The structure described by Na2Si2O5 crystallizes in the orthorhombic Pbcn space group. Na(1) is bonded to one O(2) and four equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Si(1)O4 tetrahedra, corners with four equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Si(1)O4 tetrahedra, and edges with four equivalent Na(1)O5 trigonal bipyramids. Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with four equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a 5-coordinate geometry to four equivalent Na(1) and one Si(1) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(1) and two equivalent Si(1) atoms. is represented by the CIF file [CIF]
data_Na2Si2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.874
_cell_length_b   6.388
_cell_length_c   15.427
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   480.340
_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  0.740  0.598  0.441  1.0
  Na  Na1  1  0.740  0.402  0.059  1.0
  Na  Na2  1  0.760  0.098  0.559  1.0
  Na  Na3  1  0.760  0.902  0.941  1.0
  Na  Na4  1  0.260  0.402  0.559  1.0
  Na  Na5  1  0.260  0.598  0.941  1.0
  Na  Na6  1  0.240  0.902  0.441  1.0
  Na  Na7  1  0.240  0.098  0.059  1.0
  Si  Si8  1  0.796  0.604  0.656  1.0
  Si  Si9  1  0.796  0.396  0.844  1.0
  Si  Si10  1  0.704  0.104  0.344  1.0
  Si  Si11  1  0.704  0.896  0.156  1.0
  Si  Si12  1  0.204  0.396  0.344  1.0
  Si  Si13  1  0.204  0.604  0.156  1.0
  Si  Si14  1  0.296  0.896  0.656  1.0
  Si  Si15  1  0.296  0.104  0.844  1.0
  O  O16  1  0.237  0.950  0.923  1.0
  O  O17  1  0.237  0.050  0.577  1.0
  O  O18  1  0.263  0.450  0.077  1.0
  O  O19  1  0.263  0.550  0.423  1.0
  O  O20  1  0.763  0.050  0.077  1.0
  O  O21  1  0.763  0.950  0.423  1.0
  O  O22  1  0.737  0.550  0.923  1.0
  O  O23  1  0.737  0.450  0.577  1.0
  O  O24  1  0.620  0.177  0.849  1.0
  O  O25  1  0.620  0.823  0.651  1.0
  O  O26  1  0.880  0.677  0.151  1.0
  O  O27  1  0.880  0.323  0.349  1.0
  O  O28  1  0.380  0.823  0.151  1.0
  O  O29  1  0.380  0.177  0.349  1.0
  O  O30  1  0.120  0.323  0.849  1.0
  O  O31  1  0.120  0.677  0.651  1.0
  O  O32  1  0.737  0.500  0.750  1.0
  O  O33  1  0.763  0.000  0.250  1.0
  O  O34  1  0.263  0.500  0.250  1.0
  O  O35  1  0.237  0.000  0.750  1.0
[/CIF]
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The structure described by Na2Si2O5 crystallizes in the orthorhombic Pbcn space group. Na(1) is bonded to one O(2) and four equivalent O(1) atoms to form distorted NaO5 trigonal bipyramids that share corners with four equivalent Si(1)O4 tetrahedra, corners with four equivalent Na(1)O5 trigonal bipyramids,  an edgeedge with one Si(1)O4 tetrahedra, and edges with four equivalent Na(1)O5 trigonal bipyramids. Si(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form SiO4 tetrahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with four equivalent Na(1)O5 trigonal bipyramids, and  an edgeedge with one Na(1)O5 trigonal bipyramid. There are three inequivalent O sites. In the first O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a 5-coordinate geometry to four equivalent Na(1) and one Si(1) atom. In the third O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(1) and two equivalent Si(1) atoms. is represented by the CIF file [CIF]
data_Na2Si2O5
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.874
_cell_length_b   6.388
_cell_length_c   15.427
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   480.340
_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  0.740  0.598  0.441  1.0
  Na  Na1  1  0.740  0.402  0.059  1.0
  Na  Na2  1  0.760  0.098  0.559  1.0
  Na  Na3  1  0.760  0.902  0.941  1.0
  Na  Na4  1  0.260  0.402  0.559  1.0
  Na  Na5  1  0.260  0.598  0.941  1.0
  Na  Na6  1  0.240  0.902  0.441  1.0
  Na  Na7  1  0.240  0.098  0.059  1.0
  Si  Si8  1  0.796  0.604  0.656  1.0
  Si  Si9  1  0.796  0.396  0.844  1.0
  Si  Si10  1  0.704  0.104  0.344  1.0
  Si  Si11  1  0.704  0.896  0.156  1.0
  Si  Si12  1  0.204  0.396  0.344  1.0
  Si  Si13  1  0.204  0.604  0.156  1.0
  Si  Si14  1  0.296  0.896  0.656  1.0
  Si  Si15  1  0.296  0.104  0.844  1.0
  O  O16  1  0.237  0.950  0.923  1.0
  O  O17  1  0.237  0.050  0.577  1.0
  O  O18  1  0.263  0.450  0.077  1.0
  O  O19  1  0.263  0.550  0.423  1.0
  O  O20  1  0.763  0.050  0.077  1.0
  O  O21  1  0.763  0.950  0.423  1.0
  O  O22  1  0.737  0.550  0.923  1.0
  O  O23  1  0.737  0.450  0.577  1.0
  O  O24  1  0.620  0.177  0.849  1.0
  O  O25  1  0.620  0.823  0.651  1.0
  O  O26  1  0.880  0.677  0.151  1.0
  O  O27  1  0.880  0.323  0.349  1.0
  O  O28  1  0.380  0.823  0.151  1.0
  O  O29  1  0.380  0.177  0.349  1.0
  O  O30  1  0.120  0.323  0.849  1.0
  O  O31  1  0.120  0.677  0.651  1.0
  O  O32  1  0.737  0.500  0.750  1.0
  O  O33  1  0.763  0.000  0.250  1.0
  O  O34  1  0.263  0.500  0.250  1.0
  O  O35  1  0.237  0.000  0.750  1.0
[/CIF]
.