title: (K4Li4)Al8Ge8O32.8H2O: an Li+-exchanged potassium aluminogermanate with the zeolite gismondine (GIS) topology.
abstract: The title compound, lithium potassium dialuminium digermanium octaoxide dihydrate, (K,Li)-(Al,Ge)-GIS (GIS is gismondine), is the result of a 50% Li(+) exchange into the K-(Al,Ge)-GIS structure. The (K,Li)-(Al,Ge)-GIS structure was determined from a 4 x 4 x 2 micro m octahedral single crystal at the ESRF synchrotron X-ray source. The ion exchange results in a symmetry transformation from I2/a for K-(Al,Ge)-GIS to C2/c for (K,Li)-(Al,Ge)-GIS. The structural change is due to disordering of K(+) ions with Li(+) ions along the [001] channel and ordering of water molecules in the [101] channels. The distance between sites partially occupied by K(+) ions increases from 2.19 (3) A in K-(Al,Ge)-GIS to 2.94 (3) A in (K,Li)-(Al,Ge)-GIS. The Li(+) ions occupy positions along the twofold axis at the intersection of the eight-membered-ring channels in a twofold coordination with water molecules. For the four closest framework O(2-) anions, the Li.O distances are 3.87 (4) A.
authors.affiliation: Department of Geosciences, State University of New York, Stony Brook, NY 11794-2100, USA. aaron.celestian@stonybrook.edu
authors.forename: Aaron J
authors.initials: AJ
authors.lastname: Celestian
authors.forename: John B
authors.initials: JB
authors.lastname: Parise
authors.forename: Akhilesh
authors.initials: A
authors.lastname: Tripathi
authors.forename: Ake
authors.initials: A
authors.lastname: Kvick
authors.forename: Gavin M B
authors.initials: GM
authors.lastname: Vaughan