UNd10S16 crystallizes in the tetragonal P-4 space group. U(1) is bonded to four equivalent S(3) and four equivalent S(4) atoms to form distorted US8 hexagonal bipyramids that share corners with four equivalent Nd(3)S8 hexagonal bipyramids, edges with four equivalent Nd(2)S8 hexagonal bipyramids, and faces with four equivalent Nd(3)S8 hexagonal bipyramids. There are three inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(2), one S(4), three equivalent S(1), and three equivalent S(3) atoms. In the second Nd site, Nd(2) is bonded to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms to form distorted NdS8 hexagonal bipyramids that share corners with four equivalent Nd(3)S8 hexagonal bipyramids, edges with two equivalent U(1)S8 hexagonal bipyramids, and faces with four equivalent Nd(3)S8 hexagonal bipyramids. In the third Nd site, Nd(3) is bonded to one S(1), one S(3), three equivalent S(2), and three equivalent S(4) atoms to form distorted NdS8 hexagonal bipyramids that share  a cornercorner with one U(1)S8 hexagonal bipyramid, corners with two equivalent Nd(2)S8 hexagonal bipyramids, corners with two equivalent Nd(3)S8 hexagonal bipyramids, edges with two equivalent Nd(3)S8 hexagonal bipyramids,  a faceface with one U(1)S8 hexagonal bipyramid, faces with two equivalent Nd(2)S8 hexagonal bipyramids, and faces with two equivalent Nd(3)S8 hexagonal bipyramids. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Nd(2), one Nd(3), and three equivalent Nd(1) atoms to form SNd5 trigonal bipyramids that share corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids,  a cornercorner with one S(1)Nd5 trigonal bipyramid,  an edgeedge with one S(3)Nd5U octahedra, edges with two equivalent S(4)Nd5U octahedra, edges with two equivalent S(2)Nd5 square pyramids, edges with three equivalent S(1)Nd5 trigonal bipyramids, and faces with two equivalent S(3)Nd5U octahedra. The corner-sharing octahedral tilt angles range from 22-54°. In the second S site, S(2) is bonded to one Nd(1), one Nd(2), and three equivalent Nd(3) atoms to form SNd5 square pyramids that share corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(4)Nd5U octahedra, edges with two equivalent S(3)Nd5U octahedra, edges with two equivalent S(1)Nd5 trigonal bipyramids, faces with two equivalent S(4)Nd5U octahedra, and  a faceface with one S(2)Nd5 square pyramid. The corner-sharing octahedral tilt angles range from 13-53°. In the third S site, S(3) is bonded to one U(1), one Nd(2), one Nd(3), and three equivalent Nd(1) atoms to form distorted SNd5U octahedra that share corners with three equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(4)Nd5U octahedra, edges with two equivalent S(3)Nd5U octahedra, edges with two equivalent S(2)Nd5 square pyramids,  an edgeedge with one S(1)Nd5 trigonal bipyramid,  a faceface with one S(3)Nd5U octahedra, faces with two equivalent S(4)Nd5U octahedra, and faces with two equivalent S(1)Nd5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 19-50°. In the fourth S site, S(4) is bonded to one U(1), one Nd(1), one Nd(2), and three equivalent Nd(3) atoms to form distorted SNd5U octahedra that share corners with three equivalent S(4)Nd5U octahedra, corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(3)Nd5U octahedra, edges with two equivalent S(4)Nd5U octahedra,  an edgeedge with one S(2)Nd5 square pyramid, edges with two equivalent S(1)Nd5 trigonal bipyramids,  a faceface with one S(4)Nd5U octahedra, faces with two equivalent S(3)Nd5U octahedra, and faces with two equivalent S(2)Nd5 square pyramids. The corner-sharing octahedral tilt angles range from 17-49°.
