RbSm2CuS4 crystallizes in the orthorhombic Cmcm space group. Rb(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), and four equivalent S(3) atoms. Sm(1) is bonded to one S(2), two equivalent S(1), and three equivalent S(3) atoms to form SmS6 octahedra that share corners with three equivalent Sm(1)S6 octahedra,  a cornercorner with one Cu(1)S4 tetrahedra, edges with five equivalent Sm(1)S6 octahedra, and edges with two equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 0-35°. Cu(1) is bonded to two equivalent S(2) and two equivalent S(3) atoms to form CuS4 tetrahedra that share corners with two equivalent Sm(1)S6 octahedra, corners with two equivalent Cu(1)S4 tetrahedra, and edges with four equivalent Sm(1)S6 octahedra. The corner-sharing octahedral tilt angles are 3°. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Rb(1) and four equivalent Sm(1) atoms to form distorted SRb2Sm4 octahedra that share corners with two equivalent S(1)Rb2Sm4 octahedra, corners with eight equivalent S(3)Rb2Sm3Cu octahedra, edges with two equivalent S(1)Rb2Sm4 octahedra, and edges with six equivalent S(3)Rb2Sm3Cu octahedra. The corner-sharing octahedral tilt angles range from 3-46°. In the second S site, S(2) is bonded in a 6-coordinate geometry to two equivalent Rb(1), two equivalent Sm(1), and two equivalent Cu(1) atoms. In the third S site, S(3) is bonded to two equivalent Rb(1), three equivalent Sm(1), and one Cu(1) atom to form distorted SRb2Sm3Cu octahedra that share corners with two equivalent S(3)Rb2Sm3Cu octahedra, corners with four equivalent S(1)Rb2Sm4 octahedra, edges with three equivalent S(1)Rb2Sm4 octahedra, edges with four equivalent S(3)Rb2Sm3Cu octahedra, and  a faceface with one S(3)Rb2Sm3Cu octahedra. The corner-sharing octahedral tilt angles range from 3-67°.
RbSm2CuS4 crystallizes in the orthorhombic Cmcm space group. Rb(1) is bonded in a 8-coordinate geometry to two equivalent S(1), two equivalent S(2), and four equivalent S(3) atoms. Both Rb(1)-S(1) bond lengths are 3.80 Å. Both Rb(1)-S(2) bond lengths are 3.26 Å. All Rb(1)-S(3) bond lengths are 3.37 Å. Sm(1) is bonded to one S(2), two equivalent S(1), and three equivalent S(3) atoms to form SmS6 octahedra that share corners with three equivalent Sm(1)S6 octahedra,  a cornercorner with one Cu(1)S4 tetrahedra, edges with five equivalent Sm(1)S6 octahedra, and edges with two equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles range from 0-35°. The Sm(1)-S(2) bond length is 2.76 Å. Both Sm(1)-S(1) bond lengths are 2.90 Å. There are two shorter (2.77 Å) and one longer (2.83 Å) Sm(1)-S(3) bond length. Cu(1) is bonded to two equivalent S(2) and two equivalent S(3) atoms to form CuS4 tetrahedra that share corners with two equivalent Sm(1)S6 octahedra, corners with two equivalent Cu(1)S4 tetrahedra, and edges with four equivalent Sm(1)S6 octahedra. The corner-sharing octahedral tilt angles are 3°. Both Cu(1)-S(2) bond lengths are 2.38 Å. Both Cu(1)-S(3) bond lengths are 2.35 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Rb(1) and four equivalent Sm(1) atoms to form distorted SRb2Sm4 octahedra that share corners with two equivalent S(1)Rb2Sm4 octahedra, corners with eight equivalent S(3)Rb2Sm3Cu octahedra, edges with two equivalent S(1)Rb2Sm4 octahedra, and edges with six equivalent S(3)Rb2Sm3Cu octahedra. The corner-sharing octahedral tilt angles range from 3-46°. In the second S site, S(2) is bonded in a 6-coordinate geometry to two equivalent Rb(1), two equivalent Sm(1), and two equivalent Cu(1) atoms. In the third S site, S(3) is bonded to two equivalent Rb(1), three equivalent Sm(1), and one Cu(1) atom to form distorted SRb2Sm3Cu octahedra that share corners with two equivalent S(3)Rb2Sm3Cu octahedra, corners with four equivalent S(1)Rb2Sm4 octahedra, edges with three equivalent S(1)Rb2Sm4 octahedra, edges with four equivalent S(3)Rb2Sm3Cu octahedra, and  a faceface with one S(3)Rb2Sm3Cu octahedra. The corner-sharing octahedral tilt angles range from 3-67°.