Ca6Si2H6O13 crystallizes in the trigonal P-3 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 65°. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5) and three equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. In the second Si site, Si(2) is bonded to one O(5) and three equivalent O(4) atoms to form SiO4 tetrahedra that share corners with six equivalent Ca(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-55°. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. There are five inequivalent O sites. In the first O site, O(5) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the second O site, O(1) is bonded in a distorted single-bond geometry to one Ca(2), two equivalent Ca(1), and one H(1) atom. In the third O site, O(2) is bonded in a distorted single-bond geometry to one Ca(1), two equivalent Ca(2), and one H(2) atom. In the fourth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fifth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), two equivalent Ca(1), and one Si(2) atom.
Ca6Si2H6O13 crystallizes in the trigonal P-3 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(2), one O(3), two equivalent O(1), and two equivalent O(4) atoms to form distorted CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, and  an edgeedge with one Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 65°. The Ca(1)-O(2) bond length is 2.43 Å. The Ca(1)-O(3) bond length is 2.36 Å. There is one shorter (2.35 Å) and one longer (2.44 Å) Ca(1)-O(1) bond length. There is one shorter (2.34 Å) and one longer (2.41 Å) Ca(1)-O(4) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), two equivalent O(2), and two equivalent O(3) atoms. The Ca(2)-O(1) bond length is 2.40 Å. The Ca(2)-O(4) bond length is 2.52 Å. There is one shorter (2.32 Å) and one longer (2.41 Å) Ca(2)-O(2) bond length. There is one shorter (2.38 Å) and one longer (2.59 Å) Ca(2)-O(3) bond length. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(5) and three equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Ca(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 51°. The Si(1)-O(5) bond length is 1.66 Å. All Si(1)-O(3) bond lengths are 1.64 Å. In the second Si site, Si(2) is bonded to one O(5) and three equivalent O(4) atoms to form SiO4 tetrahedra that share corners with six equivalent Ca(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 50-55°. The Si(2)-O(5) bond length is 1.66 Å. All Si(2)-O(4) bond lengths are 1.64 Å. There are two inequivalent H sites. In the first H site, H(1) is bonded in a single-bond geometry to one O(1) atom. The H(1)-O(1) bond length is 0.97 Å. In the second H site, H(2) is bonded in a single-bond geometry to one O(2) atom. The H(2)-O(2) bond length is 0.97 Å. There are five inequivalent O sites. In the first O site, O(5) is bonded in a linear geometry to one Si(1) and one Si(2) atom. In the second O site, O(1) is bonded in a distorted single-bond geometry to one Ca(2), two equivalent Ca(1), and one H(1) atom. In the third O site, O(2) is bonded in a distorted single-bond geometry to one Ca(1), two equivalent Ca(2), and one H(2) atom. In the fourth O site, O(3) is bonded in a distorted rectangular see-saw-like geometry to one Ca(1), two equivalent Ca(2), and one Si(1) atom. In the fifth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), two equivalent Ca(1), and one Si(2) atom.