Synthesis and crystal structure of Fe[SeO4]OH and prediction of polytypes in the extended R[MO4]Z family

Single crystals of Fe[SeO4]OH have been synthesized by hydrothermal treatment. The Fe[SeO4]OH structure was investigated using the superspace approach. It is shown that the structure belongs to a family of compounds including kieserite-like and pauflerite-like structure types. All these structures consist of topologically identical layers interconnected either by a mirror plane (m) or by an inversion centre (1). The sequence of these local elements of symmetry, m and 1, determines each member of the family. We used the (3 + 1)-dimension superspace group Pnam(00 gamma)000 applied to an average structure to be able to reproduce known polytypes and predict new ordered and partially or completely disordered structures in the R[MO4]Z structural family.