data_HgC
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.62
_cell_length_b   4.62
_cell_length_c   3.42
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   1
_chemical_formula_structural   HgC
_chemical_formula_sum   'Hg2 C2'
_cell_volume   72.85
_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
  Hg  Hg2  1  0.31  0.31  0.0  1.0
  Hg  Hg3  1  0.0  0.0  0.0  1.0
  C  C0  1  0.31  0.0  0.06  1.0
  C  C1  1  0.0  0.31  0.36  1.0

data_HgC
_symmetry_space_group_name_H-M   Cm
_cell_length_a   6.53
_cell_length_b   6.53
_cell_length_c   3.42
_cell_angle_alpha   90.0
_cell_angle_beta   90.0
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   HgC
_chemical_formula_sum   'Hg4 C4'
_cell_volume   145.71
_cell_formula_units_Z   4
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
  Hg  Hg0  4  0.15  0.15  -0.0  1.0
  C  C1  2  0.0  0.0  0.36  1.0
  C  C2  2  0.31  0.0  0.06  1.0

Hg Hg C C
Hg Hg C C 0 2 o o o 0 3 o o o 1 2 o o o 1 3 o o o 