data_[Cu18Hg6Se18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Cu  1.9000  1.3500  0.8200
  Hg  2.0000  1.5000  1.2450
  Se  2.5500  1.1500  1.0133
]
_symmetry_space_group_name_H-M [R-3]
_cell_length_a [6.7537]
_cell_length_b [6.7537]
_cell_length_c [22.3655]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [148]
_chemical_formula_structural [Cu3HgSe3]
_chemical_formula_sum '[Cu18 Hg6 Se18]'
_cell_volume [883.4611]
_cell_formula_units_Z [6]
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
[
  Cu  Cu0  18  0.0002  0.6677  0.4675  1.0
  Hg  Hg1  6  0.0000  0.0000  0.3335  1.0
  Se  Se2  18  0.0001  0.6693  0.2437  1.0
]