data_Mg2C3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.3
_cell_length_b   7.3
_cell_length_c   7.3
_cell_angle_alpha   21.76
_cell_angle_beta   21.76
_cell_angle_gamma   21.76
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Mg2C3
_chemical_formula_sum   'Mg2 C3'
_cell_volume   46.84
_cell_formula_units_Z   1
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  Mg3  1  0.0  0.0  0.72  1.0
  Mg  Mg4  1  0.0  0.0  0.65  1.0
  C  C0  1  0.0  0.0  0.0  1.0
  C  C1  1  0.0  0.0  0.79  1.0
  C  C2  1  0.0  0.0  0.58  1.0

data_Mg2C3
_symmetry_space_group_name_H-M   Cm
_cell_length_a   4.77
_cell_length_b   2.76
_cell_length_c   7.3
_cell_angle_alpha   90.0
_cell_angle_beta   102.59
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   8
_chemical_formula_structural   Mg2C3
_chemical_formula_sum   'Mg4 C6'
_cell_volume   93.67
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  'x, -y, z'
  3  'x+1/2, y+1/2, z'
  4  'x+1/2, -y+1/2, 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  2  0.0  0.0  0.28  1.0
  Mg  Mg1  2  0.0  0.0  0.35  1.0
  C  C2  2  0.0  0.0  0.0  1.0
  C  C3  2  0.0  0.0  0.21  1.0
  C  C4  2  0.0  0.0  0.42  1.0

Mg Mg C C C