LuCuPbSe3 crystallizes in the orthorhombic Cmcm space group. Lu(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form LuSe6 octahedra that share corners with two equivalent Lu(1)Se6 octahedra, edges with two equivalent Lu(1)Se6 octahedra, and edges with four equivalent Cu(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Lu(1)Se6 octahedra. Pb(1) is bonded in a 6-coordinate geometry to two equivalent Se(1) and four equivalent Se(2) atoms. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Lu(1), two equivalent Cu(1), and two equivalent Pb(1) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Lu(1), one Cu(1), and two equivalent Pb(1) atoms.
LuCuPbSe3 crystallizes in the orthorhombic Cmcm space group. Lu(1) is bonded to two equivalent Se(1) and four equivalent Se(2) atoms to form LuSe6 octahedra that share corners with two equivalent Lu(1)Se6 octahedra, edges with two equivalent Lu(1)Se6 octahedra, and edges with four equivalent Cu(1)Se4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. Both Lu(1)-Se(1) bond lengths are 2.82 Å. All Lu(1)-Se(2) bond lengths are 2.83 Å. Cu(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form CuSe4 tetrahedra that share corners with two equivalent Cu(1)Se4 tetrahedra and edges with four equivalent Lu(1)Se6 octahedra. Both Cu(1)-Se(1) bond lengths are 2.52 Å. Both Cu(1)-Se(2) bond lengths are 2.46 Å. Pb(1) is bonded in a 6-coordinate geometry to two equivalent Se(1) and four equivalent Se(2) atoms. Both Pb(1)-Se(1) bond lengths are 3.15 Å. All Pb(1)-Se(2) bond lengths are 3.16 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 6-coordinate geometry to two equivalent Lu(1), two equivalent Cu(1), and two equivalent Pb(1) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to two equivalent Lu(1), one Cu(1), and two equivalent Pb(1) atoms.