Structural disorder of a new zeolite-like lithosilicate, K2.6Li5.4[Li4Si16O38] center dot 4.3H(2)O
Acta Crystallographica Section B-Structural Science 62: 42-51
The framework structure of the synthetic microporous lithosilicate RUB- 30 ( K2.6Li5.4[ Li4Si16O38] center dot 4.3H(2)O) is similar to that of the fibrous zeolites such as natrolite, edingtonite and thomsonite, since all their frameworks include the same secondary structural building unit, the so- called 4 - 1 T5O10 cluster of tetrahedra. Unique to the structure of RUB- 30, each 4 - 1 unit consists of a LiSi4O10 moiety within which the single [ LiO4] tetrahedron is strictly segregated from the other four [ SiO4] tetrahedra. The connection of neighboring 4 - 1 units through edge- sharing [ LiO4] tetrahedra results in a new framework topology. The present work reports an ` average' structure of RUB- 30 solved by synchrotron X- ray single-crystal diffraction data collected at a second- generation source. A superstructure with a x 2b x c ( relative to the subcell quoted above) could be seen in X- ray diffraction data collected with better resolution and higher brightness at a third generation source. Diffuse streaks along k with l = odd and unusual superstructure hkl reflections, with k = odd and l = odd only, indicate a more complicated real structure of the material. To explain this observation we propose two different structure types which are statistically, but coherently, intergrown in RUB- 30.