AgErSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal I4_1/amd space group. Er(1) is bonded to six Se(1,1,1) atoms to form ErSe6 octahedra that share corners with two equivalent Ag(1)Se6 octahedra, corners with four equivalent Er(1)Se6 octahedra, edges with four equivalent Er(1)Se6 octahedra, and edges with eight equivalent Ag(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. Ag(1) is bonded to six Se(1,1,1) atoms to form AgSe6 octahedra that share corners with two equivalent Er(1)Se6 octahedra, corners with four equivalent Ag(1)Se6 octahedra, edges with four equivalent Ag(1)Se6 octahedra, and edges with eight equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the second Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the fourth Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°.
AgErSe2 is Caswellsilverite-like structured and crystallizes in the tetragonal I4_1/amd space group. Er(1) is bonded to six Se(1,1,1) atoms to form ErSe6 octahedra that share corners with two equivalent Ag(1)Se6 octahedra, corners with four equivalent Er(1)Se6 octahedra, edges with four equivalent Er(1)Se6 octahedra, and edges with eight equivalent Ag(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are four shorter (2.85 Å) and two longer (2.86 Å) Er(1)-Se(1,1,1) bond lengths. Ag(1) is bonded to six Se(1,1,1) atoms to form AgSe6 octahedra that share corners with two equivalent Er(1)Se6 octahedra, corners with four equivalent Ag(1)Se6 octahedra, edges with four equivalent Ag(1)Se6 octahedra, and edges with eight equivalent Er(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are four shorter (2.85 Å) and two longer (3.19 Å) Ag(1)-Se(1,1,1) bond lengths. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are two shorter (2.85 Å) and one longer (3.19 Å) Se(1)-Ag(1) bond length. In the second Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. In the third Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°. There are two shorter (2.85 Å) and one longer (2.86 Å) Se(1)-Er(1) bond length. In the fourth Se site, Se(1) is bonded to three equivalent Er(1) and three equivalent Ag(1) atoms to form a mixture of edge and corner-sharing SeEr3Ag3 octahedra. The corner-sharing octahedral tilt angles range from 0-7°.