Acta Cryst. (2009). E65, i4-i5  [ doi:10.1107/S1600536808042499 ]

Ammonium iron(III) phosphate(V) fluoride, (NH₄)_0.5[(NH₄)_0.375K_0.125]FePO₄F, with ammonium partially substituted by potassium

L. Wang, Y. Zhou, Y.-X. Huang and J.-X. Mi

Abstract: The title compound, ammonium potassium iron(III) phosphate fluoride, (NH₄)_0.875K_0.125FePO₄F, is built from zigzag chains ¹{[FeO₄F₂]^7-}, with Fe³⁺ in a distorted octahedral coordination, extending along both the [011] and [01] 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-HO and two N-HF).

Online 20 December 2008

Copyright © International Union of Crystallography
IUCr Webmaster