The crystal structure described by Na3ScSi2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(1), and two equivalent O(3) atoms. Sc(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form ScO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Sc(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-43°. There are four inequivalent O sites. In the first O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Na(2) and two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Sc(1), and one Si(1) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Sc(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Sc(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na3ScSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.401
_cell_length_b   9.458
_cell_length_c   13.233
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   675.960
_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  0.016  0.346  0.407  1.0
  Na  Na1  1  0.984  0.654  0.907  1.0
  Na  Na2  1  0.516  0.154  0.593  1.0
  Na  Na3  1  0.983  0.981  0.750  1.0
  Na  Na4  1  0.484  0.846  0.093  1.0
  Na  Na5  1  0.483  0.519  0.250  1.0
  Na  Na6  1  0.016  0.346  0.093  1.0
  Na  Na7  1  0.516  0.154  0.907  1.0
  Na  Na8  1  0.484  0.846  0.407  1.0
  Na  Na9  1  0.517  0.481  0.750  1.0
  Na  Na10  1  0.984  0.654  0.593  1.0
  Na  Na11  1  0.017  0.019  0.250  1.0
  Sc  Sc12  1  0.500  0.500  0.000  1.0
  Sc  Sc13  1  0.000  0.000  0.500  1.0
  Sc  Sc14  1  0.000  0.000  0.000  1.0
  Sc  Sc15  1  0.500  0.500  0.500  1.0
  Si  Si16  1  0.513  0.176  0.132  1.0
  Si  Si17  1  0.013  0.324  0.632  1.0
  Si  Si18  1  0.513  0.176  0.368  1.0
  Si  Si19  1  0.487  0.824  0.868  1.0
  Si  Si20  1  0.487  0.824  0.632  1.0
  Si  Si21  1  0.987  0.676  0.132  1.0
  Si  Si22  1  0.013  0.324  0.868  1.0
  Si  Si23  1  0.987  0.676  0.368  1.0
  O  O24  1  0.474  0.346  0.119  1.0
  O  O25  1  0.319  0.089  0.440  1.0
  O  O26  1  0.681  0.911  0.560  1.0
  O  O27  1  0.201  0.872  0.607  1.0
  O  O28  1  0.319  0.089  0.060  1.0
  O  O29  1  0.474  0.346  0.381  1.0
  O  O30  1  0.299  0.372  0.607  1.0
  O  O31  1  0.181  0.589  0.440  1.0
  O  O32  1  0.974  0.154  0.619  1.0
  O  O33  1  0.526  0.654  0.619  1.0
  O  O34  1  0.026  0.846  0.381  1.0
  O  O35  1  0.026  0.846  0.119  1.0
  O  O36  1  0.181  0.589  0.060  1.0
  O  O37  1  0.799  0.128  0.393  1.0
  O  O38  1  0.799  0.128  0.107  1.0
  O  O39  1  0.299  0.372  0.893  1.0
  O  O40  1  0.559  0.875  0.750  1.0
  O  O41  1  0.526  0.654  0.881  1.0
  O  O42  1  0.441  0.125  0.250  1.0
  O  O43  1  0.974  0.154  0.881  1.0
  O  O44  1  0.201  0.872  0.893  1.0
  O  O45  1  0.681  0.911  0.940  1.0
  O  O46  1  0.701  0.628  0.107  1.0
  O  O47  1  0.701  0.628  0.393  1.0
  O  O48  1  0.819  0.411  0.940  1.0
  O  O49  1  0.941  0.375  0.750  1.0
  O  O50  1  0.059  0.625  0.250  1.0
  O  O51  1  0.819  0.411  0.560  1.0
[/CIF]
.
The crystal structure described by Na3ScSi2O7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to one O(1), one O(3), and two equivalent O(2) atoms. In the second Na site, Na(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(1), and two equivalent O(3) atoms. Sc(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form ScO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra. Si(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form SiO4 tetrahedra that share corners with three equivalent Sc(1)O6 octahedra and  a cornercorner with one Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 17-43°. There are four inequivalent O sites. In the first O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Na(2) and two equivalent Si(1) atoms. In the second O site, O(1) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Sc(1), and one Si(1) atom. In the third O site, O(2) is bonded in a 4-coordinate geometry to two equivalent Na(1), one Sc(1), and one Si(1) atom. In the fourth O site, O(3) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Sc(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Na3ScSi2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.401
_cell_length_b   9.458
_cell_length_c   13.233
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   675.960
_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  0.016  0.346  0.407  1.0
  Na  Na1  1  0.984  0.654  0.907  1.0
  Na  Na2  1  0.516  0.154  0.593  1.0
  Na  Na3  1  0.983  0.981  0.750  1.0
  Na  Na4  1  0.484  0.846  0.093  1.0
  Na  Na5  1  0.483  0.519  0.250  1.0
  Na  Na6  1  0.016  0.346  0.093  1.0
  Na  Na7  1  0.516  0.154  0.907  1.0
  Na  Na8  1  0.484  0.846  0.407  1.0
  Na  Na9  1  0.517  0.481  0.750  1.0
  Na  Na10  1  0.984  0.654  0.593  1.0
  Na  Na11  1  0.017  0.019  0.250  1.0
  Sc  Sc12  1  0.500  0.500  0.000  1.0
  Sc  Sc13  1  0.000  0.000  0.500  1.0
  Sc  Sc14  1  0.000  0.000  0.000  1.0
  Sc  Sc15  1  0.500  0.500  0.500  1.0
  Si  Si16  1  0.513  0.176  0.132  1.0
  Si  Si17  1  0.013  0.324  0.632  1.0
  Si  Si18  1  0.513  0.176  0.368  1.0
  Si  Si19  1  0.487  0.824  0.868  1.0
  Si  Si20  1  0.487  0.824  0.632  1.0
  Si  Si21  1  0.987  0.676  0.132  1.0
  Si  Si22  1  0.013  0.324  0.868  1.0
  Si  Si23  1  0.987  0.676  0.368  1.0
  O  O24  1  0.474  0.346  0.119  1.0
  O  O25  1  0.319  0.089  0.440  1.0
  O  O26  1  0.681  0.911  0.560  1.0
  O  O27  1  0.201  0.872  0.607  1.0
  O  O28  1  0.319  0.089  0.060  1.0
  O  O29  1  0.474  0.346  0.381  1.0
  O  O30  1  0.299  0.372  0.607  1.0
  O  O31  1  0.181  0.589  0.440  1.0
  O  O32  1  0.974  0.154  0.619  1.0
  O  O33  1  0.526  0.654  0.619  1.0
  O  O34  1  0.026  0.846  0.381  1.0
  O  O35  1  0.026  0.846  0.119  1.0
  O  O36  1  0.181  0.589  0.060  1.0
  O  O37  1  0.799  0.128  0.393  1.0
  O  O38  1  0.799  0.128  0.107  1.0
  O  O39  1  0.299  0.372  0.893  1.0
  O  O40  1  0.559  0.875  0.750  1.0
  O  O41  1  0.526  0.654  0.881  1.0
  O  O42  1  0.441  0.125  0.250  1.0
  O  O43  1  0.974  0.154  0.881  1.0
  O  O44  1  0.201  0.872  0.893  1.0
  O  O45  1  0.681  0.911  0.940  1.0
  O  O46  1  0.701  0.628  0.107  1.0
  O  O47  1  0.701  0.628  0.393  1.0
  O  O48  1  0.819  0.411  0.940  1.0
  O  O49  1  0.941  0.375  0.750  1.0
  O  O50  1  0.059  0.625  0.250  1.0
  O  O51  1  0.819  0.411  0.560  1.0
[/CIF]
.