Cu4Bi7S12 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form CuS4 tetrahedra that share corners with four equivalent Bi(3)S5 square pyramids, corners with two equivalent Cu(1)S4 tetrahedra, and  an edgeedge with one Cu(1)S4 tetrahedra. In the second Cu site, Cu(2) is bonded in a trigonal planar geometry to one S(3), one S(5), and two equivalent S(6) atoms. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent S(6) and four equivalent S(5) atoms to form BiS6 octahedra that share corners with two equivalent Bi(4)S6 octahedra, corners with four equivalent Bi(3)S5 square pyramids, edges with two equivalent Bi(1)S6 octahedra, edges with four equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 10°. In the second Bi site, Bi(2) is bonded in a 5-coordinate geometry to two equivalent S(3) and three equivalent S(1) atoms. In the third Bi site, Bi(3) is bonded to one S(4), two equivalent S(2), and two equivalent S(5) atoms to form BiS5 square pyramids that share corners with two equivalent Bi(1)S6 octahedra, corners with four equivalent Cu(1)S4 tetrahedra,  an edgeedge with one Bi(1)S6 octahedra, edges with two equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 11°. In the fourth Bi site, Bi(4) is bonded to one S(5), two equivalent S(4), and three equivalent S(6) atoms to form BiS6 octahedra that share  a cornercorner with one Bi(1)S6 octahedra, edges with two equivalent Bi(1)S6 octahedra, edges with four equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 10°. There are six inequivalent S sites. In the first S site, S(6) is bonded to two equivalent Cu(2), one Bi(1), and three equivalent Bi(4) atoms to form a mixture of distorted corner and edge-sharing SCu2Bi4 octahedra. The corner-sharing octahedra are not tilted. In the second S site, S(1) is bonded in a 5-coordinate geometry to two equivalent Cu(1) and three equivalent Bi(2) atoms. In the third S site, S(2) is bonded to two equivalent Cu(1) and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SCu2Bi2 trigonal pyramids. In the fourth S site, S(3) is bonded in a trigonal non-coplanar geometry to one Cu(2) and two equivalent Bi(2) atoms. In the fifth S site, S(4) is bonded in a distorted trigonal non-coplanar geometry to one Bi(3) and two equivalent Bi(4) atoms. In the sixth S site, S(5) is bonded in a 6-coordinate geometry to one Cu(2), one Bi(4), two equivalent Bi(1), and two equivalent Bi(3) atoms.
Cu4Bi7S12 crystallizes in the monoclinic C2/m space group. There are two inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to two equivalent S(1) and two equivalent S(2) atoms to form CuS4 tetrahedra that share corners with four equivalent Bi(3)S5 square pyramids, corners with two equivalent Cu(1)S4 tetrahedra, and  an edgeedge with one Cu(1)S4 tetrahedra. Both Cu(1)-S(1) bond lengths are 2.34 Å. There is one shorter (2.34 Å) and one longer (2.38 Å) Cu(1)-S(2) bond length. In the second Cu site, Cu(2) is bonded in a trigonal planar geometry to one S(3), one S(5), and two equivalent S(6) atoms. The Cu(2)-S(3) bond length is 2.24 Å. The Cu(2)-S(5) bond length is 3.11 Å. Both Cu(2)-S(6) bond lengths are 2.32 Å. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent S(6) and four equivalent S(5) atoms to form BiS6 octahedra that share corners with two equivalent Bi(4)S6 octahedra, corners with four equivalent Bi(3)S5 square pyramids, edges with two equivalent Bi(1)S6 octahedra, edges with four equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 10°. Both Bi(1)-S(6) bond lengths are 2.91 Å. All Bi(1)-S(5) bond lengths are 2.80 Å. In the second Bi site, Bi(2) is bonded in a 5-coordinate geometry to two equivalent S(3) and three equivalent S(1) atoms. Both Bi(2)-S(3) bond lengths are 2.72 Å. There is one shorter (2.63 Å) and two longer (3.12 Å) Bi(2)-S(1) bond lengths. In the third Bi site, Bi(3) is bonded to one S(4), two equivalent S(2), and two equivalent S(5) atoms to form BiS5 square pyramids that share corners with two equivalent Bi(1)S6 octahedra, corners with four equivalent Cu(1)S4 tetrahedra,  an edgeedge with one Bi(1)S6 octahedra, edges with two equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 11°. The Bi(3)-S(4) bond length is 2.71 Å. Both Bi(3)-S(2) bond lengths are 2.68 Å. Both Bi(3)-S(5) bond lengths are 3.06 Å. In the fourth Bi site, Bi(4) is bonded to one S(5), two equivalent S(4), and three equivalent S(6) atoms to form BiS6 octahedra that share  a cornercorner with one Bi(1)S6 octahedra, edges with two equivalent Bi(1)S6 octahedra, edges with four equivalent Bi(4)S6 octahedra, and edges with two equivalent Bi(3)S5 square pyramids. The corner-sharing octahedral tilt angles are 10°. The Bi(4)-S(5) bond length is 2.78 Å. Both Bi(4)-S(4) bond lengths are 2.75 Å. All Bi(4)-S(6) bond lengths are 3.05 Å. There are six inequivalent S sites. In the first S site, S(6) is bonded to two equivalent Cu(2), one Bi(1), and three equivalent Bi(4) atoms to form a mixture of distorted corner and edge-sharing SCu2Bi4 octahedra. The corner-sharing octahedra are not tilted. In the second S site, S(1) is bonded in a 5-coordinate geometry to two equivalent Cu(1) and three equivalent Bi(2) atoms. In the third S site, S(2) is bonded to two equivalent Cu(1) and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SCu2Bi2 trigonal pyramids. In the fourth S site, S(3) is bonded in a trigonal non-coplanar geometry to one Cu(2) and two equivalent Bi(2) atoms. In the fifth S site, S(4) is bonded in a distorted trigonal non-coplanar geometry to one Bi(3) and two equivalent Bi(4) atoms. In the sixth S site, S(5) is bonded in a 6-coordinate geometry to one Cu(2), one Bi(4), two equivalent Bi(1), and two equivalent Bi(3) atoms.