Geometric and topological analysis of zeolite crystal structures by the tiling method: The model of structure of Na,K-paulingite (PAU) Na82K72[Al154Si518O1344] • wH2O

Cluster analysis of the crystal structures of paulingite zeolites (Na,Ca-0.5,K,K,Ba-0.5)(10)[Al10Si32O84] center dot 30H(2)O (PAU, space group Im (3) over barm) has been performed by the tiling method with the TOPOS program package. The tetrahedral T framework of PAU with 672 tetrahedra in the translated unit cell with a = 35.1 and V = 43 217 (3) has been completely decomposed into tiles, complementarily connected polycyclic (polyhedral) T clusters. The zeolite structure is represented by an ensemble consisting of nine geometrically different nanoclusters containing 16 to 48 T tetrahedra (the linear dimensions of the nanoclusters are 12 to 18 , respectively). The nanoclusters correspond to seven topologically different types of tiles: 48T-grc (2a), 32T-pau (12e), 30T-plg (16f), 24T-phi (24h), 20T-gsm (12d), 16T-opr (6b, 12e), and 16T-oto (24h, 48k). In the tiles, the positions occupied by extraframework cations A = Na+/Ca2+ and B = K+/Ba2+ have been determined. The characteristic arrangement of the Na+/Ca2+ cations only at the centers of the 8T rings has been revealed, and for them a new equivalent position in the 16T-opr (6b) tile has been determined. A common crystal-chemical formula of paulingite family zeolites has been obtained: (A,B-0.5)(154)[T672O1344]center dot wH(2)O; for the two outermost members, this formula takes the form A(154)[T672O1344]center dot wH(2)O and B-77[T672O1344]center dot wH(2)O. The composition of the alkaline Na,K-paulingite A(154)T(672)O(1344)center dot wH(2)O = Na82K72[Al154Si518O1344] center dot wH(2)O corresponds to the model of a structure with a maximal (100%) and ordered filling of the A cation positions: in the 16T-oto (24h, 48k) tiles for K+ and in the 20T-gsm (12d), 30T-plg (16f), and 16T-opr (6b, 12e) tiles for Na+. Such a distribution and the overall number of Na and K atoms are in good agreement with the data for synthetic paulingite analogues the (Na(87)K(72)TEA(15))[Al164Si508O1344]center dot wH(2)O aluminosilicate and (Na(84.5)K(70.5)TEA(24.7))[Ga179.7Si492.3O1344]center dot wH(2)O gallosilicate.