Ca2Tl2O5 crystallizes in the orthorhombic Cmc2_1 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(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. In the second Ca site, Ca(2) is bonded to one O(1), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form CaO6 octahedra that share  a cornercorner with one Tl(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, edges with two equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with three equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form TlO6 octahedra that share corners with two equivalent Ca(2)O6 octahedra, corners with two equivalent Tl(2)O6 octahedra, edges with two equivalent Tl(1)O6 octahedra, edges with three equivalent Ca(2)O6 octahedra, and edges with three equivalent Tl(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. In the second Tl site, Tl(2) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form TlO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, edges with two equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with three equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-63°. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), two equivalent Ca(1), and one Tl(2) atom to form OCa3Tl tetrahedra that share  a cornercorner with one O(4)Ca2Tl4 octahedra, corners with three equivalent O(5)Ca2Tl3 square pyramids, corners with two equivalent O(1)Ca3Tl tetrahedra, corners with four equivalent O(2)Ca2Tl3 trigonal bipyramids, corners with four equivalent O(3)Ca4Tl trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra,  an edgeedge with one O(2)Ca2Tl3 trigonal bipyramid, and  an edgeedge with one O(3)Ca4Tl trigonal bipyramid. The corner-sharing octahedral tilt angles are 9°. In the second O site, O(2) is bonded to two equivalent Ca(1), one Tl(1), and two equivalent Tl(2) atoms to form distorted OCa2Tl3 trigonal bipyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with four equivalent O(1)Ca3Tl tetrahedra, corners with three equivalent O(3)Ca4Tl trigonal bipyramids, edges with three equivalent O(4)Ca2Tl4 octahedra, edges with two equivalent O(5)Ca2Tl3 square pyramids,  an edgeedge with one O(1)Ca3Tl tetrahedra,  an edgeedge with one O(3)Ca4Tl trigonal bipyramid, and edges with two equivalent O(2)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Tl(1) atom to form distorted OCa4Tl trigonal bipyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with four equivalent O(5)Ca2Tl3 square pyramids, corners with four equivalent O(1)Ca3Tl tetrahedra, corners with three equivalent O(2)Ca2Tl3 trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra,  an edgeedge with one O(5)Ca2Tl3 square pyramid,  an edgeedge with one O(1)Ca3Tl tetrahedra,  an edgeedge with one O(2)Ca2Tl3 trigonal bipyramid, and edges with two equivalent O(3)Ca4Tl trigonal bipyramids. The corner-sharing octahedral tilt angles are 43°. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), two equivalent Tl(1), and two equivalent Tl(2) atoms to form OCa2Tl4 octahedra that share corners with two equivalent O(5)Ca2Tl3 square pyramids,  a cornercorner with one O(1)Ca3Tl tetrahedra, corners with two equivalent O(2)Ca2Tl3 trigonal bipyramids, corners with two equivalent O(3)Ca4Tl trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra, edges with three equivalent O(5)Ca2Tl3 square pyramids, edges with two equivalent O(1)Ca3Tl tetrahedra, edges with two equivalent O(3)Ca4Tl trigonal bipyramids, and edges with three equivalent O(2)Ca2Tl3 trigonal bipyramids. In the fifth O site, O(5) is bonded to two equivalent Ca(2), one Tl(2), and two equivalent Tl(1) atoms to form OCa2Tl3 square pyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with three equivalent O(1)Ca3Tl tetrahedra, corners with four equivalent O(3)Ca4Tl trigonal bipyramids, edges with three equivalent O(4)Ca2Tl4 octahedra, edges with two equivalent O(5)Ca2Tl3 square pyramids,  an edgeedge with one O(3)Ca4Tl trigonal bipyramid, and edges with two equivalent O(2)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°.
