data_Fe4Hg
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.93
_cell_length_b   7.93
_cell_length_c   7.93
_cell_angle_alpha   158.32
_cell_angle_beta   158.32
_cell_angle_gamma   30.84
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Fe4Hg
_chemical_formula_sum   'Fe4 Hg1'
_cell_volume   67.98
_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  0.0  0.79  1.0
  Fe  Fe1  1  0.0  0.0  0.17  1.0
  Fe  Fe2  1  0.0  0.0  0.12  1.0
  Fe  Fe3  1  0.0  0.0  0.5  1.0
  Hg  Hg4  1  0.0  0.0  0.0  1.0

data_Fe4Hg
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.22
_cell_length_b   4.22
_cell_length_c   7.93
_cell_angle_alpha   90.0
_cell_angle_beta   105.42
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Fe4Hg
_chemical_formula_sum   'Fe8 Hg2'
_cell_volume   135.96
_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  0.21  1.0
  Fe  Fe1  2  0.0  0.0  0.5  1.0
  Fe  Fe2  2  0.0  0.0  0.83  1.0
  Fe  Fe3  2  0.0  0.0  0.88  1.0
  Hg  Hg4  2  0.0  0.0  0.0  1.0

Fe Fe Fe Fe Hg
Fe Fe Fe Fe Hg 0 4 o o + 0 3 o o o 1 2 o o o 1 3 o o o 2 3 o o o 2 4 o o o 3 3 + o + 3 3 o + + 
Fe4Hg crystallizes in the monoclinic Cm space group. There are five inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a distorted single-bond geometry to one Fe(4) and one Hg(1) atom. The Fe(1)-Fe(4) bond length is 2.32 Å. The Fe(1)-Hg(1) bond length is 1.66 Å. In the second Fe site, Fe(2) is bonded in a single-bond geometry to one Fe(3) and one Fe(4) atom. The Fe(2)-Fe(3) bond length is 0.35 Å. The Fe(2)-Fe(4) bond length is 2.63 Å. In the third Fe site, Fe(3) is bonded in a linear geometry to one Fe(2) and one Hg(1) atom. The Fe(3)-Hg(1) bond length is 0.97 Å. In the fourth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one Fe(1), one Fe(2), and four equivalent Fe(4) atoms. All Fe(4)-Fe(4) bond lengths are 2.98 Å. In the fifth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one Fe(1), one Fe(2), and four equivalent Fe(4) atoms. The Fe(4)-Fe(1) bond length is 2.32 Å. The Fe(4)-Fe(2) bond length is 2.63 Å. Hg(1) is bonded in a linear geometry to one Fe(1) and one Fe(3) atom.