Ca11Si4O18Cl crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(2), and one Cl(1) atom. In the second Ca site, Ca(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form CaO6 octahedra that share corners with two equivalent Ca(2)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. In the third Ca site, Ca(3) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded to one Ca(3), two equivalent Ca(1), and one Si(1) atom to form distorted OCa3Si tetrahedra that share corners with two equivalent O(3)Ca6 octahedra, corners with four equivalent O(2)Ca3Si tetrahedra, and edges with three equivalent O(2)Ca3Si tetrahedra. The corner-sharing octahedral tilt angles are 65°. In the third O site, O(3) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form distorted OCa6 octahedra that share corners with two equivalent O(3)Ca6 octahedra and corners with eight equivalent O(2)Ca3Si tetrahedra. The corner-sharing octahedra are not tilted. Cl(1) is bonded in a body-centered cubic geometry to eight equivalent Ca(1) atoms.
Ca11Si4O18Cl crystallizes in the tetragonal I4/mmm space group. There are three inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(3), two equivalent O(1), two equivalent O(2), and one Cl(1) atom. The Ca(1)-O(3) bond length is 2.60 Å. Both Ca(1)-O(1) bond lengths are 2.42 Å. Both Ca(1)-O(2) bond lengths are 2.32 Å. The Ca(1)-Cl(1) bond length is 3.28 Å. In the second Ca site, Ca(2) is bonded to two equivalent O(3) and four equivalent O(1) atoms to form CaO6 octahedra that share corners with two equivalent Ca(2)O6 octahedra and corners with four equivalent Si(1)O4 tetrahedra. The corner-sharing octahedra are not tilted. Both Ca(2)-O(3) bond lengths are 2.23 Å. All Ca(2)-O(1) bond lengths are 2.40 Å. In the third Ca site, Ca(3) is bonded in a body-centered cubic geometry to eight equivalent O(2) atoms. All Ca(3)-O(2) bond lengths are 2.52 Å. Si(1) is bonded to two equivalent O(1) and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. Both Si(1)-O(1) bond lengths are 1.65 Å. Both Si(1)-O(2) bond lengths are 1.67 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded to one Ca(3), two equivalent Ca(1), and one Si(1) atom to form distorted OCa3Si tetrahedra that share corners with two equivalent O(3)Ca6 octahedra, corners with four equivalent O(2)Ca3Si tetrahedra, and edges with three equivalent O(2)Ca3Si tetrahedra. The corner-sharing octahedral tilt angles are 65°. In the third O site, O(3) is bonded to two equivalent Ca(2) and four equivalent Ca(1) atoms to form distorted OCa6 octahedra that share corners with two equivalent O(3)Ca6 octahedra and corners with eight equivalent O(2)Ca3Si tetrahedra. The corner-sharing octahedra are not tilted. Cl(1) is bonded in a body-centered cubic geometry to eight equivalent Ca(1) atoms.