data_Na2Co
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.81
_cell_length_b   7.81
_cell_length_c   6.65
_cell_angle_alpha   105.96
_cell_angle_beta   105.96
_cell_angle_gamma   20.35
_symmetry_Int_Tables_number   1
_chemical_formula_structural   Na2Co
_chemical_formula_sum   'Na4 Co2'
_cell_volume   135.56
_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  0.95  0.0  0.96  1.0
  Na  Na3  1  0.39  0.0  0.94  1.0
  Na  Na4  1  0.13  0.0  0.45  1.0
  Na  Na5  1  0.58  0.0  0.43  1.0
  Co  Co0  1  0.11  0.0  0.17  1.0
  Co  Co1  1  0.41  0.0  0.22  1.0

data_Na2Co
_symmetry_space_group_name_H-M   P-1
_cell_length_a   2.76
_cell_length_b   6.65
_cell_length_c   7.81
_cell_angle_alpha   105.96
_cell_angle_beta   100.18
_cell_angle_gamma   90.0
_symmetry_Int_Tables_number   2
_chemical_formula_structural   Na2Co
_chemical_formula_sum   'Na4 Co2'
_cell_volume   135.56
_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  0.23  0.32  1.0
  Na  Na1  2  0.0  0.25  0.87  1.0
  Co  Co2  2  0.0  0.02  0.15  1.0

Na Na Na Na Co Co
Na Na Na Na Co Co 0 4 + o + 1 5 o o + 2 4 o o o 3 5 o o o 
Na2Co crystallizes in the triclinic P-1 space group. The structure is zero-dimensional and consists of two Na2Co clusters. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a single-bond geometry to one Co(1) atom. The Na(1)-Co(1) bond length is 1.61 Å. In the second Na site, Na(2) is bonded in a single-bond geometry to one Co(1) atom. The Na(2)-Co(1) bond length is 1.80 Å. Co(1) is bonded in a distorted bent 150 degrees geometry to one Na(1) and one Na(2) atom.