MgV4O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to one O(2), one O(7), two equivalent O(3), and two equivalent O(6) atoms. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(6) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 48-55°. In the second V site, V(2) is bonded to one O(2), one O(8), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the third V site, V(3) is bonded to one O(1), one O(5), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. In the fourth V site, V(4) is bonded to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 48-55°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one V(3) and two equivalent V(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one V(2), and two equivalent V(4) atoms to form distorted OMgV3 trigonal pyramids that share corners with two equivalent O(3)Mg2V3 square pyramids, corners with two equivalent O(2)MgV3 trigonal pyramids, corners with three equivalent O(7)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, and  an edgeedge with one O(7)MgV3 trigonal pyramid. In the third O site, O(3) is bonded to two equivalent Mg(1), one V(4), and two equivalent V(2) atoms to form OMg2V3 square pyramids that share corners with three equivalent O(6)Mg2V3 trigonal bipyramids, corners with two equivalent O(2)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids,  an edgeedge with one O(6)Mg2V3 trigonal bipyramid, edges with two equivalent O(2)MgV3 trigonal pyramids, and edges with two equivalent O(7)MgV3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one V(1) and two equivalent V(3) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one V(3) and two equivalent V(2) atoms. In the sixth O site, O(6) is bonded to two equivalent Mg(1), one V(4), and two equivalent V(1) atoms to form distorted OMg2V3 trigonal bipyramids that share corners with three equivalent O(3)Mg2V3 square pyramids, corners with two equivalent O(7)MgV3 trigonal pyramids,  an edgeedge with one O(3)Mg2V3 square pyramid, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, edges with two equivalent O(2)MgV3 trigonal pyramids, and edges with two equivalent O(7)MgV3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Mg(1), one V(1), and two equivalent V(4) atoms to form OMgV3 trigonal pyramids that share corners with two equivalent O(6)Mg2V3 trigonal bipyramids, corners with two equivalent O(7)MgV3 trigonal pyramids, corners with three equivalent O(2)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, and  an edgeedge with one O(2)MgV3 trigonal pyramid. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one V(2) and two equivalent V(3) atoms.
MgV4O8 crystallizes in the triclinic P1 space group. Mg(1) is bonded in a 6-coordinate geometry to one O(2), one O(7), two equivalent O(3), and two equivalent O(6) atoms. The Mg(1)-O(2) bond length is 1.96 Å. The Mg(1)-O(7) bond length is 2.14 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) Mg(1)-O(3) bond length. There is one shorter (2.28 Å) and one longer (2.33 Å) Mg(1)-O(6) bond length. There are four inequivalent V sites. In the first V site, V(1) is bonded to one O(4), one O(7), two equivalent O(1), and two equivalent O(6) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 48-55°. The V(1)-O(4) bond length is 1.85 Å. The V(1)-O(7) bond length is 1.97 Å. There is one shorter (1.93 Å) and one longer (1.95 Å) V(1)-O(1) bond length. There is one shorter (2.12 Å) and one longer (2.16 Å) V(1)-O(6) bond length. In the second V site, V(2) is bonded to one O(2), one O(8), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. The V(2)-O(2) bond length is 1.97 Å. The V(2)-O(8) bond length is 1.83 Å. Both V(2)-O(3) bond lengths are 2.18 Å. Both V(2)-O(5) bond lengths are 1.94 Å. In the third V site, V(3) is bonded to one O(1), one O(5), two equivalent O(4), and two equivalent O(8) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 49-52°. The V(3)-O(1) bond length is 2.02 Å. The V(3)-O(5) bond length is 2.03 Å. Both V(3)-O(4) bond lengths are 2.04 Å. There is one shorter (2.06 Å) and one longer (2.07 Å) V(3)-O(8) bond length. In the fourth V site, V(4) is bonded to one O(3), one O(6), two equivalent O(2), and two equivalent O(7) atoms to form a mixture of edge and corner-sharing VO6 octahedra. The corner-sharing octahedral tilt angles range from 48-55°. The V(4)-O(3) bond length is 2.07 Å. The V(4)-O(6) bond length is 2.01 Å. There is one shorter (2.08 Å) and one longer (2.09 Å) V(4)-O(2) bond length. There is one shorter (2.02 Å) and one longer (2.03 Å) V(4)-O(7) bond length. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one V(3) and two equivalent V(1) atoms. In the second O site, O(2) is bonded to one Mg(1), one V(2), and two equivalent V(4) atoms to form distorted OMgV3 trigonal pyramids that share corners with two equivalent O(3)Mg2V3 square pyramids, corners with two equivalent O(2)MgV3 trigonal pyramids, corners with three equivalent O(7)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, and  an edgeedge with one O(7)MgV3 trigonal pyramid. In the third O site, O(3) is bonded to two equivalent Mg(1), one V(4), and two equivalent V(2) atoms to form OMg2V3 square pyramids that share corners with three equivalent O(6)Mg2V3 trigonal bipyramids, corners with two equivalent O(2)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids,  an edgeedge with one O(6)Mg2V3 trigonal bipyramid, edges with two equivalent O(2)MgV3 trigonal pyramids, and edges with two equivalent O(7)MgV3 trigonal pyramids. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one V(1) and two equivalent V(3) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one V(3) and two equivalent V(2) atoms. In the sixth O site, O(6) is bonded to two equivalent Mg(1), one V(4), and two equivalent V(1) atoms to form distorted OMg2V3 trigonal bipyramids that share corners with three equivalent O(3)Mg2V3 square pyramids, corners with two equivalent O(7)MgV3 trigonal pyramids,  an edgeedge with one O(3)Mg2V3 square pyramid, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, edges with two equivalent O(2)MgV3 trigonal pyramids, and edges with two equivalent O(7)MgV3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Mg(1), one V(1), and two equivalent V(4) atoms to form OMgV3 trigonal pyramids that share corners with two equivalent O(6)Mg2V3 trigonal bipyramids, corners with two equivalent O(7)MgV3 trigonal pyramids, corners with three equivalent O(2)MgV3 trigonal pyramids, edges with two equivalent O(3)Mg2V3 square pyramids, edges with two equivalent O(6)Mg2V3 trigonal bipyramids, and  an edgeedge with one O(2)MgV3 trigonal pyramid. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one V(2) and two equivalent V(3) atoms.