The material described by Cu6BiSe6 crystallizes in the orthorhombic Pnma space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(5) and three equivalent Se(3) atoms to form a mixture of distorted edge and corner-sharing CuSe4 tetrahedra. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one Se(2), one Se(4), and two equivalent Se(3) atoms. In the third Cu site, Cu(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Se(2) and two equivalent Se(6) atoms. In the fourth Cu site, Cu(4) is bonded to one Se(3), one Se(5), and two equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with two equivalent Bi(1)Se5 square pyramids, corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra,  an edgeedge with one Bi(1)Se5 square pyramid, and  an edgeedge with one Cu(1)Se4 tetrahedra. In the fifth Cu site, Cu(5) is bonded in a 4-coordinate geometry to one Se(1) and three equivalent Se(5) atoms. In the sixth Cu site, Cu(6) is bonded to one Se(2), one Se(4), and two equivalent Se(6) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Bi(1)Se5 square pyramids and corners with two equivalent Cu(6)Se4 tetrahedra. Bi(1) is bonded to one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms to form distorted BiSe5 square pyramids that share corners with two equivalent Cu(4)Se4 tetrahedra, corners with four equivalent Cu(6)Se4 tetrahedra, edges with two equivalent Bi(1)Se5 square pyramids, and  an edgeedge with one Cu(4)Se4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(2) is bonded in a 5-coordinate geometry to one Cu(2), one Cu(6), two equivalent Cu(3), and one Se(1) atom. In the second Se site, Se(3) is bonded in a distorted hexagonal planar geometry to one Cu(4), two equivalent Cu(2), and three equivalent Cu(1) atoms. In the third Se site, Se(4) is bonded to one Cu(2), one Cu(6), and two equivalent Bi(1) atoms to form corner-sharing SeCu2Bi2 tetrahedra. In the fourth Se site, Se(5) is bonded in a 5-coordinate geometry to one Cu(1), one Cu(4), and three equivalent Cu(5) atoms. In the fifth Se site, Se(6) is bonded in a 5-coordinate geometry to two equivalent Cu(3), two equivalent Cu(6), and one Bi(1) atom. In the sixth Se site, Se(1) is bonded in a 6-coordinate geometry to one Cu(5), two equivalent Cu(4), two equivalent Bi(1), and one Se(2) atom. is represented by the CIF card [CIF]
data_Cu6BiSe6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.020
_cell_length_b   9.653
_cell_length_c   27.284
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1058.646
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Cu  Cu0  1  0.750  0.431  0.477  1.0
  Cu  Cu1  1  0.750  0.931  0.023  1.0
  Cu  Cu2  1  0.250  0.569  0.523  1.0
  Cu  Cu3  1  0.250  0.069  0.977  1.0
  Cu  Cu4  1  0.750  0.474  0.384  1.0
  Cu  Cu5  1  0.750  0.974  0.116  1.0
  Cu  Cu6  1  0.250  0.526  0.616  1.0
  Cu  Cu7  1  0.250  0.026  0.884  1.0
  Cu  Cu8  1  0.750  0.308  0.715  1.0
  Cu  Cu9  1  0.750  0.808  0.785  1.0
  Cu  Cu10  1  0.250  0.692  0.285  1.0
  Cu  Cu11  1  0.250  0.192  0.215  1.0
  Cu  Cu12  1  0.750  0.717  0.946  1.0
  Cu  Cu13  1  0.750  0.217  0.554  1.0
  Cu  Cu14  1  0.250  0.283  0.054  1.0
