data_[As18Se21]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  As  2.1800  1.1500  0.6600
  Se  2.5500  1.1500  1.0133
]
_symmetry_space_group_name_H-M [R-3m]
_cell_length_a [7.1090]
_cell_length_b [7.1090]
_cell_length_c [22.5733]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [166]
_chemical_formula_structural [As6Se7]
_chemical_formula_sum '[As18 Se21]'
_cell_volume [987.9737]
_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
[
  As  As0  6  0.0000  0.0000  0.0838  1
  As  As1  6  0.0000  0.0000  0.1861  1
  As  As2  6  0.0000  0.0000  0.3268  1
  Se  Se3  18  0.0049  0.5025  0.0794  1
  Se  Se4  3  -0.0000  -0.0000  0.5000  1
]