data_[Rb2Mg2Nb2O8]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Rb  0.8200  2.3500  1.6600
  Mg  1.3100  1.5000  0.8600
  Nb  1.6000  1.4500  0.8200
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [P2_1/m]
_cell_length_a [5.6789]
_cell_length_b [5.9230]
_cell_length_c [8.3855]
_cell_angle_alpha [90.0000]
_cell_angle_beta [95.6427]
_cell_angle_gamma [90.0000]
_symmetry_Int_Tables_number [11]
_chemical_formula_structural [RbMgNbO4]
_chemical_formula_sum '[Rb2 Mg2 Nb2 O8]'
_cell_volume [280.6872]
_cell_formula_units_Z [2]
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
[
  Rb  Rb0  2  0.3330  0.7500  0.0579  1.0
  Mg  Mg1  2  0.3917  0.7500  0.5262  1.0
  Nb  Nb2  2  0.1441  0.2500  0.2757  1.0
  O  O3  4  0.3265  0.0089  0.3732  1.0
  O  O4  2  0.1788  0.7500  0.6970  1.0
  O  O5  2  0.1810  0.2500  0.0601  1.0
]