data_CaFeHg2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.49
_cell_length_b   5.49
_cell_length_c   5.49
_cell_angle_alpha   131.17
_cell_angle_beta   131.17
_cell_angle_gamma   71.55
_symmetry_Int_Tables_number   1
_chemical_formula_structural   CaFeHg2
_chemical_formula_sum   'Ca1 Fe1 Hg2'
_cell_volume   91.6
_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  0.45  1.0
  Hg  Hg2  1  0.0  0.27  0.23  1.0
  Hg  Hg3  1  0.27  0.0  0.23  1.0

data_CaFeHg2
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.42
_cell_length_b   6.42
_cell_length_c   5.49
_cell_angle_alpha   90.0
_cell_angle_beta   125.77
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   CaFeHg2
_chemical_formula_sum   'Ca2 Fe2 Hg4'
_cell_volume   183.21
_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  0.45  1.0
  Hg  Hg2  4  0.37  0.37  0.96  1.0

Ca Fe Hg Hg
CaFeHg2 crystallizes in the monoclinic Cm space group. Ca(1) is bonded in a water-like geometry to two equivalent Fe(1) and two equivalent Hg(1) atoms. There is one shorter (2.48 Å) and one longer (3.01 Å) Ca(1)-Fe(1) bond length. Both Ca(1)-Hg(1) bond lengths are 1.14 Å. Fe(1) is bonded in a distorted hexagonal planar geometry to two equivalent Ca(1) and four equivalent Hg(1) atoms. There are two shorter (2.47 Å) and two longer (3.33 Å) Fe(1)-Hg(1) bond lengths. Hg(1) is bonded in a single-bond geometry to one Ca(1) and two equivalent Fe(1) atoms.