The material described by Bi2Se3 is Hausmannite-like structured and crystallizes in the tetragonal P4_2/nmc space group. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted corner-sharing BiSe4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-68°. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. In the third Bi site, Bi(3) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form distorted BiSe6 octahedra that share corners with two equivalent Bi(3)Se6 octahedra, corners with four equivalent Bi(1)Se4 tetrahedra, and edges with two equivalent Bi(3)Se6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are three inequivalent Se sites. In the first Se site, Se(3) is bonded in a distorted trigonal planar geometry to one Bi(2) and two equivalent Bi(3) atoms. In the second Se site, Se(1) is bonded to one Bi(1), one Bi(2), and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SeBi4 tetrahedra. In the third Se site, Se(2) is bonded to one Bi(1), one Bi(2), and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SeBi4 tetrahedra. is represented by the CIF file [CIF]
data_Bi2Se3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.872
_cell_length_b   9.872
_cell_length_c   13.685
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1333.795
_cell_formula_units_Z   8
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  0.000  0.000  0.244  1.0
  Bi  Bi1  1  0.500  0.500  0.744  1.0
  Bi  Bi2  1  0.500  0.500  0.256  1.0
  Bi  Bi3  1  0.000  0.000  0.756  1.0
  Bi  Bi4  1  0.000  0.500  0.277  1.0
  Bi  Bi5  1  0.000  0.500  0.777  1.0
  Bi  Bi6  1  0.500  0.000  0.223  1.0
  Bi  Bi7  1  0.500  0.000  0.723  1.0
  Bi  Bi8  1  0.263  0.737  0.000  1.0
  Bi  Bi9  1  0.737  0.737  0.000  1.0
  Bi  Bi10  1  0.263  0.263  0.000  1.0
  Bi  Bi11  1  0.737  0.263  0.000  1.0
  Bi  Bi12  1  0.237  0.763  0.500  1.0
  Bi  Bi13  1  0.763  0.763  0.500  1.0
  Bi  Bi14  1  0.237  0.237  0.500  1.0
  Bi  Bi15  1  0.763  0.237  0.500  1.0
  Se  Se16  1  0.734  0.500  0.863  1.0
  Se  Se17  1  0.266  0.500  0.863  1.0
  Se  Se18  1  0.000  0.234  0.363  1.0
  Se  Se19  1  0.000  0.766  0.363  1.0
  Se  Se20  1  0.766  0.000  0.637  1.0
  Se  Se21  1  0.234  0.000  0.637  1.0
  Se  Se22  1  0.500  0.266  0.137  1.0
  Se  Se23  1  0.500  0.734  0.137  1.0
  Se  Se24  1  0.280  0.500  0.399  1.0
  Se  Se25  1  0.720  0.500  0.399  1.0
  Se  Se26  1  0.000  0.780  0.899  1.0
  Se  Se27  1  0.000  0.220  0.899  1.0
  Se  Se28  1  0.220  0.000  0.101  1.0
  Se  Se29  1  0.780  0.000  0.101  1.0
  Se  Se30  1  0.500  0.720  0.601  1.0
  Se  Se31  1  0.500  0.280  0.601  1.0
  Se  Se32  1  0.796  0.500  0.129  1.0
  Se  Se33  1  0.204  0.500  0.129  1.0
  Se  Se34  1  0.000  0.296  0.629  1.0
  Se  Se35  1  0.000  0.704  0.629  1.0
  Se  Se36  1  0.704  0.000  0.371  1.0
  Se  Se37  1  0.296  0.000  0.371  1.0
  Se  Se38  1  0.500  0.204  0.871  1.0
  Se  Se39  1  0.500  0.796  0.871  1.0
[/CIF]
.
