Structural study of sodium-type zeolite LTA by combination of Rietveld and maximum-entropy methods
- Univ. of Tsukuba, Ibaraki (Japan)
- National Inst. for Research in Inorganic Materials, Tsukuba, Ibaraki (Japan)
- National Inst. of Materials and Chemical Research, Tsukuba, Ibaraki (Japan)
The electron-density distribution in hydrated and dehydrated sodium-type zeolite LTA was visualized from X-ray powder diffraction data by combining Rietveld analysis and a maximum-entropy method. The X-ray diffraction data were analyzed on the basis of the composition Na{sub 95}Si{sub 97}Al{sub 95}O{sub 384} and a structural model (space group Fm{bar 3}c) obtained by the Rietveld refinement of time-of-flight neutron powder diffraction data for the dehydrated sample. Weighted R factors, wR{sub F}, resulting from the analysis by the maximum-entropy method reached 1.15% for the hydrated sample and 0.99% for the dehydrated one. The number of water molecules per unit cell in the hydrated sample was estimated to be ca. 255 by electron-density analysis, agreeing well with ca. 248 determined by thermogravimetry. Adsorbed water molecules are situated beside Na{sup +} ions in electron-density maps. In contrast with the dehydrated sample, Na{sup +} ions in eight-membered rings were moved a little by introducing water into the {alpha}-cages.
- OSTI ID:
- 328236
- Journal Information:
- Chemistry of Materials, Vol. 10, Issue 12; Other Information: PBD: Dec 1998
- Country of Publication:
- United States
- Language:
- English
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