National Natural Science Foundation of China [40472027]The title compound, ammonium potassium iron(III) phosphate fluoride, (NH4)(0.875)K0.125FePO4F, is built from zigzag chains∞{[FeO4F2](7-)}, with Fe3+ in a distorted octahedral coordination, extending along both the [011] and [0ㄒ1] directions. These chains are made up of alternating trans- [FeO4F2] and cis-[FeO4F2] octahedra via shared F-atom corners, and are linked by PO4 tetrahedra, resulting in an open-framework structure with channels along the [010] and [100] directions. There are two crystallographically independent ammonium sites: one in the [010] channels and the other, partially substituted by K+ ions, in the [100] channels. The ammonium in the [010] channels is fixed to the framework via eight hydrogen bonds (six N-H O and two N-H ···F)
