Ca11AlSi3O18Cl crystallizes in the orthorhombic Fmm2 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one Cl(1) atom. In the second Ca site, Ca(2) is bonded in a body-centered cubic geometry to two equivalent O(5), two equivalent O(7), and four equivalent O(3) atoms. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(6), one O(7), one O(8), and one Cl(1) atom. In the fourth Ca site, Ca(4) is bonded to one O(1), one O(4), one O(6), one O(8), and two equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. Al(1) is bonded to two equivalent O(5) and two equivalent O(8) atoms to form AlO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 44°. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. In the second Si site, Si(2) is bonded to one O(4), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded to two equivalent Ca(1), two equivalent Ca(3), and two equivalent Ca(4) atoms to form distorted OCa6 octahedra that share corners with two equivalent O(2)Ca6 octahedra, corners with two equivalent O(5)Ca3Al tetrahedra, corners with four equivalent O(3)Ca3Si trigonal pyramids, and edges with two equivalent O(8)Ca3Al trigonal pyramids. The corner-sharing octahedral tilt angles are 1°. In the third O site, O(3) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom to form distorted OCa3Si trigonal pyramids that share corners with two equivalent O(2)Ca6 octahedra,  a cornercorner with one O(5)Ca3Al tetrahedra,  a cornercorner with one O(8)Ca3Al trigonal pyramid, corners with two equivalent O(3)Ca3Si trigonal pyramids,  an edgeedge with one O(5)Ca3Al tetrahedra, and  an edgeedge with one O(3)Ca3Si trigonal pyramid. The corner-sharing octahedral tilt angles range from 65-66°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Al(1) atom to form distorted OCa3Al tetrahedra that share corners with two equivalent O(2)Ca6 octahedra, corners with two equivalent O(8)Ca3Al trigonal pyramids, corners with two equivalent O(3)Ca3Si trigonal pyramids,  an edgeedge with one O(5)Ca3Al tetrahedra, and edges with two equivalent O(3)Ca3Si trigonal pyramids. The corner-sharing octahedral tilt angles are 61°. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(3), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(3), and one Si(1) atom. In the eighth O site, O(8) is bonded to one Ca(4), two equivalent Ca(3), and one Al(1) atom to form distorted OCa3Al trigonal pyramids that share corners with two equivalent O(5)Ca3Al tetrahedra,  a cornercorner with one O(8)Ca3Al trigonal pyramid, corners with two equivalent O(3)Ca3Si trigonal pyramids, and edges with two equivalent O(2)Ca6 octahedra. Cl(1) is bonded in a body-centered cubic geometry to four equivalent Ca(1) and four equivalent Ca(3) atoms.
Ca11AlSi3O18Cl crystallizes in the orthorhombic Fmm2 space group. There are four inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 5-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(5), and one Cl(1) atom. The Ca(1)-O(1) bond length is 2.42 Å. The Ca(1)-O(2) bond length is 2.63 Å. The Ca(1)-O(3) bond length is 2.31 Å. The Ca(1)-O(4) bond length is 2.44 Å. The Ca(1)-O(5) bond length is 2.24 Å. The Ca(1)-Cl(1) bond length is 3.29 Å. In the second Ca site, Ca(2) is bonded in a body-centered cubic geometry to two equivalent O(5), two equivalent O(7), and four equivalent O(3) atoms. Both Ca(2)-O(5) bond lengths are 2.45 Å. Both Ca(2)-O(7) bond lengths are 2.59 Å. All Ca(2)-O(3) bond lengths are 2.59 Å. In the third Ca site, Ca(3) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(6), one O(7), one O(8), and one Cl(1) atom. The Ca(3)-O(2) bond length is 2.58 Å. The Ca(3)-O(3) bond length is 2.33 Å. The Ca(3)-O(6) bond length is 2.41 Å. The Ca(3)-O(7) bond length is 2.33 Å. The Ca(3)-O(8) bond length is 2.33 Å. The Ca(3)-Cl(1) bond length is 3.27 Å. In the fourth Ca site, Ca(4) is bonded to one O(1), one O(4), one O(6), one O(8), and two equivalent O(2) atoms to form CaO6 octahedra that share corners with two equivalent Ca(4)O6 octahedra,  a cornercorner with one Al(1)O4 tetrahedra,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 1°. The Ca(4)-O(1) bond length is 2.41 Å. The Ca(4)-O(4) bond length is 2.39 Å. The Ca(4)-O(6) bond length is 2.41 Å. The Ca(4)-O(8) bond length is 2.32 Å. Both Ca(4)-O(2) bond lengths are 2.21 Å. Al(1) is bonded to two equivalent O(5) and two equivalent O(8) atoms to form AlO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 44°. Both Al(1)-O(5) bond lengths are 1.79 Å. Both Al(1)-O(8) bond lengths are 1.77 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to two equivalent O(1) and two equivalent O(7) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 42°. Both Si(1)-O(1) bond lengths are 1.65 Å. Both Si(1)-O(7) bond lengths are 1.66 Å. In the second Si site, Si(2) is bonded to one O(4), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with two equivalent Ca(4)O6 octahedra. The corner-sharing octahedral tilt angles are 43°. The Si(2)-O(4) bond length is 1.65 Å. The Si(2)-O(6) bond length is 1.64 Å. Both Si(2)-O(3) bond lengths are 1.66 Å. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(1), and one Si(1) atom. In the second O site, O(2) is bonded to two equivalent Ca(1), two equivalent Ca(3), and two equivalent Ca(4) atoms to form distorted OCa6 octahedra that share corners with two equivalent O(2)Ca6 octahedra, corners with two equivalent O(5)Ca3Al tetrahedra, corners with four equivalent O(3)Ca3Si trigonal pyramids, and edges with two equivalent O(8)Ca3Al trigonal pyramids. The corner-sharing octahedral tilt angles are 1°. In the third O site, O(3) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(2) atom to form distorted OCa3Si trigonal pyramids that share corners with two equivalent O(2)Ca6 octahedra,  a cornercorner with one O(5)Ca3Al tetrahedra,  a cornercorner with one O(8)Ca3Al trigonal pyramid, corners with two equivalent O(3)Ca3Si trigonal pyramids,  an edgeedge with one O(5)Ca3Al tetrahedra, and  an edgeedge with one O(3)Ca3Si trigonal pyramid. The corner-sharing octahedral tilt angles range from 65-66°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded to one Ca(2), two equivalent Ca(1), and one Al(1) atom to form distorted OCa3Al tetrahedra that share corners with two equivalent O(2)Ca6 octahedra, corners with two equivalent O(8)Ca3Al trigonal pyramids, corners with two equivalent O(3)Ca3Si trigonal pyramids,  an edgeedge with one O(5)Ca3Al tetrahedra, and edges with two equivalent O(3)Ca3Si trigonal pyramids. The corner-sharing octahedral tilt angles are 61°. In the sixth O site, O(6) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(3), and one Si(2) atom. In the seventh O site, O(7) is bonded in a 4-coordinate geometry to one Ca(2), two equivalent Ca(3), and one Si(1) atom. In the eighth O site, O(8) is bonded to one Ca(4), two equivalent Ca(3), and one Al(1) atom to form distorted OCa3Al trigonal pyramids that share corners with two equivalent O(5)Ca3Al tetrahedra,  a cornercorner with one O(8)Ca3Al trigonal pyramid, corners with two equivalent O(3)Ca3Si trigonal pyramids, and edges with two equivalent O(2)Ca6 octahedra. Cl(1) is bonded in a body-centered cubic geometry to four equivalent Ca(1) and four equivalent Ca(3) atoms.