(CaAl2Si4O15)4(O2)3 crystallizes in the monoclinic C2/m space group. The structure consists of six water atoms inside a CaAl2Si4O15 framework. In the CaAl2Si4O15 framework, Ca(1) is bonded to one O(9), two equivalent O(11), two equivalent O(2), and two equivalent O(3) atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(1)O4 tetrahedra. Al(1) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ca(1)O7 pentagonal bipyramid. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Si(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the third O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the fourth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the fifth O site, O(7) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the sixth O site, O(9) is bonded in a single-bond geometry to one Ca(1) atom. In the seventh O site, O(11) is bonded in a single-bond geometry to one Ca(1) atom. In the eighth O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the ninth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(1) atom.
(CaAl2Si4O15)4(O2)3 crystallizes in the monoclinic C2/m space group. The structure consists of six water atoms inside a CaAl2Si4O15 framework. In the CaAl2Si4O15 framework, Ca(1) is bonded to one O(9), two equivalent O(11), two equivalent O(2), and two equivalent O(3) atoms to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and edges with two equivalent Al(1)O4 tetrahedra. The Ca(1)-O(9) bond length is 2.53 Å. Both Ca(1)-O(11) bond lengths are 2.57 Å. Both Ca(1)-O(2) bond lengths are 2.42 Å. Both Ca(1)-O(3) bond lengths are 2.34 Å. Al(1) is bonded to one O(2), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ca(1)O7 pentagonal bipyramid. The Al(1)-O(2) bond length is 1.80 Å. The Al(1)-O(3) bond length is 1.78 Å. The Al(1)-O(5) bond length is 1.75 Å. The Al(1)-O(7) bond length is 1.72 Å. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(5) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. The Si(1)-O(1) bond length is 1.64 Å. The Si(1)-O(2) bond length is 1.64 Å. The Si(1)-O(4) bond length is 1.64 Å. The Si(1)-O(5) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(6), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O7 pentagonal bipyramid,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(2)O4 tetrahedra, and corners with two equivalent Al(1)O4 tetrahedra. The Si(2)-O(3) bond length is 1.65 Å. The Si(2)-O(4) bond length is 1.64 Å. The Si(2)-O(6) bond length is 1.64 Å. The Si(2)-O(7) bond length is 1.61 Å. There are nine inequivalent O sites. In the first O site, O(3) is bonded in a distorted trigonal planar geometry to one Ca(1), one Al(1), and one Si(2) atom. In the second O site, O(4) is bonded in a bent 150 degrees geometry to one Si(1) and one Si(2) atom. In the third O site, O(5) is bonded in a distorted bent 150 degrees geometry to one Al(1) and one Si(1) atom. In the fourth O site, O(6) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the fifth O site, O(7) is bonded in a bent 150 degrees geometry to one Al(1) and one Si(2) atom. In the sixth O site, O(9) is bonded in a single-bond geometry to one Ca(1) atom. In the seventh O site, O(11) is bonded in a single-bond geometry to one Ca(1) atom. In the eighth O site, O(1) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the ninth O site, O(2) is bonded in a 3-coordinate geometry to one Ca(1), one Al(1), and one Si(1) atom.