Sr4Mg(Fe2O5)2 crystallizes in the monoclinic Cm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(4), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Mg(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form MgO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 trigonal pyramids, and  an edgeedge with one Fe(3)O4 trigonal pyramid. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form FeO5 square pyramids that share corners with four equivalent Fe(1)O5 square pyramids and  a cornercorner with one Fe(2)O4 tetrahedra. In the second Fe site, Fe(2) is bonded to one O(5), one O(6), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(1)O5 square pyramids, corners with two equivalent Mg(1)O4 tetrahedra, and corners with two equivalent Fe(3)O4 trigonal pyramids. In the third Fe site, Fe(3) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form distorted FeO4 trigonal pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with two equivalent O(5)Sr2MgFe2 square pyramids, corners with two equivalent O(6)Sr2MgFe2 trigonal bipyramids, edges with two equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles are 15°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form OSr4Fe2 octahedra that share corners with two equivalent O(2)Sr4Fe2 octahedra, corners with two equivalent O(5)Sr2MgFe2 square pyramids, corners with two equivalent O(6)Sr2MgFe2 trigonal bipyramids, edges with two equivalent O(2)Sr4Fe2 octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles are 14°. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), and one Fe(3) atom. In the fifth O site, O(5) is bonded to two equivalent Sr(1), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted OSr2MgFe2 square pyramids that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, and corners with three equivalent O(6)Sr2MgFe2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 37-59°. In the sixth O site, O(6) is bonded to two equivalent Sr(2), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted OSr2MgFe2 trigonal bipyramids that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, and corners with three equivalent O(5)Sr2MgFe2 square pyramids. The corner-sharing octahedral tilt angles range from 37-60°.
Sr4Mg(Fe2O5)2 crystallizes in the monoclinic Cm space group. There are two inequivalent Sr sites. In the first Sr site, Sr(1) is bonded in a 8-coordinate geometry to one O(4), one O(5), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Sr(1)-O(4) bond length is 2.64 Å. The Sr(1)-O(5) bond length is 2.55 Å. There is one shorter (2.63 Å) and one longer (2.66 Å) Sr(1)-O(1) bond length. There is one shorter (2.56 Å) and one longer (2.63 Å) Sr(1)-O(2) bond length. There is one shorter (2.82 Å) and one longer (2.87 Å) Sr(1)-O(3) bond length. In the second Sr site, Sr(2) is bonded in a 8-coordinate geometry to one O(4), one O(6), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Sr(2)-O(4) bond length is 2.62 Å. The Sr(2)-O(6) bond length is 2.50 Å. There is one shorter (2.62 Å) and one longer (2.77 Å) Sr(2)-O(1) bond length. There is one shorter (2.62 Å) and one longer (2.66 Å) Sr(2)-O(2) bond length. There is one shorter (2.78 Å) and one longer (2.87 Å) Sr(2)-O(3) bond length. Mg(1) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form MgO4 tetrahedra that share corners with two equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(3)O4 trigonal pyramids, and  an edgeedge with one Fe(3)O4 trigonal pyramid. The Mg(1)-O(5) bond length is 2.03 Å. The Mg(1)-O(6) bond length is 2.08 Å. Both Mg(1)-O(4) bond lengths are 2.01 Å. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form FeO5 square pyramids that share corners with four equivalent Fe(1)O5 square pyramids and  a cornercorner with one Fe(2)O4 tetrahedra. The Fe(1)-O(3) bond length is 2.01 Å. There is one shorter (1.95 Å) and one longer (1.96 Å) Fe(1)-O(1) bond length. There is one shorter (2.02 Å) and one longer (2.03 Å) Fe(1)-O(2) bond length. In the second Fe site, Fe(2) is bonded to one O(5), one O(6), and two equivalent O(3) atoms to form distorted FeO4 tetrahedra that share corners with two equivalent Fe(1)O5 square pyramids, corners with two equivalent Mg(1)O4 tetrahedra, and corners with two equivalent Fe(3)O4 trigonal pyramids. The Fe(2)-O(5) bond length is 2.06 Å. The Fe(2)-O(6) bond length is 2.12 Å. Both Fe(2)-O(3) bond lengths are 2.08 Å. In the third Fe site, Fe(3) is bonded to one O(5), one O(6), and two equivalent O(4) atoms to form distorted FeO4 trigonal pyramids that share corners with two equivalent Mg(1)O4 tetrahedra, corners with two equivalent Fe(2)O4 tetrahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The Fe(3)-O(5) bond length is 2.17 Å. The Fe(3)-O(6) bond length is 2.13 Å. Both Fe(3)-O(4) bond lengths are 2.05 Å. There are six inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form distorted OSr4Fe2 octahedra that share corners with two equivalent O(1)Sr4Fe2 octahedra, corners with two equivalent O(5)Sr2MgFe2 square pyramids, corners with two equivalent O(6)Sr2MgFe2 trigonal bipyramids, edges with two equivalent O(1)Sr4Fe2 octahedra, and faces with four equivalent O(2)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles are 15°. In the second O site, O(2) is bonded to two equivalent Sr(1), two equivalent Sr(2), and two equivalent Fe(1) atoms to form OSr4Fe2 octahedra that share corners with two equivalent O(2)Sr4Fe2 octahedra, corners with two equivalent O(5)Sr2MgFe2 square pyramids, corners with two equivalent O(6)Sr2MgFe2 trigonal bipyramids, edges with two equivalent O(2)Sr4Fe2 octahedra, and faces with four equivalent O(1)Sr4Fe2 octahedra. The corner-sharing octahedral tilt angles are 14°. In the third O site, O(3) is bonded in a 6-coordinate geometry to two equivalent Sr(1), two equivalent Sr(2), one Fe(1), and one Fe(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Sr(1), one Sr(2), one Mg(1), and one Fe(3) atom. In the fifth O site, O(5) is bonded to two equivalent Sr(1), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted OSr2MgFe2 square pyramids that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, and corners with three equivalent O(6)Sr2MgFe2 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 37-59°. In the sixth O site, O(6) is bonded to two equivalent Sr(2), one Mg(1), one Fe(2), and one Fe(3) atom to form distorted OSr2MgFe2 trigonal bipyramids that share corners with four equivalent O(1)Sr4Fe2 octahedra, corners with four equivalent O(2)Sr4Fe2 octahedra, and corners with three equivalent O(5)Sr2MgFe2 square pyramids. The corner-sharing octahedral tilt angles range from 37-60°.