data_[Na4Nb4Si4O20]
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
  Si  1.9000  1.1000  0.5400
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [C2/c]
_cell_length_a [6.9468]
_cell_length_b [8.7625]
_cell_length_c [7.4829]
_cell_angle_alpha [90.0000]
_cell_angle_beta [115.8474]
_cell_angle_gamma [90.0000]
_symmetry_Int_Tables_number [15]
_chemical_formula_structural [NaNbSiO5]
_chemical_formula_sum '[Na4 Nb4 Si4 O20]'
_cell_volume [409.9302]
_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  0.3290  0.2500  1.0
  Nb  Nb1  4  0.0000  0.0000  0.0000  1.0
  Si  Si2  4  0.0000  0.3217  0.7500  1.0
  O  O3  8  0.0833  0.2135  0.6170  1.0
  O  O4  8  0.1910  0.4372  0.8949  1.0
  O  O5  4  0.0000  0.0693  0.2500  1.0
]