data_[Na6Mg3C6O18]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Na  0.9300  1.8000  1.1600
  Mg  1.3100  1.5000  0.8600
  C  2.5500  0.7000  0.3000
  O  3.4400  0.6000  1.2600
]
_symmetry_space_group_name_H-M [R-3]
_cell_length_a [4.9983]
_cell_length_b [4.9983]
_cell_length_c [16.6217]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [148]
_chemical_formula_structural [Na2Mg(CO3)2]
_chemical_formula_sum '[Na6 Mg3 C6 O18]'
_cell_volume [359.6247]
_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  6  0.0000  0.0000  0.2011  1.0
  Mg  Mg1  3  0.0000  0.0000  0.0000  1.0
  C  C2  6  0.0000  0.0000  0.4090  1.0
  O  O3  18  0.0438  0.5908  0.2563  1.0
]