Ti7O8 crystallizes in the monoclinic Cm space group. There are seven inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(7), one O(8), and two equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra,  a cornercorner with one Ti(7)O5 square pyramid,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(2)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, edges with three equivalent Ti(5)O6 octahedra, and edges with two equivalent Ti(6)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 7-13°. In the second Ti site, Ti(2) is bonded to one O(1), one O(3), one O(6), one O(8), and two equivalent O(4) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(5)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(1)O6 octahedra, edges with two equivalent Ti(5)O6 octahedra, edges with three equivalent Ti(3)O6 octahedra, and edges with three equivalent Ti(7)O5 square pyramids. The corner-sharing octahedral tilt angles range from 1-18°. In the third Ti site, Ti(3) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(8) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra,  a cornercorner with one Ti(7)O5 square pyramid,  a cornercorner with one Ti(6)O5 trigonal bipyramid, edges with two equivalent Ti(1)O6 octahedra, edges with three equivalent Ti(2)O6 octahedra, edges with three equivalent Ti(5)O6 octahedra, and edges with two equivalent Ti(7)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-17°. In the fourth Ti site, Ti(4) is bonded in a rectangular see-saw-like geometry to one O(2), one O(3), one O(6), and one O(7) atom. In the fifth Ti site, Ti(5) is bonded to one O(4), one O(5), one O(7), one O(8), and two equivalent O(1) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(5)O6 octahedra, edges with two equivalent Ti(2)O6 octahedra, edges with three equivalent Ti(1)O6 octahedra, edges with three equivalent Ti(3)O6 octahedra,  an edgeedge with one Ti(7)O5 square pyramid, and  an edgeedge with one Ti(6)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 1-19°. In the sixth Ti site, Ti(6) is bonded to one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form TiO5 trigonal bipyramids 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,  a cornercorner with one Ti(7)O5 square pyramid, corners with two equivalent Ti(6)O5 trigonal bipyramids,  an edgeedge with one Ti(5)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-17°. In the seventh Ti site, Ti(7) is bonded to one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form distorted TiO5 square pyramids that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(7)O5 square pyramids,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(5)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with three equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-15°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ti(1), one Ti(2), one Ti(3), and two equivalent Ti(5) atoms to form OTi5 square pyramids that share  a cornercorner with one O(4)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, corners with two equivalent O(1)Ti5 square pyramids, edges with three equivalent O(8)Ti6 octahedra,  an edgeedge with one O(3)Ti5 square pyramid, edges with two equivalent O(4)Ti5 square pyramids, and edges with two equivalent O(5)Ti5 square pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ti(1), one Ti(4), and two equivalent Ti(6) atoms. In the third O site, O(3) is bonded to one Ti(2), one Ti(3), one Ti(4), and two equivalent Ti(7) atoms to form OTi5 square pyramids that share  a cornercorner with one O(8)Ti6 octahedra,  a cornercorner with one O(4)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, corners with two equivalent O(3)Ti5 square pyramids, edges with two equivalent O(8)Ti6 octahedra,  an edgeedge with one O(1)Ti5 square pyramid, and edges with two equivalent O(4)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 8°. In the fourth O site, O(4) is bonded to one Ti(3), one Ti(5), one Ti(7), and two equivalent Ti(2) atoms to form OTi5 square pyramids that share  a cornercorner with one O(1)Ti5 square pyramid,  a cornercorner with one O(3)Ti5 square pyramid, corners with two equivalent O(4)Ti5 square pyramids, edges with three equivalent O(8)Ti6 octahedra,  an edgeedge with one O(5)Ti5 square pyramid, edges with two equivalent O(1)Ti5 square pyramids, and edges with two equivalent O(3)Ti5 square pyramids. In the fifth O site, O(5) is bonded to one Ti(3), one Ti(5), one Ti(6), and two equivalent Ti(1) atoms to form OTi5 square pyramids that share  a cornercorner with one O(8)Ti6 octahedra,  a cornercorner with one O(1)Ti5 square pyramid,  a cornercorner with one O(3)Ti5 square pyramid, corners with two equivalent O(5)Ti5 square pyramids, edges with two equivalent O(8)Ti6 octahedra,  an edgeedge with one O(4)Ti5 square pyramid, and edges with two equivalent O(1)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 7°. