NH4Fe2F6 is Upper Bainite-derived structured and crystallizes in the orthorhombic Pnma space group. The structure consists of four ammonium molecules inside a FeF3 framework. In the FeF3 framework, there are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent F(2), two equivalent F(3), and two equivalent F(4) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles range from 34-55°. In the second Fe site, Fe(2) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(4) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles range from 49-56°. There are four inequivalent F sites. In the first F site, F(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one Fe(2) atom. In the second F site, F(3) is bonded in a bent 150 degrees geometry to two equivalent Fe(1) atoms. In the third F site, F(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one Fe(2) atom. In the fourth F site, F(1) is bonded in a bent 120 degrees geometry to two equivalent Fe(2) atoms.
NH4Fe2F6 is Upper Bainite-derived structured and crystallizes in the orthorhombic Pnma space group. The structure consists of four ammonium molecules inside a FeF3 framework. In the FeF3 framework, there are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent F(2), two equivalent F(3), and two equivalent F(4) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles range from 34-55°. Both Fe(1)-F(2) bond lengths are 1.94 Å. Both Fe(1)-F(3) bond lengths are 1.98 Å. Both Fe(1)-F(4) bond lengths are 1.95 Å. In the second Fe site, Fe(2) is bonded to two equivalent F(1), two equivalent F(2), and two equivalent F(4) atoms to form corner-sharing FeF6 octahedra. The corner-sharing octahedral tilt angles range from 49-56°. There is one shorter (2.03 Å) and one longer (2.11 Å) Fe(2)-F(1) bond length. Both Fe(2)-F(2) bond lengths are 2.12 Å. Both Fe(2)-F(4) bond lengths are 2.15 Å. There are four inequivalent F sites. In the first F site, F(2) is bonded in a bent 120 degrees geometry to one Fe(1) and one Fe(2) atom. In the second F site, F(3) is bonded in a bent 150 degrees geometry to two equivalent Fe(1) atoms. In the third F site, F(4) is bonded in a bent 120 degrees geometry to one Fe(1) and one Fe(2) atom. In the fourth F site, F(1) is bonded in a bent 120 degrees geometry to two equivalent Fe(2) atoms.