Th3Nd2O9 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Th sites. In the first Th site, Th(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 Th site, Th(2) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(5) atoms. 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 five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Th(1) and two equivalent Nd(1) atoms to form ONd2Th2 tetrahedra that share corners with two equivalent O(4)Nd4 tetrahedra, corners with two equivalent O(5)Th4 tetrahedra, corners with four equivalent O(1)Nd2Th2 tetrahedra, corners with four equivalent O(2)Th4 tetrahedra,  an edgeedge with one O(4)Nd4 tetrahedra,  an edgeedge with one O(5)Th4 tetrahedra, and edges with four equivalent O(3)Nd2Th2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Th(1) and two equivalent Th(2) atoms to form OTh4 tetrahedra that share corners with two equivalent O(3)Nd2Th2 tetrahedra, corners with two equivalent O(5)Th4 tetrahedra, corners with four equivalent O(1)Nd2Th2 tetrahedra, corners with eight equivalent O(2)Th4 tetrahedra,  an edgeedge with one O(3)Nd2Th2 tetrahedra, and edges with five equivalent O(5)Th4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Th(1) and two equivalent Nd(1) atoms to form ONd2Th2 tetrahedra that share corners with two equivalent O(2)Th4 tetrahedra, corners with four equivalent O(3)Nd2Th2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with four equivalent O(5)Th4 tetrahedra,  an edgeedge with one O(2)Th4 tetrahedra, and edges with four equivalent O(1)Nd2Th2 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)Nd2Th2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with eight equivalent O(3)Nd2Th2 tetrahedra, and edges with two equivalent O(1)Nd2Th2 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Th(1) and two equivalent Th(2) atoms to form OTh4 tetrahedra that share corners with two equivalent O(1)Nd2Th2 tetrahedra, corners with two equivalent O(2)Th4 tetrahedra, corners with four equivalent O(3)Nd2Th2 tetrahedra, corners with eight equivalent O(5)Th4 tetrahedra,  an edgeedge with one O(1)Nd2Th2 tetrahedra, and edges with five equivalent O(2)Th4 tetrahedra.
Th3Nd2O9 is alpha bismuth trifluoride-derived structured and crystallizes in the tetragonal I-4m2 space group. There are two inequivalent Th sites. In the first Th site, Th(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 Th(1)-O(1) bond lengths are 2.35 Å. Both Th(1)-O(2) bond lengths are 2.39 Å. Both Th(1)-O(3) bond lengths are 2.53 Å. Both Th(1)-O(5) bond lengths are 2.49 Å. In the second Th site, Th(2) is bonded in a body-centered cubic geometry to four equivalent O(2) and four equivalent O(5) atoms. All Th(2)-O(2) bond lengths are 2.49 Å. All Th(2)-O(5) bond lengths are 2.39 Å. 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 2.44 Å. Both Nd(1)-O(3) bond lengths are 2.27 Å. Both Nd(1)-O(4) bond lengths are 2.55 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Th(1) and two equivalent Nd(1) atoms to form ONd2Th2 tetrahedra that share corners with two equivalent O(4)Nd4 tetrahedra, corners with two equivalent O(5)Th4 tetrahedra, corners with four equivalent O(1)Nd2Th2 tetrahedra, corners with four equivalent O(2)Th4 tetrahedra,  an edgeedge with one O(4)Nd4 tetrahedra,  an edgeedge with one O(5)Th4 tetrahedra, and edges with four equivalent O(3)Nd2Th2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Th(1) and two equivalent Th(2) atoms to form OTh4 tetrahedra that share corners with two equivalent O(3)Nd2Th2 tetrahedra, corners with two equivalent O(5)Th4 tetrahedra, corners with four equivalent O(1)Nd2Th2 tetrahedra, corners with eight equivalent O(2)Th4 tetrahedra,  an edgeedge with one O(3)Nd2Th2 tetrahedra, and edges with five equivalent O(5)Th4 tetrahedra. In the third O site, O(3) is bonded to two equivalent Th(1) and two equivalent Nd(1) atoms to form ONd2Th2 tetrahedra that share corners with two equivalent O(2)Th4 tetrahedra, corners with four equivalent O(3)Nd2Th2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with four equivalent O(5)Th4 tetrahedra,  an edgeedge with one O(2)Th4 tetrahedra, and edges with four equivalent O(1)Nd2Th2 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)Nd2Th2 tetrahedra, corners with four equivalent O(4)Nd4 tetrahedra, corners with eight equivalent O(3)Nd2Th2 tetrahedra, and edges with two equivalent O(1)Nd2Th2 tetrahedra. In the fifth O site, O(5) is bonded to two equivalent Th(1) and two equivalent Th(2) atoms to form OTh4 tetrahedra that share corners with two equivalent O(1)Nd2Th2 tetrahedra, corners with two equivalent O(2)Th4 tetrahedra, corners with four equivalent O(3)Nd2Th2 tetrahedra, corners with eight equivalent O(5)Th4 tetrahedra,  an edgeedge with one O(1)Nd2Th2 tetrahedra, and edges with five equivalent O(2)Th4 tetrahedra.