data_FeSe3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.23
_cell_length_b   5.23
_cell_length_c   5.23
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   FeSe3
_chemical_formula_sum   'Fe2 Se6'
_cell_volume   143.17
_cell_formula_units_Z   2
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  0.62  0.62  0.62  1.0
  Fe  Fe1  1  0.0  0.0  0.0  1.0
  Se  Se2  1  0.31  0.0  0.62  1.0
  Se  Se3  1  0.92  0.0  0.62  1.0
  Se  Se4  1  0.62  0.31  0.0  1.0
  Se  Se5  1  0.62  0.92  0.0  1.0
  Se  Se6  1  0.0  0.62  0.92  1.0
  Se  Se7  1  0.0  0.62  0.31  1.0

data_FeSe3
_symmetry_space_group_name_H-M   R3
_cell_length_a   7.4
_cell_length_b   7.4
_cell_length_c   9.06
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   146
_chemical_formula_structural   FeSe3
_chemical_formula_sum   'Fe6 Se18'
_cell_volume   429.51
_cell_formula_units_Z   6
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-y, x-y, z'
  3  '-x+y, -x, z'
  4  'x+1/3, y+2/3, z+2/3'
  5  '-y+1/3, x-y+2/3, z+2/3'
  6  '-x+y+1/3, -x+2/3, z+2/3'
  7  'x+2/3, y+1/3, z+1/3'
  8  '-y+2/3, x-y+1/3, z+1/3'
  9  '-x+y+2/3, -x+1/3, z+1/3'
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  3  0.0  0.0  0.0  1.0
  Fe  Fe1  3  0.0  0.0  0.62  1.0
  Se  Se2  9  0.0  0.69  0.31  1.0
  Se  Se3  9  0.08  0.23  0.85  1.0

Fe Fe Se Se Se Se Se Se
Fe Fe Se Se Se Se Se Se 0 2 o + o 0 4 o o + 0 7 + o o 0 3 o + o 0 5 o o + 0 6 + o o 1 5 - - o 1 3 - o - 1 6 o - - 2 3 - o o 4 5 o - o 6 7 o o + 
FeSe3 crystallizes in the trigonal R3 space group. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted hexagonal planar geometry to three equivalent Se(1) and three equivalent Se(2) atoms. All Fe(1)-Se(1) bond lengths are 2.58 Å. All Fe(1)-Se(2) bond lengths are 2.58 Å. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to three equivalent Se(1) and three equivalent Se(2) atoms. All Fe(2)-Se(1) bond lengths are 2.58 Å. All Fe(2)-Se(2) bond lengths are 2.05 Å. There are two inequivalent Se sites. In the first Se site, Se(1) is bonded in a 3-coordinate geometry to one Fe(1), one Fe(2), and one Se(2) atom. The Se(1)-Se(2) bond length is 2.01 Å. In the second Se site, Se(2) is bonded in a 1-coordinate geometry to one Fe(1), one Fe(2), and one Se(1) atom.