The crystal structure described by Na2Nb2(SiO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-35°. In the second Si site, Si(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-35°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Nb(1), and one Si(1) atom. In the second O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Nb(1), and one Si(2) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Nb(1), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Nb(1), and one Si(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Nb(1) and one Si(2) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Nb(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Nb2(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.003
_cell_length_b   9.033
_cell_length_c   9.153
_cell_angle_alpha   60.535
_cell_angle_beta   90.000
_cell_angle_gamma   119.890
_symmetry_Int_Tables_number   1
_cell_volume   531.380
_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  0.616  0.500  0.250  1.0
  Na  Na1  1  0.384  0.500  0.750  1.0
  Na  Na2  1  0.500  0.000  0.500  1.0
  Na  Na3  1  0.000  0.000  0.000  1.0
  Nb  Nb4  1  0.354  0.716  0.934  1.0
  Nb  Nb5  1  0.861  0.716  0.434  1.0
  Nb  Nb6  1  0.646  0.284  0.066  1.0
  Nb  Nb7  1  0.139  0.284  0.566  1.0
  O  O8  1  0.496  0.773  0.084  1.0
  O  O9  1  0.138  0.638  0.075  1.0
  O  O10  1  0.284  0.421  0.065  1.0
  O  O11  1  0.001  0.638  0.575  1.0
  O  O12  1  0.776  0.773  0.584  1.0
  O  O13  1  0.637  0.421  0.565  1.0
  O  O14  1  0.504  0.227  0.916  1.0
  O  O15  1  0.862  0.362  0.925  1.0
  O  O16  1  0.716  0.579  0.935  1.0
  O  O17  1  0.999  0.362  0.425  1.0
  O  O18  1  0.224  0.227  0.416  1.0
  O  O19  1  0.363  0.579  0.435  1.0
  O  O20  1  0.438  0.010  0.769  1.0
  O  O21  1  0.226  0.659  0.763  1.0
  O  O22  1  0.572  0.791  0.767  1.0
  O  O23  1  0.933  0.659  0.263  1.0
  O  O24  1  0.072  0.010  0.269  1.0
  O  O25  1  0.719  0.791  0.267  1.0
  O  O26  1  0.562  0.990  0.231  1.0
  O  O27  1  0.774  0.341  0.237  1.0
  O  O28  1  0.428  0.209  0.233  1.0
  O  O29  1  0.067  0.341  0.737  1.0
  O  O30  1  0.928  0.990  0.731  1.0
  O  O31  1  0.281  0.209  0.733  1.0
  Si  Si32  1  0.535  0.786  0.255  1.0
  Si  Si33  1  0.961  0.500  0.250  1.0
  Si  Si34  1  0.249  0.214  0.245  1.0
  Si  Si35  1  0.039  0.500  0.750  1.0
  Si  Si36  1  0.751  0.786  0.755  1.0
  Si  Si37  1  0.465  0.214  0.745  1.0
[/CIF]
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The crystal structure described by Na2Nb2(SiO4)3 crystallizes in the monoclinic C2/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent O(3), two equivalent O(5), and two equivalent O(6) atoms. In the second Na site, Na(2) is bonded in a distorted hexagonal planar geometry to two equivalent O(4), two equivalent O(5), and two equivalent O(6) atoms. Nb(1) is bonded to one O(1), one O(2), one O(3), one O(4), one O(5), and one O(6) atom to form NbO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form SiO4 tetrahedra that share corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-35°. In the second Si site, Si(2) is bonded to two equivalent O(2) and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with four equivalent Nb(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 23-35°. There are six inequivalent O sites. In the first O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Nb(1), and one Si(1) atom. In the second O site, O(5) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Nb(1), and one Si(2) atom. In the third O site, O(6) is bonded in a distorted rectangular see-saw-like geometry to one Na(1), one Na(2), one Nb(1), and one Si(1) atom. In the fourth O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Na(1), one Nb(1), and one Si(1) atom. In the fifth O site, O(2) is bonded in a bent 150 degrees geometry to one Nb(1) and one Si(2) atom. In the sixth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Nb(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na2Nb2(SiO4)3
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.003
_cell_length_b   9.033
_cell_length_c   9.153
_cell_angle_alpha   60.535
_cell_angle_beta   90.000
_cell_angle_gamma   119.890
_symmetry_Int_Tables_number   1
_cell_volume   531.380
_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  0.616  0.500  0.250  1.0
  Na  Na1  1  0.384  0.500  0.750  1.0
  Na  Na2  1  0.500  0.000  0.500  1.0
  Na  Na3  1  0.000  0.000  0.000  1.0
  Nb  Nb4  1  0.354  0.716  0.934  1.0
  Nb  Nb5  1  0.861  0.716  0.434  1.0
  Nb  Nb6  1  0.646  0.284  0.066  1.0
  Nb  Nb7  1  0.139  0.284  0.566  1.0
  O  O8  1  0.496  0.773  0.084  1.0
  O  O9  1  0.138  0.638  0.075  1.0
  O  O10  1  0.284  0.421  0.065  1.0
  O  O11  1  0.001  0.638  0.575  1.0
  O  O12  1  0.776  0.773  0.584  1.0
  O  O13  1  0.637  0.421  0.565  1.0
  O  O14  1  0.504  0.227  0.916  1.0
  O  O15  1  0.862  0.362  0.925  1.0
  O  O16  1  0.716  0.579  0.935  1.0
  O  O17  1  0.999  0.362  0.425  1.0
  O  O18  1  0.224  0.227  0.416  1.0
  O  O19  1  0.363  0.579  0.435  1.0
  O  O20  1  0.438  0.010  0.769  1.0
  O  O21  1  0.226  0.659  0.763  1.0
  O  O22  1  0.572  0.791  0.767  1.0
  O  O23  1  0.933  0.659  0.263  1.0
  O  O24  1  0.072  0.010  0.269  1.0
  O  O25  1  0.719  0.791  0.267  1.0
  O  O26  1  0.562  0.990  0.231  1.0
  O  O27  1  0.774  0.341  0.237  1.0
  O  O28  1  0.428  0.209  0.233  1.0
  O  O29  1  0.067  0.341  0.737  1.0
  O  O30  1  0.928  0.990  0.731  1.0
  O  O31  1  0.281  0.209  0.733  1.0
  Si  Si32  1  0.535  0.786  0.255  1.0
  Si  Si33  1  0.961  0.500  0.250  1.0
  Si  Si34  1  0.249  0.214  0.245  1.0
  Si  Si35  1  0.039  0.500  0.750  1.0
  Si  Si36  1  0.751  0.786  0.755  1.0
  Si  Si37  1  0.465  0.214  0.745  1.0
[/CIF]
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