Y2Ti2O7 crystallizes in the monoclinic P2 space group. There are six inequivalent Y sites. In the first Y site, Y(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(8) atoms. In the second Y site, Y(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(11), one O(4), one O(5), and one O(6) atom. In the third Y site, Y(3) is bonded in a 8-coordinate geometry to two equivalent O(14), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. In the fourth Y site, Y(4) is bonded in a 7-coordinate geometry to one O(12), one O(13), one O(14), one O(3), one O(7), one O(8), and one O(9) atom. In the fifth Y site, Y(5) is bonded in a 6-coordinate geometry to two equivalent O(13), two equivalent O(2), and two equivalent O(4) atoms. In the sixth Y site, Y(6) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(11), two equivalent O(12), and two equivalent O(5) atoms. There are six inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(12) atoms. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(14), one O(4), one O(5), and one O(8) atom. In the third Ti site, Ti(3) is bonded in a tetrahedral geometry to one O(11), one O(2), one O(3), and one O(7) atom. In the fourth Ti site, Ti(4) is bonded in a 6-coordinate geometry to two equivalent O(10), two equivalent O(7), and two equivalent O(8) atoms. In the fifth Ti site, Ti(5) is bonded to two equivalent O(14), two equivalent O(6), and two equivalent O(9) atoms to form corner-sharing TiO6 octahedra. In the sixth Ti site, Ti(6) is bonded to two equivalent O(13) and two equivalent O(9) atoms to form distorted corner-sharing TiO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 32°. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one Y(1), one Y(2), one Ti(1), and one Ti(2) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(13)Y2Ti2 tetrahedra,  a cornercorner with one O(8)Y2Ti2 tetrahedra, corners with two equivalent O(1)Y2Ti2 tetrahedra,  an edgeedge with one O(8)Y2Ti2 tetrahedra, and  an edgeedge with one O(4)Y3Ti tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Y(3), one Y(5), and one Ti(3) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Y(1), one Y(4), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one Y(2), one Y(3), one Y(5), and one Ti(2) atom to form OY3Ti tetrahedra that share  a cornercorner with one O(13)Y2Ti2 tetrahedra,  a cornercorner with one O(8)Y2Ti2 tetrahedra, corners with two equivalent O(4)Y3Ti tetrahedra,  an edgeedge with one O(1)Y2Ti2 tetrahedra, and  an edgeedge with one O(13)Y2Ti2 tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Y(2), one Y(3), and one Ti(5) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Y(4), one Ti(3), and one Ti(4) atom. In the eighth O site, O(8) is bonded to one Y(1), one Y(4), one Ti(2), and one Ti(4) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(1)Y2Ti2 tetrahedra,  a cornercorner with one O(4)Y3Ti tetrahedra, corners with two equivalent O(13)Y2Ti2 tetrahedra,  an edgeedge with one O(1)Y2Ti2 tetrahedra, and  an edgeedge with one O(8)Y2Ti2 tetrahedra. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Y(4), one Ti(5), and one Ti(6) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(3) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Y(4), one Y(6), and one Ti(1) atom. In the thirteenth O site, O(13) is bonded to one Y(4), one Y(5), one Ti(2), and one Ti(6) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(1)Y2Ti2 tetrahedra,  a cornercorner with one O(4)Y3Ti tetrahedra, corners with two equivalent O(8)Y2Ti2 tetrahedra,  an edgeedge with one O(13)Y2Ti2 tetrahedra, and  an edgeedge with one O(4)Y3Ti tetrahedra. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Y(3), one Y(4), one Ti(2), and one Ti(5) atom.
Y2Ti2O7 crystallizes in the monoclinic P2 space group. There are six inequivalent Y sites. In the first Y site, Y(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(8) atoms. Both Y(1)-O(1) bond lengths are 2.48 Å. Both Y(1)-O(3) bond lengths are 2.20 Å. Both Y(1)-O(8) bond lengths are 2.22 Å. In the second Y site, Y(2) is bonded in a 6-coordinate geometry to one O(1), one O(10), one O(11), one O(4), one O(5), and one O(6) atom. The Y(2)-O(1) bond length is 2.42 Å. The Y(2)-O(10) bond length is 2.21 Å. The Y(2)-O(11) bond length is 2.27 Å. The Y(2)-O(4) bond length is 2.23 Å. The Y(2)-O(5) bond length is 2.44 Å. The Y(2)-O(6) bond length is 2.24 Å. In the third Y site, Y(3) is bonded in a 8-coordinate geometry to two equivalent O(14), two equivalent O(2), two equivalent O(4), and two equivalent O(6) atoms. Both Y(3)-O(14) bond lengths are 3.01 Å. Both Y(3)-O(2) bond lengths are 2.47 Å. Both Y(3)-O(4) bond lengths are 2.33 Å. Both Y(3)-O(6) bond lengths are 2.26 Å. In the fourth Y site, Y(4) is bonded in a 7-coordinate geometry to one O(12), one O(13), one O(14), one O(3), one O(7), one O(8), and one O(9) atom. The Y(4)-O(12) bond length is 2.29 Å. The Y(4)-O(13) bond length is 2.34 Å. The Y(4)-O(14) bond