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ti(2), one Ti(4), one Ti(6), and one Ti(7) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ti(1), one Ti(4), one Ti(5), and one Ti(6) atom. In the eighth O site, O(8) is bonded to one Ti(1), one Ti(2), one Ti(5), one Ti(7), and two equivalent Ti(3) atoms to form OTi6 octahedra that share corners with two equivalent O(8)Ti6 octahedra,  a cornercorner with one O(3)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, edges with two equivalent O(3)Ti5 square pyramids, edges with two equivalent O(5)Ti5 square pyramids, edges with three equivalent O(1)Ti5 square pyramids, and edges with three equivalent O(4)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 17°.
Ti7O8 crystallizes in the monoclinic Cm space group. There are seven inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to one O(1), one O(2), one O(7), one O(8), and two equivalent O(5) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(1)O6 octahedra,  a cornercorner with one Ti(7)O5 square pyramid,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(2)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, edges with three equivalent Ti(5)O6 octahedra, and edges with two equivalent Ti(6)O5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 7-13°. The Ti(1)-O(1) bond length is 2.13 Å. The Ti(1)-O(2) bond length is 2.02 Å. The Ti(1)-O(7) bond length is 2.21 Å. The Ti(1)-O(8) bond length is 2.11 Å. Both Ti(1)-O(5) bond lengths are 2.07 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(3), one O(6), one O(8), and two equivalent O(4) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(5)O6 octahedra, corners with two equivalent Ti(2)O6 octahedra,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(1)O6 octahedra, edges with two equivalent Ti(5)O6 octahedra, edges with three equivalent Ti(3)O6 octahedra, and edges with three equivalent Ti(7)O5 square pyramids. The corner-sharing octahedral tilt angles range from 1-18°. The Ti(2)-O(1) bond length is 2.16 Å. The Ti(2)-O(3) bond length is 2.16 Å. The Ti(2)-O(6) bond length is 2.02 Å. The Ti(2)-O(8) bond length is 2.19 Å. Both Ti(2)-O(4) bond lengths are 2.08 Å. In the third Ti site, Ti(3) is bonded to one O(1), one O(3), one O(4), one O(5), and two equivalent O(8) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(1)O6 octahedra, corners with two equivalent Ti(3)O6 octahedra,  a cornercorner with one Ti(7)O5 square pyramid,  a cornercorner with one Ti(6)O5 trigonal bipyramid, edges with two equivalent Ti(1)O6 octahedra, edges with three equivalent Ti(2)O6 octahedra, edges with three equivalent Ti(5)O6 octahedra, and edges with two equivalent Ti(7)O5 square pyramids. The corner-sharing octahedral tilt angles range from 7-17°. The Ti(3)-O(1) bond length is 2.22 Å. The Ti(3)-O(3) bond length is 2.17 Å. The Ti(3)-O(4) bond length is 2.10 Å. The Ti(3)-O(5) bond length is 2.08 Å. Both Ti(3)-O(8) bond lengths are 2.07 Å. In the fourth Ti site, Ti(4) is bonded in a rectangular see-saw-like geometry to one O(2), one O(3), one O(6), and one O(7) atom. The Ti(4)-O(2) bond length is 2.01 Å. The Ti(4)-O(3) bond length is 2.11 Å. The Ti(4)-O(6) bond length is 2.01 Å. The Ti(4)-O(7) bond length is 2.01 Å. In the fifth Ti site, Ti(5) is bonded to one O(4), one O(5), one O(7), one O(8), and two equivalent O(1) atoms to form TiO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Ti(5)O6 octahedra, edges with two equivalent Ti(2)O6 octahedra, edges with three equivalent Ti(1)O6 octahedra, edges with three equivalent Ti(3)O6 octahedra,  an edgeedge with one Ti(7)O5 square pyramid, and  an edgeedge with one Ti(6)O5 trigonal bipyramid. The corner-sharing octahedral tilt angles range from 1-19°. The Ti(5)-O(4) bond length is 2.17 Å. The Ti(5)-O(5) bond