Hf3Al3C5 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form HfC6 octahedra that share corners with three equivalent Hf(2)C6 octahedra, corners with three equivalent Al(1)C4 tetrahedra, edges with three equivalent Hf(2)C6 octahedra, edges with six equivalent Hf(1)C6 octahedra, and edges with three equivalent Al(1)C4 tetrahedra. The corner-sharing octahedral tilt angles are 3°. In the second Hf site, Hf(2) is bonded to six equivalent C(1) atoms to form a mixture of edge and corner-sharing HfC6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(3) and three equivalent C(2) atoms to form AlC4 tetrahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with seven equivalent Al(1)C4 tetrahedra, and edges with three equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles are 19°. In the second Al site, Al(2) is bonded in a trigonal planar geometry to three equivalent C(3) atoms. There are three inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Hf(1) and three equivalent Hf(2) atoms to form a mixture of edge and corner-sharing CHf6 octahedra. The corner-sharing octahedra are not tilted. In the second C site, C(2) is bonded in a 6-coordinate geometry to three equivalent Hf(1) and three equivalent Al(1) atoms. In the third C site, C(3) is bonded to two equivalent Al(1) and three equivalent Al(2) atoms to form corner-sharing CAl5 trigonal bipyramids.
Hf3Al3C5 crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Hf sites. In the first Hf site, Hf(1) is bonded to three equivalent C(1) and three equivalent C(2) atoms to form HfC6 octahedra that share corners with three equivalent Hf(2)C6 octahedra, corners with three equivalent Al(1)C4 tetrahedra, edges with three equivalent Hf(2)C6 octahedra, edges with six equivalent Hf(1)C6 octahedra, and edges with three equivalent Al(1)C4 tetrahedra. The corner-sharing octahedral tilt angles are 3°. All Hf(1)-C(1) bond lengths are 2.27 Å. All Hf(1)-C(2) bond lengths are 2.46 Å. In the second Hf site, Hf(2) is bonded to six equivalent C(1) atoms to form a mixture of edge and corner-sharing HfC6 octahedra. The corner-sharing octahedral tilt angles are 3°. All Hf(2)-C(1) bond lengths are 2.35 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one C(3) and three equivalent C(2) atoms to form AlC4 tetrahedra that share corners with three equivalent Hf(1)C6 octahedra, corners with seven equivalent Al(1)C4 tetrahedra, and edges with three equivalent Hf(1)C6 octahedra. The corner-sharing octahedral tilt angles are 19°. The Al(1)-C(3) bond length is 2.01 Å. All Al(1)-C(2) bond lengths are 2.04 Å. In the second Al site, Al(2) is bonded in a trigonal planar geometry to three equivalent C(3) atoms. All Al(2)-C(3) bond lengths are 1.91 Å. There are three inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Hf(1) and three equivalent Hf(2) atoms to form a mixture of edge and corner-sharing CHf6 octahedra. The corner-sharing octahedra are not tilted. In the second C site, C(2) is bonded in a 6-coordinate geometry to three equivalent Hf(1) and three equivalent Al(1) atoms. In the third C site, C(3) is bonded to two equivalent Al(1) and three equivalent Al(2) atoms to form corner-sharing CAl5 trigonal bipyramids.