Materials Data on Hf2Al4C5 by Materials Project

Abstract

Hf2Al4C5 crystallizes in the trigonal R-3m space group. The structure is three-dimensional. Hf4+ is bonded to six C4- atoms to form HfC6 octahedra that share corners with three equivalent HfC6 octahedra, corners with three equivalent AlC4 tetrahedra, edges with nine equivalent HfC6 octahedra, and edges with three equivalent AlC4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are three shorter (2.34 Å) and three longer (2.36 Å) Hf–C bond lengths. 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 HfC6 octahedra, corners with six equivalent AlC4 tetrahedra, corners with four equivalent AlC4 trigonal pyramids, and edges with three equivalent HfC6 octahedra. The corner-sharing octahedral tilt angles are 10°. There are one shorter (1.94 Å) and three longer (2.14 Å) Al–C bond lengths. In the second Al3+ site, Al3+ is bonded to four equivalent C4- atoms to form a mixture of edge and corner-sharing AlC4 trigonal pyramids. There are three shorter (1.95 Å) and one longer (2.18 Å) Al–C bond lengths. There are three inequivalent C4- sites. In the first C4- site, C4- is bonded to three equivalent Hf4+ and three equivalent Al3+ atoms to form CHf3Al3 octahedra that share corners with three equivalent CHf6 octahedra, corners with three equivalent CAl5 trigonal bipyramids, and edges with nine CHf3Al3 octahedra. The corner-sharing octahedral tilt angles are 1°. In the second C4- site, C4- is bonded to six equivalent Hf4+ atoms to form a mixture of edge and corner-sharing CHf6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third C4- site, C4- is bonded to five Al3+ atoms to form CAl5 trigonal bipyramids that share corners with three equivalent CHf3Al3 octahedra, corners with six equivalent CAl5 trigonal bipyramids, and edges with three equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 64°.