Materials Data on Hf2Al3C4 by Materials Project

Abstract

Hf2Al3C4 crystallizes in the hexagonal P6_3/mmc space group. The structure is three-dimensional. Hf is bonded to six C 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 (2.31 Å) and three longer (2.46 Å) Hf–C bond lengths. There are two inequivalent Al sites. In the first Al site, Al is bonded to four C atoms to form AlC4 tetrahedra that share corners with three equivalent HfC6 octahedra, corners with seven equivalent AlC4 tetrahedra, and edges with three equivalent HfC6 octahedra. The corner-sharing octahedral tilt angles are 18°. There are one shorter (2.03 Å) and three longer (2.05 Å) Al–C bond lengths. In the second Al site, Al is bonded in a trigonal planar geometry to three equivalent C atoms. All Al–C bond lengths are 1.93 Å. There are three inequivalent C sites. In the first C site, C is bonded to three equivalent Hf and three equivalent Al atoms to form distorted 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 5°. In the second C site, C is bonded to five Al atoms to form CAl5 trigonal bipyramids that share corners with six equivalent CHf3Al3 octahedra and corners with six equivalent CAl5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 70°. In the third C site, C is bonded to six equivalent Hf atoms to form a mixture of edge and corner-sharing CHf6 octahedra. The corner-sharing octahedral tilt angles are 5°.