K5.76Ga5.76Si10.24O32 center dot 3.4H(2)O, a gallo-silicate with the zeolite gismondine topology

The title compound, K-GaSi-GIS, potassium gallium silicon oxide hydrate, wa s synthesized hydrothermally and its crystal structure was determined from data collected on a single crystal of dimensions 10 x 10 x 8 mum at a synch rotron X-ray source. The compound, which has the aluminosilicate (AlSi) zeo lite gismondine (GIS) topology, Ca-4[Al8Si8O32]. 16H(2)O, crystallizes in t he tetragonal space group I4(1)/a. A disordered distribution of the framewo rk Si/Ga sites leads to higher symmetry of the GIS-type network compared wi th the usual monoclinic symmetry in AlSi-GIS. Framework Ga substitution for Al in AlSi-GIS leads to substantial distortion of the crankshaft chains, r educing the effective pore dimensions and suggesting the possibility of por e-dimension control via partial framework-cation substitution.