Ba2MgY2(Fe2O5)2 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(6), one O(8), two equivalent O(10), two equivalent O(2), and two equivalent O(9) atoms. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to one O(3), one O(8), two equivalent O(10), and two equivalent O(9) atoms. Mg(1) is bonded to one O(10), one O(5), one O(7), and two equivalent O(3) atoms to form MgO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O5 trigonal bipyramid, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Y(1)O6 octahedra. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(5), one O(6), one O(7), one O(8), and two equivalent O(4) atoms to form distorted YO6 octahedra that share corners with two equivalent Y(1)O6 octahedra,  an edgeedge with one Mg(1)O5 trigonal bipyramid, and edges with two equivalent Fe(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to one O(5), one O(6), one O(7), one O(8), two equivalent O(1), and two equivalent O(2) atoms. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted square co-planar geometry to one O(1), one O(3), and two equivalent O(7) atoms. In the second Fe site, Fe(2) is bonded to one O(10), one O(2), one O(4), and two equivalent O(8) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent Fe(2)O5 trigonal bipyramids, and edges with two equivalent Y(1)O6 octahedra. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(9), and two equivalent O(6) atoms. In the fourth Fe site, Fe(4) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), and two equivalent O(5) atoms. There are ten inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(2), one Fe(1), and one Fe(4) atom to form distorted OY2Fe2 tetrahedra that share corners with two equivalent O(1)Y2Fe2 tetrahedra and edges with two equivalent O(5)Y2MgFe2 trigonal bipyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Y(2), one Fe(2), and one Fe(3) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(2), two equivalent Mg(1), one Fe(1), and one Fe(4) atom. In the fourth O site, O(4) is bonded to two equivalent Y(1), one Fe(2), and one Fe(3) atom to form OY2Fe2 tetrahedra that share  a cornercorner with one O(10)Ba4MgFe octahedra,  a cornercorner with one O(9)Ba4Fe square pyramid, corners with two equivalent O(4)Y2Fe2 tetrahedra, and corners with two equivalent O(5)Y2MgFe2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 56°. In the fifth O site, O(5) is bonded to one Mg(1), one Y(1), one Y(2), and two equivalent Fe(4) atoms to form OY2MgFe2 trigonal bipyramids that share  a cornercorner with one O(10)Ba4MgFe octahedra, corners with two equivalent O(4)Y2Fe2 tetrahedra, corners with two equivalent O(5)Y2MgFe2 trigonal bipyramids, and edges with two equivalent O(1)Y2Fe2 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Y(1), one Y(2), and two equivalent Fe(3) atoms. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Y(1), one Y(2), and two equivalent Fe(1) atoms. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(2), one Y(1), one Y(2), and two equivalent Fe(2) atoms. In the ninth O site, O(9) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Fe(3) atom to form distorted OBa4Fe square pyramids that share corners with four equivalent O(10)Ba4MgFe octahedra,  a cornercorner with one O(4)Y2Fe2 tetrahedra, edges with two equivalent O(10)Ba4MgFe octahedra, and edges with two equivalent O(9)Ba4Fe square pyramids. The corner-sharing octahedral tilt angles range from 3-12°. In the tenth O site, O(10) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Mg(1), and one Fe(2) atom to form distorted OBa4MgFe octahedra that share corners with four equivalent O(9)Ba4Fe square pyramids,  a cornercorner with one O(4)Y2Fe2 tetrahedra,  a cornercorner with one O(5)Y2MgFe2 trigonal bipyramid, edges with two equivalent O(10)Ba4MgFe octahedra, and edges with two equivalent O(9)Ba4Fe square pyramids.
Ba2MgY2(Fe2O5)2 crystallizes in the triclinic P1 space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 8-coordinate geometry to one O(6), one O(8), two equivalent O(10), two equivalent O(2), and two equivalent O(9) atoms. The Ba(1)-O(6) bond length is 3.06 Å. The Ba(1)-O(8) bond length is 2.98 Å. There is one shorter (2.78 Å) and one longer (2.86 Å) Ba(1)-O(10) bond length. There is one shorter (3.02 Å) and one longer (3.04 Å) Ba(1)-O(2) bond length. There is one shorter (2.85 Å) and one longer (2.88 Å) Ba(1)-O(9) bond length. In the second Ba site, Ba(2) is bonded in a 6-coordinate geometry to one O(3), one O(8), two equivalent O(10), and two equivalent O(9) atoms. The Ba(2)-O(3) bond length is 3.00 Å. The Ba(2)-O(8) bond length is 2.98 Å. There is one shorter (2.78 Å) and one longer (2.81 Å) Ba(2)-O(10) bond length. There is one shorter (2.69 Å) and one longer (2.71 Å) Ba(2)-O(9) bond length. Mg(1) is bonded to one O(10), one O(5), one O(7), and two equivalent O(3) atoms to form MgO5 trigonal bipyramids that share  a cornercorner with one Fe(2)O5 trigonal bipyramid, corners with two equivalent Mg(1)O5 trigonal bipyramids, and  an