The structure described by Fe7Se8 crystallizes in the trigonal P3_121 space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. In the second Fe site, Fe(2) is bonded to one Se(1), one Se(3), two equivalent Se(2), and two equivalent Se(4) atoms to form a mixture of face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. In the third Fe site, Fe(3) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 51-58°. In the fourth Fe site, Fe(4) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. In the fifth Fe site, Fe(5) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. There are four inequivalent Se sites. In the first Se site, Se(4) is bonded to one Fe(4), two equivalent Fe(2), and two equivalent Fe(5) atoms to form a mixture of distorted corner and edge-sharing SeFe5 trigonal bipyramids. In the second Se site, Se(1) is bonded to one Fe(1), one Fe(2), one Fe(3), one Fe(4), and one Fe(5) atom to form a mixture of distorted corner and edge-sharing SeFe5 square pyramids. In the third Se site, Se(2) is bonded in a 6-coordinate geometry to one Fe(1), one Fe(3), one Fe(4), one Fe(5), and two equivalent Fe(2) atoms. In the fourth Se site, Se(3) is bonded to one Fe(1), one Fe(2), one Fe(3), and two equivalent Fe(5) atoms to form a mixture of distorted corner and edge-sharing SeFe5 trigonal bipyramids. is represented by the CIF file [CIF]
data_Fe7Se8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.263
_cell_length_b   7.263
_cell_length_c   16.025
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   732.097
_cell_formula_units_Z   3
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
  Fe  Fe0  1  0.987  0.987  0.000  1.0
  Fe  Fe1  1  0.013  0.000  0.333  1.0
  Fe  Fe2  1  0.000  0.013  0.667  1.0
  Fe  Fe3  1  0.513  0.996  0.005  1.0
  Fe  Fe4  1  0.004  0.517  0.338  1.0
  Fe  Fe5  1  0.483  0.487  0.671  1.0
  Fe  Fe6  1  0.996  0.513  0.995  1.0
  Fe  Fe7  1  0.487  0.483  0.329  1.0
  Fe  Fe8  1  0.517  0.004  0.662  1.0
  Fe  Fe9  1  0.000  0.030  0.167  1.0
  Fe  Fe10  1  0.970  0.970  0.500  1.0
  Fe  Fe11  1  0.030  0.000  0.833  1.0
  Fe  Fe12  1  0.528  0.528  0.500  1.0
  Fe  Fe13  1  0.472  0.000  0.833  1.0
  Fe  Fe14  1  0.000  0.472  0.167  1.0
  Fe  Fe15  1  0.519  0.006  0.171  1.0
  Fe  Fe16  1  0.994  0.513  0.504  1.0
  Fe  Fe17  1  0.487  0.481  0.837  1.0
  Fe  Fe18  1  0.513  0.994  0.496  1.0
  Fe  Fe19  1  0.006  0.519  0.829  1.0
  Fe  Fe20  1  0.481  0.487  0.163  1.0
  Se  Se21  1  0.167  0.342  0.076  1.0
  Se  Se22  1  0.658  0.824  0.410  1.0
  Se  Se23  1  0.176  0.833  0.743  1.0
  Se  Se24  1  0.171  0.340  0.426  1.0
  Se  Se25  1  0.660  0.832  0.759  1.0
  Se  Se26  1  0.168  0.829  0.092  1.0
  Se  Se27  1  0.162  0.338  0.756  1.0
  Se  Se28  1  0.662  0.825  0.089  1.0
  Se  Se29  1  0.175  0.838  0.422  1.0
  Se  Se30  1  0.338  0.162  0.244  1.0
  Se  Se31  1  0.838  0.175  0.578  1.0
  Se  Se32  1  0.825  0.662  0.911  1.0
  Se  Se33  1  0.340  0.171  0.574  1.0
  Se  Se34  1  0.829  0.168  0.908  1.0
  Se  Se35  1  0.832  0.660  0.241  1.0
  Se  Se36  1  0.342  0.167  0.924  1.0
  Se  Se37  1  0.833  0.176  0.257  1.0
  Se  Se38  1  0.824  0.658  0.590  1.0
  Se  Se39  1  0.673  0.336  0.087  1.0
  Se  Se40  1  0.664  0.337  0.421  1.0
  Se  Se41  1  0.663  0.327  0.754  1.0
  Se  Se42  1  0.327  0.663  0.246  1.0
  Se  Se43  1  0.337  0.664  0.579  1.0
  Se  Se44  1  0.336  0.673  0.913  1.0
[/CIF]
.
