Tb2Nb2O7 crystallizes in the cubic Fd-3m space group. Tb(1) is bonded in a body-centered cubic geometry to two equivalent O(2) and six equivalent O(1) atoms. Nb(1) is bonded to six equivalent O(1) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 56°. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Nb(1) atoms to form OTb2Nb2 tetrahedra that share corners with two equivalent O(2)Tb4 tetrahedra, corners with twelve equivalent O(1)Tb2Nb2 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with four equivalent O(1)Tb2Nb2 tetrahedra. In the second O site, O(2) is bonded to four equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with four equivalent O(2)Tb4 tetrahedra, corners with twelve equivalent O(1)Tb2Nb2 tetrahedra, and edges with six equivalent O(1)Tb2Nb2 tetrahedra.
Tb2Nb2O7 crystallizes in the cubic Fd-3m space group. Tb(1) is bonded in a body-centered cubic geometry to two equivalent O(2) and six equivalent O(1) atoms. Both Tb(1)-O(2) bond lengths are 2.25 Å. All Tb(1)-O(1) bond lengths are 2.45 Å. Nb(1) is bonded to six equivalent O(1) atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 56°. All Nb(1)-O(1) bond lengths are 2.09 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Nb(1) atoms to form OTb2Nb2 tetrahedra that share corners with two equivalent O(2)Tb4 tetrahedra, corners with twelve equivalent O(1)Tb2Nb2 tetrahedra,  an edgeedge with one O(2)Tb4 tetrahedra, and edges with four equivalent O(1)Tb2Nb2 tetrahedra. In the second O site, O(2) is bonded to four equivalent Tb(1) atoms to form OTb4 tetrahedra that share corners with four equivalent O(2)Tb4 tetrahedra, corners with twelve equivalent O(1)Tb2Nb2 tetrahedra, and edges with six equivalent O(1)Tb2Nb2 tetrahedra.