data_[Zn21Se18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Zn  1.6500  1.3500  0.8800
  Se  2.5500  1.1500  1.0133
]
_symmetry_space_group_name_H-M [R-3m]
_cell_length_a [5.9601]
_cell_length_b [5.9601]
_cell_length_c [31.1826]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [166]
_chemical_formula_structural [Zn7Se6]
_chemical_formula_sum '[Zn21 Se18]'
_cell_volume [959.2808]
_cell_formula_units_Z [3]
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
[
  Zn  Zn0  18  0.0030  0.5015  0.0876  1
  Zn  Zn1  3  -0.0000  -0.0000  0.5000  1
  Se  Se2  6  0.0000  0.0000  0.0881  1
  Se  Se3  6  0.0000  0.0000  0.1926  1
  Se  Se4  6  0.0000  0.0000  0.3668  1
]