K_5.76Ga_5.76Si_10.24O₃₂·3.4H₂O, a gallosilicate with the zeolite gismondine topology

The title compound, K–GaSi–GIS, potassium gallium silicon oxide hydrate, was synthesized hydro­thermally and its crystal structure was determined from data collected on a single crystal of dimensions 10 × 10 × 8 µm at a synchrotron X-ray source. The compound, which has the aluminosilicate (AlSi) zeolite gismondine (GIS) topology, Ca₄[Al₈Si₈O₃₂]·16H₂O, crystallizes in the tetragonal space group I4₁/a. A disordered distribution of the framework Si/Ga sites leads to higher symmetry of the GIS-type network compared with the usual monoclinic symmetry in AlSi–GIS. Framework Ga substitution for Al in AlSi–GIS leads to substantial distortion of the crankshaft chains, reducing the effective pore dimensions and suggesting the possibility of pore-dimension control via partial framework-cation substitution.