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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 5, Number 3
BKCSDE 5(3)
March 20, 1984 

 
Title
Crystal Structure of Dehydrated Cesium and Silver Exchanged Zeolite A, Cs7.3Ag4.7-A
Author
Yang Kim, Karl Seff
Keywords
Abstract
The structure of CS7.3Ag4.7Si12Al12O48, vacuum dehydrated zeolite A with all Na+ ions replaced by Cs+ and Ag+ as indicated, has been determined by single-crystal x-ray diffraction techniques in the cubic space group, Pm3m (a = 12.282 (1) Å). The structure was refined to the final error indices R1 = 0.089 and R2 (weighted) = 0.099 using 347 independent reflections for whind intlch I0 > 3σ (I0). Although deydration occurred at 360℃, no silver atoms or clusters have been observed. The 8-ring sites are occupied only by Cs+ ion, and the 4-ring sites only by a single Ag+ ion. The 6-ring sites contain Ag+ and Cs+ ions with Ag+ nearly in 6-ring planes and Cs+ well off them, one on the sodalite unit side. With regard to the 6-rings, the structure can be represented as a superposition of two types of unit cells: about 70 % have 4Ag+ and 4Cs+ ions, and the remaining 30 % have 3Ag+ and 5Cs+. In all unit cells, 3 Cs+ ions lie at the centers of the 8-rings at sites of D4h symmetry; these ions are approximately 0.3 Å further from their nearest framework-oxygen neighbors than the sum of the appropriate ionic radii would indicate. To minimize electrostatic repulsions, the Cs+ ions at Cs(1) are not likely to occupy adjacent 6-rings in the large cavity; they are likely to be tetrahedrally arranged when there are 4.
Page
117 - 121
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