The structure described by Na4Co2O5 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(2), one O(3), one O(5), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Co(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(1) atoms. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, and edges with two equivalent Na(2)O5 trigonal bipyramids. In the second Co site, Co(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Co(1) atom to form distorted ONa5Co octahedra that share corners with two equivalent O(5)Na4Co2 octahedra, corners with four equivalent O(3)Na5Co octahedra, edges with two equivalent O(5)Na4Co2 octahedra, and edges with two equivalent O(1)Na5Co octahedra. The corner-sharing octahedral tilt angles range from 12-74°. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), and two equivalent Co(1) atoms. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(4), and one Co(2) atom to form ONa5Co octahedra that share corners with two equivalent O(5)Na4Co2 octahedra, corners with four equivalent O(1)Na5Co octahedra, edges with two equivalent O(5)Na4Co2 octahedra, and edges with two equivalent O(3)Na5Co octahedra. The corner-sharing octahedral tilt angles range from 15-74°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), and two equivalent Co(2) atoms. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Co(1), and one Co(2) atom to form a mixture of distorted corner and edge-sharing ONa4Co2 octahedra. The corner-sharing octahedral tilt angles range from 12-74°. is represented by the CIF file [CIF]
data_Na4Co2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.748
_cell_length_b   9.095
_cell_length_c   12.683
_cell_angle_alpha   63.287
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   592.347
_cell_formula_units_Z   4
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  1  0.929  0.199  0.962  1.0
  Na  Na1  1  0.586  0.705  0.960  1.0
  Na  Na2  1  0.120  0.609  0.869  1.0
  Na  Na3  1  0.372  0.125  0.860  1.0
  Na  Na4  1  0.620  0.391  0.631  1.0
  Na  Na5  1  0.872  0.875  0.640  1.0
  Na  Na6  1  0.429  0.801  0.538  1.0
  Na  Na7  1  0.914  0.705  0.460  1.0
  Na  Na8  1  0.086  0.295  0.540  1.0
  Na  Na9  1  0.571  0.199  0.462  1.0
  Na  Na10  1  0.128  0.125  0.360  1.0
  Na  Na11  1  0.380  0.609  0.369  1.0
  Na  Na12  1  0.628  0.875  0.140  1.0
  Na  Na13  1  0.880  0.391  0.131  1.0
  Na  Na14  1  0.414  0.295  0.040  1.0
  Na  Na15  1  0.071  0.801  0.038  1.0
  Co  Co16  1  0.613  0.536  0.806  1.0
  Co  Co17  1  0.113  0.464  0.694  1.0
  Co  Co18  1  0.840  0.047  0.799  1.0
  Co  Co19  1  0.340  0.953  0.701  1.0
  Co  Co20  1  0.660  0.047  0.299  1.0
  Co  Co21  1  0.160  0.953  0.201  1.0
  Co  Co22  1  0.887  0.536  0.306  1.0
  Co  Co23  1  0.387  0.464  0.194  1.0
  O  O24  1  0.768  0.452  0.943  1.0
  O  O25  1  0.345  0.413  0.820  1.0
  O  O26  1  0.739  0.962  0.948  1.0
  O  O27  1  0.086  0.894  0.806  1.0
  O  O28  1  0.511  0.755  0.757  1.0
  O  O29  1  0.845  0.587  0.680  1.0
  O  O30  1  0.011  0.245  0.743  1.0
  O  O31  1  0.586  0.106  0.694  1.0
  O  O32  1  0.268  0.548  0.557  1.0
  O  O33  1  0.239  0.038  0.552  1.0
  O  O34  1  0.761  0.962  0.448  1.0
  O  O35  1  0.732  0.452  0.443  1.0
  O  O36  1  0.414  0.894  0.306  1.0
  O  O37  1  0.989  0.755  0.257  1.0
  O  O38  1  0.155  0.413  0.320  1.0
  O  O39  1  0.489  0.245  0.243  1.0
  O  O40  1  0.914  0.106  0.194  1.0
  O  O41  1  0.261  0.038  0.052  1.0
  O  O42  1  0.655  0.587  0.180  1.0
  O  O43  1  0.232  0.548  0.057  1.0
[/CIF]
.
