The structure described by Na2Cu(Si2O5)2 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 1-coordinate geometry to one Si(4), one O(1), one O(3), and one O(8) atom. In the second Na site, Na(2) is bonded in a 2-coordinate geometry to one O(2), one O(6), and one O(7) atom. Cu(1) is bonded in a 4-coordinate geometry to one O(3), one O(5), one O(6), and one O(7) atom. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(4), and one O(6) atom. In the second Si site, Si(2) is bonded in a 1-coordinate geometry to one O(10), one O(2), one O(5), and one O(8) atom. In the third Si site, Si(3) is bonded in a 3-coordinate geometry to one O(7), one O(8), and one O(9) atom. In the fourth Si site, Si(4) is bonded in a 5-coordinate geometry to one Na(1), one O(1), one O(10), one O(3), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Si(1), one Si(4), and one O(10) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Cu(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Si(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Cu(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(2), one Cu(1), and one Si(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Na(2), one Cu(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Na(1), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(2), one Si(4), and one O(1) atom. is represented by the CIF file [CIF]
data_Na2Cu(Si2O5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.003
_cell_length_b   7.793
_cell_length_c   9.871
_cell_angle_alpha   105.869
_cell_angle_beta   99.030
_cell_angle_gamma   114.325
_symmetry_Int_Tables_number   1
_cell_volume   449.233
_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  0.658  0.757  0.025  1.0
  Na  Na1  1  0.342  0.243  0.975  1.0
  Na  Na2  1  0.734  0.282  0.579  1.0
  Na  Na3  1  0.266  0.718  0.421  1.0
  Cu  Cu4  1  0.233  0.273  0.573  1.0
  Cu  Cu5  1  0.767  0.727  0.427  1.0
  Si  Si6  1  0.071  0.705  0.150  1.0
  Si  Si7  1  0.929  0.295  0.850  1.0
  Si  Si8  1  0.183  0.379  0.249  1.0
  Si  Si9  1  0.587  0.342  0.264  1.0
  Si  Si10  1  0.413  0.658  0.736  1.0
  Si  Si11  1  0.231  0.935  0.811  1.0
  Si  Si12  1  0.769  0.065  0.189  1.0
  Si  Si13  1  0.817  0.621  0.751  1.0
  O  O14  1  0.185  0.894  0.991  1.0
  O  O15  1  0.760  0.395  0.856  1.0
  O  O16  1  0.329  0.173  0.734  1.0
  O  O17  1  0.671  0.827  0.266  1.0
  O  O18  1  0.168  0.465  0.849  1.0
  O  O19  1  0.832  0.535  0.151  1.0
  O  O20  1  0.111  0.353  0.420  1.0
  O  O21  1  0.889  0.647  0.580  1.0
  O  O22  1  0.049  0.782  0.286  1.0
  O  O23  1  0.951  0.218  0.714  1.0
  O  O24  1  0.521  0.335  0.431  1.0
  O  O25  1  0.418  0.374  0.180  1.0
  O  O26  1  0.415  0.866  0.747  1.0
  O  O27  1  0.585  0.134  0.253  1.0
  O  O28  1  0.992  0.792  0.799  1.0
  O  O29  1  0.008  0.208  0.201  1.0
  O  O30  1  0.815  0.106  0.009  1.0
  O  O31  1  0.479  0.665  0.569  1.0
  O  O32  1  0.582  0.626  0.820  1.0
  O  O33  1  0.240  0.605  0.144  1.0
[/CIF]
.
The structure described by Na2Cu(Si2O5)2 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 1-coordinate geometry to one Si(4), one O(1), one O(3), and one O(8) atom. In the second Na site, Na(2) is bonded in a 2-coordinate geometry to one O(2), one O(6), and one O(7) atom. Cu(1) is bonded in a 4-coordinate geometry to one O(3), one O(5), one O(6), and one O(7) atom. There are four inequivalent Si sites. In the first Si site, Si(1) is bonded in a 3-coordinate geometry to one O(1), one O(2), one O(4), and one O(6) atom. In the second Si site, Si(2) is bonded in a 1-coordinate geometry to one O(10), one O(2), one O(5), and one O(8) atom. In the third Si site, Si(3) is bonded in a 3-coordinate geometry to one O(7), one O(8), and one O(9) atom. In the fourth Si site, Si(4) is bonded in a 5-coordinate geometry to one Na(1), one O(1), one O(10), one O(3), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Si(1), one Si(4), and one O(10) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(2), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Cu(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted single-bond geometry to one Si(1) atom. In the fifth O site, O(5) is bonded in a 2-coordinate geometry to one Cu(1) and one Si(2) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Na(2), one Cu(1), and one Si(1) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Na(2), one Cu(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Na(1), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one Si(3) and one Si(4) atom. In the tenth O site, O(10) is bonded in a bent 150 degrees geometry to one Si(2), one Si(4), and one O(1) atom. is represented by the CIF file [CIF]
data_Na2Cu(Si2O5)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.003
_cell_length_b   7.793
_cell_length_c   9.871
_cell_angle_alpha   105.869
_cell_angle_beta   99.030
_cell_angle_gamma   114.325
_symmetry_Int_Tables_number   1
_cell_volume   449.233
_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  0.658  0.757  0.025  1.0
  Na  Na1  1  0.342  0.243  0.975  1.0
  Na  Na2  1  0.734  0.282  0.579  1.0
  Na  Na3  1  0.266  0.718  0.421  1.0
  Cu  Cu4  1  0.233  0.273  0.573  1.0
  Cu  Cu5  1  0.767  0.727  0.427  1.0
  Si  Si6  1  0.071  0.705  0.150  1.0
  Si  Si7  1  0.929  0.295  0.850  1.0
  Si  Si8  1  0.183  0.379  0.249  1.0
  Si  Si9  1  0.587  0.342  0.264  1.0
  Si  Si10  1  0.413  0.658  0.736  1.0
  Si  Si11  1  0.231  0.935  0.811  1.0
  Si  Si12  1  0.769  0.065  0.189  1.0
  Si  Si13  1  0.817  0.621  0.751  1.0
  O  O14  1  0.185  0.894  0.991  1.0
  O  O15  1  0.760  0.395  0.856  1.0
  O  O16  1  0.329  0.173  0.734  1.0
  O  O17  1  0.671  0.827  0.266  1.0
  O  O18  1  0.168  0.465  0.849  1.0
  O  O19  1  0.832  0.535  0.151  1.0
  O  O20  1  0.111  0.353  0.420  1.0
  O  O21  1  0.889  0.647  0.580  1.0
  O  O22  1  0.049  0.782  0.286  1.0
  O  O23  1  0.951  0.218  0.714  1.0
  O  O24  1  0.521  0.335  0.431  1.0
  O  O25  1  0.418  0.374  0.180  1.0
  O  O26  1  0.415  0.866  0.747  1.0
  O  O27  1  0.585  0.134  0.253  1.0
  O  O28  1  0.992  0.792  0.799  1.0
  O  O29  1  0.008  0.208  0.201  1.0
  O  O30  1  0.815  0.106  0.009  1.0
  O  O31  1  0.479  0.665  0.569  1.0
  O  O32  1  0.582  0.626  0.820  1.0
  O  O33  1  0.240  0.605  0.144  1.0
[/CIF]
.