Pb4SnSe5 is Caswellsilverite-like structured and crystallizes in the trigonal R-3m space group. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded to three equivalent Se(1) and three equivalent Se(3) atoms to form PbSe6 octahedra that share corners with three equivalent Pb(2)Se6 octahedra, corners with three equivalent Sn(1)Se6 octahedra, edges with three equivalent Pb(2)Se6 octahedra, edges with three equivalent Sn(1)Se6 octahedra, and edges with six equivalent Pb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. In the second Pb site, Pb(2) is bonded to three equivalent Se(2) and three equivalent Se(3) atoms to form a mixture of corner and edge-sharing PbSe6 octahedra. The corner-sharing octahedra are not tilted. Sn(1) is bonded to six equivalent Se(1) atoms to form SnSe6 octahedra that share corners with six equivalent Pb(1)Se6 octahedra, edges with six equivalent Pb(1)Se6 octahedra, and edges with six equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 2°. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Pb(1) and three equivalent Sn(1) atoms to form SeSn3Pb3 octahedra that share corners with three equivalent Se(3)Pb6 octahedra, corners with three equivalent Se(1)Sn3Pb3 octahedra, edges with three equivalent Se(3)Pb6 octahedra, and edges with nine equivalent Se(1)Sn3Pb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Se site, Se(2) is bonded to six equivalent Pb(2) atoms to form a mixture of corner and edge-sharing SePb6 octahedra. The corner-sharing octahedra are not tilted. In the third Se site, Se(3) is bonded to three equivalent Pb(1) and three equivalent Pb(2) atoms to form SePb6 octahedra that share corners with three equivalent Se(2)Pb6 octahedra, corners with three equivalent Se(1)Sn3Pb3 octahedra, edges with three equivalent Se(2)Pb6 octahedra, edges with three equivalent Se(1)Sn3Pb3 octahedra, and edges with six equivalent Se(3)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.
Pb4SnSe5 is Caswellsilverite-like structured and crystallizes in the trigonal R-3m space group. There are two inequivalent Pb sites. In the first Pb site, Pb(1) is bonded to three equivalent Se(1) and three equivalent Se(3) atoms to form PbSe6 octahedra that share corners with three equivalent Pb(2)Se6 octahedra, corners with three equivalent Sn(1)Se6 octahedra, edges with three equivalent Pb(2)Se6 octahedra, edges with three equivalent Sn(1)Se6 octahedra, and edges with six equivalent Pb(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-2°. All Pb(1)-Se(1) bond lengths are 3.12 Å. All Pb(1)-Se(3) bond lengths are 3.09 Å. In the second Pb site, Pb(2) is bonded to three equivalent Se(2) and three equivalent Se(3) atoms to form a mixture of corner and edge-sharing PbSe6 octahedra. The corner-sharing octahedra are not tilted. All Pb(2)-Se(2) bond lengths are 3.09 Å. All Pb(2)-Se(3) bond lengths are 3.09 Å. Sn(1) is bonded to six equivalent Se(1) atoms to form SnSe6 octahedra that share corners with six equivalent Pb(1)Se6 octahedra, edges with six equivalent Pb(1)Se6 octahedra, and edges with six equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles are 2°. All Sn(1)-Se(1) bond lengths are 3.05 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded to three equivalent Pb(1) and three equivalent Sn(1) atoms to form SeSn3Pb3 octahedra that share corners with three equivalent Se(3)Pb6 octahedra, corners with three equivalent Se(1)Sn3Pb3 octahedra, edges with three equivalent Se(3)Pb6 octahedra, and edges with nine equivalent Se(1)Sn3Pb3 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. In the second Se site, Se(2) is bonded to six equivalent Pb(2) atoms to form a mixture of corner and edge-sharing SePb6 octahedra. The corner-sharing octahedra are not tilted. In the third Se site, Se(3) is bonded to three equivalent Pb(1) and three equivalent Pb(2) atoms to form SePb6 octahedra that share corners with three equivalent Se(2)Pb6 octahedra, corners with three equivalent Se(1)Sn3Pb3 octahedra, edges with three equivalent Se(2)Pb6 octahedra, edges with three equivalent Se(1)Sn3Pb3 octahedra, and edges with six equivalent Se(3)Pb6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°.