Ca2Ti9O13 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), one O(6), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. There are five inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(6) and four equivalent O(7) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 10°. In the second Ti site, Ti(2) is bonded to one O(4), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-12°. In the third Ti site, Ti(3) is bonded to one O(5), two equivalent O(6), and three equivalent O(7) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-10°. In the fourth Ti site, Ti(4) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-39°. In the fifth Ti site, Ti(5) is bonded to one O(2), one O(7), two equivalent O(5), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-39°. There are seven inequivalent O sites. In the first O site, O(7) is bonded to one Ti(5), two equivalent Ti(1), and three equivalent Ti(3) atoms to form OTi6 octahedra that share corners with two equivalent O(6)CaTi5 octahedra, corners with two equivalent O(7)Ti6 octahedra,  a cornercorner with one O(5)Ca2Ti3 trigonal bipyramid, edges with five equivalent O(6)CaTi5 octahedra, edges with five equivalent O(7)Ti6 octahedra, and edges with two equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the second O site, O(1) is bonded to two equivalent Ti(4) and four equivalent Ti(2) atoms to form OTi6 octahedra that share corners with four equivalent O(3)CaTi5 octahedra, edges with two equivalent O(1)Ti6 octahedra, edges with six equivalent O(3)CaTi5 octahedra, and edges with four equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ti(4), and one Ti(5) atom. In the fourth O site, O(3) is bonded to one Ca(1), two equivalent Ti(4), and three equivalent Ti(2) atoms to form distorted OCaTi5 octahedra that share  a cornercorner with one O(6)CaTi5 octahedra, corners with two equivalent O(1)Ti6 octahedra, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, corners with three equivalent O(4)Ca2Ti3 trigonal bipyramids, edges with three equivalent O(1)Ti6 octahedra, edges with four equivalent O(3)CaTi5 octahedra, and edges with three equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 11-50°. In the fifth O site, O(4) is bonded to two equivalent Ca(1), one Ti(2), and two equivalent Ti(4) atoms to form distorted OCa2Ti3 trigonal bipyramids that share corners with two equivalent O(6)CaTi5 octahedra, corners with three equivalent O(3)CaTi5 octahedra, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(1)Ti6 octahedra, edges with three equivalent O(3)CaTi5 octahedra,  an edgeedge with one O(5)Ca2Ti3 trigonal bipyramid, and edges with two equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 1-42°. In the sixth O site, O(5) is bonded to two equivalent Ca(1), one Ti(3), and two equivalent Ti(5) atoms to form distorted OCa2Ti3 trigonal bipyramids that share  a cornercorner with one O(7)Ti6 octahedra, corners with two equivalent O(3)CaTi5 octahedra, corners with two equivalent O(6)CaTi5 octahedra, corners with two equivalent O(4)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(7)Ti6 octahedra, edges with three equivalent O(6)CaTi5 octahedra,  an edgeedge with one O(4)Ca2Ti3 trigonal bipyramid, and edges with two equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 7-41°. In the seventh O site, O(6) is bonded to one Ca(1), one Ti(1), two equivalent Ti(3), and two equivalent Ti(5) atoms to form distorted OCaTi5 octahedra that share  a cornercorner with one O(3)CaTi5 octahedra,  a cornercorner with one O(6)CaTi5 octahedra, corners with two equivalent O(7)Ti6 octahedra, corners with two equivalent O(4)Ca2Ti3 trigonal bipyramids, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(6)CaTi5 octahedra, edges with five equivalent O(7)Ti6 octahedra, and edges with three equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-50°.
