Zr2Al3C4 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form ZrC6 octahedra that share corners with three equivalent Al(2)C6 octahedra, edges with three equivalent Al(2)C6 octahedra, and edges with six equivalent Zr(1)C6 octahedra. The corner-sharing octahedral tilt angles are 8°. In the second Zr site, Zr(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent C(3) atoms. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded in a 6-coordinate geometry to three equivalent Zr(2) and three equivalent Al(3) atoms. In the second Al site, Al(2) is bonded to three equivalent C(2) and three equivalent C(4) atoms to form AlC6 octahedra that share corners with three equivalent Zr(1)C6 octahedra, corners with three equivalent C(1)Al3C tetrahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent Al(2)C6 octahedra. The corner-sharing octahedral tilt angles are 8°. In the third Al site, Al(3) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Al(1) and three equivalent C(1) atoms. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Al(3) and one C(4) atom to form CAl3C tetrahedra that share corners with three equivalent Al(2)C6 octahedra and corners with six equivalent C(1)Al3C tetrahedra. The corner-sharing octahedral tilt angles are 53°. In the second C site, C(2) is bonded to three equivalent Zr(1) and three equivalent Al(2) atoms to form CZr3Al3 octahedra that share corners with three equivalent C(3)Zr6 octahedra, edges with three equivalent C(3)Zr6 octahedra, and edges with six equivalent C(2)Zr3Al3 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third C site, C(3) is bonded to three equivalent Zr(1) and three equivalent Zr(2) atoms to form CZr6 octahedra that share corners with three equivalent C(2)Zr3Al3 octahedra, edges with three equivalent C(2)Zr3Al3 octahedra, and edges with six equivalent C(3)Zr6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the fourth C site, C(4) is bonded in a rectangular see-saw-like geometry to three equivalent Al(2) and one C(1) atom.
Zr2Al3C4 crystallizes in the hexagonal P6_3mc space group. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded to three equivalent C(2) and three equivalent C(3) atoms to form ZrC6 octahedra that share corners with three equivalent Al(2)C6 octahedra, edges with three equivalent Al(2)C6 octahedra, and edges with six equivalent Zr(1)C6 octahedra. The corner-sharing octahedral tilt angles are 8°. All Zr(1)-C(2) bond lengths are 2.33 Å. All Zr(1)-C(3) bond lengths are 2.37 Å. In the second Zr site, Zr(2) is bonded in a 3-coordinate geometry to three equivalent Al(1) and three equivalent C(3) atoms. All Zr(2)-Al(1) bond lengths are 3.07 Å. All Zr(2)-C(3) bond lengths are 2.25 Å. There are three inequivalent Al sites. In the first Al site, Al(1) is bonded in a 6-coordinate geometry to three equivalent Zr(2) and three equivalent Al(3) atoms. All Al(1)-Al(3) bond lengths are 2.95 Å. In the second Al site, Al(2) is bonded to three equivalent C(2) and three equivalent C(4) atoms to form AlC6 octahedra that share corners with three equivalent Zr(1)C6 octahedra, corners with three equivalent C(1)Al3C tetrahedra, edges with three equivalent Zr(1)C6 octahedra, and edges with six equivalent Al(2)C6 octahedra. The corner-sharing octahedral tilt angles are 8°. All Al(2)-C(2) bond lengths are 2.13 Å. All Al(2)-C(4) bond lengths are 2.34 Å. In the third Al site, Al(3) is bonded in a distorted trigonal non-coplanar geometry to three equivalent Al(1) and three equivalent C(1) atoms. All Al(3)-C(1) bond lengths are 2.09 Å. There are four inequivalent C sites. In the first C site, C(1) is bonded to three equivalent Al(3) and one C(4) atom to form CAl3C tetrahedra that share corners with three equivalent Al(2)C6 octahedra and corners with six equivalent C(1)Al3C tetrahedra. The corner-sharing octahedral tilt angles are 53°. The C(1)-C(4) bond length is 1.31 Å. In the second C site, C(2) is bonded to three equivalent Zr(1) and three equivalent Al(2) atoms to form CZr3Al3 octahedra that share corners with three equivalent C(3)Zr6 octahedra, edges with three equivalent C(3)Zr6 octahedra, and edges with six equivalent C(2)Zr3Al3 octahedra. The corner-sharing octahedral tilt angles are 1°. In the third C site, C(3) is bonded to three equivalent Zr(1) and three equivalent Zr(2) atoms to form CZr6 octahedra that share corners with three equivalent C(2)Zr3Al3 octahedra, edges with three equivalent C(2)Zr3Al3 octahedra, and edges with six equivalent C(3)Zr6 octahedra. The corner-sharing octahedral tilt angles are 1°. In the fourth C site, C(4) is bonded in a rectangular see-saw-like geometry to three equivalent Al(2) and one C(1) atom.