Ca2Tl2O5 crystallizes in the orthorhombic Cmc2_1 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(4), two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. The Ca(1)-O(4) bond length is 2.71 Å. Both Ca(1)-O(1) bond lengths are 2.32 Å. Both Ca(1)-O(2) bond lengths are 2.52 Å. Both Ca(1)-O(3) bond lengths are 2.56 Å. In the second Ca site, Ca(2) is bonded to one O(1), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form CaO6 octahedra that share  a cornercorner with one Tl(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, edges with two equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with three equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 15-63°. The Ca(2)-O(1) bond length is 2.25 Å. The Ca(2)-O(4) bond length is 2.47 Å. Both Ca(2)-O(3) bond lengths are 2.39 Å. Both Ca(2)-O(5) bond lengths are 2.39 Å. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form TlO6 octahedra that share corners with two equivalent Ca(2)O6 octahedra, corners with two equivalent Tl(2)O6 octahedra, edges with two equivalent Tl(1)O6 octahedra, edges with three equivalent Ca(2)O6 octahedra, and edges with three equivalent Tl(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-15°. The Tl(1)-O(2) bond length is 2.16 Å. The Tl(1)-O(3) bond length is 2.12 Å. Both Tl(1)-O(4) bond lengths are 2.41 Å. Both Tl(1)-O(5) bond lengths are 2.43 Å. In the second Tl site, Tl(2) is bonded to one O(1), one O(5), two equivalent O(2), and two equivalent O(4) atoms to form TlO6 octahedra that share  a cornercorner with one Ca(2)O6 octahedra, corners with two equivalent Tl(1)O6 octahedra, edges with two equivalent Ca(2)O6 octahedra, edges with two equivalent Tl(2)O6 octahedra, and edges with three equivalent Tl(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-63°. The Tl(2)-O(1) bond length is 2.09 Å. The Tl(2)-O(5) bond length is 2.22 Å. Both Tl(2)-O(2) bond lengths are 2.40 Å. Both Tl(2)-O(4) bond lengths are 2.41 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), two equivalent Ca(1), and one Tl(2) atom to form OCa3Tl tetrahedra that share  a cornercorner with one O(4)Ca2Tl4 octahedra, corners with three equivalent O(5)Ca2Tl3 square pyramids, corners with two equivalent O(1)Ca3Tl tetrahedra, corners with four equivalent O(2)Ca2Tl3 trigonal bipyramids, corners with four equivalent O(3)Ca4Tl trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra,  an edgeedge with one O(2)Ca2Tl3 trigonal bipyramid, and  an edgeedge with one O(3)Ca4Tl trigonal bipyramid. The corner-sharing octahedral tilt angles are 9°. In the second O site, O(2) is bonded to two equivalent Ca(1), one Tl(1), and two equivalent Tl(2) atoms to form distorted OCa2Tl3 trigonal bipyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with four equivalent O(1)Ca3Tl tetrahedra, corners with three equivalent O(3)Ca4Tl trigonal bipyramids, edges with three equivalent O(4)Ca2Tl4 octahedra, edges with two equivalent O(5)Ca2Tl3 square pyramids,  an edgeedge with one O(1)Ca3Tl tetrahedra,  an edgeedge with one O(3)Ca4Tl trigonal bipyramid, and edges with two equivalent O(2)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 10°. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Tl(1) atom to form distorted OCa4Tl trigonal bipyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with four equivalent O(5)Ca2Tl3 square pyramids, corners with four equivalent O(1)Ca3Tl tetrahedra, corners with three equivalent O(2)Ca2Tl3 trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra,  an edgeedge with one O(5)Ca2Tl3 square pyramid,  an edgeedge with one O(1)Ca3Tl tetrahedra,  an edgeedge with one O(2)Ca2Tl3 trigonal bipyramid, and edges with two equivalent O(3)Ca4Tl trigonal bipyramids. The corner-sharing octahedral tilt angles are 43°. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), two equivalent Tl(1), and two equivalent Tl(2) atoms to form OCa2Tl4 octahedra that share corners with two equivalent O(5)Ca2Tl3 square pyramids,  a cornercorner with one O(1)Ca3Tl tetrahedra, corners with two equivalent O(2)Ca2Tl3 trigonal bipyramids, corners with two equivalent O(3)Ca4Tl trigonal bipyramids, edges with two equivalent O(4)Ca2Tl4 octahedra, edges with three equivalent O(5)Ca2Tl3 square pyramids, edges with two equivalent O(1)Ca3Tl tetrahedra, edges with two equivalent O(3)Ca4Tl trigonal bipyramids, and edges with three equivalent O(2)Ca2Tl3 trigonal bipyramids. In the fifth O site, O(5) is bonded to two equivalent Ca(2), one Tl(2), and two equivalent Tl(1) atoms to form OCa2Tl3 square pyramids that share corners with two equivalent O(4)Ca2Tl4 octahedra, corners with three equivalent O(1)Ca3Tl tetrahedra, corners with four equivalent O(3)Ca4Tl trigonal bipyramids, edges with three equivalent O(4)Ca2Tl4 octahedra, edges with two equivalent O(5)Ca2Tl3 square pyramids,  an edgeedge with one O(3)Ca4Tl trigonal bipyramid, and edges with two equivalent O(2)Ca2Tl3 trigonal bipyramids. The corner-sharing octahedral tilt angles are 9°.