Mg3Sn2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form distorted MgO4 trigonal pyramids that share corners with eight equivalent Sn(1)O6 octahedra and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 63-83°. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to one O(2), one O(3), and three equivalent O(1) atoms. Sn(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form SnO6 octahedra that share corners with five equivalent Sn(1)O6 octahedra and corners with four equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 46-47°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(2) and one Sn(1) atom to form OMg3Sn tetrahedra that share  a cornercorner with one O(4)Mg2Sn2 tetrahedra and corners with six equivalent O(1)Mg3Sn tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2) and two equivalent Sn(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), and two equivalent Sn(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form distorted OMg2Sn2 tetrahedra that share corners with two equivalent O(4)Mg2Sn2 tetrahedra and corners with two equivalent O(1)Mg3Sn tetrahedra.
Mg3Sn2O7 crystallizes in the orthorhombic Cmc2_1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(3) and two equivalent O(4) atoms to form distorted MgO4 trigonal pyramids that share corners with eight equivalent Sn(1)O6 octahedra and corners with two equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 63-83°. Both Mg(1)-O(3) bond lengths are 2.05 Å. There is one shorter (2.08 Å) and one longer (2.15 Å) Mg(1)-O(4) bond length. In the second Mg site, Mg(2) is bonded in a 4-coordinate geometry to one O(2), one O(3), and three equivalent O(1) atoms. The Mg(2)-O(2) bond length is 2.06 Å. The Mg(2)-O(3) bond length is 2.48 Å. There are a spread of Mg(2)-O(1) bond distances ranging from 2.02-2.09 Å. Sn(1) is bonded to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms to form SnO6 octahedra that share corners with five equivalent Sn(1)O6 octahedra and corners with four equivalent Mg(1)O4 trigonal pyramids. The corner-sharing octahedral tilt angles range from 46-47°. The Sn(1)-O(1) bond length is 2.07 Å. The Sn(1)-O(4) bond length is 2.13 Å. There is one shorter (2.06 Å) and one longer (2.10 Å) Sn(1)-O(2) bond length. There is one shorter (2.10 Å) and one longer (2.12 Å) Sn(1)-O(3) bond length. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Mg(2) and one Sn(1) atom to form OMg3Sn tetrahedra that share  a cornercorner with one O(4)Mg2Sn2 tetrahedra and corners with six equivalent O(1)Mg3Sn tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(2) and two equivalent Sn(1) atoms. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1), one Mg(2), and two equivalent Sn(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Mg(1) and two equivalent Sn(1) atoms to form distorted OMg2Sn2 tetrahedra that share corners with two equivalent O(4)Mg2Sn2 tetrahedra and corners with two equivalent O(1)Mg3Sn tetrahedra.