YbTmSe2 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 Tm(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tm(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. Tm(1) is bonded to six equivalent Se(1) atoms to form TmSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tm(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. Se(1) is bonded to three equivalent Yb(1) and three equivalent Tm(1) atoms to form a mixture of edge and corner-sharing SeYb3Tm3 octahedra. The corner-sharing octahedra are not tilted.
YbTmSe2 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 Tm(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tm(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Yb(1)-Se(1) bond lengths are 2.88 Å. Tm(1) is bonded to six equivalent Se(1) atoms to form TmSe6 octahedra that share corners with six equivalent Yb(1)Se6 octahedra, edges with six equivalent Yb(1)Se6 octahedra, and edges with six equivalent Tm(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 1°. All Tm(1)-Se(1) bond lengths are 2.84 Å. Se(1) is bonded to three equivalent Yb(1) and three equivalent Tm(1) atoms to form a mixture of edge and corner-sharing SeYb3Tm3 octahedra. The corner-sharing octahedra are not tilted.