The structure described by Cr5(Bi3Se8)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(6), one Se(7), and one Se(8) atom to form CrSe6 octahedra that share  a cornercorner with one Bi(4)Se6 pentagonal pyramid,  an edgeedge with one Cr(1)Se6 octahedra, edges with two equivalent Cr(3)Se6 octahedra, and edges with three equivalent Cr(2)Se6 octahedra. In the second Cr site, Cr(2) is bonded to one Se(1), one Se(8), two equivalent Se(3), and two equivalent Se(6) atoms to form edge-sharing CrSe6 octahedra. In the third Cr site, Cr(3) is bonded to one Se(2), one Se(7), two equivalent Se(1), and two equivalent Se(8) atoms to form CrSe6 octahedra that share  a cornercorner with one Bi(4)Se6 pentagonal pyramid, edges with two equivalent Cr(2)Se6 octahedra, and edges with four equivalent Cr(1)Se6 octahedra. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 5-coordinate geometry to one Se(3), one Se(4), one Se(5), and two equivalent Se(9) atoms. In the second Bi site, Bi(2) is bonded in a 7-coordinate geometry to one Se(10), one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(9) atoms. In the third Bi site, Bi(3) is bonded in a 6-coordinate geometry to one Se(10), one Se(6), one Se(8), one Se(9), and two equivalent Se(5) atoms. In the fourth Bi site, Bi(4) is bonded to one Se(4), one Se(7), two equivalent Se(10), and two equivalent Se(5) atoms to form distorted BiSe6 pentagonal pyramids that share  a cornercorner with one Cr(3)Se6 octahedra, corners with two equivalent Cr(1)Se6 octahedra, and corners with two equivalent Bi(4)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 47-86°. There are ten inequivalent Se sites. In the first Se site, Se(7) is bonded in a distorted rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Bi(4) atom. In the second Se site, Se(8) is bonded in a distorted rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(3), and one Bi(3) atom. In the third Se site, Se(9) is bonded in a 4-coordinate geometry to one Bi(2), one Bi(3), and two equivalent Bi(1) atoms. In the fourth Se site, Se(10) is bonded to one Bi(2), two equivalent Bi(3), and two equivalent Bi(4) atoms to form SeBi5 trigonal bipyramids that share corners with two equivalent Se(10)Bi5 trigonal bipyramids,  a cornercorner with one Se(4)Bi4 trigonal pyramid, corners with four equivalent Se(5)Bi4 trigonal pyramids,  an edgeedge with one Se(4)Bi4 trigonal pyramid, and edges with two equivalent Se(5)Bi4 trigonal pyramids. In the fifth Se site, Se(1) is bonded in a 3-coordinate geometry to one Cr(1), one Cr(2), one Cr(3), and one Bi(2) atom. In the sixth Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Bi(2) atom. In the seventh Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Bi(1) atom. In the eighth Se site, Se(4) is bonded to one Bi(2), one Bi(4), and two equivalent Bi(1) atoms to form distorted SeBi4 trigonal pyramids that share  a cornercorner with one Se(10)Bi5 trigonal bipyramid,  an edgeedge with one Se(10)Bi5 trigonal bipyramid, and edges with two equivalent Se(5)Bi4 trigonal pyramids. In the ninth Se site, Se(5) is bonded to one Bi(1), one Bi(4), and two equivalent Bi(3) atoms to form distorted SeBi4 trigonal pyramids that share corners with two equivalent Se(10)Bi5 trigonal bipyramids, corners with three equivalent Se(5)Bi4 trigonal pyramids,  an edgeedge with one Se(10)Bi5 trigonal bipyramid, and  an edgeedge with one Se(4)Bi4 trigonal pyramid. In the tenth Se site, Se(6) is bonded in a distorted rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Bi(3) atom. is represented by the CIF file [CIF]
