetry results apparently from the fact that aluminum atoms in the framework of analcime
were strictly discriminated from silicon atoms. Dependence of the populations of Si(nAl)s upon Al content was estimated from 29Si MAS NMR, and can be successfully simulated by the ordered distributions. In the simulation, a small number of defects in
the Al distribution were introduced into the ordered distribution mainly to adjust the deviation of Al content per unit cell
from the typical composition. Analysis of the powder X-ray diffraction patterns of analcime was carried out, which suggests
that the space groups proposed in the present work offer a better fit than the ones reported previously.
Received: 5 April 1997 / Revised, accepted: 12 March 1998 |
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Keywords: | Zeolite Analcime Structure Aluminum distribution |
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