The structure described by Na4Co2O5 crystallizes in the monoclinic P2_1/c space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(4), one O(5), and two equivalent O(3) atoms. In the second Na site, Na(2) is bonded to one O(2), one O(3), one O(5), and two equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share  a cornercorner with one Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, edges with two equivalent Co(1)O4 tetrahedra, and  an edgeedge with one Na(2)O5 trigonal bipyramid. In the third Na site, Na(3) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(1) atoms. In the fourth Na site, Na(4) is bonded in a 5-coordinate geometry to one O(2), one O(4), one O(5), and two equivalent O(3) atoms. There are two inequivalent Co sites. In the first Co site, Co(1) is bonded to one O(1), one O(5), and two equivalent O(2) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(2)O4 tetrahedra, corners with two equivalent Co(1)O4 tetrahedra,  a cornercorner with one Na(2)O5 trigonal bipyramid, and edges with two equivalent Na(2)O5 trigonal bipyramids. In the second Co site, Co(2) is bonded to one O(3), one O(5), and two equivalent O(4) atoms to form CoO4 tetrahedra that share  a cornercorner with one Co(1)O4 tetrahedra, corners with two equivalent Co(2)O4 tetrahedra, and corners with two equivalent Na(2)O5 trigonal bipyramids. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), two equivalent Na(2), two equivalent Na(3), and one Co(1) atom to form distorted ONa5Co octahedra that share corners with two equivalent O(5)Na4Co2 octahedra, corners with four equivalent O(3)Na5Co octahedra, edges with two equivalent O(5)Na4Co2 octahedra, and edges with two equivalent O(1)Na5Co octahedra. The corner-sharing octahedral tilt angles range from 12-74°. In the second O site, O(2) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Na(4), and two equivalent Co(1) atoms. In the third O site, O(3) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(4), and one Co(2) atom to form ONa5Co octahedra that share corners with two equivalent O(5)Na4Co2 octahedra, corners with four equivalent O(1)Na5Co octahedra, edges with two equivalent O(5)Na4Co2 octahedra, and edges with two equivalent O(3)Na5Co octahedra. The corner-sharing octahedral tilt angles range from 15-74°. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(1), one Na(3), one Na(4), and two equivalent Co(2) atoms. In the fifth O site, O(5) is bonded to one Na(1), one Na(2), one Na(3), one Na(4), one Co(1), and one Co(2) atom to form a mixture of distorted corner and edge-sharing ONa4Co2 octahedra. The corner-sharing octahedral tilt angles range from 12-74°. is represented by the CIF file [CIF]
data_Na4Co2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.748
_cell_length_b   9.095
_cell_length_c   12.683
_cell_angle_alpha   63.287
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   592.347
_cell_formula_units_Z   4
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  1  0.929  0.199  0.962  1.0
  Na  Na1  1  0.586  0.705  0.960  1.0
  Na  Na2  1  0.120  0.609  0.869  1.0
  Na  Na3  1  0.372  0.125  0.860  1.0
  Na  Na4  1  0.620  0.391  0.631  1.0
  Na  Na5  1  0.872  0.875  0.640  1.0
  Na  Na6  1  0.429  0.801  0.538  1.0
  Na  Na7  1  0.914  0.705  0.460  1.0
  Na  Na8  1  0.086  0.295  0.540  1.0
  Na  Na9  1  0.571  0.199  0.462  1.0
  Na  Na10  1  0.128  0.125  0.360  1.0
  Na  Na11  1  0.380  0.609  0.369  1.0
  Na  Na12  1  0.628  0.875  0.140  1.0
  Na  Na13  1  0.880  0.391  0.131  1.0
  Na  Na14  1  0.414  0.295  0.040  1.0
  Na  Na15  1  0.071  0.801  0.038  1.0
  Co  Co16  1  0.613  0.536  0.806  1.0
  Co  Co17  1  0.113  0.464  0.694  1.0
  Co  Co18  1  0.840  0.047  0.799  1.0
  Co  Co19  1  0.340  0.953  0.701  1.0
  Co  Co20  1  0.660  0.047  0.299  1.0
  Co  Co21  1  0.160  0.953  0.201  1.0
  Co  Co22  1  0.887  0.536  0.306  1.0
  Co  Co23  1  0.387  0.464  0.194  1.0
  O  O24  1  0.768  0.452  0.943  1.0
  O  O25  1  0.345  0.413  0.820  1.0
  O  O26  1  0.739  0.962  0.948  1.0
  O  O27  1  0.086  0.894  0.806  1.0
  O  O28  1  0.511  0.755  0.757  1.0
  O  O29  1  0.845  0.587  0.680  1.0
  O  O30  1  0.011  0.245  0.743  1.0
  O  O31  1  0.586  0.106  0.694  1.0
  O  O32  1  0.268  0.548  0.557  1.0
  O  O33  1  0.239  0.038  0.552  1.0
  O  O34  1  0.761  0.962  0.448  1.0
  O  O35  1  0.732  0.452  0.443  1.0
  O  O36  1  0.414  0.894  0.306  1.0
  O  O37  1  0.989  0.755  0.257  1.0
  O  O38  1  0.155  0.413  0.320  1.0
  O  O39  1  0.489  0.245  0.243  1.0
  O  O40  1  0.914  0.106  0.194  1.0
  O  O41  1  0.261  0.038  0.052  1.0
  O  O42  1  0.655  0.587  0.180  1.0
  O  O43  1  0.232  0.548  0.057  1.0
[/CIF]
.