MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(5), one F(3), two equivalent F(1), and two equivalent F(6) atoms to form MgOF5 octahedra that share  a cornercorner with one Fe(7)O3F tetrahedra, edges with two equivalent Mg(1)OF5 octahedra, edges with two equivalent Fe(6)F6 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. In the second Fe site, Fe(2) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. In the third Fe site, Fe(3) is bonded in a 4-coordinate geometry to one O(1), two equivalent O(3), and one F(3) atom. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, edges with two equivalent Mg(1)OF5 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form FeF6 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)OF5 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-50°. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), and one F(8) atom to form FeO3F tetrahedra that share  a cornercorner with one Mg(1)OF5 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(7)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 54-68°. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded to one Mg(1), one Fe(7), and two equivalent Fe(5) atoms to form OMgFe3 tetrahedra that share  a cornercorner with one F(3)MgFe3 tetrahedra and corners with two equivalent O(5)MgFe3 tetrahedra. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(8) and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(5) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(6) atoms to form distorted FMgFe3 tetrahedra that share  a cornercorner with one O(5)MgFe3 tetrahedra and corners with two equivalent F(3)MgFe3 tetrahedra. In the fourth F site, F(4) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a distorted trigonal planar geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(6) atom. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a 3-coordinate geometry to one Fe(7) and two equivalent Fe(1) atoms.
MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(5), one F(3), two equivalent F(1), and two equivalent F(6) atoms to form MgOF5 octahedra that share  a cornercorner with one Fe(7)O3F tetrahedra, edges with two equivalent Mg(1)OF5 octahedra, edges with two equivalent Fe(6)F6 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. The Mg(1)-O(5) bond length is 2.07 Å. The Mg(1)-F(3) bond length is 2.03 Å. Both Mg(1)-F(1) bond lengths are 2.02 Å. Both Mg(1)-F(6) bond lengths are 2.04 Å. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 52-55°. The Fe(1)-O(3) bond length is 1.86 Å. Both Fe(1)-O(2) bond lengths are 1.93 Å. The Fe(1)-F(7) bond length is 2.14 Å. Both Fe(1)-F(8) bond lengths are 2.36 Å. In the second Fe site, Fe(2) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, and edges with two equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. The Fe(2)-O(4) bond length is 1.98 Å. The Fe(2)-O(7) bond length is 2.17 Å. Both Fe(2)-O(1) bond lengths are 2.01 Å. Both Fe(2)-O(8) bond lengths are 2.08 Å. In the third Fe site, Fe(3) is bonded in a 4-coordinate geometry to one O(1), two equivalent O(3), and one F(3) atom. The Fe(3)-O(1) bond length is 1.89 Å. Both Fe(3)-O(3) bond lengths are 1.92 Å. The Fe(3)-F(3) bond length is 2.59 Å. In the fourth Fe site, Fe(4) is bonded to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-57°. The Fe(4)-O(2) bond length is 1.95 Å. Both Fe(4)-O(4) bond lengths are 1.91 Å. The Fe(4)-F(4) bond length is 2.31 Å. Both Fe(4)-F(2) bond lengths are 2.20 Å. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(7)O3F tetrahedra, edges with two equivalent Mg(1)OF5 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. The Fe(5)-O(6) bond length is 1.86 Å. Both Fe(5)-O(5) bond lengths are 2.07 Å. The Fe(5)-F(1) bond length is 2.16 Å. Both Fe(5)-F(4) bond lengths are 2.09 Å. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form FeF6 octahedra that share corners with two equivalent Fe(4)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)OF5 octahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-50°. The Fe(6)-F(2) bond length is 2.10 Å. The Fe(6)-F(6) bond length is 2.16 Å. Both Fe(6)-F(3) bond lengths are 2.15 Å. Both Fe(6)-F(5) bond lengths are 2.06 Å. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), and one F(8) atom to form FeO3F tetrahedra that share  a cornercorner with one Mg(1)OF5 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Fe(7)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 54-68°. The Fe(7)-O(5) bond length is 1.94 Å. Both Fe(7)-O(7) bond lengths are 1.85 Å. The Fe(7)-F(8) bond length is 1.99 Å. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 50-52°. The Fe(8)-O(8) bond length is 1.84 Å. Both Fe(8)-O(6) bond lengths are 2.01 Å. The Fe(8)-F(5) bond length is 2.15 Å. Both Fe(8)-F(7) bond lengths are 2.18 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(2) atoms. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded to one Mg(1), one Fe(7), and two equivalent Fe(5) atoms to form OMgFe3 tetrahedra that share  a cornercorner with one F(3)MgFe3 tetrahedra and corners with two equivalent O(5)MgFe3 tetrahedra. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Fe(8) and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(5) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(6) atoms to form distorted FMgFe3 tetrahedra that share  a cornercorner with one O(5)MgFe3 tetrahedra and corners with two equivalent F(3)MgFe3 tetrahedra. In the fourth F site, F(4) is bonded in a distorted trigonal planar geometry to one Fe(4) and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a distorted trigonal planar geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(6) atom. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a 3-coordinate geometry to one Fe(7) and two equivalent Fe(1) atoms.