Mg3(VO4)2 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra and edges with four equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. V(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form VO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with six equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one V(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one V(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(2) and one V(1) atom.
Mg3(VO4)2 crystallizes in the orthorhombic Cmce space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form MgO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra and edges with four equivalent Mg(2)O6 octahedra. Both Mg(1)-O(2) bond lengths are 2.04 Å. All Mg(1)-O(1) bond lengths are 2.12 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form MgO6 octahedra that share corners with six equivalent V(1)O4 tetrahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Mg(2)O6 octahedra. Both Mg(2)-O(1) bond lengths are 2.09 Å. Both Mg(2)-O(2) bond lengths are 2.15 Å. Both Mg(2)-O(3) bond lengths are 2.02 Å. V(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form VO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with six equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 50-57°. The V(1)-O(2) bond length is 1.80 Å. The V(1)-O(3) bond length is 1.72 Å. Both V(1)-O(1) bond lengths are 1.71 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one V(1) atom. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Mg(1), two equivalent Mg(2), and one V(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to two equivalent Mg(2) and one V(1) atom.