The structure described by Fe7Se8 crystallizes in the trigonal P3_121 space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. In the second Fe site, Fe(2) is bonded to one Se(1), one Se(3), two equivalent Se(2), and two equivalent Se(4) atoms to form a mixture of face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 47-58°. In the third Fe site, Fe(3) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(3) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 51-58°. In the fourth Fe site, Fe(4) is bonded to two equivalent Se(1), two equivalent Se(2), and two equivalent Se(4) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 51-56°. In the fifth Fe site, Fe(5) is bonded to one Se(1), one Se(2), two equivalent Se(3), and two equivalent Se(4) atoms to form a mixture of distorted face, corner, and edge-sharing FeSe6 octahedra. The corner-sharing octahedral tilt angles range from 47-53°. There are four inequivalent Se sites. In the first Se site, Se(4) is bonded to one Fe(4), two equivalent Fe(2), and two equivalent Fe(5) atoms to form a mixture of distorted corner and edge-sharing SeFe5 trigonal bipyramids. In the second Se site, Se(1) is bonded to one Fe(1), one Fe(2), one Fe(3), one Fe(4), and one Fe(5) atom to form a mixture of distorted corner and edge-sharing SeFe5 square pyramids. In the third Se site, Se(2) is bonded in a 6-coordinate geometry to one Fe(1), one Fe(3), one Fe(4), one Fe(5), and two equivalent Fe(2) atoms. In the fourth Se site, Se(3) is bonded to one Fe(1), one Fe(2), one Fe(3), and two equivalent Fe(5) atoms to form a mixture of distorted corner and edge-sharing SeFe5 trigonal bipyramids. is represented by the CIF file [CIF]
data_Fe7Se8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.263
_cell_length_b   7.263
_cell_length_c   16.025
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   732.097
_cell_formula_units_Z   3
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
  Fe  Fe0  1  0.987  0.987  0.000  1.0
  Fe  Fe1  1  0.013  0.000  0.333  1.0
  Fe  Fe2  1  0.000  0.013  0.667  1.0
  Fe  Fe3  1  0.513  0.996  0.005  1.0
  Fe  Fe4  1  0.004  0.517  0.338  1.0
  Fe  Fe5  1  0.483  0.487  0.671  1.0
  Fe  Fe6  1  0.996  0.513  0.995  1.0
  Fe  Fe7  1  0.487  0.483  0.329  1.0
  Fe  Fe8  1  0.517  0.004  0.662  1.0
  Fe  Fe9  1  0.000  0.030  0.167  1.0
  Fe  Fe10  1  0.970  0.970  0.500  1.0
  Fe  Fe11  1  0.030  0.000  0.833  1.0
  Fe  Fe12  1  0.528  0.528  0.500  1.0
  Fe  Fe13  1  0.472  0.000  0.833  1.0
  Fe  Fe14  1  0.000  0.472  0.167  1.0
  Fe  Fe15  1  0.519  0.006  0.171  1.0
  Fe  Fe16  1  0.994  0.513  0.504  1.0
  Fe  Fe17  1  0.487  0.481  0.837  1.0
  Fe  Fe18  1  0.513  0.994  0.496  1.0
  Fe  Fe19  1  0.006  0.519  0.829  1.0
  Fe  Fe20  1  0.481  0.487  0.163  1.0
  Se  Se21  1  0.167  0.342  0.076  1.0
  Se  Se22  1  0.658  0.824  0.410  1.0
  Se  Se23  1  0.176  0.833  0.743  1.0
  Se  Se24  1  0.171  0.340  0.426  1.0
  Se  Se25  1  0.660  0.832  0.759  1.0
  Se  Se26  1  0.168  0.829  0.092  1.0
  Se  Se27  1  0.162  0.338  0.756  1.0
  Se  Se28  1  0.662  0.825  0.089  1.0
  Se  Se29  1  0.175  0.838  0.422  1.0
  Se  Se30  1  0.338  0.162  0.244  1.0
  Se  Se31  1  0.838  0.175  0.578  1.0
  Se  Se32  1  0.825  0.662  0.911  1.0
  Se  Se33  1  0.340  0.171  0.574  1.0
  Se  Se34  1  0.829  0.168  0.908  1.0
  Se  Se35  1  0.832  0.660  0.241  1.0
  Se  Se36  1  0.342  0.167  0.924  1.0
  Se  Se37  1  0.833  0.176  0.257  1.0
  Se  Se38  1  0.824  0.658  0.590  1.0
  Se  Se39  1  0.673  0.336  0.087  1.0
  Se  Se40  1  0.664  0.337  0.421  1.0
  Se  Se41  1  0.663  0.327  0.754  1.0
  Se  Se42  1  0.327  0.663  0.246  1.0
  Se  Se43  1  0.337  0.664  0.579  1.0
  Se  Se44  1  0.336  0.673  0.913  1.0
[/CIF]
.