data_[Mg18C21]
loop_
 _atom_type_symbol
 _atom_type_electronegativity
 _atom_type_radius
 _atom_type_ionic_radius
[
  Mg  1.3100  1.5000  0.8600
  C  2.5500  0.7000  0.3000
]
_symmetry_space_group_name_H-M [R-3m]
_cell_length_a [5.1119]
_cell_length_b [5.1119]
_cell_length_c [28.6976]
_cell_angle_alpha [90.0000]
_cell_angle_beta [90.0000]
_cell_angle_gamma [120.0000]
_symmetry_Int_Tables_number [166]
_chemical_formula_structural [Mg6C7]
_chemical_formula_sum '[Mg18 C21]'
_cell_volume [649.4438]
_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
[
  Mg  Mg0  6  0.0000  0.0000  0.0544  1
  Mg  Mg1  6  0.0000  0.0000  0.2268  1
  Mg  Mg2  6  0.0000  0.0000  0.3410  1
  C  C3  18  0.0979  0.9021  0.4523  1
  C  C4  3  -0.0000  -0.0000  0.5000  1
]