MgMo3O7 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted MgO5 square pyramids that share  a cornercorner with one Mo(2)O5 trigonal bipyramid, corners with six equivalent Mo(1)O5 trigonal bipyramids, and  an edgeedge with one Mo(2)O5 trigonal bipyramid. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO5 trigonal bipyramids that share corners with three equivalent Mg(1)O5 square pyramids, corners with two equivalent Mo(2)O5 trigonal bipyramids,  an edgeedge with one Mo(2)O5 trigonal bipyramid, and edges with two equivalent Mo(1)O5 trigonal bipyramids. In the second Mo site, Mo(2) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 square pyramid, corners with four equivalent Mo(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 square pyramid, and edges with two equivalent Mo(1)O5 trigonal bipyramids. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the third O site, O(1) is bonded to one Mg(1), one Mo(2), and two equivalent Mo(1) atoms to form a mixture of distorted edge and corner-sharing OMgMo3 tetrahedra. In the fourth O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mo(2) and two equivalent Mo(1) atoms.
MgMo3O7 crystallizes in the orthorhombic Pnma space group. Mg(1) is bonded to one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted MgO5 square pyramids that share  a cornercorner with one Mo(2)O5 trigonal bipyramid, corners with six equivalent Mo(1)O5 trigonal bipyramids, and  an edgeedge with one Mo(2)O5 trigonal bipyramid. The Mg(1)-O(3) bond length is 2.02 Å. Both Mg(1)-O(1) bond lengths are 2.36 Å. Both Mg(1)-O(4) bond lengths are 2.01 Å. There are two inequivalent Mo sites. In the first Mo site, Mo(1) is bonded to one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO5 trigonal bipyramids that share corners with three equivalent Mg(1)O5 square pyramids, corners with two equivalent Mo(2)O5 trigonal bipyramids,  an edgeedge with one Mo(2)O5 trigonal bipyramid, and edges with two equivalent Mo(1)O5 trigonal bipyramids. The Mo(1)-O(4) bond length is 1.83 Å. There is one shorter (2.09 Å) and one longer (2.14 Å) Mo(1)-O(1) bond length. There is one shorter (2.09 Å) and one longer (2.11 Å) Mo(1)-O(2) bond length. In the second Mo site, Mo(2) is bonded to one O(3), two equivalent O(1), and two equivalent O(2) atoms to form distorted MoO5 trigonal bipyramids that share  a cornercorner with one Mg(1)O5 square pyramid, corners with four equivalent Mo(1)O5 trigonal bipyramids,  an edgeedge with one Mg(1)O5 square pyramid, and edges with two equivalent Mo(1)O5 trigonal bipyramids. The Mo(2)-O(3) bond length is 1.84 Å. Both Mo(2)-O(1) bond lengths are 2.13 Å. Both Mo(2)-O(2) bond lengths are 2.04 Å. There are four inequivalent O sites. In the first O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Mo(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Mo(1) atom. In the third O site, O(1) is bonded to one Mg(1), one Mo(2), and two equivalent Mo(1) atoms to form a mixture of distorted edge and corner-sharing OMgMo3 tetrahedra. In the fourth O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Mo(2) and two equivalent Mo(1) atoms.