data_[Na3Er6Nb3O18]
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
  Nb  1.6000  1.4500  0.8200
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R3]
_cell_length_a [5.6467]
_cell_length_b [5.6467]
_cell_length_c [15.0546]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [146]
_chemical_formula_structural [NaEr2NbO6]
_chemical_formula_sum '[Na3 Er6 Nb3 O18]'
_cell_volume [415.7046]
_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  0.2032  1
  Er  Er1  3  0.0000  0.0000  0.4782  1
  Er  Er2  3  0.0000  0.0000  0.9802  1
  Nb  Nb3  3  0.0000  0.0000  0.6831  1
  O  O4  9  0.0109  0.3668  0.4098  1
  O  O5  9  0.0262  0.7415  0.5882  1
]