Ca2Ti9O13 crystallizes in the monoclinic C2/m space group. Ca(1) is bonded in a 8-coordinate geometry to one O(3), one O(6), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. The Ca(1)-O(3) bond length is 2.57 Å. The Ca(1)-O(6) bond length is 2.71 Å. Both Ca(1)-O(2) bond lengths are 2.35 Å. Both Ca(1)-O(4) bond lengths are 2.40 Å. Both Ca(1)-O(5) bond lengths are 2.41 Å. There are five inequivalent Ti sites. In the first Ti site, Ti(1) is bonded to two equivalent O(6) and four equivalent O(7) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles are 10°. Both Ti(1)-O(6) bond lengths are 2.24 Å. All Ti(1)-O(7) bond lengths are 2.17 Å. In the second Ti site, Ti(2) is bonded to one O(4), two equivalent O(1), and three equivalent O(3) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-12°. The Ti(2)-O(4) bond length is 2.07 Å. Both Ti(2)-O(1) bond lengths are 2.20 Å. There are two shorter (2.08 Å) and one longer (2.21 Å) Ti(2)-O(3) bond length. In the third Ti site, Ti(3) is bonded to one O(5), two equivalent O(6), and three equivalent O(7) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-10°. The Ti(3)-O(5) bond length is 2.09 Å. Both Ti(3)-O(6) bond lengths are 2.10 Å. There are two shorter (2.16 Å) and one longer (2.17 Å) Ti(3)-O(7) bond length. In the fourth Ti site, Ti(4) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(4) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 0-39°. The Ti(4)-O(1) bond length is 2.14 Å. The Ti(4)-O(2) bond length is 2.02 Å. Both Ti(4)-O(3) bond lengths are 2.10 Å. Both Ti(4)-O(4) bond lengths are 2.09 Å. In the fifth Ti site, Ti(5) is bonded to one O(2), one O(7), two equivalent O(5), and two equivalent O(6) atoms to form a mixture of corner and edge-sharing TiO6 octahedra. The corner-sharing octahedral tilt angles range from 5-39°. The Ti(5)-O(2) bond length is 1.94 Å. The Ti(5)-O(7) bond length is 2.10 Å. Both Ti(5)-O(5) bond lengths are 2.10 Å. Both Ti(5)-O(6) bond lengths are 2.10 Å. There are seven inequivalent O sites. In the first O site, O(7) is bonded to one Ti(5), two equivalent Ti(1), and three equivalent Ti(3) atoms to form OTi6 octahedra that share corners with two equivalent O(6)CaTi5 octahedra, corners with two equivalent O(7)Ti6 octahedra,  a cornercorner with one O(5)Ca2Ti3 trigonal bipyramid, edges with five equivalent O(6)CaTi5 octahedra, edges with five equivalent O(7)Ti6 octahedra, and edges with two equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-12°. In the second O site, O(1) is bonded to two equivalent Ti(4) and four equivalent Ti(2) atoms to form OTi6 octahedra that share corners with four equivalent O(3)CaTi5 octahedra, edges with two equivalent O(1)Ti6 octahedra, edges with six equivalent O(3)CaTi5 octahedra, and edges with four equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 11°. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Ca(1), one Ti(4), and one Ti(5) atom. In the fourth O site, O(3) is bonded to one Ca(1), two equivalent Ti(4), and three equivalent Ti(2) atoms to form distorted OCaTi5 octahedra that share  a cornercorner with one O(6)CaTi5 octahedra, corners with two equivalent O(1)Ti6 octahedra, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, corners with three equivalent O(4)Ca2Ti3 trigonal bipyramids, edges with three equivalent O(1)Ti6 octahedra, edges with four equivalent O(3)CaTi5 octahedra, and edges with three equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 11-50°. In the fifth O site, O(4) is bonded to two equivalent Ca(1), one Ti(2), and two equivalent Ti(4) atoms to form distorted OCa2Ti3 trigonal bipyramids that share corners with two equivalent O(6)CaTi5 octahedra, corners with three equivalent O(3)CaTi5 octahedra, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(1)Ti6 octahedra, edges with three equivalent O(3)CaTi5 octahedra,  an edgeedge with one O(5)Ca2Ti3 trigonal bipyramid, and edges with two equivalent O(4)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 1-42°. In the sixth O site, O(5) is bonded to two equivalent Ca(1), one Ti(3), and two equivalent Ti(5) atoms to form distorted OCa2Ti3 trigonal bipyramids that share  a cornercorner with one O(7)Ti6 octahedra, corners with two equivalent O(3)CaTi5 octahedra, corners with two equivalent O(6)CaTi5 octahedra, corners with two equivalent O(4)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(7)Ti6 octahedra, edges with three equivalent O(6)CaTi5 octahedra,  an edgeedge with one O(4)Ca2Ti3 trigonal bipyramid, and edges with two equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 7-41°. In the seventh O site, O(6) is bonded to one Ca(1), one Ti(1), two equivalent Ti(3), and two equivalent Ti(5) atoms to form distorted OCaTi5 octahedra that share  a cornercorner with one O(3)CaTi5 octahedra,  a cornercorner with one O(6)CaTi5 octahedra, corners with two equivalent O(7)Ti6 octahedra, corners with two equivalent O(4)Ca2Ti3 trigonal bipyramids, corners with two equivalent O(5)Ca2Ti3 trigonal bipyramids, edges with two equivalent O(6)CaTi5 octahedra, edges with five equivalent O(7)Ti6 octahedra, and edges with three equivalent O(5)Ca2Ti3 trigonal bipyramids. The corner-sharing octahedral tilt angles range from 0-50°.