Mg3Ti2(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted TiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Ti(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 tetrahedra. In the second Ti site, Ti(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form TiO6 octahedra that share corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-50°. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Mg(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 68-70°. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Ti(2), and one Si(2) atom to form corner-sharing OMg2TiSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Ti(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Ti(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom.
Mg3Ti2(Si2O7)2 crystallizes in the monoclinic C2/c space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(4), and two equivalent O(7) atoms. The Mg(1)-O(1) bond length is 2.19 Å. The Mg(1)-O(2) bond length is 1.98 Å. The Mg(1)-O(4) bond length is 2.59 Å. There is one shorter (2.04 Å) and one longer (2.08 Å) Mg(1)-O(7) bond length. In the second Mg site, Mg(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted MgO4 tetrahedra that share corners with two equivalent Ti(2)O6 octahedra, corners with four equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles are 59°. Both Mg(2)-O(1) bond lengths are 2.15 Å. Both Mg(2)-O(3) bond lengths are 2.01 Å. There are two inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted TiO6 octahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, edges with two equivalent Ti(2)O6 octahedra, and  an edgeedge with one Mg(2)O4 tetrahedra. Both Ti(1)-O(2) bond lengths are 1.92 Å. Both Ti(1)-O(3) bond lengths are 2.18 Å. Both Ti(1)-O(4) bond lengths are 2.15 Å. In the second Ti site, Ti(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form TiO6 octahedra that share corners with two equivalent Mg(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Ti(1)O6 octahedra. Both Ti(2)-O(1) bond lengths are 2.27 Å. Both Ti(2)-O(2) bond lengths are 1.94 Å. Both Ti(2)-O(4) bond lengths are 2.09 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(4), one O(5), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 46-50°. The Si(1)-O(4) bond length is 1.63 Å. The Si(1)-O(5) bond length is 1.65 Å. The Si(1)-O(6) bond length is 1.65 Å. The Si(1)-O(7) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Mg(2)O4 tetrahedra, and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 68-70°. The Si(2)-O(1) bond length is 1.68 Å. The Si(2)-O(3) bond length is 1.62 Å. The Si(2)-O(5) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.67 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Mg(2), one Ti(2), and one Si(2) atom to form corner-sharing OMg2TiSi tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Mg(1), one Ti(1), and one Ti(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Mg(2), one Ti(1), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Mg(1), one Ti(1), one Ti(2), and one Si(1) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Si(1) atom.