BaSrMg(FeO2)4 crystallizes in the trigonal P312 space group. Ba(1) is bonded in a distorted hexagonal planar geometry to three equivalent O(2) and three equivalent O(3) atoms. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra and edges with three equivalent Mg(1)O6 octahedra. Mg(1) is bonded to six equivalent O(1) atoms to form distorted MgO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra and edges with three equivalent Sr(1)O6 octahedra. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 4-coordinate geometry to one O(3) and three equivalent O(1) atoms. In the second Fe site, Fe(2) is bonded to one O(2) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra, and  a cornercorner with one Fe(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-59°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a distorted linear geometry to three equivalent Ba(1) and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a linear geometry to three equivalent Ba(1) and two equivalent Fe(1) atoms.
BaSrMg(FeO2)4 crystallizes in the trigonal P312 space group. Ba(1) is bonded in a distorted hexagonal planar geometry to three equivalent O(2) and three equivalent O(3) atoms. All Ba(1)-O(2) bond lengths are 3.17 Å. All Ba(1)-O(3) bond lengths are 3.17 Å. Sr(1) is bonded to six equivalent O(1) atoms to form SrO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra and edges with three equivalent Mg(1)O6 octahedra. All Sr(1)-O(1) bond lengths are 2.49 Å. Mg(1) is bonded to six equivalent O(1) atoms to form distorted MgO6 octahedra that share corners with six equivalent Fe(2)O4 tetrahedra and edges with three equivalent Sr(1)O6 octahedra. All Mg(1)-O(1) bond lengths are 2.23 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a 4-coordinate geometry to one O(3) and three equivalent O(1) atoms. The Fe(1)-O(3) bond length is 1.81 Å. All Fe(1)-O(1) bond lengths are 1.99 Å. In the second Fe site, Fe(2) is bonded to one O(2) and three equivalent O(1) atoms to form FeO4 tetrahedra that share corners with three equivalent Sr(1)O6 octahedra, corners with three equivalent Mg(1)O6 octahedra, and  a cornercorner with one Fe(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 44-59°. The Fe(2)-O(2) bond length is 2.06 Å. All Fe(2)-O(1) bond lengths are 1.94 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Sr(1), one Mg(1), one Fe(1), and one Fe(2) atom. In the second O site, O(2) is bonded in a distorted linear geometry to three equivalent Ba(1) and two equivalent Fe(2) atoms. In the third O site, O(3) is bonded in a linear geometry to three equivalent Ba(1) and two equivalent Fe(1) atoms.