Materials Data on HfU(TaC2)2 by Materials Project
UHf(TaC2)2 is alpha Po-derived structured and crystallizes in the trigonal R3m space group. The structure is three-dimensional. U4+ is bonded to six C4- atoms to form UC6 octahedra that share corners with three equivalent HfC6 octahedra, corners with three equivalent TaC6 octahedra, edges with three equivalent HfC6 octahedra, edges with three equivalent TaC6 octahedra, and edges with six equivalent UC6 octahedra. The corner-sharing octahedra tilt angles range from 3–7°. There are three shorter (2.42 Å) and three longer (2.45 Å) U–C bond lengths. Hf4+ is bonded to six C4- atoms to form HfC6 octahedra that share corners with three equivalent UC6 octahedra, corners with three equivalent TaC6 octahedra, edges with three equivalent UC6 octahedra, edges with three equivalent TaC6 octahedra, and edges with six equivalent HfC6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are three shorter (2.31 Å) and three longer (2.32 Å) Hf–C bond lengths. There are two inequivalent Ta4+ sites. In the first Ta4+ site, Ta4+ is bonded to six C4- atoms to form TaC6 octahedra that share corners with three equivalent UC6 octahedra, corners with three equivalent TaC6 octahedra, edges with three equivalent UC6 octahedra, and edges with nine TaC6 octahedra. The corner-sharing octahedra tilt angles range from 1–7°. There are three shorter (2.23 Å) and three longer (2.28 Å) Ta–C bond lengths. In the second Ta4+ site, Ta4+ is bonded to six C4- atoms to form TaC6 octahedra that share corners with three equivalent HfC6 octahedra, corners with three equivalent TaC6 octahedra, edges with three equivalent HfC6 octahedra, and edges with nine TaC6 octahedra. The corner-sharing octahedra tilt angles range from 1–3°. There are three shorter (2.24 Å) and three longer (2.26 Å) Ta–C bond lengths. There are four inequivalent C4- sites. In the first C4- site, C4- is bonded to six Ta4+ atoms to form CTa6 octahedra that share corners with six CHf3Ta3 octahedra and edges with twelve CTa6 octahedra. The corner-sharing octahedra tilt angles range from 1–2°. In the second C4- site, C4- is bonded to three equivalent Hf4+ and three equivalent Ta4+ atoms to form a mixture of edge and corner-sharing CHf3Ta3 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the third C4- site, C4- is bonded to three equivalent U4+ and three equivalent Hf4+ atoms to form a mixture of edge and corner-sharing CHf3U3 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. In the fourth C4- site, C4- is bonded to three equivalent U4+ and three equivalent Ta4+ atoms to form a mixture of edge and corner-sharing CU3Ta3 octahedra. The corner-sharing octahedra tilt angles range from 1–2°.