The crystal structure described by Na2Te4O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(5), one O(6), one O(8), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(4), one O(8), one O(9), and two equivalent O(6) atoms. There are four inequivalent Te sites. In the first Te site, Te(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(4), and one O(9) atom. In the second Te site, Te(2) is bonded in a distorted see-saw-like geometry to one O(3), one O(6), one O(7), and one O(8) atom. In the third Te site, Te(3) is bonded in a distorted rectangular see-saw-like geometry to one O(4), one O(7), one O(8), and one O(9) atom. In the fourth Te site, Te(4) is bonded to one O(1), one O(3), one O(7), and two equivalent O(5) atoms to form distorted edge-sharing TeO5 square pyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Te(1) and one Te(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one Te(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Te(2) and one Te(4) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Te(1), and one Te(3) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1) and two equivalent Te(4) atoms. In the sixth O site, O(6) is bonded to one Na(1), two equivalent Na(2), and one Te(2) atom to form distorted ONa3Te trigonal pyramids that share corners with two equivalent O(8)Na2Te2 tetrahedra,  an edgeedge with one O(8)Na2Te2 tetrahedra, and  an edgeedge with one O(6)Na3Te trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Te(2), one Te(3), and one Te(4) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Te(2), and one Te(3) atom to form a mixture of distorted corner and edge-sharing ONa2Te2 tetrahedra. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Na(2), one Te(1), and one Te(3) atom. is represented by the CIF file [CIF]
data_Na2Te4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.879
_cell_length_b   7.357
_cell_length_c   10.485
_cell_angle_alpha   69.790
_cell_angle_beta   90.306
_cell_angle_gamma   69.605
_symmetry_Int_Tables_number   1
_cell_volume   461.937
_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  Na0  1  0.021  0.178  0.364  1.0
  Na  Na1  1  0.979  0.822  0.636  1.0
  Na  Na2  1  0.523  0.221  0.512  1.0
  Na  Na3  1  0.477  0.779  0.488  1.0
  Te  Te4  1  0.974  0.328  0.669  1.0
  Te  Te5  1  0.026  0.672  0.331  1.0
  Te  Te6  1  0.483  0.204  0.196  1.0
  Te  Te7  1  0.517  0.796  0.804  1.0
  Te  Te8  1  0.540  0.636  0.213  1.0
  Te  Te9  1  0.460  0.364  0.787  1.0
  Te  Te10  1  0.988  0.284  0.011  1.0
  Te  Te11  1  0.012  0.716  0.989  1.0
  O  O12  1  0.035  0.159  0.860  1.0
  O  O13  1  0.965  0.841  0.140  1.0
  O  O14  1  0.960  0.877  0.403  1.0
  O  O15  1  0.040  0.123  0.597  1.0
  O  O16  1  0.285  0.139  0.093  1.0
  O  O17  1  0.715  0.861  0.907  1.0
  O  O18  1  0.663  0.332  0.666  1.0
  O  O19  1  0.337  0.668  0.334  1.0
  O  O20  1  0.941  0.497  0.116  1.0
  O  O21  1  0.059  0.503  0.884  1.0
  O  O22  1  0.365  0.141  0.354  1.0
  O  O23  1  0.635  0.859  0.646  1.0
  O  O24  1  0.333  0.501  0.112  1.0
  O  O25  1  0.667  0.499  0.888  1.0
  O  O26  1  0.338  0.657  0.701  1.0
  O  O27  1  0.662  0.343  0.299  1.0
  O  O28  1  0.713  0.689  0.332  1.0
  O  O29  1  0.287  0.311  0.668  1.0
[/CIF]
.
The crystal structure described by Na2Te4O9 crystallizes in the triclinic P-1 space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(5), one O(6), one O(8), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(4), one O(8), one O(9), and two equivalent O(6) atoms. There are four inequivalent Te sites. In the first Te site, Te(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(4), and one O(9) atom. In the second Te site, Te(2) is bonded in a distorted see-saw-like geometry to one O(3), one O(6), one O(7), and one O(8) atom. In the third Te site, Te(3) is bonded in a distorted rectangular see-saw-like geometry to one O(4), one O(7), one O(8), and one O(9) atom. In the fourth Te site, Te(4) is bonded to one O(1), one O(3), one O(7), and two equivalent O(5) atoms to form distorted edge-sharing TeO5 square pyramids. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 120 degrees geometry to one Te(1) and one Te(4) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Na(1) and one Te(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Te(2) and one Te(4) atom. In the fourth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Te(1), and one Te(3) atom. In the fifth O site, O(5) is bonded in a distorted T-shaped geometry to one Na(1) and two equivalent Te(4) atoms. In the sixth O site, O(6) is bonded to one Na(1), two equivalent Na(2), and one Te(2) atom to form distorted ONa3Te trigonal pyramids that share corners with two equivalent O(8)Na2Te2 tetrahedra,  an edgeedge with one O(8)Na2Te2 tetrahedra, and  an edgeedge with one O(6)Na3Te trigonal pyramid. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Te(2), one Te(3), and one Te(4) atom. In the eighth O site, O(8) is bonded to one Na(1), one Na(2), one Te(2), and one Te(3) atom to form a mixture of distorted corner and edge-sharing ONa2Te2 tetrahedra. In the ninth O site, O(9) is bonded in a distorted trigonal planar geometry to one Na(2), one Te(1), and one Te(3) atom. is represented by the CIF file [CIF]
data_Na2Te4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.879
_cell_length_b   7.357
_cell_length_c   10.485
_cell_angle_alpha   69.790
_cell_angle_beta   90.306
_cell_angle_gamma   69.605
_symmetry_Int_Tables_number   1
_cell_volume   461.937
_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  Na0  1  0.021  0.178  0.364  1.0
  Na  Na1  1  0.979  0.822  0.636  1.0
  Na  Na2  1  0.523  0.221  0.512  1.0
  Na  Na3  1  0.477  0.779  0.488  1.0
  Te  Te4  1  0.974  0.328  0.669  1.0
  Te  Te5  1  0.026  0.672  0.331  1.0
  Te  Te6  1  0.483  0.204  0.196  1.0
  Te  Te7  1  0.517  0.796  0.804  1.0
  Te  Te8  1  0.540  0.636  0.213  1.0
  Te  Te9  1  0.460  0.364  0.787  1.0
  Te  Te10  1  0.988  0.284  0.011  1.0
  Te  Te11  1  0.012  0.716  0.989  1.0
  O  O12  1  0.035  0.159  0.860  1.0
  O  O13  1  0.965  0.841  0.140  1.0
  O  O14  1  0.960  0.877  0.403  1.0
  O  O15  1  0.040  0.123  0.597  1.0
  O  O16  1  0.285  0.139  0.093  1.0
  O  O17  1  0.715  0.861  0.907  1.0
  O  O18  1  0.663  0.332  0.666  1.0
  O  O19  1  0.337  0.668  0.334  1.0
  O  O20  1  0.941  0.497  0.116  1.0
  O  O21  1  0.059  0.503  0.884  1.0
  O  O22  1  0.365  0.141  0.354  1.0
  O  O23  1  0.635  0.859  0.646  1.0
  O  O24  1  0.333  0.501  0.112  1.0
  O  O25  1  0.667  0.499  0.888  1.0
  O  O26  1  0.338  0.657  0.701  1.0
  O  O27  1  0.662  0.343  0.299  1.0
  O  O28  1  0.713  0.689  0.332  1.0
  O  O29  1  0.287  0.311  0.668  1.0
[/CIF]
.