The material described by Sn4Bi2Se7 crystallizes in the monoclinic C2/m space group. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form SnSe6 octahedra that share  a cornercorner with one Sn(2)Se6 octahedra,  a cornercorner with one Bi(1)Se6 octahedra, corners with three equivalent Sn(1)Se6 octahedra,  an edgeedge with one Sn(1)Se6 octahedra, edges with four equivalent Bi(1)Se6 octahedra, and edges with five equivalent Sn(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second Sn site, Sn(2) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form SnSe6 octahedra that share  a cornercorner with one Sn(1)Se6 octahedra, corners with two equivalent Sn(2)Se6 octahedra, corners with two equivalent Bi(1)Se6 octahedra, edges with three equivalent Sn(2)Se6 octahedra, edges with three equivalent Bi(1)Se6 octahedra, and edges with five equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 1-5°. Bi(1) is bonded to one Se(2), one Se(3), one Se(4), and three equivalent Se(1) atoms to form BiSe6 octahedra that share  a cornercorner with one Sn(1)Se6 octahedra, corners with two equivalent Sn(2)Se6 octahedra, corners with three equivalent Bi(1)Se6 octahedra, edges with two equivalent Bi(1)Se6 octahedra, edges with three equivalent Sn(2)Se6 octahedra, and edges with four equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Sn(1), one Sn(2), and three equivalent Bi(1) atoms to form SeSn2Bi3 square pyramids that share corners with two equivalent Se(3)Sn5Bi octahedra, corners with two equivalent Se(1)Sn2Bi3 square pyramids, corners with three equivalent Se(2)Sn4Bi square pyramids, edges with three equivalent Se(3)Sn5Bi octahedra, edges with two equivalent Se(1)Sn2Bi3 square pyramids, and edges with two equivalent Se(2)Sn4Bi square pyramids. The corner-sharing octahedral tilt angles range from 1-3°. In the second Se site, Se(2) is bonded to two equivalent Sn(1), two equivalent Sn(2), and one Bi(1) atom to form SeSn4Bi square pyramids that share  a cornercorner with one Se(3)Sn5Bi octahedra, corners with two equivalent Se(2)Sn4Bi square pyramids, corners with three equivalent Se(1)Sn2Bi3 square pyramids, edges with five equivalent Se(3)Sn5Bi octahedra,  an edgeedge with one Se(2)Sn4Bi square pyramid, and edges with two equivalent Se(1)Sn2Bi3 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the third Se site, Se(3) is bonded to two equivalent Sn(1), three equivalent Sn(2), and one Bi(1) atom to form SeSn5Bi octahedra that share corners with two equivalent Se(3)Sn5Bi octahedra,  a cornercorner with one Se(2)Sn4Bi square pyramid, corners with two equivalent Se(1)Sn2Bi3 square pyramids, edges with three equivalent Se(3)Sn5Bi octahedra, edges with three equivalent Se(1)Sn2Bi3 square pyramids, and edges with five equivalent Se(2)Sn4Bi square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fourth Se site, Se(4) is bonded in a square co-planar geometry to two equivalent Sn(1) and two equivalent Bi(1) atoms. is represented by the CIF file [CIF]
data_Sn4Bi2Se7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.430
_cell_length_b   7.430
_cell_length_c   9.503
_cell_angle_alpha   81.596
_cell_angle_beta   81.596
_cell_angle_gamma   47.739
_symmetry_Int_Tables_number   1
_cell_volume   383.231
_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
  Sn  Sn0  1  0.426  0.426  0.234  1.0
  Sn  Sn1  1  0.142  0.142  0.061  1.0
  Sn  Sn2  1  0.858  0.858  0.939  1.0
  Sn  Sn3  1  0.574  0.574  0.766  1.0
  Bi  Bi4  1  0.712  0.712  0.355  1.0
  Bi  Bi5  1  0.288  0.288  0.645  1.0
  Se  Se6  1  0.219  0.219  0.366  1.0
  Se  Se7  1  0.919  0.919  0.211  1.0
  Se  Se8  1  0.648  0.648  0.071  1.0
  Se  Se9  1  0.352  0.352  0.929  1.0
  Se  Se10  1  0.081  0.081  0.789  1.0
  Se  Se11  1  0.781  0.781  0.634  1.0
  Se  Se12  1  0.500  0.500  0.500  1.0
[/CIF]
