Mg2Ti7O15 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-46°. In the second Mg site, Mg(2) is bonded to one O(3), one O(9), two equivalent O(6), and two equivalent O(8) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with four equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-46°. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(2) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Ti(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ti(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-48°. In the second Ti site, Ti(2) is bonded to one O(5), one O(9), two equivalent O(6), and two equivalent O(8) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Ti(3)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-51°. In the third Ti site, Ti(3) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Ti(2)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-49°. In the fourth Ti site, Ti(4) is bonded in a 6-coordinate geometry to one O(4), one O(9), two equivalent O(5), and two equivalent O(7) atoms. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a distorted T-shaped geometry to one Ti(1), one Ti(3), and one Ti(4) atom. In the second O site, O(8) is bonded to one Mg(2), one Ti(3), and two equivalent Ti(2) atoms to form OMgTi3 trigonal pyramids that share  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(3)Mg2Ti2 trigonal pyramid,  an edgeedge with one O(8)MgTi3 trigonal pyramid,  an edgeedge with one O(9)MgTi3 trigonal pyramid, and  an edgeedge with one O(5)Ti4 trigonal pyramid. In the third O site, O(9) is bonded to one Mg(2), one Ti(4), and two equivalent Ti(2) atoms to form distorted OMgTi3 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(4)MgTi3 trigonal pyramid, corners with two equivalent O(8)MgTi3 trigonal pyramids, edges with two equivalent O(8)MgTi3 trigonal pyramids, and edges with two equivalent O(5)Ti4 trigonal pyramids. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ti(1), and one Ti(3) atom. In the fifth O site, O(2) is bonded to one Mg(1), one Ti(3), and two equivalent Ti(1) atoms to form OMgTi3 trigonal pyramids that share  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(4)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(3)Mg2Ti2 trigonal pyramid,  an edgeedge with one O(2)MgTi3 trigonal pyramid,  an edgeedge with one O(4)MgTi3 trigonal pyramid, and  an edgeedge with one O(5)Ti4 trigonal pyramid. In the sixth O site, O(3) is bonded to one Mg(1), one Mg(2), and two equivalent Ti(3) atoms to form distorted OMg2Ti2 trigonal pyramids that share  a cornercorner with one O(4)MgTi3 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid, corners with two equivalent O(5)Ti4 trigonal pyramids, edges with two equivalent O(2)MgTi3 trigonal pyramids, and edges with two equivalent O(8)MgTi3 trigonal pyramids. In the seventh O site, O(4) is bonded to one Mg(1), one Ti(4), and two equivalent Ti(1) atoms to form distorted OMgTi3 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid, corners with two equivalent O(2)MgTi3 trigonal pyramids, edges with two equivalent O(2)MgTi3 trigonal pyramids, and edges with two equivalent O(5)Ti4 trigonal pyramids. In the eighth O site, O(5) is bonded to one Ti(1), one Ti(2), one Ti(3), and one Ti(4) atom to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(2)MgTi3 trigonal pyramid,  an edgeedge with one O(4)MgTi3 trigonal pyramid,  an edgeedge with one O(8)MgTi3 trigonal pyramid, and  an edgeedge with one O(9)MgTi3 trigonal pyramid. In the ninth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(2) and two equivalent Ti(2) atoms.
Mg2Ti7O15 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with four equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-46°. The Mg(1)-O(3) bond length is 2.05 Å. The Mg(1)-O(4) bond length is 2.09 Å. Both Mg(1)-O(1) bond lengths are 2.00 Å. Both Mg(1)-O(2) bond lengths are 2.17 Å. In the second Mg site, Mg(2) is bonded to one O(3), one O(9), two equivalent O(6), and two equivalent O(8) atoms to form distorted MgO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with four equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-46°. The Mg(2)-O(3) bond length is 2.05 Å. The Mg(2)-O(9) bond length is 2.09 Å. Both Mg(2)-O(6) bond lengths are 1.99 Å. Both Mg(2)-O(8) bond lengths are 2.17 Å. