CaAl2Si2(O4Cl)2 crystallizes in the trigonal R3m space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent Cl(1) atoms. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent Cl(2) atoms. In the third Ca site, Ca(3) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(4) atoms. Al(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form AlO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(3) is bonded to one Ca(1), one Ca(3), and two equivalent Al(1) atoms to form distorted edge-sharing OCa2Al2 tetrahedra. In the third O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), and two equivalent Si(1) atoms. In the fourth O site, O(5) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the fifth O site, O(6) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the sixth O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Al(1) atoms. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a single-bond geometry to one Ca(1) atom. In the second Cl site, Cl(2) is bonded in a single-bond geometry to one Ca(2) atom.
CaAl2Si2(O4Cl)2 crystallizes in the trigonal R3m space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent Cl(1) atoms. All Ca(1)-O(3) bond lengths are 2.32 Å. All Ca(1)-Cl(1) bond lengths are 2.85 Å. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to three equivalent O(4) and three equivalent Cl(2) atoms. All Ca(2)-O(4) bond lengths are 2.39 Å. All Ca(2)-Cl(2) bond lengths are 2.81 Å. In the third Ca site, Ca(3) is bonded in a 6-coordinate geometry to three equivalent O(3) and three equivalent O(4) atoms. All Ca(3)-O(3) bond lengths are 2.46 Å. All Ca(3)-O(4) bond lengths are 2.85 Å. Al(1) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form AlO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. The Al(1)-O(1) bond length is 1.74 Å. The Al(1)-O(3) bond length is 1.82 Å. The Al(1)-O(5) bond length is 1.73 Å. The Al(1)-O(6) bond length is 1.75 Å. Si(1) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Si(1)O4 tetrahedra. The Si(1)-O(2) bond length is 1.65 Å. The Si(1)-O(4) bond length is 1.72 Å. The Si(1)-O(5) bond length is 1.59 Å. The Si(1)-O(6) bond length is 1.60 Å. There are six inequivalent O sites. In the first O site, O(2) is bonded in a distorted bent 120 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(3) is bonded to one Ca(1), one Ca(3), and two equivalent Al(1) atoms to form distorted edge-sharing OCa2Al2 tetrahedra. In the third O site, O(4) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), and two equivalent Si(1) atoms. In the fourth O site, O(5) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the fifth O site, O(6) is bonded in a linear geometry to one Al(1) and one Si(1) atom. In the sixth O site, O(1) is bonded in a bent 120 degrees geometry to two equivalent Al(1) atoms. There are two inequivalent Cl sites. In the first Cl site, Cl(1) is bonded in a single-bond geometry to one Ca(1) atom. In the second Cl site, Cl(2) is bonded in a single-bond geometry to one Ca(2) atom.