Ca9(Si3O16)2 crystallizes in the triclinic P-1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(10), one O(11), one O(12), and two equivalent O(4) atoms to form distorted CaO6 octahedra that share  a cornercorner with one Ca(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)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 56°. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(11), one O(14), one O(2), one O(9), and two equivalent O(3) atoms. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(12), one O(15), one O(2), one O(4), and two equivalent O(10) atoms. In the fourth Ca site, Ca(4) is bonded in a 7-coordinate geometry to one O(11), one O(13), one O(2), one O(3), one O(7), and two equivalent O(9) atoms. In the fifth Ca site, Ca(5) is bonded to two equivalent O(12), two equivalent O(15), and two equivalent O(16) atoms to form distorted CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent O(2)Ca3O tetrahedra. The corner-sharing octahedral tilt angles are 56°. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-68°. In the third Si site, Si(3) is bonded to one O(10), one O(6), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(3), and one Si(1) atom. In the second O site, O(2) is bonded to one Ca(2), one Ca(3), one Ca(4), and one O(15) atom to form distorted OCa3O tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent O(10)Ca3Si tetrahedra, and corners with three equivalent O(9)Ca3Si trigonal pyramids. The corner-sharing octahedral tilt angles are 41°. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(3), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Ca(4), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one O(13) atom. In the ninth O site, O(9) is bonded to one Ca(2), two equivalent Ca(4), and one Si(3) atom to form distorted OCa3Si trigonal pyramids that share  a cornercorner with one O(10)Ca3Si tetrahedra, corners with three equivalent O(2)Ca3O tetrahedra, and  an edgeedge with one O(9)Ca3Si trigonal pyramid. In the tenth O site, O(10) is bonded to one Ca(1), two equivalent Ca(3), and one Si(3) atom to form distorted OCa3Si tetrahedra that share corners with two equivalent O(2)Ca3O tetrahedra,  a cornercorner with one O(9)Ca3Si trigonal pyramid, and  an edgeedge with one O(10)Ca3Si tetrahedra. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Ca(4) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ca(1), one Ca(3), and one Ca(5) atom. In the thirteenth O site, O(13) is bonded in a water-like geometry to one Ca(4) and one O(8) atom. In the fourteenth O site, O(14) is bonded in an L-shaped geometry to one Ca(2) and one O(16) atom. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one O(2) atom. In the sixteenth O site, O(16) is bonded in a 2-coordinate geometry to one Ca(5) and one O(14) atom.
Ca9(Si3O16)2 crystallizes in the triclinic P-1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(1), one O(10), one O(11), one O(12), and two equivalent O(4) atoms to form distorted CaO6 octahedra that share  a cornercorner with one Ca(5)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra,  a cornercorner with one Si(3)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 56°. The Ca(1)-O(1) bond length is 2.44 Å. The Ca(1)-O(10) bond length is 2.48 Å. The Ca(1)-O(11) bond length is 2.27 Å. The Ca(1)-O(12) bond length is 2.27 Å. There is one shorter (2.49 Å) and one longer (2.60 Å) Ca(1)-O(4) bond length. In the second Ca site, Ca(2) is bonded in a 6-coordinate geometry to one O(11), one O(14), one O(2), one O(9), and two equivalent O(3) atoms. The Ca(2)-O(11) bond length is 2.23 Å. The Ca(2)-O(14) bond length is 2.68 Å. The Ca(2)-O(2) bond length is 2.60 Å. The Ca(2)-O(9) bond length is 2.29 Å. There is one shorter (2.35 Å) and one longer (2.38 Å) Ca(2)-O(3) bond length. