KNi 0.93 Fe II 0.07 Fe III (PO 4 ) 2 : a new type of structure for a compound of composition M I M II M III (PO 4 ) 2

The solid solution KNi 0.93 Fe II 0.07 Fe III (PO 4 ) 2 {potassium [nickel(II)/iron(II)] iron(III) bis(orthophosphate)} has been prepared by the flux method. The compound shows a new type of structure for a phosphate with the general composition M I M II M III (PO 4 ) 2 . The framework is formed by [(Ni/Fe)O 6 ] polyhedra [Fe site occupancy = 0.069 (14)] linked via shared oxygen vertices forming a cis ‐like parallel chain stretching along a and [FeO 5 ] polyhedra (located on alternate sides of the chains) connected via two types of PO 4 groups into a three‐dimensional structure. The K atoms are disordered between two sites, denoted K1 A and K1 B , with occupancies of 0.930 (9) and 0.070 (9), respectively, and reside inside channels along the a axis. Calculations of the Voronoi–Dirichlet polyhedra of the K atoms give a coordination scheme for K1 A of [9 + 3] and for K1 B of [10 + 2]. The most remarkable feature of the structure is the splitting of the K‐atom site and the population of the K1 A and K1 B positions due to substitution of Ni by Fe in the (Ni/Fe) position.