data_[Ba6Na6Nb3O18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Ba  0.8900  2.1500  1.4900
  Na  0.9300  1.8000  1.1600
  Nb  1.6000  1.4500  0.8200
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R-3m]
_cell_length_a [6.4142]
_cell_length_b [6.4142]
_cell_length_c [15.9674]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [166]
_chemical_formula_structural [Ba2Na2NbO6]
_chemical_formula_sum '[Ba6 Na6 Nb3 O18]'
_cell_volume [568.9158]
_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
[
  Ba  Ba0  6  0.0000  0.0000  0.2148  1
  Na  Na1  6  0.0000  0.0000  0.4205  1
  Nb  Nb2  3  0.0000  0.0000  0.0000  1
  O  O3  18  0.0493  0.5246  0.7460  1
]