MgV3O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, and edges with two equivalent V(3)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form VO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent V(3)O6 octahedra, and  a cornercorner with one V(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 28-54°. In the second V site, V(2) is bonded to one O(3), one O(5), one O(6), and one O(9) atom to form VO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent V(3)O6 octahedra, and  a cornercorner with one V(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-70°. In the third V site, V(3) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Mg(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent V(3) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one V(2), and one V(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one V(1), and one V(3) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one V(2), and one V(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one V(2), and one V(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mg(1) and one V(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one V(1) and one V(2) atom.
MgV3O8 crystallizes in the monoclinic C2 space group. Mg(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, and edges with two equivalent V(3)O6 octahedra. The corner-sharing octahedral tilt angles are 6°. The Mg(1)-O(1) bond length is 2.00 Å. The Mg(1)-O(3) bond length is 2.09 Å. The Mg(1)-O(4) bond length is 2.09 Å. The Mg(1)-O(5) bond length is 2.05 Å. The Mg(1)-O(6) bond length is 2.27 Å. The Mg(1)-O(8) bond length is 2.01 Å. There are three inequivalent V sites. In the first V site, V(1) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form VO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with two equivalent V(3)O6 octahedra, and  a cornercorner with one V(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 28-54°. The V(1)-O(4) bond length is 1.75 Å. The V(1)-O(7) bond length is 1.69 Å. The V(1)-O(8) bond length is 1.64 Å. The V(1)-O(9) bond length is 1.81 Å. In the second V site, V(2) is bonded to one O(3), one O(5), one O(6), and one O(9) atom to form VO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra, corners with three equivalent V(3)O6 octahedra, and  a cornercorner with one V(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 36-70°. The V(2)-O(3) bond length is 1.75 Å. The V(2)-O(5) bond length is 1.72 Å. The V(2)-O(6) bond length is 1.72 Å. The V(2)-O(9) bond length is 1.71 Å. In the third V site, V(3) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra, corners with two equivalent V(1)O4 tetrahedra, corners with three equivalent V(2)O4 tetrahedra, and edges with two equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. The V(3)-O(2) bond length is 1.80 Å. The V(3)-O(3) bond length is 2.03 Å. The V(3)-O(4) bond length is 2.00 Å. The V(3)-O(5) bond length is 2.09 Å. The V(3)-O(6) bond length is 2.01 Å. The V(3)-O(7) bond length is 1.94 Å. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to two equivalent Mg(1) atoms. In the second O site, O(2) is bonded in a linear geometry to two equivalent V(3) atoms. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(1), one V(2), and one V(3) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one V(1), and one V(3) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Mg(1), one V(2), and one V(3) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one V(2), and one V(3) atom. In the seventh O site, O(7) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the eighth O site, O(8) is bonded in a bent 150 degrees geometry to one Mg(1) and one V(1) atom. In the ninth O site, O(9) is bonded in a bent 150 degrees geometry to one V(1) and one V(2) atom.