data_Fe3Hg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.84
_cell_length_b   2.84
_cell_length_c   8.45
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   120.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Fe3Hg
_chemical_formula_sum   'Fe3 Hg1'
_cell_volume   59.1
_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  0.0  0.64  0.6  1.0
  Fe  Fe1  1  0.0  0.64  0.85  1.0
  Fe  Fe2  1  0.0  0.0  0.0  1.0
  Hg  Hg3  1  0.0  0.0  0.23  1.0

data_Fe3Hg
_symmetry_space_group_name_H-M   Cm
_cell_length_a   2.84
_cell_length_b   4.92
_cell_length_c   8.45
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Fe3Hg
_chemical_formula_sum   'Fe6 Hg2'
_cell_volume   118.2
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  2  0.0  0.0  0.0  1.0
  Fe  Fe1  2  0.14  0.5  0.6  1.0
  Fe  Fe2  2  0.14  0.5  0.85  1.0
  Hg  Hg3  2  0.0  0.0  0.23  1.0

Fe Fe Fe Hg
Fe3Hg crystallizes in the monoclinic Cm space group. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted single-bond geometry to one Fe(2), six equivalent Fe(1), and one Hg(1) atom. The Fe(1)-Fe(2) bond length is 2.08 Å. All Fe(1)-Fe(1) bond lengths are 2.84 Å. The Fe(1)-Hg(1) bond length is 3.35 Å. In the second Fe site, Fe(2) is bonded in a 3-coordinate geometry to one Fe(1) and two equivalent Fe(3) atoms. There is one shorter (1.63 Å) and one longer (2.22 Å) Fe(2)-Fe(3) bond length. In the third Fe site, Fe(3) is bonded in a 2-coordinate geometry to two equivalent Fe(2) and one Hg(1) atom. The Fe(3)-Hg(1) bond length is 1.91 Å. Hg(1) is bonded in a single-bond geometry to one Fe(1) and one Fe(3) atom.