Mg3Fe4(SbO4)6 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(2)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. In the second Mg site, Mg(2) is bonded to one O(11), one O(2), one O(5), one O(6), and one O(7) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Sb(2)O4 tetrahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(6), one O(7), one O(9), and two equivalent O(4) atoms to form FeO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Sb(3)O4 tetrahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with three equivalent Sb(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 53°. In the second Fe site, Fe(2) is bonded to one O(10), one O(11), one O(12), one O(5), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(2)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. There are three inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(10), one O(11), one O(3), and one O(6) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 30-65°. In the second Sb site, Sb(2) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, and  a cornercorner with one Mg(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 37-57°. In the third Sb site, Sb(3) is bonded to one O(12), one O(2), one O(5), and one O(9) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 27-65°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Sb(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Sb(3) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Sb(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Mg(2), one Fe(2), and one Sb(3) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Sb(1) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Sb(2) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to two equivalent Fe(2) and one Sb(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one Sb(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Fe(2) and one Sb(1) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Mg(2), one Fe(2), and one Sb(1) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Fe(2) and one Sb(3) atom.
Mg3Fe4(SbO4)6 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form distorted MgO6 octahedra that share corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(2)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 53°. Both Mg(1)-O(1) bond lengths are 1.99 Å. Both Mg(1)-O(2) bond lengths are 2.57 Å. Both Mg(1)-O(3) bond lengths are 2.15 Å. In the second Mg site, Mg(2) is bonded to one O(11), one O(2), one O(5), one O(6), and one O(7) atom to form MgO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Sb(2)O4 tetrahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles are 55°. The Mg(2)-O(11) bond length is 2.09 Å. The Mg(2)-O(2) bond length is 2.03 Å. The Mg(2)-O(5) bond length is 2.06 Å. The Mg(2)-O(6) bond length is 2.04 Å. The Mg(2)-O(7) bond length is 2.05 Å. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), one O(6), one O(7), one O(9), and two equivalent O(4) atoms to form FeO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Sb(3)O4 tetrahedra, corners with two equivalent Sb(1)O4 tetrahedra, corners with three equivalent Sb(2)O4 tetrahedra,  an edgeedge with one Fe(1)O6 octahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 53°. The Fe(1)-O(3) bond length is 2.11 Å. The Fe(1)-O(6) bond length is 2.08 Å. The Fe(1)-O(7) bond length is 2.01 Å. The Fe(1)-O(9) bond length is 1.90 Å. There is one shorter (2.07 Å) and one longer (2.11 Å) Fe(1)-O(4) bond length. In the second Fe site, Fe(2) is bonded to one O(10), one O(11), one O(12), one O(5), and two equivalent O(8) atoms to form FeO6 octahedra that share corners with two equivalent Sb(1)O4 tetrahedra, corners with two equivalent Sb(2)O4 tetrahedra, corners with two equivalent Sb(3)O4 tetrahedra,  an edgeedge with one Fe(2)O6 octahedra, and  an edgeedge with one Mg(2)O5 trigonal bipyramid. The Fe(2)-O(10) bond length is 1.95 Å. The Fe(2)-O(11) bond length is 2.02 Å. The Fe(2)-O(12) bond length is 1.92 Å. The Fe(2)-O(5) bond length is 2.15 Å. There is one shorter (2.02 Å) and one longer (2.15 Å) Fe(2)-O(8) bond length. There are three inequivalent Sb sites. In the first Sb site, Sb(1) is bonded to one O(10), one O(11), one O(3), and one O(6) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 30-65°. The Sb(1)-O(10) bond length is 1.88 Å. The Sb(1)-O(11) bond length is 1.92 Å. The Sb(1)-O(3) bond length is 1.93 Å. The Sb(1)-O(6) bond length is 1.91 Å. In the second Sb site, Sb(2) is bonded to one O(1), one O(4), one O(7), and one O(8) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, and  a cornercorner with one Mg(2)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 37-57°. The Sb(2)-O(1) bond length is 1.86 Å. The Sb(2)-O(4) bond length is 1.93 Å. The Sb(2)-O(7) bond length is 1.92 Å. The Sb(2)-O(8) bond length is 1.91 Å. In the third Sb site, Sb(3) is bonded to one O(12), one O(2), one O(5), and one O(9) atom to form SbO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Fe(1)O6 octahedra, corners with two equivalent Fe(2)O6 octahedra, and corners with two equivalent Mg(2)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 27-65°. The Sb(3)-O(12) bond length is 1.89 Å. The Sb(3)-O(2) bond length is 1.91 Å. The Sb(3)-O(5) bond length is 1.92 Å. The Sb(3)-O(9) bond length is 1.89 Å. There are twelve inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Sb(2) atom. In the second O site, O(2) is bonded in a trigonal planar geometry to one Mg(1), one Mg(2), and one Sb(3) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one Fe(1), and one Sb(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to two equivalent Fe(1) and one Sb(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Mg(2), one Fe(2), and one Sb(3) atom. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Sb(1) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(2), one Fe(1), and one Sb(2) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to two equivalent Fe(2) and one Sb(2) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one Fe(1) and one Sb(3) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Fe(2) and one Sb(1) atom. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Mg(2), one Fe(2), and one Sb(1) atom. In the twelfth O site, O(12) is bonded in a bent 150 degrees geometry to one Fe(2) and one Sb(3) atom.