UHfZr2C4 is alpha Po-derived structured and crystallizes in the trigonal R3m space group. U(1) is bonded to three equivalent C(3) and three equivalent C(4) atoms to form UC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Zr(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent U(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Hf(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form HfC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Zr(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Zr(2)C6 octahedra, and edges with six equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent C(1) and three equivalent C(4) atoms to form ZrC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Zr(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Zr(2)C6 octahedra, and edges with six equivalent Zr(1)C6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second Zr site, Zr(2) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form ZrC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Zr(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent Zr(2)C6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Zr(1) and three equivalent Zr(2) atoms to form CZr6 octahedra that share corners with three equivalent C(2)Hf3Zr3 octahedra, corners with three equivalent C(4)Zr3U3 octahedra, edges with three equivalent C(2)Hf3Zr3 octahedra, edges with three equivalent C(4)Zr3U3 octahedra, and edges with six equivalent C(1)Zr6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second C site, C(2) is bonded to three equivalent Hf(1) and three equivalent Zr(2) atoms to form CHf3Zr3 octahedra that share corners with three equivalent C(3)Hf3U3 octahedra, corners with three equivalent C(1)Zr6 octahedra, edges with three equivalent C(3)Hf3U3 octahedra, edges with three equivalent C(1)Zr6 octahedra, and edges with six equivalent C(2)Hf3Zr3 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. In the third C site, C(3) is bonded to three equivalent U(1) and three equivalent Hf(1) atoms to form CHf3U3 octahedra that share corners with three equivalent C(2)Hf3Zr3 octahedra, corners with three equivalent C(4)Zr3U3 octahedra, edges with three equivalent C(2)Hf3Zr3 octahedra, edges with three equivalent C(4)Zr3U3 octahedra, and edges with six equivalent C(3)Hf3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the fourth C site, C(4) is bonded to three equivalent U(1) and three equivalent Zr(1) atoms to form CZr3U3 octahedra that share corners with three equivalent C(3)Hf3U3 octahedra, corners with three equivalent C(1)Zr6 octahedra, edges with three equivalent C(3)Hf3U3 octahedra, edges with three equivalent C(1)Zr6 octahedra, and edges with six equivalent C(4)Zr3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-3°.
UHfZr2C4 is alpha Po-derived structured and crystallizes in the trigonal R3m space group. U(1) is bonded to three equivalent C(3) and three equivalent C(4) atoms to form UC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Zr(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent U(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. All U(1)-C(3) bond lengths are 2.42 Å. All U(1)-C(4) bond lengths are 2.41 Å. Hf(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form HfC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Zr(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Zr(2)C6 octahedra, and edges with six equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles range from 0-3°. All Hf(1)-C(2) bond lengths are 2.31 Å. All Hf(1)-C(3) bond lengths are 2.41 Å. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent C(1) and three equivalent C(4) atoms to form ZrC6 octahedra that share corners with three equivalent U(1)C6 octahedra, corners with three equivalent Zr(2)C6 octahedra, edges with three equivalent U(1)C6 octahedra, edges with three equivalent Zr(2)C6 octahedra, and edges with six equivalent Zr(1)C6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Zr(1)-C(1) bond lengths are 2.34 Å. All Zr(1)-C(4) bond lengths are 2.43 Å. In the second Zr site, Zr(2) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form ZrC6 octahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with three equivalent Zr(1)C6 octahedra, edges with three equivalent Hf(1)C6 octahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent Zr(2)C6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. All Zr(2)-C(1) bond lengths are 2.37 Å. All Zr(2)-C(2) bond lengths are 2.39 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Zr(1) and three equivalent Zr(2) atoms to form CZr6 octahedra that share corners with three equivalent C(2)Hf3Zr3 octahedra, corners with three equivalent C(4)Zr3U3 octahedra, edges with three equivalent C(2)Hf3Zr3 octahedra, edges with three equivalent C(4)Zr3U3 octahedra, and edges with six equivalent C(1)Zr6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the second C site, C(2) is bonded to three equivalent Hf(1) and three equivalent Zr(2) atoms to form CHf3Zr3 octahedra that share corners with three equivalent C(3)Hf3U3 octahedra, corners with three equivalent C(1)Zr6 octahedra, edges with three equivalent C(3)Hf3U3 octahedra, edges with three equivalent C(1)Zr6 octahedra, and edges with six equivalent C(2)Hf3Zr3 octahedra. The corner-sharing octahedral tilt angles range from 1-4°. In the third C site, C(3) is bonded to three equivalent U(1) and three equivalent Hf(1) atoms to form CHf3U3 octahedra that share corners with three equivalent C(2)Hf3Zr3 octahedra, corners with three equivalent C(4)Zr3U3 octahedra, edges with three equivalent C(2)Hf3Zr3 octahedra, edges with three equivalent C(4)Zr3U3 octahedra, and edges with six equivalent C(3)Hf3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-4°. In the fourth C site, C(4) is bonded to three equivalent U(1) and three equivalent Zr(1) atoms to form CZr3U3 octahedra that share corners with three equivalent C(3)Hf3U3 octahedra, corners with three equivalent C(1)Zr6 octahedra, edges with three equivalent C(3)Hf3U3 octahedra, edges with three equivalent C(1)Zr6 octahedra, and edges with six equivalent C(4)Zr3U3 octahedra. The corner-sharing octahedral tilt angles range from 0-3°.