DOE OSTI2020
YbAl3C3 crystallizes in the hexagonal P6_3mc space group. The structure is three-dimensional. Yb3+ is bonded to six C4- atoms to form YbC6 octahedra that share corners with six AlC4 tetrahedra, edges with six equivalent YbC6 octahedra, and edges with six AlC4 tetrahedra. There are three shorter (2.61 Å) and three longer (2.65 Å) Yb–C bond lengths. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent YbC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent YbC6 octahedra. The corner-sharing octahedral tilt angles are 26°. There are one shorter (2.05 Å) and three longer (2.06 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded to four C4- atoms to form AlC4 tetrahedra that share corners with three equivalent YbC6 octahedra, corners with seven AlC4 tetrahedra, and edges with three equivalent YbC6 octahedra. The corner-sharing octahedral tilt angles are 23°. There are one shorter (2.03 Å) and three longer (2.08 Å) Al–C bond lengths. In the third Al3+ site, Al3+ is bonded in a distorted trigonal planar geometry to four C4- atoms. There are three shorter (1.98 Å) and one longer (2.54 Å) Al–C bond lengths. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to five Al3+ atoms to form corner-sharing CAl5 trigonal bipyramids. In the second C4- site, C4- is bonded in a 3-coordinate geometry to three equivalent Yb3+ and four Al3+ atoms. In the third C4- site, C4- is bonded in a 6-coordinate geometry to three equivalent Yb3+ and three equivalent Al3+ atoms.