DOE OSTI2020
Tb(AlC)3 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Tb3+ is bonded to six equivalent C4- atoms to form TbC6 octahedra that share corners with six equivalent AlC4 tetrahedra, edges with six equivalent TbC6 octahedra, and edges with six equivalent AlC4 tetrahedra. All Tb–C bond lengths are 2.57 Å. There are two 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 TbC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent TbC6 octahedra. The corner-sharing octahedral tilt angles are 20°. There are one shorter (2.02 Å) and three longer (2.11 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded in a trigonal planar geometry to three equivalent C4- atoms. All Al–C bond lengths are 1.99 Å. There are two inequivalent C4- sites. In the first C4- site, C4- is bonded in a 6-coordinate geometry to three equivalent Tb3+ and three equivalent Al3+ atoms. In the second C4- site, C4- is bonded to five Al3+ atoms to form corner-sharing CAl5 trigonal bipyramids.