MgV4O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), one O(5), one O(7), and one O(8) atom to form MgO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, corners with two equivalent V(4)O4 tetrahedra, and  an edgeedge with one V(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form VO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent V(3)O4 tetrahedra, corners with three equivalent V(4)O4 tetrahedra, and edges with two equivalent V(2)O6 octahedra. In the second V site, V(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form VO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent V(3)O4 tetrahedra, corners with three equivalent V(4)O4 tetrahedra, and edges with two equivalent V(1)O6 octahedra. In the third V site, V(3) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form VO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-58°. In the fourth V site, V(4) is bonded to one O(4), one O(6), one O(7), and one O(8) atom to form VO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-55°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one V(2) and one V(3) atom. In the third O site, O(3) is bonded to one Mg(1), one V(1), one V(2), and one V(3) atom to form distorted edge-sharing OMgV3 tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(4) atom. In the fifth O site, O(5) is bonded to one Mg(1), one V(1), one V(2), and one V(3) atom to form distorted edge-sharing OMgV3 tetrahedra. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(4) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(1), one V(1), and one V(4) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Mg(1), one V(2), and one V(4) atom.
MgV4O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded to one O(3), one O(5), one O(7), and one O(8) atom to form MgO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, corners with two equivalent V(4)O4 tetrahedra, and  an edgeedge with one V(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 63-67°. The Mg(1)-O(3) bond length is 2.09 Å. The Mg(1)-O(5) bond length is 2.10 Å. The Mg(1)-O(7) bond length is 1.96 Å. The Mg(1)-O(8) bond length is 1.96 Å. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form VO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent V(3)O4 tetrahedra, corners with three equivalent V(4)O4 tetrahedra, and edges with two equivalent V(2)O6 octahedra. The V(1)-O(1) bond length is 1.92 Å. The V(1)-O(3) bond length is 2.16 Å. The V(1)-O(4) bond length is 2.07 Å. The V(1)-O(5) bond length is 2.17 Å. The V(1)-O(6) bond length is 2.07 Å. The V(1)-O(7) bond length is 2.04 Å. In the second V site, V(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(8) atom to form VO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent V(3)O4 tetrahedra, corners with three equivalent V(4)O4 tetrahedra, and edges with two equivalent V(1)O6 octahedra. The V(2)-O(2) bond length is 1.92 Å. The V(2)-O(3) bond length is 2.17 Å. The V(2)-O(4) bond length is 2.08 Å. The V(2)-O(5) bond length is 2.17 Å. The V(2)-O(6) bond length is 2.07 Å. The V(2)-O(8) bond length is 2.04 Å. In the third V site, V(3) is bonded to one O(1), one O(2), one O(3), and one O(5) atom to form VO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-58°. The V(3)-O(1) bond length is 1.76 Å. The V(3)-O(2) bond length is 1.76 Å. The V(3)-O(3) bond length is 1.89 Å. The V(3)-O(5) bond length is 1.89 Å. In the fourth V site, V(4) is bonded to one O(4), one O(6), one O(7), and one O(8) atom to form VO4 tetrahedra that share corners with three equivalent V(1)O6 octahedra, corners with three equivalent V(2)O6 octahedra, and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 51-55°. The V(4)-O(4) bond length is 1.83 Å. The V(4)-O(6) bond length is 1.84 Å. The V(4)-O(7) bond length is 1.84 Å. The V(4)-O(8) bond length is 1.84 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one V(1) and one V(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one V(2) and one V(3) atom. In the third O site, O(3) is bonded to one Mg(1), one V(1), one V(2), and one V(3) atom to form distorted edge-sharing OMgV3 tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(4) atom. In the fifth O site, O(5) is bonded to one Mg(1), one V(1), one V(2), and one V(3) atom to form distorted edge-sharing OMgV3 tetrahedra. In the sixth O site, O(6) is bonded in a distorted trigonal planar geometry to one V(1), one V(2), and one V(4) atom. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Mg(1), one V(1), and one V(4) atom. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Mg(1), one V(2), and one V(4) atom.