data_[Na2Er2S2]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Na  0.9300  1.8000  1.1600
  Er  1.2400  1.7500  1.0300
  S  2.5800  1.0000  0.8800
]
_symmetry_space_group_name_H-M [P-6m2]
_cell_length_a [3.6894]
_cell_length_b [3.6894]
_cell_length_c [13.7219]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [187]
_chemical_formula_structural [NaErS]
_chemical_formula_sum '[Na2 Er2 S2]'
_cell_volume [161.7571]
_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
[
  Na  Na0  2  0.0000  0.0000  0.1183  1
  Er  Er1  2  0.3333  0.6667  0.3686  1
  S  S2  1  0.0000  0.0000  0.5000  1
  S  S3  1  0.3333  0.6667  0.0000  1
]