MgV4O8 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(3), one O(7), and two equivalent O(2) atoms to form MgO5 square pyramids that share  a cornercorner with one V(1)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids,  an edgeedge with one V(1)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and edges with two equivalent V(4)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(1), one O(3), one O(5), one O(7), and two equivalent O(4) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra,  a cornercorner with one V(4)O6 octahedra, corners with two equivalent V(1)O6 octahedra,  a cornercorner with one Mg(1)O5 square pyramid,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, edges with two equivalent V(4)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 6-29°. In the second V site, V(2) is bonded to one O(2), one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra,  a cornercorner with one V(4)O6 octahedra, corners with two equivalent V(2)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent V(1)O6 octahedra, edges with two equivalent V(3)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-20°. In the third V site, V(3) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(8) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(3)O6 octahedra,  an edgeedge with one V(1)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 6-29°. In the fourth V site, V(4) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(7) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(4)O6 octahedra,  an edgeedge with one V(2)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(1)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-27°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1), one V(1), and one V(3) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one V(2), and one V(4) atom. In the third O site, O(3) is bonded to one Mg(1), one V(1), one V(3), and two equivalent V(2) atoms to form OMgV4 square pyramids that share corners with two equivalent O(3)MgV4 square pyramids and edges with two equivalent O(4)V4 trigonal pyramids. In the fourth O site, O(4) is bonded to one V(2), one V(4), and two equivalent V(1) atoms to form OV4 trigonal pyramids that share corners with two equivalent O(4)V4 trigonal pyramids and edges with two equivalent O(3)MgV4 square pyramids. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one V(1), one V(3), and one V(4) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one V(2), one V(3), and one V(4) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(1), and two equivalent V(4) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one V(2) and two equivalent V(3) atoms.
MgV4O8 crystallizes in the monoclinic Cm space group. Mg(1) is bonded to one O(1), one O(3), one O(7), and two equivalent O(2) atoms to form MgO5 square pyramids that share  a cornercorner with one V(1)O6 octahedra, corners with two equivalent Mg(1)O5 square pyramids,  an edgeedge with one V(1)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and edges with two equivalent V(4)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. The Mg(1)-O(1) bond length is 2.11 Å. The Mg(1)-O(3) bond length is 2.07 Å. The Mg(1)-O(7) bond length is 1.95 Å. Both Mg(1)-O(2) bond lengths are 2.03 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(5), one O(7), and two equivalent O(4) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra,  a cornercorner with one V(4)O6 octahedra, corners with two equivalent V(1)O6 octahedra,  a cornercorner with one Mg(1)O5 square pyramid,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(2)O6 octahedra, edges with two equivalent V(4)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 6-29°. The V(1)-O(1) bond length is 1.87 Å. The V(1)-O(3) bond length is 2.31 Å. The V(1)-O(5) bond length is 2.03 Å. The V(1)-O(7) bond length is 2.09 Å. Both V(1)-O(4) bond lengths are 2.07 Å. In the second V site, V(2) is bonded to one O(2), one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form VO6 octahedra that share  a cornercorner with one V(3)O6 octahedra,  a cornercorner with one V(4)O6 octahedra, corners with two equivalent V(2)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent V(1)O6 octahedra, edges with two equivalent V(3)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-20°. The V(2)-O(2) bond length is 2.10 Å. The V(2)-O(4) bond length is 2.01 Å. The V(2)-O(6) bond length is 1.90 Å. The V(2)-O(8) bond length is 1.86 Å. Both V(2)-O(3) bond lengths are 2.02 Å. In the third V site, V(3) is bonded to one O(1), one O(3), one O(5), one O(6), and two equivalent O(8) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(3)O6 octahedra,  an edgeedge with one V(1)O6 octahedra,  an edgeedge with one V(4)O6 octahedra, edges with two equivalent V(2)O6 octahedra, and  an edgeedge with one Mg(1)O5 square pyramid. The corner-sharing octahedral tilt angles range from 6-29°. The V(3)-O(1) bond length is 1.90 Å. The V(3)-O(3) bond length is 2.13 Å. The V(3)-O(5) bond length is 2.13 Å. The V(3)-O(6) bond length is 1.93 Å. Both V(3)-O(8) bond lengths are 2.07 Å. In the fourth V site, V(4) is bonded to one O(2), one O(4), one O(5), one O(6), and two equivalent O(7) atoms to form distorted VO6 octahedra that share  a cornercorner with one V(1)O6 octahedra,  a cornercorner with one V(2)O6 octahedra, corners with two equivalent V(4)O6 octahedra,  an edgeedge with one V(2)O6 octahedra,  an edgeedge with one V(3)O6 octahedra, edges with two equivalent V(1)O6 octahedra, and edges with two equivalent Mg(1)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-27°. The V(4)-O(2) bond length is 2.00 Å. The V(4)-O(4) bond length is 2.09 Å. The V(4)-O(5) bond length is 1.77 Å. The V(4)-O(6) bond length is 2.09 Å. Both V(4)-O(7) bond lengths are 2.03 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a T-shaped geometry to one Mg(1), one V(1), and one V(3) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(1), one V(2), and one V(4) atom. In the third O site, O(3) is bonded to one Mg(1), one V(1), one V(3), and two equivalent V(2) atoms to form OMgV4 square pyramids that share corners with two equivalent O(3)MgV4 square pyramids and edges with two equivalent O(4)V4 trigonal pyramids. In the fourth O site, O(4) is bonded to one V(2), one V(4), and two equivalent V(1) atoms to form OV4 trigonal pyramids that share corners with two equivalent O(4)V4 trigonal pyramids and edges with two equivalent O(3)MgV4 square pyramids. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one V(1), one V(3), and one V(4) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one V(2), one V(3), and one V(4) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Mg(1), one V(1), and two equivalent V(4) atoms. In the eighth O site, O(8) is bonded in a 3-coordinate geometry to one V(2) and two equivalent V(3) atoms.