YbErSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Yb(1) is bonded to six equivalent Se(1) atoms to form YbSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. Er(1) is bonded to six equivalent Se(1) atoms to form ErSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. Se(1) is bonded to three equivalent Yb(1) and three equivalent Er(1) atoms to form a mixture of corner and edge-sharing SeYb3Er3 octahedra. The corner-sharing octahedra are not tilted.
YbErSe2 is Caswellsilverite structured and crystallizes in the trigonal R-3m space group. Yb(1) is bonded to six equivalent Se(1) atoms to form YbSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Yb(1)-Se(1) bond lengths are 2.88 Å. Er(1) is bonded to six equivalent Se(1) atoms to form ErSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Er(1)-Se(1) bond lengths are 2.86 Å. Se(1) is bonded to three equivalent Yb(1) and three equivalent Er(1) atoms to form a mixture of corner and edge-sharing SeYb3Er3 octahedra. The corner-sharing octahedra are not tilted.