ErCuPbS3 crystallizes in the orthorhombic Cmc2_1 space group. Er(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form ErS6 octahedra that share corners with two equivalent Er(1)S6 octahedra, edges with two equivalent Er(1)S6 octahedra, and edges with four equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. Cu(1) is bonded to one S(1), one S(2), and two equivalent S(3) atoms to form CuS4 tetrahedra that share corners with two equivalent Cu(1)S4 tetrahedra and edges with four equivalent Er(1)S6 octahedra. Pb(1) is bonded in a 4-coordinate geometry to two equivalent S(2) and two equivalent S(3) atoms. There are three inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one Cu(1) atom. In the second S site, S(2) is bonded in a 5-coordinate geometry to two equivalent Er(1), one Cu(1), and two equivalent Pb(1) atoms. In the third S site, S(3) is bonded in a 6-coordinate geometry to two equivalent Er(1), two equivalent Cu(1), and two equivalent Pb(1) atoms.
ErCuPbS3 crystallizes in the orthorhombic Cmc2_1 space group. Er(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form ErS6 octahedra that share corners with two equivalent Er(1)S6 octahedra, edges with two equivalent Er(1)S6 octahedra, and edges with four equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. Both Er(1)-S(1) bond lengths are 2.71 Å. Both Er(1)-S(2) bond lengths are 2.75 Å. Both Er(1)-S(3) bond lengths are 2.71 Å. Cu(1) is bonded to one S(1), one S(2), and two equivalent S(3) atoms to form CuS4 tetrahedra that share corners with two equivalent Cu(1)S4 tetrahedra and edges with four equivalent Er(1)S6 octahedra. The Cu(1)-S(1) bond length is 2.33 Å. The Cu(1)-S(2) bond length is 2.32 Å. Both Cu(1)-S(3) bond lengths are 2.40 Å. Pb(1) is bonded in a 4-coordinate geometry to two equivalent S(2) and two equivalent S(3) atoms. Both Pb(1)-S(2) bond lengths are 2.98 Å. Both Pb(1)-S(3) bond lengths are 3.03 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded in a 3-coordinate geometry to two equivalent Er(1) and one Cu(1) atom. In the second S site, S(2) is bonded in a 5-coordinate geometry to two equivalent Er(1), one Cu(1), and two equivalent Pb(1) atoms. In the third S site, S(3) is bonded in a 6-coordinate geometry to two equivalent Er(1), two equivalent Cu(1), and two equivalent Pb(1) atoms.