data_CaFeHg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.44
_cell_length_b   3.44
_cell_length_c   6.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaFeHg2
_chemical_formula_sum   'Ca1 Fe1 Hg2'
_cell_volume   82.11
_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
  Ca  Ca0  1  0.0  0.0  0.0  1.0
  Fe  Fe1  1  0.0  0.0  0.47  1.0
  Hg  Hg2  1  0.72  0.72  0.91  1.0
  Hg  Hg3  1  0.72  0.72  0.02  1.0

data_CaFeHg2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.87
_cell_length_b   4.87
_cell_length_c   6.94
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   CaFeHg2
_chemical_formula_sum   'Ca2 Fe2 Hg4'
_cell_volume   164.21
_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
  Ca  Ca0  2  0.0  0.0  0.0  1.0
  Fe  Fe1  2  0.0  0.0  0.47  1.0
  Hg  Hg2  2  0.22  0.5  0.02  1.0
  Hg  Hg3  2  0.22  0.5  0.91  1.0

Ca Fe Hg Hg
CaFeHg2 crystallizes in the monoclinic Cm space group. Ca(1) is bonded in a 2-coordinate geometry to two equivalent Fe(1), one Hg(1), and one Hg(2) atom. There is one shorter (3.25 Å) and one longer (3.68 Å) Ca(1)-Fe(1) bond length. The Ca(1)-Hg(1) bond length is 1.49 Å. The Ca(1)-Hg(2) bond length is 1.37 Å. Fe(1) is bonded to two equivalent Ca(1), four equivalent Fe(1), one Hg(1), and one Hg(2) atom to form a mixture of distorted corner and edge-sharing FeCa2Fe4Hg2 hexagonal bipyramids. All Fe(1)-Fe(1) bond lengths are 3.44 Å. The Fe(1)-Hg(1) bond length is 3.38 Å. The Fe(1)-Hg(2) bond length is 3.38 Å. There are two inequivalent Hg sites. In the first Hg site, Hg(1) is bonded in a 2-coordinate geometry to one Ca(1), one Fe(1), and one Hg(2) atom. The Hg(1)-Hg(2) bond length is 0.76 Å. In the second Hg site, Hg(2) is bonded in a distorted L-shaped geometry to one Ca(1), one Fe(1), and one Hg(1) atom.