length is 2.21 Å. The Y(4)-O(3) bond length is 2.72 Å. The Y(4)-O(7) bond length is 2.17 Å. The Y(4)-O(8) bond length is 2.41 Å. The Y(4)-O(9) bond length is 2.43 Å. In the fifth Y site, Y(5) is bonded in a 6-coordinate geometry to two equivalent O(13), two equivalent O(2), and two equivalent O(4) atoms. Both Y(5)-O(13) bond lengths are 2.28 Å. Both Y(5)-O(2) bond lengths are 2.15 Å. Both Y(5)-O(4) bond lengths are 2.37 Å. In the sixth Y site, Y(6) is bonded in a 8-coordinate geometry to two equivalent O(10), two equivalent O(11), two equivalent O(12), and two equivalent O(5) atoms. Both Y(6)-O(10) bond lengths are 2.42 Å. Both Y(6)-O(11) bond lengths are 2.37 Å. Both Y(6)-O(12) bond lengths are 2.45 Å. Both Y(6)-O(5) bond lengths are 2.72 Å. There are six inequivalent Ti sites. In the first Ti site, Ti(1) is bonded in a distorted rectangular see-saw-like geometry to two equivalent O(1) and two equivalent O(12) atoms. Both Ti(1)-O(1) bond lengths are 1.96 Å. Both Ti(1)-O(12) bond lengths are 1.79 Å. In the second Ti site, Ti(2) is bonded in a 6-coordinate geometry to one O(1), one O(13), one O(14), one O(4), one O(5), and one O(8) atom. The Ti(2)-O(1) bond length is 2.09 Å. The Ti(2)-O(13) bond length is 2.45 Å. The Ti(2)-O(14) bond length is 1.88 Å. The Ti(2)-O(4) bond length is 2.23 Å. The Ti(2)-O(5) bond length is 1.81 Å. The Ti(2)-O(8) bond length is 2.04 Å. In the third Ti site, Ti(3) is bonded in a tetrahedral geometry to one O(11), one O(2), one O(3), and one O(7) atom. The Ti(3)-O(11) bond length is 1.83 Å. The Ti(3)-O(2) bond length is 1.83 Å. The Ti(3)-O(3) bond length is 1.82 Å. The Ti(3)-O(7) bond length is 1.83 Å. In the fourth Ti site, Ti(4) is bonded in a 6-coordinate geometry to two equivalent O(10), two equivalent O(7), and two equivalent O(8) atoms. Both Ti(4)-O(10) bond lengths are 1.83 Å. Both Ti(4)-O(7) bond lengths are 2.24 Å. Both Ti(4)-O(8) bond lengths are 2.03 Å. In the fifth Ti site, Ti(5) is bonded to two equivalent O(14), two equivalent O(6), and two equivalent O(9) atoms to form corner-sharing TiO6 octahedra. Both Ti(5)-O(14) bond lengths are 2.17 Å. Both Ti(5)-O(6) bond lengths are 1.83 Å. Both Ti(5)-O(9) bond lengths are 2.02 Å. In the sixth Ti site, Ti(6) is bonded to two equivalent O(13) and two equivalent O(9) atoms to form distorted corner-sharing TiO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 32°. Both Ti(6)-O(13) bond lengths are 1.83 Å. Both Ti(6)-O(9) bond lengths are 1.86 Å. There are fourteen inequivalent O sites. In the first O site, O(1) is bonded to one Y(1), one Y(2), one Ti(1), and one Ti(2) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(13)Y2Ti2 tetrahedra,  a cornercorner with one O(8)Y2Ti2 tetrahedra, corners with two equivalent O(1)Y2Ti2 tetrahedra,  an edgeedge with one O(8)Y2Ti2 tetrahedra, and  an edgeedge with one O(4)Y3Ti tetrahedra. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Y(3), one Y(5), and one Ti(3) atom. In the third O site, O(3) is bonded in a 2-coordinate geometry to one Y(1), one Y(4), and one Ti(3) atom. In the fourth O site, O(4) is bonded to one Y(2), one Y(3), one Y(5), and one Ti(2) atom to form OY3Ti tetrahedra that share  a cornercorner with one O(13)Y2Ti2 tetrahedra,  a cornercorner with one O(8)Y2Ti2 tetrahedra, corners with two equivalent O(4)Y3Ti tetrahedra,  an edgeedge with one O(1)Y2Ti2 tetrahedra, and  an edgeedge with one O(13)Y2Ti2 tetrahedra. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(2) atom. In the sixth O site, O(6) is bonded in a 3-coordinate geometry to one Y(2), one Y(3), and one Ti(5) atom. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Y(4), one Ti(3), and one Ti(4) atom. In the eighth O site, O(8) is bonded to one Y(1), one Y(4), one Ti(2), and one Ti(4) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(1)Y2Ti2 tetrahedra,  a cornercorner with one O(4)Y3Ti tetrahedra, corners with two equivalent O(13)Y2Ti2 tetrahedra,  an edgeedge with one O(1)Y2Ti2 tetrahedra, and  an edgeedge with one O(8)Y2Ti2 tetrahedra. In the ninth O site, O(9) is bonded in a distorted T-shaped geometry to one Y(4), one Ti(5), and one Ti(6) atom. In the tenth O site, O(10) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(4) atom. In the eleventh O site, O(11) is bonded in a 3-coordinate geometry to one Y(2), one Y(6), and one Ti(3) atom. In the twelfth O site, O(12) is bonded in a 3-coordinate geometry to one Y(4), one Y(6), and one Ti(1) atom. In the thirteenth O site, O(13) is bonded to one Y(4), one Y(5), one Ti(2), and one Ti(6) atom to form distorted OY2Ti2 tetrahedra that share  a cornercorner with one O(1)Y2Ti2 tetrahedra,  a cornercorner with one O(4)Y3Ti tetrahedra, corners with two equivalent O(8)Y2Ti2 tetrahedra,  an edgeedge with one O(13)Y2Ti2 tetrahedra, and  an edgeedge with one O(4)Y3Ti tetrahedra. In the fourteenth O site, O(14) is bonded in a 3-coordinate geometry to one Y(3), one Y(4), one Ti(2), and one Ti(5) atom.