The compound described by Na2CuO2 crystallizes in the monoclinic P2_1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted trigonal planar geometry to one O(5) and two equivalent O(1) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(5), and one O(7) atom. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(6), and one O(8) atom. In the sixth Na site, Na(6) is bonded in a 5-coordinate geometry to one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a 4-coordinate geometry to one O(6), one O(8), and two equivalent O(7) atoms. In the eighth Na site, Na(8) is bonded in a 4-coordinate geometry to one O(3), one O(6), and two equivalent O(8) atoms. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(3) atom. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), and one O(6) atom. In the third Cu site, Cu(3) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. In the fourth Cu site, Cu(4) is bonded in a 3-coordinate geometry to one O(5), one O(7), and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Cu(1) atom to form distorted ONa5Cu octahedra that share corners with two equivalent O(2)Na4Cu2 octahedra, corners with two equivalent O(1)Na5Cu octahedra, and  an edgeedge with one O(2)Na4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 33-49°. In the second O site, O(2) is bonded to one Na(3), one Na(5), two equivalent Na(1), one Cu(1), and one Cu(2) atom to form distorted ONa4Cu2 octahedra that share  a cornercorner with one O(8)Na5Cu octahedra, corners with two equivalent O(2)Na4Cu2 octahedra, corners with two equivalent O(1)Na5Cu octahedra, and  an edgeedge with one O(1)Na5Cu octahedra. The corner-sharing octahedral tilt angles range from 33-70°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(5), one Na(8), one Cu(1), and one Cu(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(3), one Na(4), one Na(6), one Cu(2), and one Cu(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(2), one Na(4), one Na(6), one Cu(3), and one Cu(4) atom. In the sixth O site, O(6) is bonded in a 7-coordinate geometry to one Na(3), one Na(5), one Na(6), one Na(7), one Na(8), one Cu(2), and one Cu(3) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Na(4), one Na(6), two equivalent Na(7), one Cu(3), and one Cu(4) atom. In the eighth O site, O(8) is bonded to one Na(5), one Na(6), one Na(7), two equivalent Na(8), and one Cu(4) atom to form distorted ONa5Cu octahedra that share  a cornercorner with one O(2)Na4Cu2 octahedra and corners with two equivalent O(8)Na5Cu octahedra. The corner-sharing octahedral tilt angles are 49°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2CuO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.708
_cell_length_b   8.766
_cell_length_c   11.491
_cell_angle_alpha   87.518
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   574.378
_cell_formula_units_Z   8
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  0.531  0.146  0.025  1.0
  Na  Na1  1  0.894  0.486  0.073  1.0
  Na  Na2  1  0.574  0.808  0.134  1.0
  Na  Na3  1  0.353  0.436  0.211  1.0
  Na  Na4  1  0.650  0.054  0.292  1.0
  Na  Na5  1  0.447  0.685  0.372  1.0
  Na  Na6  1  0.450  0.338  0.486  1.0
  Na  Na7  1  0.097  0.009  0.425  1.0
  Na  Na8  1  0.597  0.991  0.575  1.0
  Na  Na9  1  0.950  0.662  0.514  1.0
  Na  Na10  1  0.947  0.315  0.628  1.0
  Na  Na11  1  0.150  0.946  0.708  1.0
  Na  Na12  1  0.853  0.564  0.789  1.0
  Na  Na13  1  0.074  0.192  0.866  1.0
  Na  Na14  1  0.394  0.514  0.927  1.0
  Na  Na15  1  0.031  0.854  0.975  1.0
  Cu  Cu16  1  0.082  0.167  0.118  1.0
  Cu  Cu17  1  0.055  0.886  0.215  1.0
  Cu  Cu18  1  0.968  0.613  0.284  1.0
  Cu  Cu19  1  0.896  0.335  0.375  1.0
  Cu  Cu20  1  0.396  0.665  0.625  1.0
  Cu  Cu21  1  0.468  0.387  0.716  1.0
  Cu  Cu22  1  0.555  0.114  0.785  1.0
  Cu  Cu23  1  0.582  0.833  0.882  1.0
  O  O24  1  0.222  0.333  0.041  1.0
  O  O25  1  0.838  0.022  0.112  1.0
  O  O26  1  0.283  0.046  0.222  1.0
  O  O27  1  0.222  0.700  0.193  1.0
  O  O28  1  0.721  0.463  0.266  1.0
  O  O29  1  0.805  0.806  0.327  1.0
  O  O30  1  0.154  0.470  0.387  1.0
  O  O31  1  0.779  0.168  0.459  1.0
  O  O32  1  0.279  0.832  0.541  1.0
  O  O33  1  0.654  0.530  0.613  1.0
  O  O34  1  0.305  0.194  0.673  1.0
  O  O35  1  0.221  0.537  0.734  1.0
  O  O36  1  0.722  0.300  0.807  1.0
  O  O37  1  0.783  0.954  0.778  1.0
  O  O38  1  0.338  0.978  0.888  1.0
  O  O39  1  0.722  0.667  0.959  1.0
[/CIF]
.
