Crystal structure of calcium dinickel(II) iron(III) tris-(orthophosphate): CaNiFe(PO).

The title compound, CaNiFe(PO), was synthesized by solid-state reactions. Its structure is closely related to that of α-CrPO in the space group . Except for two O atoms in general positions, all atoms are located in special positions. The three-dimensional framework is built up from two types of sheets extending parallel to (100). The first sheet is made up from two edge-sharing [NiO] octa-hedra, leading to the formation of [NiO] double octa-hedra that are connected to two PO tetra-hedra through a common edge and corners. The second sheet results from rows of corner-sharing [FeO] octa-hedra and PO tetra-hedra forming an infinite linear chain. These layers are linked together through common corners of PO tetra-hedra and [FeO] octa-hedra, resulting in an open three-dimensional framework that delimits two types of channels parallel to [100] and [010] in which the eightfold-coordinated Ca cations are located.