The crystal structure described by Na2SeO9 crystallizes in the tetragonal P4_122 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form distorted edge-sharing NaO6 octahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Se(1) is bonded in a see-saw-like geometry to two equivalent O(4) and two equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(4) is bonded in a distorted T-shaped geometry to two equivalent Na(1) and one Se(1) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to one Na(1) and one O(3) atom. In the third O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Se(1) atoms. In the fourth O site, O(2) is bonded in a distorted L-shaped geometry to one Na(2) and one O(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Na(2) and one O(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2SeO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.880
_cell_length_b   7.880
_cell_length_c   12.039
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   747.548
_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  0.500  0.685  0.000  1.0
  Na  Na1  1  0.500  0.315  0.500  1.0
  Na  Na2  1  0.315  0.500  0.250  1.0
  Na  Na3  1  0.685  0.500  0.750  1.0
  Na  Na4  1  0.000  0.248  0.000  1.0
  Na  Na5  1  0.000  0.752  0.500  1.0
  Na  Na6  1  0.752  0.000  0.250  1.0
  Na  Na7  1  0.248  0.000  0.750  1.0
  Se  Se8  1  0.500  0.307  0.000  1.0
  Se  Se9  1  0.500  0.693  0.500  1.0
  Se  Se10  1  0.693  0.500  0.250  1.0
  Se  Se11  1  0.307  0.500  0.750  1.0
  O  O12  1  0.143  0.216  0.262  1.0
  O  O13  1  0.857  0.784  0.762  1.0
  O  O14  1  0.784  0.143  0.512  1.0
  O  O15  1  0.857  0.216  0.738  1.0
  O  O16  1  0.216  0.857  0.012  1.0
  O  O17  1  0.143  0.784  0.238  1.0
  O  O18  1  0.216  0.143  0.488  1.0
  O  O19  1  0.784  0.857  0.988  1.0
  O  O20  1  0.989  0.565  0.051  1.0
  O  O21  1  0.011  0.435  0.551  1.0
  O  O22  1  0.435  0.989  0.301  1.0
  O  O23  1  0.011  0.565  0.949  1.0
  O  O24  1  0.565  0.011  0.801  1.0
  O  O25  1  0.989  0.435  0.449  1.0
  O  O26  1  0.565  0.989  0.699  1.0
  O  O27  1  0.435  0.011  0.199  1.0
  O  O28  1  0.009  0.188  0.206  1.0
  O  O29  1  0.991  0.812  0.706  1.0
  O  O30  1  0.812  0.009  0.456  1.0
  O  O31  1  0.991  0.188  0.794  1.0
  O  O32  1  0.188  0.991  0.956  1.0
  O  O33  1  0.009  0.812  0.294  1.0
  O  O34  1  0.188  0.009  0.544  1.0
  O  O35  1  0.812  0.991  0.044  1.0
  O  O36  1  0.567  0.354  0.316  1.0
  O  O37  1  0.433  0.646  0.816  1.0
  O  O38  1  0.646  0.567  0.566  1.0
  O  O39  1  0.433  0.354  0.684  1.0
  O  O40  1  0.354  0.433  0.066  1.0
  O  O41  1  0.567  0.646  0.184  1.0
  O  O42  1  0.354  0.567  0.434  1.0
  O  O43  1  0.646  0.433  0.934  1.0
  O  O44  1  0.679  0.679  0.375  1.0
  O  O45  1  0.321  0.321  0.875  1.0
  O  O46  1  0.321  0.679  0.625  1.0
  O  O47  1  0.679  0.321  0.125  1.0
[/CIF]
.
The crystal structure described by Na2SeO9 crystallizes in the tetragonal P4_122 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(1) and four equivalent O(4) atoms to form distorted edge-sharing NaO6 octahedra. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to two equivalent O(2) and four equivalent O(3) atoms. Se(1) is bonded in a see-saw-like geometry to two equivalent O(4) and two equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(4) is bonded in a distorted T-shaped geometry to two equivalent Na(1) and one Se(1) atom. In the second O site, O(1) is bonded in a bent 120 degrees geometry to one Na(1) and one O(3) atom. In the third O site, O(5) is bonded in a distorted bent 120 degrees geometry to two equivalent Se(1) atoms. In the fourth O site, O(2) is bonded in a distorted L-shaped geometry to one Na(2) and one O(2) atom. In the fifth O site, O(3) is bonded in a trigonal planar geometry to two equivalent Na(2) and one O(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2SeO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.880
_cell_length_b   7.880
_cell_length_c   12.039
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   747.548
_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  0.500  0.685  0.000  1.0
  Na  Na1  1  0.500  0.315  0.500  1.0
  Na  Na2  1  0.315  0.500  0.250  1.0
  Na  Na3  1  0.685  0.500  0.750  1.0
  Na  Na4  1  0.000  0.248  0.000  1.0
  Na  Na5  1  0.000  0.752  0.500  1.0
  Na  Na6  1  0.752  0.000  0.250  1.0
  Na  Na7  1  0.248  0.000  0.750  1.0
  Se  Se8  1  0.500  0.307  0.000  1.0
  Se  Se9  1  0.500  0.693  0.500  1.0
  Se  Se10  1  0.693  0.500  0.250  1.0
  Se  Se11  1  0.307  0.500  0.750  1.0
  O  O12  1  0.143  0.216  0.262  1.0
  O  O13  1  0.857  0.784  0.762  1.0
  O  O14  1  0.784  0.143  0.512  1.0
  O  O15  1  0.857  0.216  0.738  1.0
  O  O16  1  0.216  0.857  0.012  1.0
  O  O17  1  0.143  0.784  0.238  1.0
  O  O18  1  0.216  0.143  0.488  1.0
  O  O19  1  0.784  0.857  0.988  1.0
  O  O20  1  0.989  0.565  0.051  1.0
  O  O21  1  0.011  0.435  0.551  1.0
  O  O22  1  0.435  0.989  0.301  1.0
  O  O23  1  0.011  0.565  0.949  1.0
  O  O24  1  0.565  0.011  0.801  1.0
  O  O25  1  0.989  0.435  0.449  1.0
  O  O26  1  0.565  0.989  0.699  1.0
  O  O27  1  0.435  0.011  0.199  1.0
  O  O28  1  0.009  0.188  0.206  1.0
  O  O29  1  0.991  0.812  0.706  1.0
  O  O30  1  0.812  0.009  0.456  1.0
  O  O31  1  0.991  0.188  0.794  1.0
  O  O32  1  0.188  0.991  0.956  1.0
  O  O33  1  0.009  0.812  0.294  1.0
  O  O34  1  0.188  0.009  0.544  1.0
  O  O35  1  0.812  0.991  0.044  1.0
  O  O36  1  0.567  0.354  0.316  1.0
  O  O37  1  0.433  0.646  0.816  1.0
  O  O38  1  0.646  0.567  0.566  1.0
  O  O39  1  0.433  0.354  0.684  1.0
  O  O40  1  0.354  0.433  0.066  1.0
  O  O41  1  0.567  0.646  0.184  1.0
  O  O42  1  0.354  0.567  0.434  1.0
  O  O43  1  0.646  0.433  0.934  1.0
  O  O44  1  0.679  0.679  0.375  1.0
  O  O45  1  0.321  0.321  0.875  1.0
  O  O46  1  0.321  0.679  0.625  1.0
  O  O47  1  0.679  0.321  0.125  1.0
[/CIF]
.