Structural investigations on scholzite

Schòlzite, Zn₂Ca[PO₄]₂·2H₂O, has a substructure with Pbcn symmetry, and subperiod B = b/3. Its actual structure (symmetry Pbc2₁) is a distortion of the substructure model with small shifts (mainly parallel to x) of the atomic positions in three adjacent subcells. The refinetnent of this distortion-structure model, which contains 45 atoms in the asymmetric unit, reduced the R value to 8.1 percent for 1924 observed reflections. The structure shows chains of ZnO₄ tetrahedra parallel to [001]. These chains are “Einereinfachketten”, which are connected to other similar chains by isolated PO₄ tetrahedra. The calcium atoms are surrounded by distorted oxygen octahedra which are formed by one oxygen from each of four different PO₄ tetrahedra and two oxygens from two water molecules. The water molecules, in groups of four, occupy cages surrounded by two CaO₆ octahedra and four PO₄ tetrahedra.