Tl5Se2Br crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 3-coordinate geometry to three equivalent Se(1) atoms. In the second Tl site, Tl(2) is bonded to four equivalent Se(1) and two equivalent Br(1) atoms to form corner-sharing TlSe4Br2 octahedra. The corner-sharing octahedral tilt angles range from 0-40°. Se(1) is bonded in a 8-coordinate geometry to two equivalent Tl(2) and six equivalent Tl(1) atoms. Br(1) is bonded in a linear geometry to two equivalent Tl(2) atoms.
Tl5Se2Br crystallizes in the tetragonal I4/mcm space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded in a 3-coordinate geometry to three equivalent Se(1) atoms. There is one shorter (3.06 Å) and two longer (3.27 Å) Tl(1)-Se(1) bond lengths. In the second Tl site, Tl(2) is bonded to four equivalent Se(1) and two equivalent Br(1) atoms to form corner-sharing TlSe4Br2 octahedra. The corner-sharing octahedral tilt angles range from 0-40°. All Tl(2)-Se(1) bond lengths are 3.29 Å. Both Tl(2)-Br(1) bond lengths are 3.28 Å. Se(1) is bonded in a 8-coordinate geometry to two equivalent Tl(2) and six equivalent Tl(1) atoms. Br(1) is bonded in a linear geometry to two equivalent Tl(2) atoms.