EuSmCuS3 crystallizes in the orthorhombic Pnma space group. Eu(1) is bonded in a 7-coordinate geometry to two equivalent S(2), two equivalent S(3), and three equivalent S(1) atoms. Sm(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form SmS6 octahedra that share corners with two equivalent Sm(1)S6 octahedra, edges with two equivalent Sm(1)S6 octahedra, and edges with four equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. 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 Sm(1)S6 octahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Eu(1), two equivalent Sm(1), and one Cu(1) atom to form distorted SSm2Eu3Cu octahedra that share corners with two equivalent S(3)Sm2Eu2Cu2 octahedra, corners with six equivalent S(2)Sm2Eu2Cu square pyramids, edges with four equivalent S(1)Sm2Eu3Cu octahedra, edges with five equivalent S(3)Sm2Eu2Cu2 octahedra,  an edgeedge with one S(2)Sm2Eu2Cu square pyramid, and  a faceface with one S(2)Sm2Eu2Cu square pyramid. The corner-sharing octahedral tilt angles are 27°. In the second S site, S(2) is bonded to two equivalent Eu(1), two equivalent Sm(1), and one Cu(1) atom to form distorted SSm2Eu2Cu square pyramids that share corners with four equivalent S(3)Sm2Eu2Cu2 octahedra, corners with six equivalent S(1)Sm2Eu3Cu octahedra,  an edgeedge with one S(1)Sm2Eu3Cu octahedra, edges with three equivalent S(3)Sm2Eu2Cu2 octahedra, edges with two equivalent S(2)Sm2Eu2Cu square pyramids, and  a faceface with one S(1)Sm2Eu3Cu octahedra. The corner-sharing octahedral tilt angles range from 5-83°. In the third S site, S(3) is bonded to two equivalent Eu(1), two equivalent Sm(1), and two equivalent Cu(1) atoms to form distorted SSm2Eu2Cu2 octahedra that share corners with two equivalent S(3)Sm2Eu2Cu2 octahedra, corners with two equivalent S(1)Sm2Eu3Cu octahedra, corners with four equivalent S(2)Sm2Eu2Cu square pyramids, edges with two equivalent S(3)Sm2Eu2Cu2 octahedra, edges with five equivalent S(1)Sm2Eu3Cu octahedra, and edges with three equivalent S(2)Sm2Eu2Cu square pyramids. The corner-sharing octahedral tilt angles range from 8-27°.
EuSmCuS3 crystallizes in the orthorhombic Pnma space group. Eu(1) is bonded in a 7-coordinate geometry to two equivalent S(2), two equivalent S(3), and three equivalent S(1) atoms. Both Eu(1)-S(2) bond lengths are 3.05 Å. Both Eu(1)-S(3) bond lengths are 2.97 Å. There are two shorter (3.02 Å) and one longer (3.17 Å) Eu(1)-S(1) bond length. Sm(1) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form SmS6 octahedra that share corners with two equivalent Sm(1)S6 octahedra, edges with two equivalent Sm(1)S6 octahedra, and edges with four equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles are 42°. Both Sm(1)-S(1) bond lengths are 2.84 Å. Both Sm(1)-S(2) bond lengths are 2.79 Å. There is one shorter (2.82 Å) and one longer (2.83 Å) Sm(1)-S(3) bond length. 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 Sm(1)S6 octahedra. The Cu(1)-S(1) bond length is 2.36 Å. The Cu(1)-S(2) bond length is 2.35 Å. Both Cu(1)-S(3) bond lengths are 2.40 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to three equivalent Eu(1), two equivalent Sm(1), and one Cu(1) atom to form distorted SSm2Eu3Cu octahedra that share corners with two equivalent S(3)Sm2Eu2Cu2 octahedra, corners with six equivalent S(2)Sm2Eu2Cu square pyramids, edges with four equivalent S(1)Sm2Eu3Cu octahedra, edges with five equivalent S(3)Sm2Eu2Cu2 octahedra,  an edgeedge with one S(2)Sm2Eu2Cu square pyramid, and  a faceface with one S(2)Sm2Eu2Cu square pyramid. The corner-sharing octahedral tilt angles are 27°. In the second S site, S(2) is bonded to two equivalent Eu(1), two equivalent Sm(1), and one Cu(1) atom to form distorted SSm2Eu2Cu square pyramids that share corners with four equivalent S(3)Sm2Eu2Cu2 octahedra, corners with six equivalent S(1)Sm2Eu3Cu octahedra,  an edgeedge with one S(1)Sm2Eu3Cu octahedra, edges with three equivalent S(3)Sm2Eu2Cu2 octahedra, edges with two equivalent S(2)Sm2Eu2Cu square pyramids, and  a faceface with one S(1)Sm2Eu3Cu octahedra. The corner-sharing octahedral tilt angles range from 5-83°. In the third S site, S(3) is bonded to two equivalent Eu(1), two equivalent Sm(1), and two equivalent Cu(1) atoms to form distorted SSm2Eu2Cu2 octahedra that share corners with two equivalent S(3)Sm2Eu2Cu2 octahedra, corners with two equivalent S(1)Sm2Eu3Cu octahedra, corners with four equivalent S(2)Sm2Eu2Cu square pyramids, edges with two equivalent S(3)Sm2Eu2Cu2 octahedra, edges with five equivalent S(1)Sm2Eu3Cu octahedra, and edges with three equivalent S(2)Sm2Eu2Cu square pyramids. The corner-sharing octahedral tilt angles range from 8-27°.