data_Na2C
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.77
_cell_length_b   4.77
_cell_length_c   8.76
_cell_angle_alpha   114.64
_cell_angle_beta   114.64
_cell_angle_gamma   48.06
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2C
_chemical_formula_sum   'Na4 C2'
_cell_volume   131.75
_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
  Na  Na2  1  0.35  0.0  0.1  1.0
  Na  Na3  1  0.87  0.0  0.18  1.0
  Na  Na4  1  0.84  0.0  0.61  1.0
  Na  Na5  1  0.36  0.0  0.69  1.0
  C  C0  1  0.39  0.0  0.24  1.0
  C  C1  1  0.32  0.0  0.55  1.0

data_Na2C
_symmetry_space_group_name_H-M   P-1
_cell_length_a   3.88
_cell_length_b   4.77
_cell_length_c   8.04
_cell_angle_alpha   82.01
_cell_angle_beta   76.02
_cell_angle_gamma   65.97
_symmetry_Int_Tables_number   2
_chemical_formula_structural   Na2C
_chemical_formula_sum   'Na4 C2'
_cell_volume   131.75
_cell_formula_units_Z   2
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
  2  '-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  2  0.0  0.21  0.3  1.0
  Na  Na1  2  0.0  0.23  0.79  1.0
  C  C2  2  0.0  0.31  0.15  1.0

Na Na Na Na C C