MgCr6O16 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Cr(3)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Cr(4)O6 octahedra. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(8) atoms to form corner-sharing CrO6 octahedra. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, and corners with two equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-55°. In the third Cr site, Cr(3) is bonded to one O(3), one O(5), one O(6), and one O(8) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(4)O6 octahedra, and corners with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-47°. In the fourth Cr site, Cr(4) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(3)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Cr(1) and one Cr(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one Cr(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one Cr(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one Cr(3) atom.
MgCr6O16 crystallizes in the monoclinic P2 space group. Mg(1) is bonded to two equivalent O(4), two equivalent O(6), and two equivalent O(7) atoms to form MgO6 octahedra that share corners with two equivalent Cr(3)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Cr(4)O6 octahedra. Both Mg(1)-O(4) bond lengths are 2.19 Å. Both Mg(1)-O(6) bond lengths are 2.01 Å. Both Mg(1)-O(7) bond lengths are 2.17 Å. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(8) atoms to form corner-sharing CrO6 octahedra. Both Cr(1)-O(2) bond lengths are 2.03 Å. Both Cr(1)-O(3) bond lengths are 1.99 Å. Both Cr(1)-O(8) bond lengths are 1.99 Å. In the second Cr site, Cr(2) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra, corners with two equivalent Mg(1)O6 octahedra, and corners with two equivalent Cr(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 38-55°. The Cr(2)-O(1) bond length is 1.58 Å. The Cr(2)-O(2) bond length is 1.66 Å. The Cr(2)-O(4) bond length is 1.74 Å. The Cr(2)-O(7) bond length is 1.74 Å. In the third Cr site, Cr(3) is bonded to one O(3), one O(5), one O(6), and one O(8) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Cr(4)O6 octahedra, and corners with two equivalent Cr(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 44-47°. The Cr(3)-O(3) bond length is 1.68 Å. The Cr(3)-O(5) bond length is 1.68 Å. The Cr(3)-O(6) bond length is 1.63 Å. The Cr(3)-O(8) bond length is 1.68 Å. In the fourth Cr site, Cr(4) is bonded to two equivalent O(4), two equivalent O(5), and two equivalent O(7) atoms to form CrO6 octahedra that share corners with two equivalent Cr(3)O4 tetrahedra, corners with four equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. Both Cr(4)-O(4) bond lengths are 2.05 Å. Both Cr(4)-O(5) bond lengths are 1.99 Å. Both Cr(4)-O(7) bond lengths are 2.06 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Cr(1) and one Cr(2) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one Cr(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one Cr(4) atom. In the fifth O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Cr(3) and one Cr(4) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one Cr(3) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(2), and one Cr(4) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one Cr(3) atom.