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Bulletin of the Korean Chemical Society (BKCS)

ISSN 0253-2964(Print)
ISSN 1229-5949(Online)
Volume 10, Number 3
BKCSDE 10(3)
March 20, 1989 

 
Title
Reaction of Dehydrated Ag2Ca5-A with Cesium. Crystal Structures of Fully Dehydrated Ag2Ca5-A and Ag2Cs10-A
Author
Yang Kim*, Seong Hwan Song, Jong Yul Park, Un Sik Kim
Keywords
Abstract
Two crystal structures of dehydrated Ag+ and Ca2+ exchanged zeolite A, Ag2Ca5-A, reacting with 0.01 Torr of Cs vapor at 200℃ for 2 hours and 0.1 Torr of Cs vapor at 250℃ for 48 hours, respectively, have been determined by single crystal X-ray diffraction techniques. Their structures were solved and refined in the cubic space group Pm3m at 21(1)℃. The stoichiometry of first crystal was Ag2Ca5-A (a = 12.294(1)Å), indicating that Cs vapor did not react with cations in zeolite A and that of second crystal was Ag2Cs10-A (a = 12.166(1) Å), indicating that all Ca2+ ions were reduced by Cs vapor and replaced by Cs+ ions. Full-matrix least-squares refinements of Ag2Ca5-A and Ag2Cs10-A has converged to the final error indices, R1 = 0.041 and R2 = 0.048 with 227 reflections, and R1 = 0.117 an n fdd R2 = 0.120 with 167 reflections, respectively, for which I > 3σ(I). In the structure of Ag2Ca5-A, both Ag+ ions and Ca2+ ions lie on two crystal symmetrically independent threefold axis sites on the 6-rings; 2 Ag+ ions are recessed 0.33 Å from the (111) planes of three O(3) oxygens and 5 Ca2+ ions lie on the nearly center of each 6-oxygen planes. In the structure of Ag2Cs10-A, Cs+ ions lie on the 5 different crystallographic sites. 3 Cs+ ions lie at the centers of the 8-rings at sites of D4h symmetry. 6 Cs+ ions lie on the threefold axes of unit cell: 4 Cs+ ions are found deep in the large cavity and 2 Cs+ ions are found in the sodalite cavity. One Cs+ ion is found in the large cavity near a 4-ring.
Page
243 - 247
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