data_[Na3Tb6Nb3O18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Na  0.9300  1.8000  1.1600
  Tb  1.1000  1.7500  0.9815
  Nb  1.6000  1.4500  0.8200
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R3]
_cell_length_a [5.7121]
_cell_length_b [5.7121]
_cell_length_c [15.1035]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [146]
_chemical_formula_structural [NaTb2NbO6]
_chemical_formula_sum '[Na3 Tb6 Nb3 O18]'
_cell_volume [426.7789]
_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
[
  Na  Na0  3  0.0000  0.0000  0.2011  1.0
  Tb  Tb1  3  0.0000  0.0000  0.4764  1.0
  Tb  Tb2  3  0.0000  0.0000  0.9778  1.0
  Nb  Nb3  3  0.0000  0.0000  0.6834  1.0
  O  O4  9  0.0129  0.3749  0.4108  1.0
  O  O5  9  0.0165  0.7376  0.5892  1.0
]