TiNb2O7 crystallizes in the monoclinic Cm space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(13), one O(15), one O(3), one O(7), and two equivalent O(11) atoms. In the second Ti site, Ti(2) is bonded to one O(1), one O(17), one O(21), one O(5), and two equivalent O(9) atoms to form TiO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-10°. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(12), one O(14), one O(4), one O(6), and two equivalent O(10) atoms. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(16), one O(7), and two equivalent O(4) atoms. In the second Nb site, Nb(2) is bonded to one O(19), one O(20), one O(5), one O(8), and two equivalent O(2) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and edges with two equivalent Nb(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-32°. In the third Nb site, Nb(3) is bonded to one O(11), one O(16), one O(18), one O(8), and two equivalent O(13) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 11-35°. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(15), one O(19), one O(7), and two equivalent O(12) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-29°. In the fifth Nb site, Nb(5) is bonded to one O(14), one O(17), one O(2), one O(3), and two equivalent O(20) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 9-33°. In the sixth Nb site, Nb(6) is bonded in a 6-coordinate geometry to one O(13), one O(15), one O(21), one O(6), and two equivalent O(18) atoms. There are twenty-one inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Ti(2) and one Nb(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Ti(1) and one Nb(5) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a linear geometry to one Ti(2) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ti(3) and one Nb(6) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ti(1), one Nb(1), and one Nb(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the ninth O site, O(9) is bonded in a linear geometry to two equivalent Ti(2) atoms. In the tenth O site, O(10) is bonded to two equivalent Ti(3), one Nb(1), and one Nb(4) atom to form distorted corner-sharing OTi2Nb2 tetrahedra. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to two equivalent Ti(1) and one Nb(3) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Nb(4) atoms. In the thirteenth O site, O(13) is bonded to one Ti(1), one Nb(6), and two equivalent Nb(3) atoms to form distorted corner-sharing OTiNb3 tetrahedra. In the fourteenth O site, O(14) is bonded in a linear geometry to one Ti(3) and one Nb(5) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Ti(1), one Nb(4), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a linear geometry to one Nb(1) and one Nb(3) atom. In the seventeenth O site, O(17) is bonded in a linear geometry to one Ti(2) and one Nb(5) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent Nb(6) atoms. In the nineteenth O site, O(19) is bonded in a linear geometry to one Nb(2) and one Nb(4) atom. In the twentieth O site, O(20) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(5) atoms. In the twenty-first O site, O(21) is bonded in a linear geometry to one Ti(2) and one Nb(6) atom.
TiNb2O7 crystallizes in the monoclinic Cm space group. There are three inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a 6-coordinate geometry to one O(13), one O(15), one O(3), one O(7), and two equivalent O(11) atoms. The Ti(1)-O(13) bond length is 2.27 Å. The Ti(1)-O(15) bond length is 2.40 Å. The Ti(1)-O(3) bond length is 1.78 Å. The Ti(1)-O(7) bond length is 1.89 Å. Both Ti(1)-O(11) bond lengths are 1.98 Å. In the second Ti site, Ti(2) is bonded to one O(1), one O(17), one O(21), one O(5), and two equivalent O(9) atoms to form TiO6 octahedra that share  a cornercorner with one Nb(2)O6 octahedra,  a cornercorner with one Nb(5)O6 octahedra, and corners with two equivalent Ti(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-10°. The Ti(2)-O(1) bond length is 2.06 Å. The Ti(2)-O(17) bond length is 1.95 Å. The Ti(2)-O(21) bond length is 2.07 Å. The Ti(2)-O(5) bond length is 1.98 Å. Both Ti(2)-O(9) bond lengths are 1.91 Å. In the third Ti site, Ti(3) is bonded in a 6-coordinate geometry to one O(12), one O(14), one O(4), one O(6), and two equivalent O(10) atoms. The Ti(3)-O(12) bond length is 2.23 Å. The Ti(3)-O(14) bond length is 1.77 Å. The Ti(3)-O(4) bond length is 2.31 Å. The Ti(3)-O(6) bond length is 1.84 Å. Both Ti(3)-O(10) bond lengths are 2.02 Å. There are six inequivalent Nb sites. In the first Nb site, Nb(1) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(16), one