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KMID : 1059519890330010018
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Journal of the Korean Chemical Society
1989 Volume.33 No. 1 p.18 ~ p.24
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Two Crystal Structures of Dehydrated Ag+ and Rb+ Exchanged Zeolite A, Ag12-χRbχ-A, χ = 2 and 3
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Kim Yang
Song Seong-Hwan
Kim Duk-Soo
Han Young-Wook
Park Dong-Kyu
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Abstract
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Two crystal structures of dehydrated Ag+ and Rb+ exchanged zeolite A, stoichiometries of Ag9Rb3-A (a = 12.278(2)Å) and Ag10Rb2-A (a = 12.286(2)Å) per unit cell, 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 crystals of Ag10Rb2-A and Ag9Rb3-A were prepared by flow methods using exchanged solution in which mole ratios of AgNO3 and RbNO3 were 1:5 and 1:50, respectively, with the total concentration of 0.05 M. The structures of the dehydrated Ag9Rb3-A and the Ag10Rb2-A were refined to the final error indices, R1 = 0.064 and R2 = 0.060 with 291 reflections, and R1 = 0.063 and R2 = 0.080 with 416 reflections respectively, for which I >3σ(I). In both structures, one reduced silver atom per unit cell was found inside the sodalite cavity. It may be present as a hexasilver cluster in 1/6 of the sodalite units or as an isolated Ag atom coordinated to 4 Ag+ ions in each sodalite unit to give (Ag5)4+, symmetry 4 mm. In the structure of dehydrated Ag9Rb3-A, 8 Ag+ ions lie on the threefold axis and each is nearly at the center of the 8-rings at the sites of D4h symmetry. In the structure of dehydrated Ag10Rb2-A, two crystallographically different eight 6-ring Ag+ ions were found; 7Ag+ ions in the (111) planes of their O(3) framework oxygens and one Ag+ ion inside of sodalite cavity. Two crystallographically different 8-ring cations were also found; two Rb+ ions at the centers of the 8-oxygen rings and one Ag+ ion into the large cavity. Both structures indicate that Rb+ ions prefer to occupy the 8-ring sites, while Ag+ ions prefer to occupy the 6-ring sites.
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