The material described by Fe9Se8 is Matlockite-derived structured and crystallizes in the tetragonal P4mm space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share  a cornercorner with one Fe(3)Se5 square pyramid, corners with two equivalent Fe(1)Se4 tetrahedra, corners with two equivalent Fe(2)Se4 tetrahedra,  an edgeedge with one Fe(3)Se5 square pyramid, edges with two equivalent Fe(1)Se4 tetrahedra, and edges with two equivalent Fe(2)Se4 tetrahedra. In the second Fe site, Fe(2) is bonded to one Se(3), one Se(4), and two equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share corners with two equivalent Fe(3)Se5 square pyramids, corners with two equivalent Fe(1)Se4 tetrahedra, corners with two equivalent Fe(2)Se4 tetrahedra, edges with two equivalent Fe(1)Se4 tetrahedra, and edges with two equivalent Fe(2)Se4 tetrahedra. In the third Fe site, Fe(3) is bonded to one Se(2) and four equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing FeSe5 square pyramids. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Fe(3), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Fe(3) and four equivalent Fe(1) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to two equivalent Fe(1) and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to four equivalent Fe(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Fe9Se8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.199
_cell_length_b   7.199
_cell_length_c   6.063
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   314.213
_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
  Fe  Fe0  1  0.000  0.243  0.232  1.0
  Fe  Fe1  1  0.000  0.757  0.232  1.0
  Fe  Fe2  1  0.757  0.000  0.232  1.0
  Fe  Fe3  1  0.243  0.000  0.232  1.0
  Fe  Fe4  1  0.751  0.500  0.249  1.0
  Fe  Fe5  1  0.249  0.500  0.249  1.0
  Fe  Fe6  1  0.500  0.249  0.249  1.0
  Fe  Fe7  1  0.500  0.751  0.249  1.0
  Fe  Fe8  1  0.000  0.000  0.563  1.0
  Se  Se9  1  0.752  0.248  0.493  1.0
  Se  Se10  1  0.248  0.752  0.493  1.0
  Se  Se11  1  0.248  0.248  0.493  1.0
  Se  Se12  1  0.752  0.752  0.493  1.0
  Se  Se13  1  0.000  0.000  0.958  1.0
  Se  Se14  1  0.000  0.500  0.999  1.0
  Se  Se15  1  0.500  0.000  0.999  1.0
  Se  Se16  1  0.500  0.500  0.009  1.0
[/CIF]
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The material described by Fe9Se8 is Matlockite-derived structured and crystallizes in the tetragonal P4mm space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one Se(2), one Se(3), and two equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share  a cornercorner with one Fe(3)Se5 square pyramid, corners with two equivalent Fe(1)Se4 tetrahedra, corners with two equivalent Fe(2)Se4 tetrahedra,  an edgeedge with one Fe(3)Se5 square pyramid, edges with two equivalent Fe(1)Se4 tetrahedra, and edges with two equivalent Fe(2)Se4 tetrahedra. In the second Fe site, Fe(2) is bonded to one Se(3), one Se(4), and two equivalent Se(1) atoms to form distorted FeSe4 tetrahedra that share corners with two equivalent Fe(3)Se5 square pyramids, corners with two equivalent Fe(1)Se4 tetrahedra, corners with two equivalent Fe(2)Se4 tetrahedra, edges with two equivalent Fe(1)Se4 tetrahedra, and edges with two equivalent Fe(2)Se4 tetrahedra. In the third Fe site, Fe(3) is bonded to one Se(2) and four equivalent Se(1) atoms to form a mixture of distorted corner and edge-sharing FeSe5 square pyramids. There are four inequivalent Se sites. In the first Se site, Se(1) is bonded in a 5-coordinate geometry to one Fe(3), two equivalent Fe(1), and two equivalent Fe(2) atoms. In the second Se site, Se(2) is bonded in a 5-coordinate geometry to one Fe(3) and four equivalent Fe(1) atoms. In the third Se site, Se(3) is bonded in a 4-coordinate geometry to two equivalent Fe(1) and two equivalent Fe(2) atoms. In the fourth Se site, Se(4) is bonded in a 4-coordinate geometry to four equivalent Fe(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Fe9Se8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.199
_cell_length_b   7.199
_cell_length_c   6.063
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   314.213
_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
  Fe  Fe0  1  0.000  0.243  0.232  1.0
  Fe  Fe1  1  0.000  0.757  0.232  1.0
  Fe  Fe2  1  0.757  0.000  0.232  1.0
  Fe  Fe3  1  0.243  0.000  0.232  1.0
  Fe  Fe4  1  0.751  0.500  0.249  1.0
  Fe  Fe5  1  0.249  0.500  0.249  1.0
  Fe  Fe6  1  0.500  0.249  0.249  1.0
  Fe  Fe7  1  0.500  0.751  0.249  1.0
  Fe  Fe8  1  0.000  0.000  0.563  1.0
  Se  Se9  1  0.752  0.248  0.493  1.0
  Se  Se10  1  0.248  0.752  0.493  1.0
  Se  Se11  1  0.248  0.248  0.493  1.0
  Se  Se12  1  0.752  0.752  0.493  1.0
  Se  Se13  1  0.000  0.000  0.958  1.0
  Se  Se14  1  0.000  0.500  0.999  1.0
  Se  Se15  1  0.500  0.000  0.999  1.0
  Se  Se16  1  0.500  0.500  0.009  1.0
[/CIF]
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