<p>This thesis is focussing on the crystallographic challenges and what knowledge we can gain from studying the different open-framework germanates. Five new open-framework germanates have been synthesized and the structures have been determined by single crystal X-ray diffraction. A thorough description is made of the different problems raised with the different compounds, whether it is choice of crystal system in SU-61, twinning and possible ordering in SU-46, superstructure and variation in elemental content in SU-57, template disorder in JLG-5 or framework disorder in SU-44.</p><p>Open-framework germanates are often built from one type of cluster, such as the Ge₇ [Ge₇X₁₉], Ge₈ [Ge₈X₂₀], Ge₉ [Ge₉X_n, n =25-26] and Ge₁₀ [Ge₁₀X₂₈], (X =O, OH, F) clusters. The structures built by clusters containing different kinds of polyhedra are discussed, with a focus on the 4-coordinated Ge₇ clusters, the larger cluster aggregate found in SU-8 and SU-44 and the structures built by the Ge₁₀ clusters.</p>

This thesis is focussing on the crystallographic challenges and what knowledge we can gain from studying the different open-framework germanates. Five new open-framework germanates have been synthesized and the structures have been determined by single crystal X-ray diffraction. A thorough description is made of the different problems raised with the different compounds, whether it is choice of crystal system in SU-61, twinning and possible ordering in SU-46, superstructure and variation in elemental content in SU-57, template disorder in JLG-5 or framework disorder in SU-44. Open-framework germanates are often built from one type of cluster, such as the Ge7 [Ge7X19], Ge8 [Ge8X20], Ge9 [Ge9Xn, n =25-26] and Ge10 [Ge10X28], (X =O, OH, F) clusters. The structures built by clusters containing different kinds of polyhedra are discussed, with a focus on the 4-coordinated Ge7 clusters, the larger cluster aggregate found in SU-8 and SU-44 and the structures built by the Ge10 clusters.