Tb2Ti2O7 crystallizes in the cubic Fd-3m space group. Tb(1) is bonded to two equivalent O(1) and six equivalent O(2) atoms to form distorted TbO8 hexagonal bipyramids that share edges with six equivalent Tb(1)O8 hexagonal bipyramids and edges with six equivalent Ti(1)O6 octahedra. Ti(1) is bonded to six equivalent O(2) atoms to form TiO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra and edges with six equivalent Tb(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 48°. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with four equivalent O(1)Tb4 tetrahedra, corners with twelve equivalent O(2)Tb2Ti2 tetrahedra, and edges with six equivalent O(2)Tb2Ti2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Ti(1) atoms to form distorted OTb2Ti2 tetrahedra that share corners with two equivalent O(1)Tb4 tetrahedra, corners with twelve equivalent O(2)Tb2Ti2 tetrahedra,  an edgeedge with one O(1)Tb4 tetrahedra, and edges with four equivalent O(2)Tb2Ti2 tetrahedra.
Tb2Ti2O7 crystallizes in the cubic Fd-3m space group. Tb(1) is bonded to two equivalent O(1) and six equivalent O(2) atoms to form distorted TbO8 hexagonal bipyramids that share edges with six equivalent Tb(1)O8 hexagonal bipyramids and edges with six equivalent Ti(1)O6 octahedra. Both Tb(1)-O(1) bond lengths are 2.19 Å. All Tb(1)-O(2) bond lengths are 2.49 Å. Ti(1) is bonded to six equivalent O(2) atoms to form TiO6 octahedra that share corners with six equivalent Ti(1)O6 octahedra and edges with six equivalent Tb(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 48°. All Ti(1)-O(2) bond lengths are 1.96 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with four equivalent O(1)Tb4 tetrahedra, corners with twelve equivalent O(2)Tb2Ti2 tetrahedra, and edges with six equivalent O(2)Tb2Ti2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Tb(1) and two equivalent Ti(1) atoms to form distorted OTb2Ti2 tetrahedra that share corners with two equivalent O(1)Tb4 tetrahedra, corners with twelve equivalent O(2)Tb2Ti2 tetrahedra,  an edgeedge with one O(1)Tb4 tetrahedra, and edges with four equivalent O(2)Tb2Ti2 tetrahedra.