data_[Na4Nb8O20]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  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 [Cmcm]
_cell_length_a [3.8638]
_cell_length_b [10.7011]
_cell_length_c [10.4491]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [90.0000]
_symmetry_Int_Tables_number [63]
_chemical_formula_structural [NaNb2O5]
_chemical_formula_sum '[Na4 Nb8 O20]'
_cell_volume [432.0390]
_cell_formula_units_Z [4]
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  4  0.0000  0.4085  0.7500  1
  Nb  Nb1  8  0.0000  0.1334  0.5687  1
  O  O2  8  0.0000  0.0379  0.1158  1
  O  O3  8  0.0000  0.3200  0.0393  1
  O  O4  4  0.0000  0.1872  0.7500  1
]