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The material described by Sn4Bi2Se7 crystallizes in the monoclinic C2/m space group. There are two inequivalent Sn sites. In the first Sn site, Sn(1) is bonded to one Se(1), one Se(4), two equivalent Se(2), and two equivalent Se(3) atoms to form SnSe6 octahedra that share  a cornercorner with one Sn(2)Se6 octahedra,  a cornercorner with one Bi(1)Se6 octahedra, corners with three equivalent Sn(1)Se6 octahedra,  an edgeedge with one Sn(1)Se6 octahedra, edges with four equivalent Bi(1)Se6 octahedra, and edges with five equivalent Sn(2)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-9°. In the second Sn site, Sn(2) is bonded to one Se(1), two equivalent Se(2), and three equivalent Se(3) atoms to form SnSe6 octahedra that share  a cornercorner with one Sn(1)Se6 octahedra, corners with two equivalent Sn(2)Se6 octahedra, corners with two equivalent Bi(1)Se6 octahedra, edges with three equivalent Sn(2)Se6 octahedra, edges with three equivalent Bi(1)Se6 octahedra, and edges with five equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 1-5°. Bi(1) is bonded to one Se(2), one Se(3), one Se(4), and three equivalent Se(1) atoms to form BiSe6 octahedra that share  a cornercorner with one Sn(1)Se6 octahedra, corners with two equivalent Sn(2)Se6 octahedra, corners with three equivalent Bi(1)Se6 octahedra, edges with two equivalent Bi(1)Se6 octahedra, edges with three equivalent Sn(2)Se6 octahedra, and edges with four equivalent Sn(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 0-6°. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded to one Sn(1), one Sn(2), and three equivalent Bi(1) atoms to form SeSn2Bi3 square pyramids that share corners with two equivalent Se(3)Sn5Bi octahedra, corners with two equivalent Se(1)Sn2Bi3 square pyramids, corners with three equivalent Se(2)Sn4Bi square pyramids, edges with three equivalent Se(3)Sn5Bi octahedra, edges with two equivalent Se(1)Sn2Bi3 square pyramids, and edges with two equivalent Se(2)Sn4Bi square pyramids. The corner-sharing octahedral tilt angles range from 1-3°. In the second Se site, Se(2) is bonded to two equivalent Sn(1), two equivalent Sn(2), and one Bi(1) atom to form SeSn4Bi square pyramids that share  a cornercorner with one Se(3)Sn5Bi octahedra, corners with two equivalent Se(2)Sn4Bi square pyramids, corners with three equivalent Se(1)Sn2Bi3 square pyramids, edges with five equivalent Se(3)Sn5Bi octahedra,  an edgeedge with one Se(2)Sn4Bi square pyramid, and edges with two equivalent Se(1)Sn2Bi3 square pyramids. The corner-sharing octahedral tilt angles are 2°. In the third Se site, Se(3) is bonded to two equivalent Sn(1), three equivalent Sn(2), and one Bi(1) atom to form SeSn5Bi octahedra that share corners with two equivalent Se(3)Sn5Bi octahedra,  a cornercorner with one Se(2)Sn4Bi square pyramid, corners with two equivalent Se(1)Sn2Bi3 square pyramids, edges with three equivalent Se(3)Sn5Bi octahedra, edges with three equivalent Se(1)Sn2Bi3 square pyramids, and edges with five equivalent Se(2)Sn4Bi square pyramids. The corner-sharing octahedral tilt angles are 5°. In the fourth Se site, Se(4) is bonded in a square co-planar geometry to two equivalent Sn(1) and two equivalent Bi(1) atoms. is represented by the CIF file [CIF]
data_Sn4Bi2Se7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.430
_cell_length_b   7.430
_cell_length_c   9.503
_cell_angle_alpha   81.596
_cell_angle_beta   81.596
_cell_angle_gamma   47.739
_symmetry_Int_Tables_number   1
_cell_volume   383.231
_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
  Sn  Sn0  1  0.426  0.426  0.234  1.0
  Sn  Sn1  1  0.142  0.142  0.061  1.0
  Sn  Sn2  1  0.858  0.858  0.939  1.0
  Sn  Sn3  1  0.574  0.574  0.766  1.0
  Bi  Bi4  1  0.712  0.712  0.355  1.0
  Bi  Bi5  1  0.288  0.288  0.645  1.0
  Se  Se6  1  0.219  0.219  0.366  1.0
  Se  Se7  1  0.919  0.919  0.211  1.0
  Se  Se8  1  0.648  0.648  0.071  1.0
  Se  Se9  1  0.352  0.352  0.929  1.0
  Se  Se10  1  0.081  0.081  0.789  1.0
  Se  Se11  1  0.781  0.781  0.634  1.0
  Se  Se12  1  0.500  0.500  0.500  1.0
[/CIF]
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