TlErSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Er(1) is bonded to six equivalent Se(1) atoms to form ErSe6 octahedra that share corners with six equivalent Tl(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 11°. Tl(1) is bonded to six equivalent Se(1) atoms to form distorted TlSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 11°. Se(1) is bonded to three equivalent Er(1) and three equivalent Tl(1) atoms to form a mixture of distorted edge and corner-sharing SeEr3Tl3 octahedra. The corner-sharing octahedra are not tilted.
TlErSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Er(1) is bonded to six equivalent Se(1) atoms to form ErSe6 octahedra that share corners with six equivalent Tl(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 11°. All Er(1)-Se(1) bond lengths are 2.85 Å. Tl(1) is bonded to six equivalent Se(1) atoms to form distorted TlSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent Tl(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 11°. All Tl(1)-Se(1) bond lengths are 3.32 Å. Se(1) is bonded to three equivalent Er(1) and three equivalent Tl(1) atoms to form a mixture of distorted edge and corner-sharing SeEr3Tl3 octahedra. The corner-sharing octahedra are not tilted.