THE CRYSTAL-STRUCTURES OF (NH4)(3)HGE7O16-CENTER-DOT-NH(2)O AND LI4-XHXGE7O16-CENTER-DOT-NH(2)O DETERMINED FROM POWDER DIFFRACTION DATA USING SYNCHROTRON-RADIATION

The structures of two hydrated microporous germanates (NH4)(3)HGe7O16. nH(2)O and Li4-xHxGe7O16. nH(2)O [n = 2.72(3) and 5.61(5), respective ly], have been determined in space group P(4) over bar3$ m, Z = 1, wit h a = 7.71069(1) Angstrom and 7.71936(1) Angstrom respectively, from R ietveld refinement of powder diffraction patterns collected using sync hrotron radiation. The profiles contain 119 and 104 reflections, respe ctively. The structure of these germanates consists of a three-dimensi onal framework with charge compensating cations and water molecules oc cupying the interconnecting channels. The ammonium cations occupy site s near the centre of a 3.3 Angstrom window and form a disordered hydro gen-bonded network with the water molecules. This is presumably respon sible for the ionic conductivity observed in this material.