The material structure described by FeCr2Se4 crystallizes in the monoclinic C2/m space group. Cr(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form CrSe6 octahedra that share corners with six equivalent Fe(1)Se6 octahedra, edges with six equivalent Cr(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. Fe(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form FeSe6 octahedra that share corners with twelve equivalent Cr(1)Se6 octahedra, edges with two equivalent Fe(1)Se6 octahedra, and faces with two equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(1) and one Fe(1) atom. In the second Se site, Se(1) is bonded to three equivalent Cr(1) and two equivalent Fe(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Fe2 square pyramids. is represented by the CIF file [CIF]
data_Cr2FeSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.693
_cell_length_b   6.388
_cell_length_c   6.755
_cell_angle_alpha   117.997
_cell_angle_beta   105.864
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   133.782
_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
  Cr  Cr0  1  0.256  0.239  0.511  1.0
  Cr  Cr1  1  0.744  0.761  0.489  1.0
  Fe  Fe2  1  0.000  0.000  0.000  1.0
  Se  Se3  1  0.630  0.295  0.261  1.0
  Se  Se4  1  0.370  0.705  0.739  1.0
  Se  Se5  1  0.122  0.791  0.244  1.0
  Se  Se6  1  0.878  0.209  0.756  1.0
[/CIF]
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The material structure described by FeCr2Se4 crystallizes in the monoclinic C2/m space group. Cr(1) is bonded to three equivalent Se(1) and three equivalent Se(2) atoms to form CrSe6 octahedra that share corners with six equivalent Fe(1)Se6 octahedra, edges with six equivalent Cr(1)Se6 octahedra, and  a faceface with one Fe(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. Fe(1) is bonded to two equivalent Se(2) and four equivalent Se(1) atoms to form FeSe6 octahedra that share corners with twelve equivalent Cr(1)Se6 octahedra, edges with two equivalent Fe(1)Se6 octahedra, and faces with two equivalent Cr(1)Se6 octahedra. The corner-sharing octahedral tilt angles range from 50-51°. There are two inequivalent Se sites. In the first Se site, Se(2) is bonded in a rectangular see-saw-like geometry to three equivalent Cr(1) and one Fe(1) atom. In the second Se site, Se(1) is bonded to three equivalent Cr(1) and two equivalent Fe(1) atoms to form a mixture of distorted edge and corner-sharing SeCr3Fe2 square pyramids. is represented by the CIF file [CIF]
data_Cr2FeSe4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.693
_cell_length_b   6.388
_cell_length_c   6.755
_cell_angle_alpha   117.997
_cell_angle_beta   105.864
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   133.782
_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
  Cr  Cr0  1  0.256  0.239  0.511  1.0
  Cr  Cr1  1  0.744  0.761  0.489  1.0
  Fe  Fe2  1  0.000  0.000  0.000  1.0
  Se  Se3  1  0.630  0.295  0.261  1.0
  Se  Se4  1  0.370  0.705  0.739  1.0
  Se  Se5  1  0.122  0.791  0.244  1.0
  Se  Se6  1  0.878  0.209  0.756  1.0
[/CIF]
.