Cu(Cu_0.44Cr_4.56)Ge₂O₁₂: a close-packed oxide with CuO₄ tetra­hedra

The structure of the title compound is described as a cubic close-packed arrangement of O atoms containing Cu⁺/Cu²⁺ ions in a tetra­hedral coordination. Slabs of edge-sharing CrO₆ octa­hedra and isolated CuO₄ and GeO₄ tetra­hedra are aligned parallel to the bc plane and are separated from each other by GeO₄ tetra­hedra along a.

Dicalcium hepta­germanate Ca₂Ge₇O₁₆ revised

The crystal structure of Ca₂Ge₇O₁₆ has been redetermined in tetra­gonal symmetry and some comparison is made with Cd₂Ge₇O₁₆ and AB₄O₉ structures having A = Sr, P and Ba, and B = Ge.

Ca₃GeO₄Cl₂ with a norbergite-like structure

The structural topology of the new synthetic material Ca₃GeO₄Cl₂ is described and compared with the olivine-type Ca₂GeO₄ and norbergite-type Mg₃SiO₄F₂.

Yttrium pyrogermanate, Y₂Ge₂O₇

The structure and absolute configuration of tetra­gonal Y₂Ge₂O₇ was determined from X-ray diffraction data. A comparison is made with related lanthanide pyrogermanates of the series R₂Ge₂O₇ (R = Eu and Tb-Lu).