Eu2CuS3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Eu sites. In the first Eu site, Eu(1) is bonded in a 7-coordinate geometry to two equivalent S(2), two equivalent S(3), and three equivalent S(1) atoms. In the second Eu site, Eu(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form EuS6 octahedra that share corners with two equivalent Eu(2)S6 octahedra, edges with two equivalent Eu(2)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 Eu(2)S6 octahedra. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Eu(2), three equivalent Eu(1), and one Cu(1) atom to form distorted SEu5Cu octahedra that share corners with two equivalent S(3)Eu4Cu2 octahedra, corners with six equivalent S(2)Eu4Cu square pyramids, edges with four equivalent S(1)Eu5Cu octahedra, edges with five equivalent S(3)Eu4Cu2 octahedra,  an edgeedge with one S(2)Eu4Cu square pyramid, and  a faceface with one S(2)Eu4Cu square pyramid. The corner-sharing octahedral tilt angles are 28°. In the second S site, S(2) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Cu(1) atom to form distorted SEu4Cu square pyramids that share corners with four equivalent S(3)Eu4Cu2 octahedra, corners with six equivalent S(1)Eu5Cu octahedra,  an edgeedge with one S(1)Eu5Cu octahedra, edges with three equivalent S(3)Eu4Cu2 octahedra, edges with two equivalent S(2)Eu4Cu square pyramids, and  a faceface with one S(1)Eu5Cu octahedra. The corner-sharing octahedral tilt angles range from 5-81°. In the third S site, S(3) is bonded to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Cu(1) atoms to form distorted SEu4Cu2 octahedra that share corners with two equivalent S(3)Eu4Cu2 octahedra, corners with two equivalent S(1)Eu5Cu octahedra, corners with four equivalent S(2)Eu4Cu square pyramids, edges with two equivalent S(3)Eu4Cu2 octahedra, edges with five equivalent S(1)Eu5Cu octahedra, and edges with three equivalent S(2)Eu4Cu square pyramids. The corner-sharing octahedral tilt angles range from 7-28°.
Eu2CuS3 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Eu sites. In the first Eu site, 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 2.99 Å. Both Eu(1)-S(3) bond lengths are 2.95 Å. There are two shorter (2.97 Å) and one longer (3.24 Å) Eu(1)-S(1) bond length. In the second Eu site, Eu(2) is bonded to two equivalent S(1), two equivalent S(2), and two equivalent S(3) atoms to form EuS6 octahedra that share corners with two equivalent Eu(2)S6 octahedra, edges with two equivalent Eu(2)S6 octahedra, and edges with four equivalent Cu(1)S4 tetrahedra. The corner-sharing octahedral tilt angles are 41°. Both Eu(2)-S(1) bond lengths are 2.85 Å. Both Eu(2)-S(2) bond lengths are 2.81 Å. There is one shorter (2.85 Å) and one longer (2.86 Å) Eu(2)-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 Eu(2)S6 octahedra. The Cu(1)-S(1) bond length is 2.34 Å. The Cu(1)-S(2) bond length is 2.30 Å. Both Cu(1)-S(3) bond lengths are 2.38 Å. There are three inequivalent S sites. In the first S site, S(1) is bonded to two equivalent Eu(2), three equivalent Eu(1), and one Cu(1) atom to form distorted SEu5Cu octahedra that share corners with two equivalent S(3)Eu4Cu2 octahedra, corners with six equivalent S(2)Eu4Cu square pyramids, edges with four equivalent S(1)Eu5Cu octahedra, edges with five equivalent S(3)Eu4Cu2 octahedra,  an edgeedge with one S(2)Eu4Cu square pyramid, and  a faceface with one S(2)Eu4Cu square pyramid. The corner-sharing octahedral tilt angles are 28°. In the second S site, S(2) is bonded to two equivalent Eu(1), two equivalent Eu(2), and one Cu(1) atom to form distorted SEu4Cu square pyramids that share corners with four equivalent S(3)Eu4Cu2 octahedra, corners with six equivalent S(1)Eu5Cu octahedra,  an edgeedge with one S(1)Eu5Cu octahedra, edges with three equivalent S(3)Eu4Cu2 octahedra, edges with two equivalent S(2)Eu4Cu square pyramids, and  a faceface with one S(1)Eu5Cu octahedra. The corner-sharing octahedral tilt angles range from 5-81°. In the third S site, S(3) is bonded to two equivalent Eu(1), two equivalent Eu(2), and two equivalent Cu(1) atoms to form distorted SEu4Cu2 octahedra that share corners with two equivalent S(3)Eu4Cu2 octahedra, corners with two equivalent S(1)Eu5Cu octahedra, corners with four equivalent S(2)Eu4Cu square pyramids, edges with two equivalent S(3)Eu4Cu2 octahedra, edges with five equivalent S(1)Eu5Cu octahedra, and edges with three equivalent S(2)Eu4Cu square pyramids. The corner-sharing octahedral tilt angles range from 7-28°.