UNd10S16 crystallizes in the tetragonal P-4 space group. U(1) is bonded to four equivalent S(3) and four equivalent S(4) atoms to form distorted US8 hexagonal bipyramids that share corners with four equivalent Nd(3)S8 hexagonal bipyramids, edges with four equivalent Nd(2)S8 hexagonal bipyramids, and faces with four equivalent Nd(3)S8 hexagonal bipyramids. All U(1)-S(3) bond lengths are 2.83 Å. All U(1)-S(4) bond lengths are 3.01 Å. There are three inequivalent Nd sites. In the first Nd site, Nd(1) is bonded in a 8-coordinate geometry to one S(2), one S(4), three equivalent S(1), and three equivalent S(3) atoms. The Nd(1)-S(2) bond length is 2.83 Å. The Nd(1)-S(4) bond length is 3.00 Å. There are a spread of Nd(1)-S(1) bond distances ranging from 2.83-3.01 Å. There are a spread of Nd(1)-S(3) bond distances ranging from 2.91-3.18 Å. In the second Nd site, Nd(2) is bonded to two equivalent S(1), two equivalent S(2), two equivalent S(3), and two equivalent S(4) atoms to form distorted NdS8 hexagonal bipyramids that share corners with four equivalent Nd(3)S8 hexagonal bipyramids, edges with two equivalent U(1)S8 hexagonal bipyramids, and faces with four equivalent Nd(3)S8 hexagonal bipyramids. Both Nd(2)-S(1) bond lengths are 2.85 Å. Both Nd(2)-S(2) bond lengths are 2.98 Å. Both Nd(2)-S(3) bond lengths are 3.05 Å. Both Nd(2)-S(4) bond lengths are 2.90 Å. In the third Nd site, Nd(3) is bonded to one S(1), one S(3), three equivalent S(2), and three equivalent S(4) atoms to form distorted NdS8 hexagonal bipyramids that share  a cornercorner with one U(1)S8 hexagonal bipyramid, corners with two equivalent Nd(2)S8 hexagonal bipyramids, corners with two equivalent Nd(3)S8 hexagonal bipyramids, edges with two equivalent Nd(3)S8 hexagonal bipyramids,  a faceface with one U(1)S8 hexagonal bipyramid, faces with two equivalent Nd(2)S8 hexagonal bipyramids, and faces with two equivalent Nd(3)S8 hexagonal bipyramids. The Nd(3)-S(1) bond length is 3.03 Å. The Nd(3)-S(3) bond length is 2.89 Å. There are a spread of Nd(3)-S(2) bond distances ranging from 2.86-3.03 Å. There are a spread of Nd(3)-S(4) bond distances ranging from 2.90-3.14 Å. There are four inequivalent S sites. In the first S site, S(1) is bonded to one Nd(2), one Nd(3), and three equivalent Nd(1) atoms to form SNd5 trigonal bipyramids that share corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids,  a cornercorner with one S(1)Nd5 trigonal bipyramid,  an edgeedge with one S(3)Nd5U octahedra, edges with two equivalent S(4)Nd5U octahedra, edges with two equivalent S(2)Nd5 square pyramids, edges with three equivalent S(1)Nd5 trigonal bipyramids, and faces with two equivalent S(3)Nd5U octahedra. The corner-sharing octahedral tilt angles range from 22-54°. In the second S site, S(2) is bonded to one Nd(1), one Nd(2), and three equivalent Nd(3) atoms to form SNd5 square pyramids that share corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(4)Nd5U octahedra, edges with two equivalent S(3)Nd5U octahedra, edges with two equivalent S(1)Nd5 trigonal bipyramids, faces with two equivalent S(4)Nd5U octahedra, and  a faceface with one S(2)Nd5 square pyramid. The corner-sharing octahedral tilt angles range from 13-53°. In the third S site, S(3) is bonded to one U(1), one Nd(2), one Nd(3), and three equivalent Nd(1) atoms to form distorted SNd5U octahedra that share corners with three equivalent S(3)Nd5U octahedra, corners with four equivalent S(4)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(4)Nd5U octahedra, edges with two equivalent S(3)Nd5U octahedra, edges with two equivalent S(2)Nd5 square pyramids,  an edgeedge with one S(1)Nd5 trigonal bipyramid,  a faceface with one S(3)Nd5U octahedra, faces with two equivalent S(4)Nd5U octahedra, and faces with two equivalent S(1)Nd5 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 19-50°. In the fourth S site, S(4) is bonded to one U(1), one Nd(1), one Nd(2), and three equivalent Nd(3) atoms to form distorted SNd5U octahedra that share corners with three equivalent S(4)Nd5U octahedra, corners with four equivalent S(3)Nd5U octahedra, corners with four equivalent S(2)Nd5 square pyramids, corners with four equivalent S(1)Nd5 trigonal bipyramids,  an edgeedge with one S(3)Nd5U octahedra, edges with two equivalent S(4)Nd5U octahedra,  an edgeedge with one S(2)Nd5 square pyramid, edges with two equivalent S(1)Nd5 trigonal bipyramids,  a faceface with one S(4)Nd5U octahedra, faces with two equivalent S(3)Nd5U octahedra, and faces with two equivalent S(2)Nd5 square pyramids. The corner-sharing octahedral tilt angles range from 17-49°.