Cr3TlSe5 crystallizes in the monoclinic C2/m space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. In the second Cr site, Cr(2) is bonded to two equivalent Se(3) and four equivalent Se(5) atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the third Cr site, Cr(3) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(4) atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. In the fourth Cr site, Cr(4) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 48°. Tl(1) is bonded in a 4-coordinate geometry to two equivalent Se(4) and two equivalent Se(5) atoms. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Cr(3), one Cr(4), and two equivalent Cr(1) atoms. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to one Cr(1) and two equivalent Cr(4) atoms. In the third Se site, Se(3) is bonded to one Cr(2), two equivalent Cr(3), and two equivalent Cr(4) atoms to form a mixture of distorted edge and corner-sharing SeCr5 square pyramids. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to three equivalent Cr(3) and two equivalent Tl(1) atoms. In the fifth Se site, Se(5) is bonded in a 3-coordinate geometry to one Cr(4), two equivalent Cr(2), and two equivalent Tl(1) atoms.
Cr3TlSe5 crystallizes in the monoclinic C2/m space group. There are four inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 49°. Both Cr(1)-Se(2) bond lengths are 2.57 Å. All Cr(1)-Se(1) bond lengths are 2.53 Å. In the second Cr site, Cr(2) is bonded to two equivalent Se(3) and four equivalent Se(5) atoms to form a mixture of edge and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 50°. Both Cr(2)-Se(3) bond lengths are 2.56 Å. All Cr(2)-Se(5) bond lengths are 2.56 Å. In the third Cr site, Cr(3) is bonded to one Se(1), two equivalent Se(3), and three equivalent Se(4) atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-50°. The Cr(3)-Se(1) bond length is 2.56 Å. Both Cr(3)-Se(3) bond lengths are 2.60 Å. There is one shorter (2.50 Å) and two longer (2.52 Å) Cr(3)-Se(4) bond lengths. In the fourth Cr site, Cr(4) is bonded to one Se(1), one Se(5), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of edge, face, and corner-sharing CrSe6 octahedra. The corner-sharing octahedral tilt angles are 48°. The Cr(4)-Se(1) bond length is 2.57 Å. The Cr(4)-Se(5) bond length is 2.51 Å. Both Cr(4)-Se(2) bond lengths are 2.50 Å. Both Cr(4)-Se(3) bond lengths are 2.67 Å. Tl(1) is bonded in a 4-coordinate geometry to two equivalent Se(4) and two equivalent Se(5) atoms. Both Tl(1)-Se(4) bond lengths are 3.38 Å. Both Tl(1)-Se(5) bond lengths are 3.33 Å. There are five inequivalent Se sites. In the first Se site, Se(1) is bonded in a rectangular see-saw-like geometry to one Cr(3), one Cr(4), and two equivalent Cr(1) atoms. In the second Se site, Se(2) is bonded in a distorted T-shaped geometry to one Cr(1) and two equivalent Cr(4) atoms. In the third Se site, Se(3) is bonded to one Cr(2), two equivalent Cr(3), and two equivalent Cr(4) atoms to form a mixture of distorted edge and corner-sharing SeCr5 square pyramids. In the fourth Se site, Se(4) is bonded in a 3-coordinate geometry to three equivalent Cr(3) and two equivalent Tl(1) atoms. In the fifth Se site, Se(5) is bonded in a 3-coordinate geometry to one Cr(4), two equivalent Cr(2), and two equivalent Tl(1) atoms.