MgMoO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mo(1)O4 tetrahedra, corners with four equivalent Mo(2)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mo(2)O4 tetrahedra, corners with four equivalent Mo(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form MoO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-60°. In the second Mo site, Mo(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form MoO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-57°. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Mg(2) and one Mo(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Mg(2), and one Mo(1) atom to form distorted edge-sharing OMg3Mo tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Mo(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(2) atom.
MgMoO4 crystallizes in the monoclinic C2/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form MgO6 octahedra that share corners with two equivalent Mo(1)O4 tetrahedra, corners with four equivalent Mo(2)O4 tetrahedra, and edges with two equivalent Mg(2)O6 octahedra. The Mg(1)-O(1) bond length is 2.03 Å. The Mg(1)-O(3) bond length is 2.14 Å. Both Mg(1)-O(4) bond lengths are 2.11 Å. Both Mg(1)-O(5) bond lengths are 2.06 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with two equivalent Mo(2)O4 tetrahedra, corners with four equivalent Mo(1)O4 tetrahedra,  an edgeedge with one Mg(2)O6 octahedra, and edges with two equivalent Mg(1)O6 octahedra. Both Mg(2)-O(2) bond lengths are 2.04 Å. Both Mg(2)-O(3) bond lengths are 2.15 Å. Both Mg(2)-O(4) bond lengths are 2.07 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form MoO4 tetrahedra that share corners with two equivalent Mg(1)O6 octahedra and corners with four equivalent Mg(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-60°. The Mo(1)-O(1) bond length is 1.76 Å. The Mo(1)-O(3) bond length is 1.84 Å. Both Mo(1)-O(2) bond lengths are 1.73 Å. In the second Mo site, Mo(2) is bonded to two equivalent O(4) and two equivalent O(5) atoms to form MoO4 tetrahedra that share corners with two equivalent Mg(2)O6 octahedra and corners with four equivalent Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 19-57°. Both Mo(2)-O(4) bond lengths are 1.80 Å. Both Mo(2)-O(5) bond lengths are 1.74 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Mg(2) and one Mo(1) atom. In the third O site, O(3) is bonded to one Mg(1), two equivalent Mg(2), and one Mo(1) atom to form distorted edge-sharing OMg3Mo tetrahedra. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Mg(1), one Mg(2), and one Mo(2) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(2) atom.