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(1), one O(12), one O(15), one O(2), one O(4), and two equivalent O(10) atoms. The Ca(3)-O(1) bond length is 2.37 Å. The Ca(3)-O(12) bond length is 2.26 Å. The Ca(3)-O(15) bond length is 2.74 Å. The Ca(3)-O(2) bond length is 2.71 Å. The Ca(3)-O(4) bond length is 2.41 Å. There is one shorter (2.35 Å) and one longer (2.49 Å) Ca(3)-O(10) bond length. In the fourth Ca site, Ca(4) is bonded in a 7-coordinate geometry to one O(11), one O(13), one O(2), one O(3), one O(7), and two equivalent O(9) atoms. The Ca(4)-O(11) bond length is 2.22 Å. The Ca(4)-O(13) bond length is 2.51 Å. The Ca(4)-O(2) bond length is 2.50 Å. The Ca(4)-O(3) bond length is 2.61 Å. The Ca(4)-O(7) bond length is 2.63 Å. There is one shorter (2.39 Å) and one longer (2.47 Å) Ca(4)-O(9) bond length. In the fifth Ca site, Ca(5) is bonded to two equivalent O(12), two equivalent O(15), and two equivalent O(16) atoms to form distorted CaO6 octahedra that share corners with two equivalent Ca(1)O6 octahedra and corners with two equivalent O(2)Ca3O tetrahedra. The corner-sharing octahedral tilt angles are 56°. Both Ca(5)-O(12) bond lengths are 2.16 Å. Both Ca(5)-O(15) bond lengths are 2.51 Å. Both Ca(5)-O(16) bond lengths are 2.70 Å. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(5), one O(6), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Si(2)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles are 64°. The Si(1)-O(1) bond length is 1.59 Å. The Si(1)-O(5) bond length is 1.63 Å. The Si(1)-O(6) bond length is 1.64 Å. The Si(1)-O(8) bond length is 1.77 Å. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-68°. The Si(2)-O(3) bond length is 1.64 Å. The Si(2)-O(4) bond length is 1.62 Å. The Si(2)-O(5) bond length is 1.66 Å. The Si(2)-O(7) bond length is 1.66 Å. In the third Si site, Si(3) is bonded to one O(10), one O(6), one O(7), and one O(9) atom to form SiO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles are 67°. The Si(3)-O(10) bond length is 1.62 Å. The Si(3)-O(6) bond length is 1.66 Å. The Si(3)-O(7) bond length is 1.65 Å. The Si(3)-O(9) bond length is 1.63 Å. There are sixteen inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Ca(1), one Ca(3), and one Si(1) atom. In the second O site, O(2) is bonded to one Ca(2), one Ca(3), one Ca(4), and one O(15) atom to form distorted OCa3O tetrahedra that share  a cornercorner with one Ca(5)O6 octahedra, corners with two equivalent O(10)Ca3Si tetrahedra, and corners with three equivalent O(9)Ca3Si trigonal pyramids. The corner-sharing octahedral tilt angles are 41°. The O(2)-O(15) bond length is 1.31 Å. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(4), two equivalent Ca(2), and one Si(2) atom. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ca(3), two equivalent Ca(1), and one Si(2) atom. In the fifth O site, O(5) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the seventh O site, O(7) is bonded in a distorted bent 150 degrees geometry to one Ca(4), one Si(2), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Si(1) and one O(13) atom. The O(8)-O(13) bond length is 1.35 Å. In the ninth O site, O(9) is bonded to one Ca(2), two equivalent Ca(4), and one Si(3) atom to form distorted OCa3Si trigonal pyramids that share  a cornercorner with one O(10)Ca3Si tetrahedra, corners with three equivalent O(2)Ca3O tetrahedra, and  an edgeedge with one O(9)Ca3Si trigonal pyramid. In the tenth O site, O(10) is bonded to one Ca(1), two equivalent Ca(3), and one Si(3) atom to form distorted OCa3Si tetrahedra that share corners with two equivalent O(2)Ca3O tetrahedra,  a cornercorner with one O(9)Ca3Si trigonal pyramid, and  an edgeedge with one O(10)Ca3Si tetrahedra. In the eleventh O site, O(11) is bonded in a trigonal planar geometry to one Ca(1), one Ca(2), and one Ca(4) atom. In the twelfth O site, O(12) is bonded in a trigonal planar geometry to one Ca(1), one Ca(3), and one Ca(5) atom. In the thirteenth O site, O(13) is bonded in a water-like geometry to one Ca(4) and one O(8) atom. In the fourteenth O site, O(14) is bonded in an L-shaped geometry to one Ca(2) and one O(16) atom. The O(14)-O(16) bond length is 1.26 Å. In the fifteenth O site, O(15) is bonded in a 3-coordinate geometry to one Ca(3), one Ca(5), and one O(2) atom. In the sixteenth O site, O(16) is bonded in a 2-coordinate geometry to one Ca(5) and one O(14) atom.