  Cu  Cu15  1  0.250  0.783  0.446  1.0
  Cu  Cu16  1  0.750  0.419  0.004  1.0
  Cu  Cu17  1  0.750  0.919  0.496  1.0
  Cu  Cu18  1  0.250  0.581  0.996  1.0
  Cu  Cu19  1  0.250  0.081  0.504  1.0
  Cu  Cu20  1  0.750  0.351  0.241  1.0
  Cu  Cu21  1  0.750  0.851  0.259  1.0
  Cu  Cu22  1  0.250  0.649  0.759  1.0
  Cu  Cu23  1  0.250  0.149  0.741  1.0
  Bi  Bi24  1  0.750  0.397  0.862  1.0
  Bi  Bi25  1  0.750  0.897  0.638  1.0
  Bi  Bi26  1  0.250  0.603  0.138  1.0
  Bi  Bi27  1  0.250  0.103  0.362  1.0
  Se  Se28  1  0.750  0.364  0.100  1.0
  Se  Se29  1  0.750  0.864  0.400  1.0
  Se  Se30  1  0.250  0.636  0.900  1.0
  Se  Se31  1  0.250  0.136  0.600  1.0
  Se  Se32  1  0.750  0.183  0.168  1.0
  Se  Se33  1  0.750  0.683  0.332  1.0
  Se  Se34  1  0.250  0.817  0.832  1.0
  Se  Se35  1  0.250  0.317  0.668  1.0
  Se  Se36  1  0.750  0.970  0.934  1.0
  Se  Se37  1  0.750  0.470  0.566  1.0
  Se  Se38  1  0.250  0.030  0.066  1.0
  Se  Se39  1  0.250  0.530  0.434  1.0
  Se  Se40  1  0.750  0.287  0.328  1.0
  Se  Se41  1  0.750  0.787  0.172  1.0
  Se  Se42  1  0.250  0.713  0.672  1.0
  Se  Se43  1  0.250  0.213  0.828  1.0
  Se  Se44  1  0.750  0.170  0.464  1.0
  Se  Se45  1  0.750  0.670  0.036  1.0
  Se  Se46  1  0.250  0.830  0.536  1.0
  Se  Se47  1  0.250  0.330  0.964  1.0
  Se  Se48  1  0.750  0.011  0.731  1.0
  Se  Se49  1  0.750  0.511  0.769  1.0
  Se  Se50  1  0.250  0.989  0.269  1.0
  Se  Se51  1  0.250  0.489  0.231  1.0
[/CIF]
.
The material described by Cu6BiSe6 crystallizes in the orthorhombic Pnma space group. There are six inequivalent Cu sites. In the first Cu site, Cu(1) is bonded to one Se(5) and three equivalent Se(3) atoms to form a mixture of distorted edge and corner-sharing CuSe4 tetrahedra. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one Se(2), one Se(4), and two equivalent Se(3) atoms. In the third Cu site, Cu(3) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Se(2) and two equivalent Se(6) atoms. In the fourth Cu site, Cu(4) is bonded to one Se(3), one Se(5), and two equivalent Se(1) atoms to form distorted CuSe4 tetrahedra that share corners with two equivalent Bi(1)Se5 square pyramids, corners with two equivalent Cu(1)Se4 tetrahedra, corners with two equivalent Cu(4)Se4 tetrahedra,  an edgeedge with one Bi(1)Se5 square pyramid, and  an edgeedge with one Cu(1)Se4 tetrahedra. In the fifth Cu site, Cu(5) is bonded in a 4-coordinate geometry to one Se(1) and three equivalent Se(5) atoms. In the sixth Cu site, Cu(6) is bonded to one Se(2), one Se(4), and two equivalent Se(6) atoms to form distorted CuSe4 tetrahedra that share corners with four equivalent Bi(1)Se5 square pyramids and corners with two equivalent Cu(6)Se4 tetrahedra. Bi(1) is bonded to one Se(6), two equivalent Se(1), and two equivalent Se(4) atoms to form distorted BiSe5 square pyramids that share corners with two equivalent Cu(4)Se4 tetrahedra, corners with four equivalent Cu(6)Se4 tetrahedra, edges with two equivalent Bi(1)Se5 square pyramids, and  an edgeedge with one Cu(4)Se4 tetrahedra. There are six inequivalent Se sites. In the first Se site, Se(2) is