The compound described by Na2CuO2 crystallizes in the monoclinic P2_1 space group. There are eight inequivalent Na sites. In the first Na site, Na(1) is bonded in a 3-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a distorted trigonal planar geometry to one O(5) and two equivalent O(1) atoms. In the third Na site, Na(3) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), one O(4), and one O(6) atom. In the fourth Na site, Na(4) is bonded in a 4-coordinate geometry to one O(1), one O(4), one O(5), and one O(7) atom. In the fifth Na site, Na(5) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(6), and one O(8) atom. In the sixth Na site, Na(6) is bonded in a 5-coordinate geometry to one O(4), one O(5), one O(6), one O(7), and one O(8) atom. In the seventh Na site, Na(7) is bonded in a 4-coordinate geometry to one O(6), one O(8), and two equivalent O(7) atoms. In the eighth Na site, Na(8) is bonded in a 4-coordinate geometry to one O(3), one O(6), and two equivalent O(8) atoms. There are four inequivalent Cu sites. In the first Cu site, Cu(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), and one O(3) atom. In the second Cu site, Cu(2) is bonded in a 4-coordinate geometry to one O(2), one O(3), one O(4), and one O(6) atom. In the third Cu site, Cu(3) is bonded in a 4-coordinate geometry to one O(4), one O(5), one O(6), and one O(7) atom. In the fourth Cu site, Cu(4) is bonded in a 3-coordinate geometry to one O(5), one O(7), and one O(8) atom. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Na(1), one Na(3), one Na(4), two equivalent Na(2), and one Cu(1) atom to form distorted ONa5Cu octahedra that share corners with two equivalent O(2)Na4Cu2 octahedra, corners with two equivalent O(1)Na5Cu octahedra, and  an edgeedge with one O(2)Na4Cu2 octahedra. The corner-sharing octahedral tilt angles range from 33-49°. In the second O site, O(2) is bonded to one Na(3), one Na(5), two equivalent Na(1), one Cu(1), and one Cu(2) atom to form distorted ONa4Cu2 octahedra that share  a cornercorner with one O(8)Na5Cu octahedra, corners with two equivalent O(2)Na4Cu2 octahedra, corners with two equivalent O(1)Na5Cu octahedra, and  an edgeedge with one O(1)Na5Cu octahedra. The corner-sharing octahedral tilt angles range from 33-70°. In the third O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Na(3), one Na(5), one Na(8), one Cu(1), and one Cu(2) atom. In the fourth O site, O(4) is bonded in a 5-coordinate geometry to one Na(3), one Na(4), one Na(6), one Cu(2), and one Cu(3) atom. In the fifth O site, O(5) is bonded in a 5-coordinate geometry to one Na(2), one Na(4), one Na(6), one Cu(3), and one Cu(4) atom. In the sixth O site, O(6) is bonded in a 7-coordinate geometry to one Na(3), one Na(5), one Na(6), one Na(7), one Na(8), one Cu(2), and one Cu(3) atom. In the seventh O site, O(7) is bonded in a 6-coordinate geometry to one Na(4), one Na(6), two equivalent Na(7), one Cu(3), and one Cu(4) atom. In the eighth O site, O(8) is bonded to one Na(5), one Na(6), one Na(7), two equivalent Na(8), and one Cu(4) atom to form distorted ONa5Cu octahedra that share  a cornercorner with one O(2)Na4Cu2 octahedra and corners with two equivalent O(8)Na5Cu octahedra. The corner-sharing octahedral tilt angles are 49°. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2CuO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.708
_cell_length_b   8.766
_cell_length_c   11.491
_cell_angle_alpha   87.518
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   574.378
_cell_formula_units_Z   8
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  0.531  0.146  0.025  1.0
  Na  Na1  1  0.894  0.486  0.073  1.0
  Na  Na2  1  0.574  0.808  0.134  1.0
  Na  Na3  1  0.353  0.436  0.211  1.0
  Na  Na4  1  0.650  0.054  0.292  1.0
  Na  Na5  1  0.447  0.685  0.372  1.0
  Na  Na6  1  0.450  0.338  0.486  1.0
  Na  Na7  1  0.097  0.009  0.425  1.0
  Na  Na8  1  0.597  0.991  0.575  1.0
  Na  Na9  1  0.950  0.662  0.514  1.0
  Na  Na10  1  0.947  0.315  0.628  1.0
  Na  Na11  1  0.150  0.946  0.708  1.0
  Na  Na12  1  0.853  0.564  0.789  1.0
  Na  Na13  1  0.074  0.192  0.866  1.0
  Na  Na14  1  0.394  0.514  0.927  1.0
  Na  Na15  1  0.031  0.854  0.975  1.0
  Cu  Cu16  1  0.082  0.167  0.118  1.0
  Cu  Cu17  1  0.055  0.886  0.215  1.0
  Cu  Cu18  1  0.968  0.613  0.284  1.0
  Cu  Cu19  1  0.896  0.335  0.375  1.0
  Cu  Cu20  1  0.396  0.665  0.625  1.0
  Cu  Cu21  1  0.468  0.387  0.716  1.0
  Cu  Cu22  1  0.555  0.114  0.785  1.0
  Cu  Cu23  1  0.582  0.833  0.882  1.0
  O  O24  1  0.222  0.333  0.041  1.0
  O  O25  1  0.838  0.022  0.112  1.0
  O  O26  1  0.283  0.046  0.222  1.0
  O  O27  1  0.222  0.700  0.193  1.0
  O  O28  1  0.721  0.463  0.266  1.0
  O  O29  1  0.805  0.806  0.327  1.0
  O  O30  1  0.154  0.470  0.387  1.0
  O  O31  1  0.779  0.168  0.459  1.0
  O  O32  1  0.279  0.832  0.541  1.0
  O  O33  1  0.654  0.530  0.613  1.0
  O  O34  1  0.305  0.194  0.673  1.0
  O  O35  1  0.221  0.537  0.734  1.0
  O  O36  1  0.722  0.300  0.807  1.0
  O  O37  1  0.783  0.954  0.778  1.0
  O  O38  1  0.338  0.978  0.888  1.0
  O  O39  1  0.722  0.667  0.959  1.0
[/CIF]
.