Ca5(Si3O11)2 crystallizes in the triclinic P1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(20), one O(5), one O(6), one O(8), and one O(9) atom. In the second Ca site, Ca(2) is bonded to one O(10), one O(11), one O(19), one O(5), one O(6), one O(7), and one O(9) atom to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(5)O4 tetrahedra, and  an edgeedge with one Si(6)O4 tetrahedra. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(12), one O(18), one O(6), one O(7), and one O(8) atom. In the fourth Ca site, Ca(4) is bonded in a 7-coordinate geometry to one O(11), one O(12), one O(17), one O(5), one O(7), one O(8), and one O(9) atom. In the fifth Ca site, Ca(5) is bonded in a 6-coordinate geometry to one O(13), one O(16), one O(17), one O(21), one O(22), and one O(3) atom. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(11), one O(13), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O7 pentagonal bipyramids,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(5)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(12), one O(14), one O(2), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(1), one O(15), one O(17), and one O(3) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(15), one O(18), one O(2), and one O(4) atom to form corner-sharing SiO4 tetrahedra. In the fifth Si site, Si(5) is bonded to one O(13), one O(3), one O(5), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O7 pentagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. In the sixth Si site, Si(6) is bonded to one O(10), one O(14), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  an edgeedge with one Ca(2)O7 pentagonal bipyramid. There are twenty-two inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(5), one Si(3), and one Si(5) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(4) and one Si(6) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Si(5) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(6) atom to form a mixture of distorted edge and corner-sharing OCa3Si trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(2), one Ca(3), one Ca(4), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Si(5) atom. In the tenth O site, O(10) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(6) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), one Ca(4), and one Si(1) atom. In the twelfth O site, O(12) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Ca(5), one Si(1), and one Si(5) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(6) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Si(3) and one Si(4) atom. In the sixteenth O site, O(16) is bonded in a single-bond geometry to one Ca(5) atom. In the seventeenth O site, O(17) is bonded in a distorted trigonal planar geometry to one Ca(4), one Ca(5), and one Si(3) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Ca(3) and one Si(4) atom. In the nineteenth O site, O(19) is bonded in a single-bond geometry to one Ca(2) atom. In the twentieth O site, O(20) is bonded in a trigonal planar geometry to one Ca(1), one O(21), and one O(22) atom. In the twenty-first O site, O(21) is bonded in a water-like geometry to one Ca(5) and one O(20) atom. In the twenty-second O site, O(22) is bonded in an L-shaped geometry to one Ca(5) and one O(20) atom.
Ca5(Si3O11)2 crystallizes in the triclinic P1 space group. There are five inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(10), one O(12), one O(20), one O(5), one O(6), one O(8), and one O(9) atom. The Ca(1)-O(10) bond length is 2.41 Å. The Ca(1)-O(12) bond length is 2.42 Å. The Ca(1)-O(20) bond length is 2.90 Å. The Ca(1)-O(5) bond length is 2.51 Å. The Ca(1)-O(6) bond length is 2.36 Å. The Ca(1)-O(8) bond length is 2.33 Å. The Ca(1)-O(9) bond length is 2.56 Å. In the second Ca site, Ca(2) is bonded to one O(10), one O(11), one O(19), one O(5), one O(6), one O(7), and one O(9) atom to form distorted CaO7 pentagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(5)O4 tetrahedra, and  an edgeedge with one Si(6)O4 tetrahedra. The Ca(2)-O(10) bond length is 2.49 Å. The Ca(2)-O(11) bond length is 2.38 Å. The Ca(2)-O(19) bond length is 2.41 Å. The Ca(2)-O(5) bond length is 2.38 Å. The Ca(2)-O(6) bond length is 2.50 Å. The Ca(2)-O(7) bond length is 2.34 Å. The Ca(2)-O(9) bond length is 2.40 Å. In the third Ca site, Ca(3) is bonded in a 7-coordinate geometry to one O(10), one O(11), one O(12), one O(18), one O(6), one O(7), and one O(8) atom. The Ca(3)-O(10) bond length is 2.40 Å. The Ca(3)-O(11) bond length is 2.88 Å. The Ca(3)-O(12) bond length is 2.39 Å. The Ca(3)-O(18) bond length is 2.46 Å. The Ca(3)-O(6) bond length is 2.43 Å. The Ca(3)-O(7) bond length is 2.65 Å. The Ca(3)-O(8) bond length is 2.40 Å. In the fourth Ca site, Ca(4) is bonded in a 7-coordinate geometry to one O(11), one O(12), one O(17), one O(5), one O(7), one O(8), and one O(9) atom. The Ca(4)-O(11) bond length is 2.43 Å. The Ca(4)-O(12) bond length is 2.52 Å. The Ca(4)-O(17) bond length is 2.50 Å. The Ca(4)-O(5) bond length is 2.44 Å. The Ca(4)-O(7) bond