CaAlSi crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to three equivalent Al(1), three equivalent Al(2), three equivalent Si(1), and three equivalent Si(2) atoms to form a mixture of face and edge-sharing CaAl6Si6 cuboctahedra. In the second Ca site, Ca(2) is bonded to six equivalent Al(1) and six equivalent Si(1) atoms to form a mixture of face and edge-sharing CaAl6Si6 cuboctahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ca(2), and three equivalent Si(1) atoms. In the second Al site, Al(2) is bonded in a distorted trigonal planar geometry to six equivalent Ca(1) and three equivalent Si(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ca(2), and three equivalent Al(1) atoms. In the second Si site, Si(2) is bonded in a distorted trigonal planar geometry to six equivalent Ca(1) and three equivalent Al(2) atoms.
CaAlSi crystallizes in the hexagonal P6_3/mmc space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to three equivalent Al(1), three equivalent Al(2), three equivalent Si(1), and three equivalent Si(2) atoms to form a mixture of face and edge-sharing CaAl6Si6 cuboctahedra. All Ca(1)-Al(1) bond lengths are 3.18 Å. All Ca(1)-Al(2) bond lengths are 3.25 Å. All Ca(1)-Si(1) bond lengths are 3.37 Å. All Ca(1)-Si(2) bond lengths are 3.25 Å. In the second Ca site, Ca(2) is bonded to six equivalent Al(1) and six equivalent Si(1) atoms to form a mixture of face and edge-sharing CaAl6Si6 cuboctahedra. All Ca(2)-Al(1) bond lengths are 3.38 Å. All Ca(2)-Si(1) bond lengths are 3.19 Å. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ca(2), and three equivalent Si(1) atoms. All Al(1)-Si(1) bond lengths are 2.44 Å. In the second Al site, Al(2) is bonded in a distorted trigonal planar geometry to six equivalent Ca(1) and three equivalent Si(2) atoms. All Al(2)-Si(2) bond lengths are 2.42 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded in a 9-coordinate geometry to three equivalent Ca(1), three equivalent Ca(2), and three equivalent Al(1) atoms. In the second Si site, Si(2) is bonded in a distorted trigonal planar geometry to six equivalent Ca(1) and three equivalent Al(2) atoms.