data_Cr5(Bi3Se8)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.622
_cell_length_b   9.622
_cell_length_c   11.569
_cell_angle_alpha   88.389
_cell_angle_beta   88.389
_cell_angle_gamma   142.215
_symmetry_Int_Tables_number   1
_cell_volume   653.708
_cell_formula_units_Z   1
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
  Cr  Cr0  1  0.614  0.814  0.487  1.0
  Cr  Cr1  1  0.814  0.614  0.487  1.0
  Cr  Cr2  1  0.007  0.404  0.484  1.0
  Cr  Cr3  1  0.404  0.007  0.484  1.0
  Cr  Cr4  1  0.217  0.217  0.491  1.0
  Bi  Bi5  1  0.110  0.444  0.837  1.0
  Bi  Bi6  1  0.444  0.110  0.837  1.0
  Bi  Bi7  1  0.800  0.800  0.833  1.0
  Bi  Bi8  1  0.817  0.486  0.136  1.0
  Bi  Bi9  1  0.486  0.817  0.136  1.0
  Bi  Bi10  1  0.193  0.193  0.141  1.0
  Se  Se11  1  0.930  0.126  0.613  1.0
  Se  Se12  1  0.126  0.930  0.613  1.0
  Se  Se13  1  0.537  0.537  0.609  1.0
  Se  Se14  1  0.320  0.719  0.604  1.0
  Se  Se15  1  0.719  0.320  0.604  1.0
  Se  Se16  1  0.235  0.235  0.889  1.0
  Se  Se17  1  0.038  0.371  0.089  1.0
  Se  Se18  1  0.371  0.038  0.089  1.0
  Se  Se19  1  0.686  0.089  0.363  1.0
  Se  Se20  1  0.089  0.686  0.363  1.0
  Se  Se21  1  0.906  0.906  0.368  1.0
  Se  Se22  1  0.299  0.499  0.363  1.0
  Se  Se23  1  0.499  0.299  0.363  1.0
  Se  Se24  1  0.896  0.561  0.883  1.0
  Se  Se25  1  0.561  0.896  0.883  1.0
  Se  Se26  1  0.704  0.704  0.087  1.0
[/CIF]
.
The structure described by Cr5(Bi3Se8)2 crystallizes in the monoclinic Cm space group. There are three inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one Se(1), one Se(2), one Se(3), one Se(6), one Se(7), and one Se(8) atom to form CrSe6 octahedra that share  a cornercorner with one Bi(4)Se6 pentagonal pyramid,  an edgeedge with one Cr(1)Se6 octahedra, edges with two equivalent Cr(3)Se6 octahedra, and edges with three equivalent Cr(2)Se6 octahedra. In the second Cr site, Cr(2) is bonded to one Se(1), one Se(8), two equivalent Se(3), and two equivalent Se(6) atoms to form edge-sharing CrSe6 octahedra. In the third Cr site, Cr(3) is bonded to one Se(2), one Se(7), two equivalent Se(1), and two equivalent Se(8) atoms to form CrSe6 octahedra that share  a cornercorner with one Bi(4)Se6 pentagonal pyramid, edges with two equivalent Cr(2)Se6 octahedra, and edges with four equivalent Cr(1)Se6 octahedra. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a 5-coordinate geometry to one Se(3), one Se(4), one Se(5), and two equivalent Se(9) atoms. In the second Bi site, Bi(2) is bonded in a 7-coordinate geometry to one Se(10), one Se(2), one Se(4), two equivalent Se(1), and two equivalent Se(9) atoms. In the third Bi site, Bi(3) is bonded in a 6-coordinate geometry to one Se(10), one Se(6), one Se(8), one Se(9), and two equivalent Se(5) atoms. In the fourth Bi site, Bi(4) is bonded to one Se(4), one Se(7), two equivalent Se(10), and two equivalent Se(5) atoms to form distorted BiSe6 pentagonal pyramids that share  a cornercorner with one Cr(3)Se6 octahedra, corners with two equivalent Cr(1)Se6 octahedra, and corners with two equivalent Bi(4)Se6 pentagonal pyramids. The corner-sharing octahedral tilt angles range from 47-86°. There are ten inequivalent Se sites. In the first Se site, Se(7) is bonded in a distorted rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Bi(4) atom. In the second Se site, Se(8) is bonded in a distorted rectangular see-saw-like geometry to one Cr(1), one Cr(2), one Cr(3), and one Bi(3) atom. In the third Se site, Se(9) is bonded in a 4-coordinate geometry to one Bi(2), one Bi(3), and two equivalent Bi(1) atoms. In the fourth Se site, Se(10) is bonded to one Bi(2), two equivalent Bi(3), and two equivalent Bi(4) atoms to form SeBi5 trigonal bipyramids that share corners with two equivalent Se(10)Bi5 trigonal bipyramids,  a cornercorner with one Se(4)Bi4 trigonal pyramid, corners with four equivalent Se(5)Bi4 trigonal pyramids,  an edgeedge with one Se(4)Bi4 trigonal pyramid, and edges with two equivalent Se(5)Bi4 trigonal pyramids. In the fifth Se site, Se(1) is bonded in a 3-coordinate geometry to one Cr(1), one Cr(2), one Cr(3), and one Bi(2) atom. In the sixth Se site, Se(2) is bonded in a distorted rectangular see-saw-like geometry to one Cr(3), two equivalent Cr(1), and one Bi(2) atom. In the seventh Se site, Se(3) is bonded in a rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Bi(1) atom. In the eighth Se site, Se(4) is bonded to one Bi(2), one Bi(4), and two equivalent Bi(1) atoms to form distorted SeBi4 trigonal pyramids that share  a cornercorner with one Se(10)Bi5 trigonal bipyramid,  an edgeedge with one Se(10)Bi5 trigonal bipyramid, and edges with two equivalent Se(5)Bi4 trigonal pyramids. In the ninth Se site, Se(5) is bonded to one Bi(1), one Bi(4), and two equivalent Bi(3) atoms to form distorted SeBi4 trigonal pyramids that share corners with two equivalent Se(10)Bi5 trigonal bipyramids, corners with three equivalent Se(5)Bi4 trigonal pyramids,  an edgeedge with one Se(10)Bi5 trigonal bipyramid, and  an edgeedge with one Se(4)Bi4 trigonal pyramid. In the tenth Se site, Se(6) is bonded in a distorted rectangular see-saw-like geometry to one Cr(1), two equivalent Cr(2), and one Bi(3) atom. is represented by the CIF file [CIF]
data_Cr5(Bi3Se8)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.622
_cell_length_b   9.622
_cell_length_c   11.569
_cell_angle_alpha   88.389
_cell_angle_beta   88.389
_cell_angle_gamma   142.215
_symmetry_Int_Tables_number   1
_cell_volume   653.708
_cell_formula_units_Z   1
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
  Cr  Cr0  1  0.614  0.814  0.487  1.0
  Cr  Cr1  1  0.814  0.614  0.487  1.0
  Cr  Cr2  1  0.007  0.404  0.484  1.0
  Cr  Cr3  1  0.404  0.007  0.484  1.0
  Cr  Cr4  1  0.217  0.217  0.491  1.0
  Bi  Bi5  1  0.110  0.444  0.837  1.0
  Bi  Bi6  1  0.444  0.110  0.837  1.0
  Bi  Bi7  1  0.800  0.800  0.833  1.0
  Bi  Bi8  1  0.817  0.486  0.136  1.0
  Bi  Bi9  1  0.486  0.817  0.136  1.0
  Bi  Bi10  1  0.193  0.193  0.141  1.0
  Se  Se11  1  0.930  0.126  0.613  1.0
  Se  Se12  1  0.126  0.930  0.613  1.0
  Se  Se13  1  0.537  0.537  0.609  1.0
  Se  Se14  1  0.320  0.719  0.604  1.0
  Se  Se15  1  0.719  0.320  0.604  1.0
  Se  Se16  1  0.235  0.235  0.889  1.0
  Se  Se17  1  0.038  0.371  0.089  1.0
  Se  Se18  1  0.371  0.038  0.089  1.0
  Se  Se19  1  0.686  0.089  0.363  1.0
  Se  Se20  1  0.089  0.686  0.363  1.0
  Se  Se21  1  0.906  0.906  0.368  1.0
  Se  Se22  1  0.299  0.499  0.363  1.0
  Se  Se23  1  0.499  0.299  0.363  1.0
  Se  Se24  1  0.896  0.561  0.883  1.0
  Se  Se25  1  0.561  0.896  0.883  1.0
  Se  Se26  1  0.704  0.704  0.087  1.0
[/CIF]
.