MgWP2O7 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form MgO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent W(1)O5 square pyramids. W(1) is bonded to one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted WO5 square pyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent W(1)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent W(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one W(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one W(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Mg(1), one W(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one W(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one W(1), and one P(1) atom.
MgWP2O7 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded to one O(2), one O(3), one O(5), one O(6), and one O(7) atom to form MgO5 trigonal bipyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent W(1)O5 square pyramids. The Mg(1)-O(2) bond length is 1.96 Å. The Mg(1)-O(3) bond length is 2.12 Å. The Mg(1)-O(5) bond length is 2.06 Å. The Mg(1)-O(6) bond length is 2.08 Å. The Mg(1)-O(7) bond length is 2.12 Å. W(1) is bonded to one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form distorted WO5 square pyramids that share corners with two equivalent P(1)O4 tetrahedra, corners with three equivalent P(2)O4 tetrahedra, and edges with two equivalent Mg(1)O5 trigonal bipyramids. The W(1)-O(3) bond length is 2.23 Å. The W(1)-O(4) bond length is 2.15 Å. The W(1)-O(5) bond length is 2.70 Å. The W(1)-O(6) bond length is 2.25 Å. The W(1)-O(7) bond length is 2.20 Å. There are two inequivalent P sites. In the first P site, P(1) is bonded to one O(1), one O(2), one O(4), and one O(7) atom to form PO4 tetrahedra that share corners with two equivalent W(1)O5 square pyramids,  a cornercorner with one P(2)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. The P(1)-O(1) bond length is 1.63 Å. The P(1)-O(2) bond length is 1.51 Å. The P(1)-O(4) bond length is 1.51 Å. The P(1)-O(7) bond length is 1.56 Å. In the second P site, P(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form PO4 tetrahedra that share corners with three equivalent W(1)O5 square pyramids,  a cornercorner with one P(1)O4 tetrahedra, and corners with three equivalent Mg(1)O5 trigonal bipyramids. The P(2)-O(1) bond length is 1.59 Å. The P(2)-O(3) bond length is 1.56 Å. The P(2)-O(5) bond length is 1.51 Å. The P(2)-O(6) bond length is 1.55 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one P(1) and one P(2) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(1) and one P(1) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Mg(1), one W(1), and one P(2) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one W(1) and one P(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Mg(1), one W(1), and one P(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Mg(1), one W(1), and one P(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Mg(1), one W(1), and one P(1) atom.