Nonapotassium trialuminium hexa­phosphate

In the title compound, K(9)Al(3)(PO(4))(6), the anionic substructure is built of inter-linked [PO(4)] and [AlO(4)] tetra-hedra. Each O atom of the [AlO(4)] tetra-hedron is common to a positionally different [PO(4)] tetra-hedron; thus, each [AlO(4)] tetra-hedron is surrounded by four positionally different [PO(4)] tetra-hedra. On the other hand, each [PO(4)] tetra-hedron shares its two O atoms with two positionally different [AlO(4)] tetra-hedra; the other two phosphate O atoms are terminal ones coordinated by K atoms. The terminal O atoms are usually closer to the K atoms than the bridging O atoms between the [AlO(4)] and [PO(4)] tetra-hedra. There are nine symmetry-independent K atoms in the structure. The coordination numbers of the K atoms are 6 or 7 or 8 up to a distance of 3.31 Å. There are channels in the anionic substructure oriented along the [10] direction that are filled by K atoms.