Sm2Ce2O7 crystallizes in the cubic Fd-3m space group. Sm(1) is bonded in a body-centered cubic geometry to two equivalent O(2) and six equivalent O(1) atoms. Ce(1) is bonded to six equivalent O(1) atoms to form distorted corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sm(1) and two equivalent Ce(1) atoms to form OCe2Sm2 tetrahedra that share corners with two equivalent O(2)Sm4 tetrahedra, corners with twelve equivalent O(1)Ce2Sm2 tetrahedra,  an edgeedge with one O(2)Sm4 tetrahedra, and edges with four equivalent O(1)Ce2Sm2 tetrahedra. In the second O site, O(2) is bonded to four equivalent Sm(1) atoms to form OSm4 tetrahedra that share corners with four equivalent O(2)Sm4 tetrahedra, corners with twelve equivalent O(1)Ce2Sm2 tetrahedra, and edges with six equivalent O(1)Ce2Sm2 tetrahedra.
Sm2Ce2O7 crystallizes in the cubic Fd-3m space group. Sm(1) is bonded in a body-centered cubic geometry to two equivalent O(2) and six equivalent O(1) atoms. Both Sm(1)-O(2) bond lengths are 2.39 Å. All Sm(1)-O(1) bond lengths are 2.56 Å. Ce(1) is bonded to six equivalent O(1) atoms to form distorted corner-sharing CeO6 octahedra. The corner-sharing octahedral tilt angles are 59°. All Ce(1)-O(1) bond lengths are 2.24 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Sm(1) and two equivalent Ce(1) atoms to form OCe2Sm2 tetrahedra that share corners with two equivalent O(2)Sm4 tetrahedra, corners with twelve equivalent O(1)Ce2Sm2 tetrahedra,  an edgeedge with one O(2)Sm4 tetrahedra, and edges with four equivalent O(1)Ce2Sm2 tetrahedra. In the second O site, O(2) is bonded to four equivalent Sm(1) atoms to form OSm4 tetrahedra that share corners with four equivalent O(2)Sm4 tetrahedra, corners with twelve equivalent O(1)Ce2Sm2 tetrahedra, and edges with six equivalent O(1)Ce2Sm2 tetrahedra.