Mg3W3As4O16 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form MgO4 trigonal pyramids that share corners with two equivalent W(1)O5 trigonal bipyramids. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share edges with two equivalent W(1)O5 trigonal bipyramids. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(4), one O(7), and one O(8) atom to form WO5 trigonal bipyramids that share corners with two equivalent Mg(1)O4 trigonal pyramids and  an edgeedge with one Mg(2)O6 octahedra. In the second W site, W(2) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. There are two inequivalent As sites. In the first As site, As(1) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(6), and one O(8) atom. In the second As site, As(2) is bonded in a water-like geometry to one O(2) and one O(3) atom. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the second O site, O(8) is bonded in a trigonal planar geometry to one Mg(2), one W(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2), one W(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one As(1), and one As(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom.
Mg3W3As4O16 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(1), one O(3), one O(4), and one O(5) atom to form MgO4 trigonal pyramids that share corners with two equivalent W(1)O5 trigonal bipyramids. The Mg(1)-O(1) bond length is 1.96 Å. The Mg(1)-O(3) bond length is 2.08 Å. The Mg(1)-O(4) bond length is 1.95 Å. The Mg(1)-O(5) bond length is 1.94 Å. In the second Mg site, Mg(2) is bonded to two equivalent O(2), two equivalent O(6), and two equivalent O(8) atoms to form MgO6 octahedra that share edges with two equivalent W(1)O5 trigonal bipyramids. Both Mg(2)-O(2) bond lengths are 2.05 Å. Both Mg(2)-O(6) bond lengths are 2.14 Å. Both Mg(2)-O(8) bond lengths are 2.10 Å. There are two inequivalent W sites. In the first W site, W(1) is bonded to one O(1), one O(2), one O(4), one O(7), and one O(8) atom to form WO5 trigonal bipyramids that share corners with two equivalent Mg(1)O4 trigonal pyramids and  an edgeedge with one Mg(2)O6 octahedra. The W(1)-O(1) bond length is 1.84 Å. The W(1)-O(2) bond length is 2.16 Å. The W(1)-O(4) bond length is 1.81 Å. The W(1)-O(7) bond length is 1.87 Å. The W(1)-O(8) bond length is 1.87 Å. In the second W site, W(2) is bonded in a square co-planar geometry to two equivalent O(5) and two equivalent O(7) atoms. Both W(2)-O(5) bond lengths are 1.88 Å. Both W(2)-O(7) bond lengths are 2.08 Å. There are two inequivalent As sites. In the first As site, As(1) is bonded in a distorted trigonal non-coplanar geometry to one O(3), one O(6), and one O(8) atom. The As(1)-O(3) bond length is 1.97 Å. The As(1)-O(6) bond length is 1.68 Å. The As(1)-O(8) bond length is 2.17 Å. In the second As site, As(2) is bonded in a water-like geometry to one O(2) and one O(3) atom. The As(2)-O(2) bond length is 1.79 Å. The As(2)-O(3) bond length is 1.90 Å. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a bent 150 degrees geometry to one W(1) and one W(2) atom. In the second O site, O(8) is bonded in a trigonal planar geometry to one Mg(2), one W(1), and one As(1) atom. In the third O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the fourth O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2), one W(1), and one As(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to one Mg(1), one As(1), and one As(2) atom. In the sixth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(1) atom. In the seventh O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one W(2) atom. In the eighth O site, O(6) is bonded in a bent 150 degrees geometry to one Mg(2) and one As(1) atom.