edgeedge with one Y(1)O6 octahedra. The Mg(1)-O(10) bond length is 2.03 Å. The Mg(1)-O(5) bond length is 2.15 Å. The Mg(1)-O(7) bond length is 2.13 Å. Both Mg(1)-O(3) bond lengths are 2.04 Å. There are two inequivalent Y sites. In the first Y site, Y(1) is bonded to one O(5), one O(6), one O(7), one O(8), and two equivalent O(4) atoms to form distorted YO6 octahedra that share corners with two equivalent Y(1)O6 octahedra,  an edgeedge with one Mg(1)O5 trigonal bipyramid, and edges with two equivalent Fe(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. The Y(1)-O(5) bond length is 2.37 Å. The Y(1)-O(6) bond length is 2.26 Å. The Y(1)-O(7) bond length is 2.34 Å. The Y(1)-O(8) bond length is 2.39 Å. Both Y(1)-O(4) bond lengths are 2.18 Å. In the second Y site, Y(2) is bonded in a 8-coordinate geometry to one O(5), one O(6), one O(7), one O(8), two equivalent O(1), and two equivalent O(2) atoms. The Y(2)-O(5) bond length is 2.69 Å. The Y(2)-O(6) bond length is 2.24 Å. The Y(2)-O(7) bond length is 3.08 Å. The Y(2)-O(8) bond length is 2.38 Å. There is one shorter (2.50 Å) and one longer (2.51 Å) Y(2)-O(1) bond length. There is one shorter (2.42 Å) and one longer (2.43 Å) Y(2)-O(2) bond length. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted square co-planar geometry to one O(1), one O(3), and two equivalent O(7) atoms. The Fe(1)-O(1) bond length is 1.99 Å. The Fe(1)-O(3) bond length is 2.18 Å. Both Fe(1)-O(7) bond lengths are 2.07 Å. In the second Fe site, Fe(2) is bonded to one O(10), one O(2), one O(4), and two equivalent O(8) atoms to form distorted FeO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 trigonal bipyramid, corners with two equivalent Fe(2)O5 trigonal bipyramids, and edges with two equivalent Y(1)O6 octahedra. The Fe(2)-O(10) bond length is 2.22 Å. The Fe(2)-O(2) bond length is 2.03 Å. The Fe(2)-O(4) bond length is 2.06 Å. There is one shorter (2.05 Å) and one longer (2.07 Å) Fe(2)-O(8) bond length. In the third Fe site, Fe(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(9), and two equivalent O(6) atoms. The Fe(3)-O(2) bond length is 2.06 Å. The Fe(3)-O(4) bond length is 2.14 Å. The Fe(3)-O(9) bond length is 1.96 Å. Both Fe(3)-O(6) bond lengths are 2.13 Å. In the fourth Fe site, Fe(4) is bonded in a rectangular see-saw-like geometry to one O(1), one O(3), and two equivalent O(5) atoms. The Fe(4)-O(1) bond length is 1.98 Å. The Fe(4)-O(3) bond length is 2.11 Å. There is one shorter (2.07 Å) and one longer (2.08 Å) Fe(4)-O(5) bond length. There are ten inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(2), one Fe(1), and one Fe(4) atom to form distorted OY2Fe2 tetrahedra that share corners with two equivalent O(1)Y2Fe2 tetrahedra and edges with two equivalent O(5)Y2MgFe2 trigonal bipyramids. In the second O site, O(2) is bonded in a 6-coordinate geometry to two equivalent Ba(1), two equivalent Y(2), one Fe(2), and one Fe(3) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ba(2), two equivalent Mg(1), one Fe(1), and one Fe(4) atom. In the fourth O site, O(4) is bonded to two equivalent Y(1), one Fe(2), and one Fe(3) atom to form OY2Fe2 tetrahedra that share  a cornercorner with one O(10)Ba4MgFe octahedra,  a cornercorner with one O(9)Ba4Fe square pyramid, corners with two equivalent O(4)Y2Fe2 tetrahedra, and corners with two equivalent O(5)Y2MgFe2 trigonal bipyramids. The corner-sharing octahedral tilt angles are 56°. In the fifth O site, O(5) is bonded to one Mg(1), one Y(1), one Y(2), and two equivalent Fe(4) atoms to form OY2MgFe2 trigonal bipyramids that share  a cornercorner with one O(10)Ba4MgFe octahedra, corners with two equivalent O(4)Y2Fe2 tetrahedra, corners with two equivalent O(5)Y2MgFe2 trigonal bipyramids, and edges with two equivalent O(1)Y2Fe2 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ba(1), one Y(1), one Y(2), and two equivalent Fe(3) atoms. In the seventh O site, O(7) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), one Y(1), one Y(2), and two equivalent Fe(1) atoms. In the eighth O site, O(8) is bonded in a 6-coordinate geometry to one Ba(1), one Ba(2), one Y(1), one Y(2), and two equivalent Fe(2) atoms. In the ninth O site, O(9) is bonded to two equivalent Ba(1), two equivalent Ba(2), and one Fe(3) atom to form distorted OBa4Fe square pyramids that share corners with four equivalent O(10)Ba4MgFe octahedra,  a cornercorner with one O(4)Y2Fe2 tetrahedra, edges with two equivalent O(10)Ba4MgFe octahedra, and edges with two equivalent O(9)Ba4Fe square pyramids. The corner-sharing octahedral tilt angles range from 3-12°. In the tenth O site, O(10) is bonded to two equivalent Ba(1), two equivalent Ba(2), one Mg(1), and one Fe(2) atom to form distorted OBa4MgFe octahedra that share corners with four equivalent O(9)Ba4Fe square pyramids,  a cornercorner with one O(4)Y2Fe2 tetrahedra,  a cornercorner with one O(5)Y2MgFe2 trigonal bipyramid, edges with two equivalent O(10)Ba4MgFe octahedra, and edges with two equivalent O(9)Ba4Fe square pyramids.