bonded in a 5-coordinate geometry to one Cu(2), one Cu(6), two equivalent Cu(3), and one Se(1) atom. In the second Se site, Se(3) is bonded in a distorted hexagonal planar geometry to one Cu(4), two equivalent Cu(2), and three equivalent Cu(1) atoms. In the third Se site, Se(4) is bonded to one Cu(2), one Cu(6), and two equivalent Bi(1) atoms to form corner-sharing SeCu2Bi2 tetrahedra. In the fourth Se site, Se(5) is bonded in a 5-coordinate geometry to one Cu(1), one Cu(4), and three equivalent Cu(5) atoms. In the fifth Se site, Se(6) is bonded in a 5-coordinate geometry to two equivalent Cu(3), two equivalent Cu(6), and one Bi(1) atom. In the sixth Se site, Se(1) is bonded in a 6-coordinate geometry to one Cu(5), two equivalent Cu(4), two equivalent Bi(1), and one Se(2) atom. is represented by the CIF card [CIF]
data_Cu6BiSe6
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.020
_cell_length_b   9.653
_cell_length_c   27.284
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1058.646
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Cu  Cu0  1  0.750  0.431  0.477  1.0
  Cu  Cu1  1  0.750  0.931  0.023  1.0
  Cu  Cu2  1  0.250  0.569  0.523  1.0
  Cu  Cu3  1  0.250  0.069  0.977  1.0
  Cu  Cu4  1  0.750  0.474  0.384  1.0
  Cu  Cu5  1  0.750  0.974  0.116  1.0
  Cu  Cu6  1  0.250  0.526  0.616  1.0
  Cu  Cu7  1  0.250  0.026  0.884  1.0
  Cu  Cu8  1  0.750  0.308  0.715  1.0
  Cu  Cu9  1  0.750  0.808  0.785  1.0
  Cu  Cu10  1  0.250  0.692  0.285  1.0
  Cu  Cu11  1  0.250  0.192  0.215  1.0
  Cu  Cu12  1  0.750  0.717  0.946  1.0
  Cu  Cu13  1  0.750  0.217  0.554  1.0
  Cu  Cu14  1  0.250  0.283  0.054  1.0
  Cu  Cu15  1  0.250  0.783  0.446  1.0
  Cu  Cu16  1  0.750  0.419  0.004  1.0
  Cu  Cu17  1  0.750  0.919  0.496  1.0
  Cu  Cu18  1  0.250  0.581  0.996  1.0
  Cu  Cu19  1  0.250  0.081  0.504  1.0
  Cu  Cu20  1  0.750  0.351  0.241  1.0
  Cu  Cu21  1  0.750  0.851  0.259  1.0
  Cu  Cu22  1  0.250  0.649  0.759  1.0
  Cu  Cu23  1  0.250  0.149  0.741  1.0
  Bi  Bi24  1  0.750  0.397  0.862  1.0
  Bi  Bi25  1  0.750  0.897  0.638  1.0
  Bi  Bi26  1  0.250  0.603  0.138  1.0
  Bi  Bi27  1  0.250  0.103  0.362  1.0
  Se  Se28  1  0.750  0.364  0.100  1.0
  Se  Se29  1  0.750  0.864  0.400  1.0
  Se  Se30  1  0.250  0.636  0.900  1.0
  Se  Se31  1  0.250  0.136  0.600  1.0
  Se  Se32  1  0.750  0.183  0.168  1.0
  Se  Se33  1  0.750  0.683  0.332  1.0
  Se  Se34  1  0.250  0.817  0.832  1.0
  Se  Se35  1  0.250  0.317  0.668  1.0
  Se  Se36  1  0.750  0.970  0.934  1.0
  Se  Se37  1  0.750  0.470  0.566  1.0
  Se  Se38  1  0.250  0.030  0.066  1.0
  Se  Se39  1  0.250  0.530  0.434  1.0
  Se  Se40  1  0.750  0.287  0.328  1.0
  Se  Se41  1  0.750  0.787  0.172  1.0
  Se  Se42  1  0.250  0.713  0.672  1.0
  Se  Se43  1  0.250  0.213  0.828  1.0
  Se  Se44  1  0.750  0.170  0.464  1.0
  Se  Se45  1  0.750  0.670  0.036  1.0
  Se  Se46  1  0.250  0.830  0.536  1.0
  Se  Se47  1  0.250  0.330  0.964  1.0
  Se  Se48  1  0.750  0.011  0.731  1.0
  Se  Se49  1  0.750  0.511  0.769  1.0
  Se  Se50  1  0.250  0.989  0.269  1.0
  Se  Se51  1  0.250  0.489  0.231  1.0
[/CIF]
.