Tl3In3SnSe8 crystallizes in the monoclinic C2 space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to two equivalent Se(1) and two equivalent Se(3) atoms to form distorted edge-sharing TlSe4 tetrahedra. In the second Tl site, Tl(2) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form edge-sharing TlSe4 tetrahedra. There are two inequivalent In sites. In the first In site, In(1) is bonded in a see-saw-like geometry to one Se(3), one Se(4), and two equivalent Se(2) atoms. In the second In site, In(2) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. Sn(1) is bonded in a distorted see-saw-like geometry to two equivalent Se(2) and two equivalent Se(4) atoms. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted L-shaped geometry to one Tl(1), one Tl(2), and one In(2) atom. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Tl(2), two equivalent In(1), and one Sn(1) atom. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Tl(1), one Tl(2), one In(1), and one In(2) atom. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Tl(2), one In(1), and one Sn(1) atom.
Tl3In3SnSe8 crystallizes in the monoclinic C2 space group. There are two inequivalent Tl sites. In the first Tl site, Tl(1) is bonded to two equivalent Se(1) and two equivalent Se(3) atoms to form distorted edge-sharing TlSe4 tetrahedra. Both Tl(1)-Se(1) bond lengths are 2.77 Å. Both Tl(1)-Se(3) bond lengths are 2.83 Å. In the second Tl site, Tl(2) is bonded to one Se(1), one Se(2), one Se(3), and one Se(4) atom to form edge-sharing TlSe4 tetrahedra. The Tl(2)-Se(1) bond length is 2.71 Å. The Tl(2)-Se(2) bond length is 2.72 Å. The Tl(2)-Se(3) bond length is 2.76 Å. The Tl(2)-Se(4) bond length is 2.70 Å. There are two inequivalent In sites. In the first In site, In(1) is bonded in a see-saw-like geometry to one Se(3), one Se(4), and two equivalent Se(2) atoms. The In(1)-Se(3) bond length is 2.90 Å. The In(1)-Se(4) bond length is 2.80 Å. There is one shorter (2.85 Å) and one longer (2.86 Å) In(1)-Se(2) bond length. In the second In site, In(2) is bonded in a 4-coordinate geometry to two equivalent Se(1) and two equivalent Se(3) atoms. Both In(2)-Se(1) bond lengths are 3.31 Å. Both In(2)-Se(3) bond lengths are 3.22 Å. Sn(1) is bonded in a distorted see-saw-like geometry to two equivalent Se(2) and two equivalent Se(4) atoms. Both Sn(1)-Se(2) bond lengths are 3.06 Å. Both Sn(1)-Se(4) bond lengths are 2.80 Å. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a distorted L-shaped geometry to one Tl(1), one Tl(2), and one In(2) atom. In the second Se site, Se(2) is bonded in a rectangular see-saw-like geometry to one Tl(2), two equivalent In(1), and one Sn(1) atom. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to one Tl(1), one Tl(2), one In(1), and one In(2) atom. In the fourth Se site, Se(4) is bonded in a trigonal non-coplanar geometry to one Tl(2), one In(1), and one Sn(1) atom.