O(7), and two equivalent O(4) atoms. The Nb(1)-O(1) bond length is 1.80 Å. The Nb(1)-O(10) bond length is 2.42 Å. The Nb(1)-O(16) bond length is 2.05 Å. The Nb(1)-O(7) bond length is 2.07 Å. Both Nb(1)-O(4) bond lengths are 1.99 Å. In the second Nb site, Nb(2) is bonded to one O(19), one O(20), one O(5), one O(8), and two equivalent O(2) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra,  a cornercorner with one Nb(3)O6 octahedra,  a cornercorner with one Nb(4)O6 octahedra, corners with two equivalent Nb(2)O6 octahedra, and edges with two equivalent Nb(5)O6 octahedra. The corner-sharing octahedral tilt angles range from 3-32°. The Nb(2)-O(19) bond length is 2.00 Å. The Nb(2)-O(20) bond length is 2.31 Å. The Nb(2)-O(5) bond length is 1.80 Å. The Nb(2)-O(8) bond length is 2.04 Å. Both Nb(2)-O(2) bond lengths are 1.99 Å. In the third Nb site, Nb(3) is bonded to one O(11), one O(16), one O(18), one O(8), and two equivalent O(13) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 11-35°. The Nb(3)-O(11) bond length is 2.20 Å. The Nb(3)-O(16) bond length is 1.87 Å. The Nb(3)-O(18) bond length is 2.28 Å. The Nb(3)-O(8) bond length is 1.83 Å. Both Nb(3)-O(13) bond lengths are 2.01 Å. In the fourth Nb site, Nb(4) is bonded to one O(10), one O(15), one O(19), one O(7), and two equivalent O(12) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles range from 3-29°. The Nb(4)-O(10) bond length is 2.24 Å. The Nb(4)-O(15) bond length is 1.89 Å. The Nb(4)-O(19) bond length is 1.87 Å. The Nb(4)-O(7) bond length is 2.28 Å. Both Nb(4)-O(12) bond lengths are 1.98 Å. In the fifth Nb site, Nb(5) is bonded to one O(14), one O(17), one O(2), one O(3), and two equivalent O(20) atoms to form distorted NbO6 octahedra that share  a cornercorner with one Ti(2)O6 octahedra, corners with two equivalent Nb(5)O6 octahedra, and edges with two equivalent Nb(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 9-33°. The Nb(5)-O(14) bond length is 2.04 Å. The Nb(5)-O(17) bond length is 1.81 Å. The Nb(5)-O(2) bond length is 2.33 Å. The Nb(5)-O(3) bond length is 2.03 Å. Both Nb(5)-O(20) bond lengths are 2.00 Å. In the sixth Nb site, Nb(6) is bonded in a 6-coordinate geometry to one O(13), one O(15), one O(21), one O(6), and two equivalent O(18) atoms. The Nb(6)-O(13) bond length is 2.46 Å. The Nb(6)-O(15) bond length is 2.16 Å. The Nb(6)-O(21) bond length is 1.80 Å. The Nb(6)-O(6) bond length is 1.94 Å. Both Nb(6)-O(18) bond lengths are 2.01 Å. There are twenty-one inequivalent O sites. In the first O site, O(1) is bonded in a linear geometry to one Ti(2) and one Nb(1) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Nb(5) and two equivalent Nb(2) atoms. In the third O site, O(3) is bonded in a linear geometry to one Ti(1) and one Nb(5) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Nb(1) atoms. In the fifth O site, O(5) is bonded in a linear geometry to one Ti(2) and one Nb(2) atom. In the sixth O site, O(6) is bonded in a linear geometry to one Ti(3) and one Nb(6) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Ti(1), one Nb(1), and one Nb(4) atom. In the eighth O site, O(8) is bonded in a linear geometry to one Nb(2) and one Nb(3) atom. In the ninth O site, O(9) is bonded in a linear geometry to two equivalent Ti(2) atoms. In the tenth O site, O(10) is bonded to two equivalent Ti(3), one Nb(1), and one Nb(4) atom to form distorted corner-sharing OTi2Nb2 tetrahedra. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to two equivalent Ti(1) and one Nb(3) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Ti(3) and two equivalent Nb(4) atoms. In the thirteenth O site, O(13) is bonded to one Ti(1), one Nb(6), and two equivalent Nb(3) atoms to form distorted corner-sharing OTiNb3 tetrahedra. In the fourteenth O site, O(14) is bonded in a linear geometry to one Ti(3) and one Nb(5) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Ti(1), one Nb(4), and one Nb(6) atom. In the sixteenth O site, O(16) is bonded in a linear geometry to one Nb(1) and one Nb(3) atom. In the seventeenth O site, O(17) is bonded in a linear geometry to one Ti(2) and one Nb(5) atom. In the eighteenth O site, O(18) is bonded in a 3-coordinate geometry to one Nb(3) and two equivalent Nb(6) atoms. In the nineteenth O site, O(19) is bonded in a linear geometry to one Nb(2) and one Nb(4) atom. In the twentieth O site, O(20) is bonded in a 3-coordinate geometry to one Nb(2) and two equivalent Nb(5) atoms. In the twenty-first O site, O(21) is bonded in a linear geometry to one Ti(2) and one Nb(6) atom.