The compound 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 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), and two equivalent O(8) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(3), one O(6), one O(7), one O(9), and two equivalent O(5) atoms. Cu(1) is bonded in a rectangular see-saw-like 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 to one O(1), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(10), one O(2), one O(5), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(1), one O(10), one O(3), and one O(9) atom to form corner-sharing SiO4 tetrahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(4) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cu(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(3) atom. In the fifth O site, O(5) is bonded to two equivalent Na(2), one Cu(1), and one Si(2) atom to form distorted edge-sharing ONa2CuSi trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar 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 trigonal planar geometry to one Na(2), one Cu(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one Na(2), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(2), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [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   9.923
_cell_angle_alpha   102.863
_cell_angle_beta   103.068
_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  0.342  0.243  0.025  1.0
  Na  Na1  1  0.658  0.757  0.975  1.0
  Na  Na2  1  0.266  0.718  0.579  1.0
  Na  Na3  1  0.734  0.282  0.421  1.0
  Cu  Cu4  1  0.767  0.727  0.573  1.0
  Cu  Cu5  1  0.233  0.273  0.427  1.0
  Si  Si6  1  0.929  0.295  0.150  1.0
  Si  Si7  1  0.071  0.705  0.850  1.0
  Si  Si8  1  0.817  0.621  0.249  1.0
  Si  Si9  1  0.413  0.658  0.264  1.0
  Si  Si10  1  0.587  0.342  0.736  1.0
  Si  Si11  1  0.769  0.065  0.811  1.0
  Si  Si12  1  0.231  0.935  0.189  1.0
  Si  Si13  1  0.183  0.379  0.751  1.0
  O  O14  1  0.815  0.106  0.991  1.0
  O  O15  1  0.240  0.605  0.856  1.0
  O  O16  1  0.671  0.827  0.734  1.0
  O  O17  1  0.329  0.173  0.266  1.0
  O  O18  1  0.832  0.535  0.849  1.0
  O  O19  1  0.168  0.465  0.151  1.0
  O  O20  1  0.889  0.647  0.420  1.0
  O  O21  1  0.111  0.353  0.580  1.0
  O  O22  1  0.951  0.218  0.286  1.0
  O  O23  1  0.049  0.782  0.714  1.0
  O  O24  1  0.479  0.665  0.431  1.0
  O  O25  1  0.582  0.626  0.180  1.0
  O  O26  1  0.585  0.134  0.747  1.0
  O  O27  1  0.415  0.866  0.253  1.0
  O  O28  1  0.008  0.208  0.799  1.0
  O  O29  1  0.992  0.792  0.201  1.0
  O  O30  1  0.185  0.894  0.009  1.0
  O  O31  1  0.521  0.335  0.569  1.0
  O  O32  1  0.418  0.374  0.820  1.0
  O  O33  1  0.760  0.395  0.144  1.0
[/CIF]
.
The compound 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 7-coordinate geometry to one O(1), one O(10), one O(2), one O(3), one O(4), and two equivalent O(8) atoms. In the second Na site, Na(2) is bonded in a 6-coordinate geometry to one O(3), one O(6), one O(7), one O(9), and two equivalent O(5) atoms. Cu(1) is bonded in a rectangular see-saw-like 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 to one O(1), one O(2), one O(4), and one O(6) atom to form corner-sharing SiO4 tetrahedra. In the second Si site, Si(2) is bonded to one O(10), one O(2), one O(5), and one O(8) atom to form corner-sharing SiO4 tetrahedra. In the third Si site, Si(3) is bonded to one O(4), one O(7), one O(8), and one O(9) atom to form corner-sharing SiO4 tetrahedra. In the fourth Si site, Si(4) is bonded to one O(1), one O(10), one O(3), and one O(9) atom to form corner-sharing SiO4 tetrahedra. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(4) atom. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Na(1), one Si(1), and one Si(2) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Cu(1), and one Si(4) atom. In the fourth O site, O(4) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(1), and one Si(3) atom. In the fifth O site, O(5) is bonded to two equivalent Na(2), one Cu(1), and one Si(2) atom to form distorted edge-sharing ONa2CuSi trigonal pyramids. In the sixth O site, O(6) is bonded in a distorted trigonal non-coplanar 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 trigonal planar geometry to one Na(2), one Cu(1), and one Si(3) atom. In the eighth O site, O(8) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Si(2), and one Si(3) atom. In the ninth O site, O(9) is bonded in a 2-coordinate geometry to one Na(2), one Si(3), and one Si(4) atom. In the tenth O site, O(10) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Si(2), and one Si(4) atom. is represented by the Crystallographic Information File (CIF) [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   9.923
_cell_angle_alpha   102.863
_cell_angle_beta   103.068
_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  0.342  0.243  0.025  1.0
  Na  Na1  1  0.658  0.757  0.975  1.0
  Na  Na2  1  0.266  0.718  0.579  1.0
  Na  Na3  1  0.734  0.282  0.421  1.0
  Cu  Cu4  1  0.767  0.727  0.573  1.0
  Cu  Cu5  1  0.233  0.273  0.427  1.0
  Si  Si6  1  0.929  0.295  0.150  1.0
  Si  Si7  1  0.071  0.705  0.850  1.0
  Si  Si8  1  0.817  0.621  0.249  1.0
  Si  Si9  1  0.413  0.658  0.264  1.0
  Si  Si10  1  0.587  0.342  0.736  1.0
  Si  Si11  1  0.769  0.065  0.811  1.0
  Si  Si12  1  0.231  0.935  0.189  1.0
  Si  Si13  1  0.183  0.379  0.751  1.0
  O  O14  1  0.815  0.106  0.991  1.0
  O  O15  1  0.240  0.605  0.856  1.0
  O  O16  1  0.671  0.827  0.734  1.0
  O  O17  1  0.329  0.173  0.266  1.0
  O  O18  1  0.832  0.535  0.849  1.0
  O  O19  1  0.168  0.465  0.151  1.0
  O  O20  1  0.889  0.647  0.420  1.0
  O  O21  1  0.111  0.353  0.580  1.0
  O  O22  1  0.951  0.218  0.286  1.0
  O  O23  1  0.049  0.782  0.714  1.0
  O  O24  1  0.479  0.665  0.431  1.0
  O  O25  1  0.582  0.626  0.180  1.0
  O  O26  1  0.585  0.134  0.747  1.0
  O  O27  1  0.415  0.866  0.253  1.0
  O  O28  1  0.008  0.208  0.799  1.0
  O  O29  1  0.992  0.792  0.201  1.0
  O  O30  1  0.185  0.894  0.009  1.0
  O  O31  1  0.521  0.335  0.569  1.0
  O  O32  1  0.418  0.374  0.820  1.0
  O  O33  1  0.760  0.395  0.144  1.0
[/CIF]
.