The material described by Bi2Se3 is Hausmannite-like structured and crystallizes in the tetragonal P4_2/nmc space group. There are three inequivalent Bi sites. In the first Bi site, Bi(1) is bonded to two equivalent Se(1) and two equivalent Se(2) atoms to form distorted corner-sharing BiSe4 tetrahedra. The corner-sharing octahedral tilt angles range from 65-68°. In the second Bi site, Bi(2) is bonded in a 6-coordinate geometry to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms. In the third Bi site, Bi(3) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form distorted BiSe6 octahedra that share corners with two equivalent Bi(3)Se6 octahedra, corners with four equivalent Bi(1)Se4 tetrahedra, and edges with two equivalent Bi(3)Se6 octahedra. The corner-sharing octahedral tilt angles are 58°. There are three inequivalent Se sites. In the first Se site, Se(3) is bonded in a distorted trigonal planar geometry to one Bi(2) and two equivalent Bi(3) atoms. In the second Se site, Se(1) is bonded to one Bi(1), one Bi(2), and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SeBi4 tetrahedra. In the third Se site, Se(2) is bonded to one Bi(1), one Bi(2), and two equivalent Bi(3) atoms to form a mixture of corner and edge-sharing SeBi4 tetrahedra. is represented by the CIF file [CIF]
data_Bi2Se3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.872
_cell_length_b   9.872
_cell_length_c   13.685
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   1333.795
_cell_formula_units_Z   8
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  0.000  0.000  0.244  1.0
  Bi  Bi1  1  0.500  0.500  0.744  1.0
  Bi  Bi2  1  0.500  0.500  0.256  1.0
  Bi  Bi3  1  0.000  0.000  0.756  1.0
  Bi  Bi4  1  0.000  0.500  0.277  1.0
  Bi  Bi5  1  0.000  0.500  0.777  1.0
  Bi  Bi6  1  0.500  0.000  0.223  1.0
  Bi  Bi7  1  0.500  0.000  0.723  1.0
  Bi  Bi8  1  0.263  0.737  0.000  1.0
  Bi  Bi9  1  0.737  0.737  0.000  1.0
  Bi  Bi10  1  0.263  0.263  0.000  1.0
  Bi  Bi11  1  0.737  0.263  0.000  1.0
  Bi  Bi12  1  0.237  0.763  0.500  1.0
  Bi  Bi13  1  0.763  0.763  0.500  1.0
  Bi  Bi14  1  0.237  0.237  0.500  1.0
  Bi  Bi15  1  0.763  0.237  0.500  1.0
  Se  Se16  1  0.734  0.500  0.863  1.0
  Se  Se17  1  0.266  0.500  0.863  1.0
  Se  Se18  1  0.000  0.234  0.363  1.0
  Se  Se19  1  0.000  0.766  0.363  1.0
  Se  Se20  1  0.766  0.000  0.637  1.0
  Se  Se21  1  0.234  0.000  0.637  1.0
  Se  Se22  1  0.500  0.266  0.137  1.0
  Se  Se23  1  0.500  0.734  0.137  1.0
  Se  Se24  1  0.280  0.500  0.399  1.0
  Se  Se25  1  0.720  0.500  0.399  1.0
  Se  Se26  1  0.000  0.780  0.899  1.0
  Se  Se27  1  0.000  0.220  0.899  1.0
  Se  Se28  1  0.220  0.000  0.101  1.0
  Se  Se29  1  0.780  0.000  0.101  1.0
  Se  Se30  1  0.500  0.720  0.601  1.0
  Se  Se31  1  0.500  0.280  0.601  1.0
  Se  Se32  1  0.796  0.500  0.129  1.0
  Se  Se33  1  0.204  0.500  0.129  1.0
  Se  Se34  1  0.000  0.296  0.629  1.0
  Se  Se35  1  0.000  0.704  0.629  1.0
  Se  Se36  1  0.704  0.000  0.371  1.0
  Se  Se37  1  0.296  0.000  0.371  1.0
  Se  Se38  1  0.500  0.204  0.871  1.0
  Se  Se39  1  0.500  0.796  0.871  1.0
[/CIF]
.