UHf(NbC2)2 is alpha Po-derived structured and crystallizes in the trigonal R3m space group. U(1) is bonded to three equivalent C(1) and three equivalent C(4) atoms to form UC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Nb(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Nb(1)C6 octahedra, and edges with six equivalent U(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. Hf(1) is bonded to three equivalent C(3) and three equivalent C(4) atoms to form HfC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Nb(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Nb(2)C6 octahedra, and edges with six equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form NbC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Nb(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Nb(2)C6 octahedra, and edges with six equivalent Nb(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the second Nb site, Nb(2) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form NbC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Nb(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Nb(1)C6 octahedra, and edges with six equivalent Nb(2)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent U(1) and three equivalent Nb(1) atoms to form CU3Nb3 octahedra that share corners with three equivalent C(4)Hf3U3 octahedra, corners with three equivalent C(2)Nb6 octahedra, edges with three equivalent C(4)Hf3U3 octahedra, edges with three equivalent C(2)Nb6 octahedra, and edges with six equivalent C(1)U3Nb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second C site, C(2) is bonded to three equivalent Nb(1) and three equivalent Nb(2) atoms to form CNb6 octahedra that share corners with three equivalent C(3)Hf3Nb3 octahedra, corners with three equivalent C(1)U3Nb3 octahedra, edges with three equivalent C(3)Hf3Nb3 octahedra, edges with three equivalent C(1)U3Nb3 octahedra, and edges with six equivalent C(2)Nb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third C site, C(3) is bonded to three equivalent Hf(1) and three equivalent Nb(2) atoms to form CHf3Nb3 octahedra that share corners with three equivalent C(4)Hf3U3 octahedra, corners with three equivalent C(2)Nb6 octahedra, edges with three equivalent C(4)Hf3U3 octahedra, edges with three equivalent C(2)Nb6 octahedra, and edges with six equivalent C(3)Hf3Nb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth C site, C(4) is bonded to three equivalent U(1) and three equivalent Hf(1) atoms to form CHf3U3 octahedra that share corners with three equivalent C(3)Hf3Nb3 octahedra, corners with three equivalent C(1)U3Nb3 octahedra, edges with three equivalent C(3)Hf3Nb3 octahedra, edges with three equivalent C(1)U3Nb3 octahedra, and edges with six equivalent C(4)Hf3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
UHf(NbC2)2 is alpha Po-derived structured and crystallizes in the trigonal R3m space group. U(1) is bonded to three equivalent C(1) and three equivalent C(4) atoms to form UC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Nb(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Nb(1)C6 octahedra, and edges with six equivalent U(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 3-4°. All U(1)-C(1) bond lengths are 2.42 Å. All U(1)-C(4) bond lengths are 2.42 Å. Hf(1) is bonded to three equivalent C(3) and three equivalent C(4) atoms to form HfC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Nb(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Nb(2)C6 octahedra, and edges with six equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. All Hf(1)-C(3) bond lengths are 2.30 Å. All Hf(1)-C(4) bond lengths are 2.33 Å. There are two inequivalent Nb sites. In the first Nb site, Nb(1) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form NbC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Nb(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Nb(2)C6 octahedra, and edges with six equivalent Nb(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. All Nb(1)-C(1) bond lengths are 2.29 Å. All Nb(1)-C(2) bond lengths are 2.26 Å. In the second Nb site, Nb(2) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form NbC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Nb(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Nb(1)C6 octahedra, and edges with six equivalent Nb(2)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. All Nb(2)-C(2) bond lengths are 2.26 Å. All Nb(2)-C(3) bond lengths are 2.28 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent U(1) and three equivalent Nb(1) atoms to form CU3Nb3 octahedra that share corners with three equivalent C(4)Hf3U3 octahedra, corners with three equivalent C(2)Nb6 octahedra, edges with three equivalent C(4)Hf3U3 octahedra, edges with three equivalent C(2)Nb6 octahedra, and edges with six equivalent C(1)U3Nb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second C site, C(2) is bonded to three equivalent Nb(1) and three equivalent Nb(2) atoms to form CNb6 octahedra that share corners with three equivalent C(3)Hf3Nb3 octahedra, corners with three equivalent C(1)U3Nb3 octahedra, edges with three equivalent C(3)Hf3Nb3 octahedra, edges with three equivalent C(1)U3Nb3 octahedra, and edges with six equivalent C(2)Nb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the third C site, C(3) is bonded to three equivalent Hf(1) and three equivalent Nb(2) atoms to form CHf3Nb3 octahedra that share corners with three equivalent C(4)Hf3U3 octahedra, corners with three equivalent C(2)Nb6 octahedra, edges with three equivalent C(4)Hf3U3 octahedra, edges with three equivalent C(2)Nb6 octahedra, and edges with six equivalent C(3)Hf3Nb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the fourth C site, C(4) is bonded to three equivalent U(1) and three equivalent Hf(1) atoms to form CHf3U3 octahedra that share corners with three equivalent C(3)Hf3Nb3 octahedra, corners with three equivalent C(1)U3Nb3 octahedra, edges with three equivalent C(3)Hf3Nb3 octahedra, edges with three equivalent C(1)U3Nb3 octahedra, and edges with six equivalent C(4)Hf3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.