Al4C3 is Aluminum carbonitride-derived structured and crystallizes in the trigonal R-3m space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent C(1) atoms to form a mixture of distorted corner and edge-sharing AlC4 trigonal pyramids. In the second Al site, Al(2) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of distorted corner and edge-sharing AlC4 tetrahedra. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Al(2) and four equivalent Al(1) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(2)Al6 octahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. In the second C site, C(2) is bonded to six equivalent Al(2) atoms to form CAl6 octahedra that share corners with six equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(2)Al6 octahedra.
Al4C3 is Aluminum carbonitride-derived structured and crystallizes in the trigonal R-3m space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to four equivalent C(1) atoms to form a mixture of distorted corner and edge-sharing AlC4 trigonal pyramids. There are three shorter (1.95 Å) and one longer (2.16 Å) Al(1)-C(1) bond length. In the second Al site, Al(2) is bonded to one C(1) and three equivalent C(2) atoms to form a mixture of distorted corner and edge-sharing AlC4 tetrahedra. The Al(2)-C(1) bond length is 1.91 Å. All Al(2)-C(2) bond lengths are 2.17 Å. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Al(2) and four equivalent Al(1) atoms to form CAl5 trigonal bipyramids that share corners with three equivalent C(2)Al6 octahedra, corners with six equivalent C(1)Al5 trigonal bipyramids, and edges with three equivalent C(1)Al5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 63°. In the second C site, C(2) is bonded to six equivalent Al(2) atoms to form CAl6 octahedra that share corners with six equivalent C(1)Al5 trigonal bipyramids and edges with six equivalent C(2)Al6 octahedra.