Ti12AlSi3C8 is MAX Phase-derived structured and crystallizes in the trigonal P-3m1 space group. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to six equivalent C(1) atoms to form edge-sharing TiC6 octahedra. In the second Ti site, Ti(2) is bonded to two equivalent C(2) and four equivalent C(1) atoms to form edge-sharing TiC6 octahedra. In the third Ti site, Ti(3) is bonded in a 3-coordinate geometry to one Al(1), two equivalent Si(1), one C(2), and two equivalent C(1) atoms. In the fourth Ti site, Ti(4) is bonded in a 3-coordinate geometry to three equivalent Si(1) and three equivalent C(1) atoms. Al(1) is bonded to six equivalent Ti(3) atoms to form distorted AlTi6 cuboctahedra that share corners with six equivalent C(2)Ti6 octahedra and edges with six equivalent C(1)Ti6 octahedra. The corner-sharing octahedral tilt angles are 17°. Si(1) is bonded in a 6-coordinate geometry to two equivalent Ti(4) and four equivalent Ti(3) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Ti(1), one Ti(4), two equivalent Ti(2), and two equivalent Ti(3) atoms to form CTi6 octahedra that share corners with three equivalent C(1)Ti6 octahedra,  an edgeedge with one Al(1)Ti6 cuboctahedra, edges with three equivalent C(2)Ti6 octahedra, and edges with six equivalent C(1)Ti6 octahedra. The corner-sharing octahedra are not tilted. In the second C site, C(2) is bonded to three equivalent Ti(2) and three equivalent Ti(3) atoms to form CTi6 octahedra that share corners with three equivalent Al(1)Ti6 cuboctahedra, corners with three equivalent C(2)Ti6 octahedra, and edges with nine equivalent C(1)Ti6 octahedra. The corner-sharing octahedra are not tilted.
Ti12AlSi3C8 is MAX Phase-derived structured and crystallizes in the trigonal P-3m1 space group. There are four inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to six equivalent C(1) atoms to form edge-sharing TiC6 octahedra. All Ti(1)-C(1) bond lengths are 2.20 Å. In the second Ti site, Ti(2) is bonded to two equivalent C(2) and four equivalent C(1) atoms to form edge-sharing TiC6 octahedra. Both Ti(2)-C(2) bond lengths are 2.18 Å. All Ti(2)-C(1) bond lengths are 2.19 Å. In the third Ti site, Ti(3) is bonded in a 3-coordinate geometry to one Al(1), two equivalent Si(1), one C(2), and two equivalent C(1) atoms. The Ti(3)-Al(1) bond length is 2.76 Å. Both Ti(3)-Si(1) bond lengths are 2.73 Å. The Ti(3)-C(2) bond length is 2.08 Å. Both Ti(3)-C(1) bond lengths are 2.09 Å. In the fourth Ti site, Ti(4) is bonded in a 3-coordinate geometry to three equivalent Si(1) and three equivalent C(1) atoms. All Ti(4)-Si(1) bond lengths are 2.75 Å. All Ti(4)-C(1) bond lengths are 2.11 Å. Al(1) is bonded to six equivalent Ti(3) atoms to form distorted AlTi6 cuboctahedra that share corners with six equivalent C(2)Ti6 octahedra and edges with six equivalent C(1)Ti6 octahedra. The corner-sharing octahedral tilt angles are 17°. Si(1) is bonded in a 6-coordinate geometry to two equivalent Ti(4) and four equivalent Ti(3) atoms. There are two inequivalent C sites. In the first C site, C(1) is bonded to one Ti(1), one Ti(4), two equivalent Ti(2), and two equivalent Ti(3) atoms to form CTi6 octahedra that share corners with three equivalent C(1)Ti6 octahedra,  an edgeedge with one Al(1)Ti6 cuboctahedra, edges with three equivalent C(2)Ti6 octahedra, and edges with six equivalent C(1)Ti6 octahedra. The corner-sharing octahedra are not tilted. In the second C site, C(2) is bonded to three equivalent Ti(2) and three equivalent Ti(3) atoms to form CTi6 octahedra that share corners with three equivalent Al(1)Ti6 cuboctahedra, corners with three equivalent C(2)Ti6 octahedra, and edges with nine equivalent C(1)Ti6 octahedra. The corner-sharing octahedra are not tilted.