U6Cu2S13 crystallizes in the monoclinic C2/c space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(4), one S(5), one S(6), and two equivalent S(7) atoms. In the second U site, U(2) is bonded in a 8-coordinate geometry to one S(1), one S(4), one S(6), one S(7), two equivalent S(2), and two equivalent S(5) atoms. In the third U site, U(3) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(4), one S(5), one S(6), one S(7), and two equivalent S(3) atoms. Cu(1) is bonded in a distorted trigonal non-coplanar geometry to one S(3), one S(4), and one S(6) atom. There are seven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent U(1), two equivalent U(2), and two equivalent U(3) atoms to form corner-sharing SU6 octahedra. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the third S site, S(3) is bonded to one U(1), two equivalent U(3), and one Cu(1) atom to form distorted SU3Cu tetrahedra that share corners with three equivalent S(1)U6 octahedra,  an edgeedge with one S(3)U3Cu tetrahedra, and edges with two equivalent S(6)U3Cu tetrahedra. The corner-sharing octahedral tilt angles range from 40-47°. In the fourth S site, S(4) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one U(2), one U(3), and one Cu(1) atom. In the fifth S site, S(5) is bonded in a rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the sixth S site, S(6) is bonded to one U(1), one U(2), one U(3), and one Cu(1) atom to form distorted SU3Cu tetrahedra that share corners with three equivalent S(1)U6 octahedra and edges with two equivalent S(3)U3Cu tetrahedra. The corner-sharing octahedral tilt angles range from 40-45°. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms.
U6Cu2S13 crystallizes in the monoclinic C2/c space group. There are three inequivalent U sites. In the first U site, U(1) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(3), one S(4), one S(5), one S(6), and two equivalent S(7) atoms. The U(1)-S(1) bond length is 2.89 Å. The U(1)-S(2) bond length is 2.81 Å. The U(1)-S(3) bond length is 2.70 Å. The U(1)-S(4) bond length is 2.76 Å. The U(1)-S(5) bond length is 2.84 Å. The U(1)-S(6) bond length is 2.83 Å. There is one shorter (2.68 Å) and one longer (2.84 Å) U(1)-S(7) bond length. In the second U site, U(2) is bonded in a 8-coordinate geometry to one S(1), one S(4), one S(6), one S(7), two equivalent S(2), and two equivalent S(5) atoms. The U(2)-S(1) bond length is 2.87 Å. The U(2)-S(4) bond length is 2.78 Å. The U(2)-S(6) bond length is 2.69 Å. The U(2)-S(7) bond length is 2.84 Å. There is one shorter (2.74 Å) and one longer (2.83 Å) U(2)-S(2) bond length. There is one shorter (2.72 Å) and one longer (2.91 Å) U(2)-S(5) bond length. In the third U site, U(3) is bonded in a 8-coordinate geometry to one S(1), one S(2), one S(4), one S(5), one S(6), one S(7), and two equivalent S(3) atoms. The U(3)-S(1) bond length is 2.86 Å. The U(3)-S(2) bond length is 2.78 Å. The U(3)-S(4) bond length is 2.78 Å. The U(3)-S(5) bond length is 2.80 Å. The U(3)-S(6) bond length is 2.88 Å. The U(3)-S(7) bond length is 2.81 Å. There is one shorter (2.75 Å) and one longer (2.76 Å) U(3)-S(3) bond length. Cu(1) is bonded in a distorted trigonal non-coplanar geometry to one S(3), one S(4), and one S(6) atom. The Cu(1)-S(3) bond length is 2.24 Å. The Cu(1)-S(4) bond length is 2.18 Å. The Cu(1)-S(6) bond length is 2.22 Å. There are seven inequivalent S sites. In the first S site, S(1) is bonded to two equivalent U(1), two equivalent U(2), and two equivalent U(3) atoms to form corner-sharing SU6 octahedra. In the second S site, S(2) is bonded in a rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the third S site, S(3) is bonded to one U(1), two equivalent U(3), and one Cu(1) atom to form distorted SU3Cu tetrahedra that share corners with three equivalent S(1)U6 octahedra,  an edgeedge with one S(3)U3Cu tetrahedra, and edges with two equivalent S(6)U3Cu tetrahedra. The corner-sharing octahedral tilt angles range from 40-47°. In the fourth S site, S(4) is bonded in a distorted rectangular see-saw-like geometry to one U(1), one U(2), one U(3), and one Cu(1) atom. In the fifth S site, S(5) is bonded in a rectangular see-saw-like geometry to one U(1), one U(3), and two equivalent U(2) atoms. In the sixth S site, S(6) is bonded to one U(1), one U(2), one U(3), and one Cu(1) atom to form distorted SU3Cu tetrahedra that share corners with three equivalent S(1)U6 octahedra and edges with two equivalent S(3)U3Cu tetrahedra. The corner-sharing octahedral tilt angles range from 40-45°. In the seventh S site, S(7) is bonded in a rectangular see-saw-like geometry to one U(2), one U(3), and two equivalent U(1) atoms.