Tl2Ba2CuO6 crystallizes in the monoclinic C2/m space group. Ba(1) is bonded in a 9-coordinate geometry to one O(3), four equivalent O(1), and four equivalent O(2) atoms. Cu(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. Tl(1) is bonded in a 5-coordinate geometry to one O(1) and four equivalent O(3) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to four equivalent Ba(1) and one Tl(1) atom. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Cu(1) atoms to form distorted OBa4Cu2 octahedra that share corners with two equivalent O(2)Ba4Cu2 octahedra, corners with four equivalent O(3)BaTl4 square pyramids, edges with two equivalent O(2)Ba4Cu2 octahedra, and faces with four equivalent O(2)Ba4Cu2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Ba(1) and four equivalent Tl(1) atoms to form distorted OBaTl4 square pyramids that share corners with four equivalent O(2)Ba4Cu2 octahedra, corners with six equivalent O(3)BaTl4 square pyramids, and edges with three equivalent O(3)BaTl4 square pyramids. The corner-sharing octahedral tilt angles range from 43-47°.
Tl2Ba2CuO6 crystallizes in the monoclinic C2/m space group. Ba(1) is bonded in a 9-coordinate geometry to one O(3), four equivalent O(1), and four equivalent O(2) atoms. The Ba(1)-O(3) bond length is 3.12 Å. There are a spread of Ba(1)-O(1) bond distances ranging from 2.86-2.94 Å. All Ba(1)-O(2) bond lengths are 2.75 Å. Cu(1) is bonded in a square co-planar geometry to four equivalent O(2) atoms. All Cu(1)-O(2) bond lengths are 1.95 Å. Tl(1) is bonded in a 5-coordinate geometry to one O(1) and four equivalent O(3) atoms. The Tl(1)-O(1) bond length is 2.03 Å. There are a spread of Tl(1)-O(3) bond distances ranging from 2.08-2.77 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded in a 5-coordinate geometry to four equivalent Ba(1) and one Tl(1) atom. In the second O site, O(2) is bonded to four equivalent Ba(1) and two equivalent Cu(1) atoms to form distorted OBa4Cu2 octahedra that share corners with two equivalent O(2)Ba4Cu2 octahedra, corners with four equivalent O(3)BaTl4 square pyramids, edges with two equivalent O(2)Ba4Cu2 octahedra, and faces with four equivalent O(2)Ba4Cu2 octahedra. The corner-sharing octahedra are not tilted. In the third O site, O(3) is bonded to one Ba(1) and four equivalent Tl(1) atoms to form distorted OBaTl4 square pyramids that share corners with four equivalent O(2)Ba4Cu2 octahedra, corners with six equivalent O(3)BaTl4 square pyramids, and edges with three equivalent O(3)BaTl4 square pyramids. The corner-sharing octahedral tilt angles range from 43-47°.