Ca4Tl3O9 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. In the second Ca site, Ca(2) is bonded to one O(3), two equivalent O(4), and three equivalent O(2) atoms to form CaO6 octahedra that share  a cornercorner with one Tl(1)O6 octahedra, corners with two equivalent Tl(2)O6 octahedra, edges with three equivalent Tl(2)O6 octahedra, and edges with four equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-62°. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(3), two equivalent O(5), and three equivalent O(1) atoms to form TlO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, and edges with five equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. In the second Tl site, Tl(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form TlO6 octahedra that share corners with four equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with six equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles are 7°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Tl(1) atoms to form distorted OCa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ca2Tl4 octahedra, corners with five equivalent O(3)Ca3Tl tetrahedra, corners with two equivalent O(4)Ca4Tl trigonal bipyramids, edges with three equivalent O(5)Ca2Tl4 octahedra,  an edgeedge with one O(3)Ca3Tl tetrahedra,  an edgeedge with one O(4)Ca4Tl trigonal bipyramid, and edges with four equivalent O(1)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 8°. In the second O site, O(2) is bonded to three equivalent Ca(2) and two equivalent Tl(2) atoms to form OCa3Tl2 square pyramids that share corners with two equivalent O(2)Ca3Tl2 square pyramids, corners with three equivalent O(3)Ca3Tl tetrahedra, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, edges with five equivalent O(2)Ca3Tl2 square pyramids, and edges with three equivalent O(4)Ca4Tl trigonal bipyramids. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Tl(1) atom to form OCa3Tl tetrahedra that share corners with three equivalent O(2)Ca3Tl2 square pyramids, corners with two equivalent O(3)Ca3Tl tetrahedra, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, corners with five equivalent O(1)Ca2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ca2Tl4 octahedra,  an edgeedge with one O(1)Ca2Tl3 trigonal bipyramid, and  an edgeedge with one O(4)Ca4Tl trigonal bipyramid. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Tl(2) atom to form distorted OCa4Tl trigonal bipyramids that share corners with two equivalent O(5)Ca2Tl4 octahedra, corners with four equivalent O(2)Ca3Tl2 square pyramids, corners with four equivalent O(3)Ca3Tl tetrahedra,  a cornercorner with one O(4)Ca4Tl trigonal bipyramid, corners with two equivalent O(1)Ca2Tl3 trigonal bipyramids, edges with three equivalent O(2)Ca3Tl2 square pyramids,  an edgeedge with one O(3)Ca3Tl tetrahedra,  an edgeedge with one O(1)Ca2Tl3 trigonal bipyramid, and edges with two equivalent O(4)Ca4Tl trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. In the fifth O site, O(5) is bonded to two equivalent Ca(1) and four equivalent Tl(1) atoms to form OCa2Tl4 octahedra that share corners with four equivalent O(1)Ca2Tl3 trigonal bipyramids, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, edges with two equivalent O(5)Ca2Tl4 octahedra, edges with four equivalent O(3)Ca3Tl tetrahedra, and edges with six equivalent O(1)Ca2Tl3 trigonal bipyramids.
Ca4Tl3O9 crystallizes in the monoclinic C2/m space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a 7-coordinate geometry to one O(5), two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. The Ca(1)-O(5) bond length is 2.81 Å. Both Ca(1)-O(1) bond lengths are 2.57 Å. Both Ca(1)-O(3) bond lengths are 2.32 Å. Both Ca(1)-O(4) bond lengths are 2.54 Å. In the second Ca site, Ca(2) is bonded to one O(3), two equivalent O(4), and three equivalent O(2) atoms to form CaO6 octahedra that share  a cornercorner with one Tl(1)O6 octahedra, corners with two equivalent Tl(2)O6 octahedra, edges with three equivalent Tl(2)O6 octahedra, and edges with four equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 7-62°. The Ca(2)-O(3) bond length is 2.27 Å. Both Ca(2)-O(4) bond lengths are 2.41 Å. There are two shorter (2.42 Å) and one longer (2.43 Å) Ca(2)-O(2) bond length. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(3), two equivalent O(5), and three equivalent O(1) atoms to form TlO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, and edges with five equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-62°. The Tl(1)-O(3) bond length is 2.11 Å. Both Tl(1)-O(5) bond lengths are 2.40 Å. There is one shorter (2.20 Å) and two longer (2.44 Å) Tl(1)-O(1) bond lengths. In the second Tl site, Tl(2) is bonded to two equivalent O(4) and four equivalent O(2) atoms to form TlO6 octahedra that share corners with four equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with six equivalent Ca(2)O6 octahedra. The corner-sharing octahedral tilt angles are 7°. Both Tl(2)-O(4) bond lengths are 2.22 Å. All Tl(2)-O(2) bond lengths are 2.39 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Ca(1) and three equivalent Tl(1) atoms to form distorted OCa2Tl3 trigonal bipyramids that share corners with two equivalent O(5)Ca2Tl4 octahedra, corners with five equivalent O(3)Ca3Tl tetrahedra, corners with two equivalent O(4)Ca4Tl trigonal bipyramids, edges with three equivalent O(5)Ca2Tl4 octahedra,  an edgeedge with one O(3)Ca3Tl tetrahedra,  an edgeedge with one O(4)Ca4Tl trigonal bipyramid, and edges with four equivalent O(1)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 8°. In the second O site, O(2) is bonded to three equivalent Ca(2) and two equivalent Tl(2) atoms to form OCa3Tl2 square pyramids that share corners with two equivalent O(2)Ca3Tl2 square pyramids, corners with three equivalent O(3)Ca3Tl tetrahedra, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, edges with five equivalent O(2)Ca3Tl2 square pyramids, and edges with three equivalent O(4)Ca4Tl trigonal bipyramids. In the third O site, O(3) is bonded to one Ca(2), two equivalent Ca(1), and one Tl(1) atom to form OCa3Tl tetrahedra that share corners with three equivalent O(2)Ca3Tl2 square pyramids, corners with two equivalent O(3)Ca3Tl tetrahedra, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, corners with five equivalent O(1)Ca2Tl3 trigonal bipyramids, edges with two equivalent O(5)Ca2Tl4 octahedra,  an edgeedge with one O(1)Ca2Tl3 trigonal bipyramid, and  an edgeedge with one O(4)Ca4Tl trigonal bipyramid. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Tl(2) atom to form distorted OCa4Tl trigonal bipyramids that share corners with two equivalent O(5)Ca2Tl4 octahedra, corners with four equivalent O(2)Ca3Tl2 square pyramids, corners with four equivalent O(3)Ca3Tl tetrahedra,  a cornercorner with one O(4)Ca4Tl trigonal bipyramid, corners with two equivalent O(1)Ca2Tl3 trigonal bipyramids, edges with three equivalent O(2)Ca3Tl2 square pyramids,  an edgeedge with one O(3)Ca3Tl tetrahedra,  an edgeedge with one O(1)Ca2Tl3 trigonal bipyramid, and edges with two equivalent O(4)Ca4Tl trigonal bipyramids. The corner-sharing octahedral tilt angles are 44°. In the fifth O site, O(5) is bonded to two equivalent Ca(1) and four equivalent Tl(1) atoms to form OCa2Tl4 octahedra that share corners with four equivalent O(1)Ca2Tl3 trigonal bipyramids, corners with four equivalent O(4)Ca4Tl trigonal bipyramids, edges with two equivalent O(5)Ca2Tl4 octahedra, edges with four equivalent O(3)Ca3Tl tetrahedra, and edges with six equivalent O(1)Ca2Tl3 trigonal bipyramids.