data_[Na3Cu6P6O21]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Na  0.9300  1.8000  1.1600
  Cu  1.9000  1.3500  0.8200
  P  2.1900  1.0000  0.5500
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R32]
_cell_length_a [5.2992]
_cell_length_b [5.2992]
_cell_length_c [21.6180]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [155]
_chemical_formula_structural [NaCu2P2O7]
_chemical_formula_sum '[Na3 Cu6 P6 O21]'
_cell_volume [525.7283]
_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  0.5000  1.0
  Cu  Cu1  6  0.0000  0.0000  0.2436  1.0
  P  P2  6  0.0000  0.0000  0.0737  1.0
  O  O3  18  0.0021  0.2778  0.9054  1.0
  O  O4  3  0.0000  0.0000  0.0000  1.0
]