ErLaSe2 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 La(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 5°. La(1) is bonded to six equivalent Se(1) atoms to form LaSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 5°. Se(1) is bonded to three equivalent Er(1) and three equivalent La(1) atoms to form a mixture of corner and edge-sharing SeLa3Er3 octahedra. The corner-sharing octahedra are not tilted.
ErLaSe2 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 La(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 5°. All Er(1)-Se(1) bond lengths are 2.85 Å. La(1) is bonded to six equivalent Se(1) atoms to form LaSe6 octahedra that share corners with six equivalent Er(1)Se6 octahedra, edges with six equivalent Er(1)Se6 octahedra, and edges with six equivalent La(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 5°. All La(1)-Se(1) bond lengths are 3.05 Å. Se(1) is bonded to three equivalent Er(1) and three equivalent La(1) atoms to form a mixture of corner and edge-sharing SeLa3Er3 octahedra. The corner-sharing octahedra are not tilted.