Nd2Ce3O9 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I-4m2 space group. Nd(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Nd(1) and two equivalent Ce(1) atoms to form OCe2Nd2 tetrahedra that share corners with two equivalent O(5)Ce4 tetrahedra, corners with two equivalent O(4)Nd4 tetrahedra, corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with four equivalent O(2)Ce4 tetrahedra,  an edgeedge with one O(5)Ce4 tetrahedra,  an edgeedge with one O(4)Nd4 tetrahedra, and edges with four equivalent O(3)Ce2Nd2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(3)Ce2Nd2 tetrahedra, corners with two equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with eight equivalent O(2)Ce4 tetrahedra,  an edgeedge with one O(3)Ce2Nd2 tetrahedra, and edges with five equivalent O(5)Ce4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Nd(1) and two equivalent Ce(1) atoms to form OCe2Nd2 tetrahedra that share corners with two equivalent O(2)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Nd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra,  an edgeedge with one O(2)Ce4 tetrahedra, and edges with four equivalent O(1)Ce2Nd2 tetrahedra. In the fourth O site, O(4) is bonded to four equivalent Nd(1) atoms to form ONd4 tetrahedra that share corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with eight equivalent O(3)Ce2Nd2 tetrahedra, and edges with two equivalent O(1)Ce2Nd2 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(1)Ce2Nd2 tetrahedra, corners with two equivalent O(2)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Nd2 tetrahedra, corners with eight equivalent O(5)Ce4 tetrahedra,  an edgeedge with one O(1)Ce2Nd2 tetrahedra, and edges with five equivalent O(2)Ce4 tetrahedra.
Nd2Ce3O9 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I-4m2 space group. Nd(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. Both Nd(1)-O(1) bond lengths are 2.41 Å. Both Nd(1)-O(3) bond lengths are 2.25 Å. Both Nd(1)-O(4) bond lengths are 2.52 Å. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Ce(1)-O(1) bond lengths are 2.31 Å. Both Ce(1)-O(2) bond lengths are 2.33 Å. Both Ce(1)-O(3) bond lengths are 2.47 Å. Both Ce(1)-O(5) bond lengths are 2.43 Å. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(5) atoms. All Ce(2)-O(2) bond lengths are 2.43 Å. All Ce(2)-O(5) bond lengths are 2.33 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Nd(1) and two equivalent Ce(1) atoms to form OCe2Nd2 tetrahedra that share corners with two equivalent O(5)Ce4 tetrahedra, corners with two equivalent O(4)Nd4 tetrahedra, corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with four equivalent O(2)Ce4 tetrahedra,  an edgeedge with one O(5)Ce4 tetrahedra,  an edgeedge with one O(4)Nd4 tetrahedra, and edges with four equivalent O(3)Ce2Nd2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(3)Ce2Nd2 tetrahedra, corners with two equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with eight equivalent O(2)Ce4 tetrahedra,  an edgeedge with one O(3)Ce2Nd2 tetrahedra, and edges with five equivalent O(5)Ce4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Nd(1) and two equivalent Ce(1) atoms to form OCe2Nd2 tetrahedra that share corners with two equivalent O(2)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Nd2 tetrahedra, corners with four equivalent O(5)Ce4 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra,  an edgeedge with one O(2)Ce4 tetrahedra, and edges with four equivalent O(1)Ce2Nd2 tetrahedra. In the fourth O site, O(4) is bonded to four equivalent Nd(1) atoms to form ONd4 tetrahedra that share corners with four equivalent O(1)Ce2Nd2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with eight equivalent O(3)Ce2Nd2 tetrahedra, and edges with two equivalent O(1)Ce2Nd2 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(1)Ce2Nd2 tetrahedra, corners with two equivalent O(2)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Nd2 tetrahedra, corners with eight equivalent O(5)Ce4 tetrahedra,  an edgeedge with one O(1)Ce2Nd2 tetrahedra, and edges with five equivalent O(2)Ce4 tetrahedra.