length is 2.12 Å. The Ti(5)-O(7) bond length is 2.04 Å. The Ti(5)-O(8) bond length is 2.17 Å. Both Ti(5)-O(1) bond lengths are 2.08 Å. In the sixth Ti site, Ti(6) is bonded to one O(5), one O(6), one O(7), and two equivalent O(2) atoms to form TiO5 trigonal bipyramids 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,  a cornercorner with one Ti(7)O5 square pyramid, corners with two equivalent Ti(6)O5 trigonal bipyramids,  an edgeedge with one Ti(5)O6 octahedra, and edges with two equivalent Ti(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-17°. The Ti(6)-O(5) bond length is 2.07 Å. The Ti(6)-O(6) bond length is 2.08 Å. The Ti(6)-O(7) bond length is 2.02 Å. Both Ti(6)-O(2) bond lengths are 2.08 Å. In the seventh Ti site, Ti(7) is bonded to one O(4), one O(6), one O(8), and two equivalent O(3) atoms to form distorted TiO5 square pyramids that share  a cornercorner with one Ti(1)O6 octahedra,  a cornercorner with one Ti(3)O6 octahedra, corners with two equivalent Ti(7)O5 square pyramids,  a cornercorner with one Ti(6)O5 trigonal bipyramid,  an edgeedge with one Ti(5)O6 octahedra, edges with two equivalent Ti(3)O6 octahedra, and edges with three equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 4-15°. The Ti(7)-O(4) bond length is 2.23 Å. The Ti(7)-O(6) bond length is 1.99 Å. The Ti(7)-O(8) bond length is 2.17 Å. Both Ti(7)-O(3) bond lengths are 2.07 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ti(1), one Ti(2), one Ti(3), and two equivalent Ti(5) atoms to form OTi5 square pyramids that share  a cornercorner with one O(4)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, corners with two equivalent O(1)Ti5 square pyramids, edges with three equivalent O(8)Ti6 octahedra,  an edgeedge with one O(3)Ti5 square pyramid, edges with two equivalent O(4)Ti5 square pyramids, and edges with two equivalent O(5)Ti5 square pyramids. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to one Ti(1), one Ti(4), and two equivalent Ti(6) atoms. In the third O site, O(3) is bonded to one Ti(2), one Ti(3), one Ti(4), and two equivalent Ti(7) atoms to form OTi5 square pyramids that share  a cornercorner with one O(8)Ti6 octahedra,  a cornercorner with one O(4)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, corners with two equivalent O(3)Ti5 square pyramids, edges with two equivalent O(8)Ti6 octahedra,  an edgeedge with one O(1)Ti5 square pyramid, and edges with two equivalent O(4)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 8°. In the fourth O site, O(4) is bonded to one Ti(3), one Ti(5), one Ti(7), and two equivalent Ti(2) atoms to form OTi5 square pyramids that share  a cornercorner with one O(1)Ti5 square pyramid,  a cornercorner with one O(3)Ti5 square pyramid, corners with two equivalent O(4)Ti5 square pyramids, edges with three equivalent O(8)Ti6 octahedra,  an edgeedge with one O(5)Ti5 square pyramid, edges with two equivalent O(1)Ti5 square pyramids, and edges with two equivalent O(3)Ti5 square pyramids. In the fifth O site, O(5) is bonded to one Ti(3), one Ti(5), one Ti(6), and two equivalent Ti(1) atoms to form OTi5 square pyramids that share  a cornercorner with one O(8)Ti6 octahedra,  a cornercorner with one O(1)Ti5 square pyramid,  a cornercorner with one O(3)Ti5 square pyramid, corners with two equivalent O(5)Ti5 square pyramids, edges with two equivalent O(8)Ti6 octahedra,  an edgeedge with one O(4)Ti5 square pyramid, and edges with two equivalent O(1)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 7°. In the sixth O site, O(6) is bonded in a rectangular see-saw-like geometry to one Ti(2), one Ti(4), one Ti(6), and one Ti(7) atom. In the seventh O site, O(7) is bonded in a rectangular see-saw-like geometry to one Ti(1), one Ti(4), one Ti(5), and one Ti(6) atom. In the eighth O site, O(8) is bonded to one Ti(1), one Ti(2), one Ti(5), one Ti(7), and two equivalent Ti(3) atoms to form OTi6 octahedra that share corners with two equivalent O(8)Ti6 octahedra,  a cornercorner with one O(3)Ti5 square pyramid,  a cornercorner with one O(5)Ti5 square pyramid, edges with two equivalent O(3)Ti5 square pyramids, edges with two equivalent O(5)Ti5 square pyramids, edges with three equivalent O(1)Ti5 square pyramids, and edges with three equivalent O(4)Ti5 square pyramids. The corner-sharing octahedral tilt angles are 17°.