data_Bi4Se3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.85
_cell_length_b   13.85
_cell_length_c   13.85
_cell_angle_alpha   17.97
_cell_angle_beta   17.97
_cell_angle_gamma   17.97
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Bi4Se3
_chemical_formula_sum   'Bi4 Se3'
_cell_volume   220.8
_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
  Bi  Bi0  1  0.0  0.0  0.94  1.0
  Bi  Bi1  1  0.0  0.0  0.92  1.0
  Bi  Bi2  1  0.0  0.0  0.75  1.0
  Bi  Bi3  1  0.0  0.0  0.11  1.0
  Se  Se4  1  0.0  0.0  0.02  1.0
  Se  Se5  1  0.0  0.0  0.84  1.0
  Se  Se6  1  0.0  0.0  0.0  1.0

data_Bi4Se3
_symmetry_space_group_name_H-M   Cm
_cell_length_a   7.49
_cell_length_b   4.33
_cell_length_c   13.85
_cell_angle_alpha   90.0
_cell_angle_beta   100.39
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Bi4Se3
_chemical_formula_sum   'Bi8 Se6'
_cell_volume   441.59
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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
  Bi  Bi0  2  0.0  0.0  0.06  1.0
  Bi  Bi1  2  0.0  0.0  0.08  1.0
  Bi  Bi2  2  0.0  0.0  0.25  1.0
  Bi  Bi3  2  0.0  0.0  0.89  1.0
  Se  Se4  2  0.0  0.0  0.0  1.0
  Se  Se5  2  0.0  0.0  0.16  1.0
  Se  Se6  2  0.0  0.0  0.98  1.0

Bi Bi Bi Bi Se Se Se
Bi4Se3 is Indium-like structured and crystallizes in the monoclinic Cm space group. The structure is zero-dimensional and consists of two Bi4Se3 clusters. There are four inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a linear geometry to one Bi(2) and one Se(3) atom. The Bi(1)-Bi(2) bond length is 0.21 Å. The Bi(1)-Se(3) bond length is 0.85 Å. In the second Bi site, Bi(2) is bonded in a linear geometry to one Bi(1) and one Se(2) atom. The Bi(2)-Se(2) bond length is 1.19 Å. In the third Bi site, Bi(3) is bonded in a single-bond geometry to one Se(2) atom. The Bi(3)-Se(2) bond length is 1.19 Å. In the fourth Bi site, Bi(4) is bonded in a single-bond geometry to one Se(1) atom. The Bi(4)-Se(1) bond length is 1.19 Å. There are three inequivalent Se sites. In the first Se site, Se(1) is bonded in a linear geometry to one Bi(4) and one Se(3) atom. The Se(1)-Se(3) bond length is 0.34 Å. In the second Se site, Se(2) is bonded in a linear geometry to one Bi(2) and one Bi(3) atom. In the third Se site, Se(3) is bonded in a linear geometry to one Bi(1) and one Se(1) atom.