The material described by Na8Al6Si6O25 crystallizes in the trigonal R3 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), one O(7), and one O(9) atom. In the second Na site, Na(2) is bonded in a distorted rectangular see-saw-like geometry to one O(9) and three equivalent O(4) atoms. In the third Na site, Na(3) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(6) atom. In the fourth Na site, Na(4) is bonded to one O(9) and three equivalent O(8) atoms to form NaO4 tetrahedra that share corners with three equivalent Al(1)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Na(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)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(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Na(4)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Al(2)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one Si(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(2), and one Si(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Al(1), and one Si(1) atom. In the fourth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Na(4), one Al(1), and one Si(1) atom. In the fifth O site, O(9) is bonded in a trigonal bipyramidal geometry to one Na(2), one Na(4), and three equivalent Na(1) atoms. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(2), and one Si(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(1), and one Si(2) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Al(2), and one Si(1) atom. In the ninth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Al(2), and one Si(2) atom. is represented by the CIF file [CIF]
data_Na8Al6Si6O25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.958
_cell_length_b   8.958
_cell_length_c   8.958
_cell_angle_alpha   90.302
_cell_angle_beta   90.302
_cell_angle_gamma   90.302
_symmetry_Int_Tables_number   1
_cell_volume   718.755
_cell_formula_units_Z   1
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  0.844  0.156  0.156  1.0
  Na  Na1  1  0.874  0.874  0.874  1.0
  Na  Na2  1  0.700  0.306  0.698  1.0
  Na  Na3  1  0.698  0.700  0.306  1.0
  Na  Na4  1  0.306  0.698  0.700  1.0
  Na  Na5  1  0.190  0.190  0.190  1.0
  Na  Na6  1  0.156  0.156  0.844  1.0
  Na  Na7  1  0.156  0.844  0.156  1.0
  Al  Al8  1  0.006  0.253  0.502  1.0
  Al  Al9  1  0.753  0.504  0.002  1.0
  Al  Al10  1  0.504  0.002  0.753  1.0
  Al  Al11  1  0.502  0.006  0.253  1.0
  Al  Al12  1  0.253  0.502  0.006  1.0
  Al  Al13  1  0.002  0.753  0.504  1.0
  Si  Si14  1  0.002  0.501  0.252  1.0
  Si  Si15  1  0.754  0.003  0.504  1.0
  Si  Si16  1  0.504  0.754  0.003  1.0
  Si  Si17  1  0.501  0.252  0.002  1.0
  Si  Si18  1  0.252  0.002  0.501  1.0
  Si  Si19  1  0.003  0.504  0.754  1.0
  O  O20  1  0.938  0.637  0.357  1.0
  O  O21  1  0.941  0.366  0.649  1.0
  O  O22  1  0.861  0.439  0.151  1.0
  O  O23  1  0.864  0.566  0.854  1.0
  O  O24  1  0.853  0.143  0.441  1.0
  O  O25  1  0.854  0.864  0.566  1.0
  O  O26  1  0.654  0.066  0.644  1.0
  O  O27  1  0.649  0.941  0.366  1.0
  O  O28  1  0.637  0.357  0.938  1.0
  O  O29  1  0.644  0.654  0.066  1.0
  O  O30  1  0.568  0.149  0.137  1.0
  O  O31  1  0.566  0.854  0.864  1.0
  O  O32  1  0.439  0.151  0.861  1.0
  O  O33  1  0.441  0.853  0.143  1.0
  O  O34  1  0.359  0.348  0.064  1.0
  O  O35  1  0.366  0.649  0.941  1.0
  O  O36  1  0.348  0.064  0.359  1.0
  O  O37  1  0.357  0.938  0.637  1.0
  O  O38  1  0.149  0.137  0.568  1.0
  O  O39  1  0.151  0.861  0.439  1.0
  O  O40  1  0.137  0.568  0.149  1.0
  O  O41  1  0.143  0.441  0.853  1.0
  O  O42  1  0.064  0.359  0.348  1.0
  O  O43  1  0.066  0.644  0.654  1.0
  O  O44  1  0.031  0.031  0.031  1.0
[/CIF]
.