length is 2.50 Å. The Ca(4)-O(8) bond length is 2.62 Å. The Ca(4)-O(9) bond length is 2.41 Å. In the fifth Ca site, Ca(5) is bonded in a 6-coordinate geometry to one O(13), one O(16), one O(17), one O(21), one O(22), and one O(3) atom. The Ca(5)-O(13) bond length is 2.40 Å. The Ca(5)-O(16) bond length is 2.49 Å. The Ca(5)-O(17) bond length is 2.26 Å. The Ca(5)-O(21) bond length is 2.44 Å. The Ca(5)-O(22) bond length is 2.42 Å. The Ca(5)-O(3) bond length is 2.53 Å. There are six inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(11), one O(13), and one O(7) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O7 pentagonal bipyramids,  a cornercorner with one Si(3)O4 tetrahedra, and  a cornercorner with one Si(5)O4 tetrahedra. The Si(1)-O(1) bond length is 1.65 Å. The Si(1)-O(11) bond length is 1.63 Å. The Si(1)-O(13) bond length is 1.69 Å. The Si(1)-O(7) bond length is 1.62 Å. In the second Si site, Si(2) is bonded to one O(12), one O(14), one O(2), and one O(8) atom to form corner-sharing SiO4 tetrahedra. The Si(2)-O(12) bond length is 1.64 Å. The Si(2)-O(14) bond length is 1.64 Å. The Si(2)-O(2) bond length is 1.65 Å. The Si(2)-O(8) bond length is 1.62 Å. In the third Si site, Si(3) is bonded to one O(1), one O(15), one O(17), and one O(3) atom to form corner-sharing SiO4 tetrahedra. The Si(3)-O(1) bond length is 1.66 Å. The Si(3)-O(15) bond length is 1.63 Å. The Si(3)-O(17) bond length is 1.61 Å. The Si(3)-O(3) bond length is 1.67 Å. In the fourth Si site, Si(4) is bonded to one O(15), one O(18), one O(2), and one O(4) atom to form corner-sharing SiO4 tetrahedra. The Si(4)-O(15) bond length is 1.62 Å. The Si(4)-O(18) bond length is 1.65 Å. The Si(4)-O(2) bond length is 1.63 Å. The Si(4)-O(4) bond length is 1.64 Å. In the fifth Si site, Si(5) is bonded to one O(13), one O(3), one O(5), and one O(9) atom to form SiO4 tetrahedra that share corners with two equivalent Ca(2)O7 pentagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and  a cornercorner with one Si(3)O4 tetrahedra. The Si(5)-O(13) bond length is 1.68 Å. The Si(5)-O(3) bond length is 1.66 Å. The Si(5)-O(5) bond length is 1.62 Å. The Si(5)-O(9) bond length is 1.60 Å. In the sixth Si site, Si(6) is bonded to one O(10), one O(14), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra,  a cornercorner with one Si(4)O4 tetrahedra, and  an edgeedge with one Ca(2)O7 pentagonal bipyramid. The Si(6)-O(10) bond length is 1.63 Å. The Si(6)-O(14) bond length is 1.64 Å. The Si(6)-O(4) bond length is 1.66 Å. The Si(6)-O(6) bond length is 1.63 Å. There are twenty-two inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Si(1) and one Si(3) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(4) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Ca(5), one Si(3), and one Si(5) atom. In the fourth O site, O(4) is bonded in a bent 120 degrees geometry to one Si(4) and one Si(6) atom. In the fifth O site, O(5) is bonded to one Ca(1), one Ca(2), one Ca(4), and one Si(5) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the sixth O site, O(6) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(6) atom to form a mixture of distorted edge and corner-sharing OCa3Si trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(2), one Ca(3), one Ca(4), and one Si(1) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the eighth O site, O(8) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the ninth O site, O(9) is bonded in a 4-coordinate geometry to one Ca(1), one Ca(2), one Ca(4), and one Si(5) atom. In the tenth O site, O(10) is bonded to one Ca(1), one Ca(2), one Ca(3), and one Si(6) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the eleventh O site, O(11) is bonded in a 4-coordinate geometry to one Ca(2), one Ca(3), one Ca(4), and one Si(1) atom. In the twelfth O site, O(12) is bonded to one Ca(1), one Ca(3), one Ca(4), and one Si(2) atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the thirteenth O site, O(13) is bonded in a 3-coordinate geometry to one Ca(5), one Si(1), and one Si(5) atom. In the fourteenth O site, O(14) is bonded in a bent 150 degrees geometry to one Si(2) and one Si(6) atom. In the fifteenth O site, O(15) is bonded in a linear geometry to one Si(3) and one Si(4) atom. In the sixteenth O site, O(16) is bonded in a single-bond geometry to one Ca(5) atom. In the seventeenth O site, O(17) is bonded in a distorted trigonal planar geometry to one Ca(4), one Ca(5), and one Si(3) atom. In the eighteenth O site, O(18) is bonded in a bent 120 degrees geometry to one Ca(3) and one Si(4) atom. In the nineteenth O site, O(19) is bonded in a single-bond geometry to one Ca(2) atom. In the twentieth O site, O(20) is bonded in a trigonal planar geometry to one Ca(1), one O(21), and one O(22) atom. The O(20)-O(21) bond length is 1.33 Å. The O(20)-O(22) bond length is 1.41 Å. In the twenty-first O site, O(21) is bonded in a water-like geometry to one Ca(5) and one O(20) atom. In the twenty-second O site, O(22) is bonded in an L-shaped geometry to one Ca(5) and one O(20) atom.