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(4), one O(5), one O(7), and two equivalent O(2) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Ti(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, and edges with two equivalent Ti(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-48°. The Ti(1)-O(1) bond length is 1.95 Å. The Ti(1)-O(4) bond length is 2.06 Å. The Ti(1)-O(5) bond length is 1.98 Å. The Ti(1)-O(7) bond length is 1.88 Å. There is one shorter (1.94 Å) and one longer (2.12 Å) Ti(1)-O(2) bond length. In the second Ti site, Ti(2) is bonded to one O(5), one O(9), two equivalent O(6), and two equivalent O(8) atoms to form distorted TiO6 octahedra that share  a cornercorner with one Mg(2)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Ti(3)O6 octahedra, edges with two equivalent Mg(2)O6 octahedra, and edges with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 27-51°. The Ti(2)-O(5) bond length is 1.97 Å. The Ti(2)-O(9) bond length is 2.07 Å. There is one shorter (1.82 Å) and one longer (1.96 Å) Ti(2)-O(6) bond length. There is one shorter (1.93 Å) and one longer (2.16 Å) Ti(2)-O(8) bond length. In the third Ti site, Ti(3) is bonded to one O(1), one O(2), one O(3), one O(5), one O(7), and one O(8) atom to form distorted TiO6 octahedra that share  a cornercorner with one Mg(1)O6 octahedra,  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra,  an edgeedge with one Mg(1)O6 octahedra,  an edgeedge with one Mg(2)O6 octahedra,  an edgeedge with one Ti(2)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 30-49°. The Ti(3)-O(1) bond length is 1.82 Å. The Ti(3)-O(2) bond length is 1.96 Å. The Ti(3)-O(3) bond length is 2.00 Å. The Ti(3)-O(5) bond length is 2.17 Å. The Ti(3)-O(7) bond length is 2.05 Å. The Ti(3)-O(8) bond length is 1.95 Å. In the fourth Ti site, Ti(4) is bonded in a 6-coordinate geometry to one O(4), one O(9), two equivalent O(5), and two equivalent O(7) atoms. The Ti(4)-O(4) bond length is 2.01 Å. The Ti(4)-O(9) bond length is 2.00 Å. Both Ti(4)-O(5) bond lengths are 2.15 Å. Both Ti(4)-O(7) bond lengths are 1.94 Å. There are nine inequivalent O sites. In the first O site, O(7) is bonded in a distorted T-shaped geometry to one Ti(1), one Ti(3), and one Ti(4) atom. In the second O site, O(8) is bonded to one Mg(2), one Ti(3), and two equivalent Ti(2) atoms to form OMgTi3 trigonal pyramids that share  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(3)Mg2Ti2 trigonal pyramid,  an edgeedge with one O(8)MgTi3 trigonal pyramid,  an edgeedge with one O(9)MgTi3 trigonal pyramid, and  an edgeedge with one O(5)Ti4 trigonal pyramid. In the third O site, O(9) is bonded to one Mg(2), one Ti(4), and two equivalent Ti(2) atoms to form distorted OMgTi3 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(4)MgTi3 trigonal pyramid, corners with two equivalent O(8)MgTi3 trigonal pyramids, edges with two equivalent O(8)MgTi3 trigonal pyramids, and edges with two equivalent O(5)Ti4 trigonal pyramids. In the fourth O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Mg(1), one Ti(1), and one Ti(3) atom. In the fifth O site, O(2) is bonded to one Mg(1), one Ti(3), and two equivalent Ti(1) atoms to form OMgTi3 trigonal pyramids that share  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(4)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(3)Mg2Ti2 trigonal pyramid,  an edgeedge with one O(2)MgTi3 trigonal pyramid,  an edgeedge with one O(4)MgTi3 trigonal pyramid, and  an edgeedge with one O(5)Ti4 trigonal pyramid. In the sixth O site, O(3) is bonded to one Mg(1), one Mg(2), and two equivalent Ti(3) atoms to form distorted OMg2Ti2 trigonal pyramids that share  a cornercorner with one O(4)MgTi3 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid, corners with two equivalent O(5)Ti4 trigonal pyramids, edges with two equivalent O(2)MgTi3 trigonal pyramids, and edges with two equivalent O(8)MgTi3 trigonal pyramids. In the seventh O site, O(4) is bonded to one Mg(1), one Ti(4), and two equivalent Ti(1) atoms to form distorted OMgTi3 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(9)MgTi3 trigonal pyramid, corners with two equivalent O(2)MgTi3 trigonal pyramids, edges with two equivalent O(2)MgTi3 trigonal pyramids, and edges with two equivalent O(5)Ti4 trigonal pyramids. In the eighth O site, O(5) is bonded to one Ti(1), one Ti(2), one Ti(3), and one Ti(4) atom to form distorted OTi4 trigonal pyramids that share  a cornercorner with one O(3)Mg2Ti2 trigonal pyramid,  a cornercorner with one O(2)MgTi3 trigonal pyramid,  a cornercorner with one O(8)MgTi3 trigonal pyramid,  a cornercorner with one O(5)Ti4 trigonal pyramid,  an edgeedge with one O(2)MgTi3 trigonal pyramid,  an edgeedge with one O(4)MgTi3 trigonal pyramid,  an edgeedge with one O(8)MgTi3 trigonal pyramid, and  an edgeedge with one O(9)MgTi3 trigonal pyramid. In the ninth O site, O(6) is bonded in a distorted T-shaped geometry to one Mg(2) and two equivalent Ti(2) atoms.