The material described by Na8Al6Si6O25 crystallizes in the trigonal R3 space group. There are four inequivalent Na sites. In the first Na site, Na(1) is bonded in a rectangular see-saw-like geometry to one O(3), one O(5), one O(7), and one O(9) atom. In the second Na site, Na(2) is bonded in a distorted rectangular see-saw-like geometry to one O(9) and three equivalent O(4) atoms. In the third Na site, Na(3) is bonded in a trigonal non-coplanar geometry to one O(1), one O(2), and one O(6) atom. In the fourth Na site, Na(4) is bonded to one O(9) and three equivalent O(8) atoms to form NaO4 tetrahedra that share corners with three equivalent Al(1)O4 tetrahedra and corners with three equivalent Si(1)O4 tetrahedra. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(5), one O(7), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Na(4)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and corners with two equivalent Si(2)O4 tetrahedra. In the second Al site, Al(2) is bonded to one O(1), one O(3), one O(4), and one O(6) atom to form AlO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)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(7), and one O(8) atom to form SiO4 tetrahedra that share  a cornercorner with one Na(4)O4 tetrahedra, corners with two equivalent Al(1)O4 tetrahedra, and corners with two equivalent Al(2)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(2), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with two equivalent Al(1)O4 tetrahedra and corners with two equivalent Al(2)O4 tetrahedra. There are nine inequivalent O sites. In the first O site, O(5) is bonded in a 3-coordinate geometry to one Na(1), one Al(1), and one Si(2) atom. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(2), and one Si(2) atom. In the third O site, O(7) is bonded in a distorted trigonal planar geometry to one Na(1), one Al(1), and one Si(1) atom. In the fourth O site, O(8) is bonded in a distorted trigonal non-coplanar geometry to one Na(4), one Al(1), and one Si(1) atom. In the fifth O site, O(9) is bonded in a trigonal bipyramidal geometry to one Na(2), one Na(4), and three equivalent Na(1) atoms. In the sixth O site, O(1) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(2), and one Si(1) atom. In the seventh O site, O(2) is bonded in a distorted trigonal planar geometry to one Na(3), one Al(1), and one Si(2) atom. In the eighth O site, O(3) is bonded in a 3-coordinate geometry to one Na(1), one Al(2), and one Si(1) atom. In the ninth O site, O(4) is bonded in a 3-coordinate geometry to one Na(2), one Al(2), and one Si(2) atom. is represented by the CIF file [CIF]
data_Na8Al6Si6O25
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.958
_cell_length_b   8.958
_cell_length_c   8.958
_cell_angle_alpha   90.302
_cell_angle_beta   90.302
_cell_angle_gamma   90.302
_symmetry_Int_Tables_number   1
_cell_volume   718.755
_cell_formula_units_Z   1
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  0.844  0.156  0.156  1.0
  Na  Na1  1  0.874  0.874  0.874  1.0
  Na  Na2  1  0.700  0.306  0.698  1.0
  Na  Na3  1  0.698  0.700  0.306  1.0
  Na  Na4  1  0.306  0.698  0.700  1.0
  Na  Na5  1  0.190  0.190  0.190  1.0
  Na  Na6  1  0.156  0.156  0.844  1.0
  Na  Na7  1  0.156  0.844  0.156  1.0
  Al  Al8  1  0.006  0.253  0.502  1.0
  Al  Al9  1  0.753  0.504  0.002  1.0
  Al  Al10  1  0.504  0.002  0.753  1.0
  Al  Al11  1  0.502  0.006  0.253  1.0
  Al  Al12  1  0.253  0.502  0.006  1.0
  Al  Al13  1  0.002  0.753  0.504  1.0
  Si  Si14  1  0.002  0.501  0.252  1.0
  Si  Si15  1  0.754  0.003  0.504  1.0
  Si  Si16  1  0.504  0.754  0.003  1.0
  Si  Si17  1  0.501  0.252  0.002  1.0
  Si  Si18  1  0.252  0.002  0.501  1.0
  Si  Si19  1  0.003  0.504  0.754  1.0
  O  O20  1  0.938  0.637  0.357  1.0
  O  O21  1  0.941  0.366  0.649  1.0
  O  O22  1  0.861  0.439  0.151  1.0
  O  O23  1  0.864  0.566  0.854  1.0
  O  O24  1  0.853  0.143  0.441  1.0
  O  O25  1  0.854  0.864  0.566  1.0
  O  O26  1  0.654  0.066  0.644  1.0
  O  O27  1  0.649  0.941  0.366  1.0
  O  O28  1  0.637  0.357  0.938  1.0
  O  O29  1  0.644  0.654  0.066  1.0
  O  O30  1  0.568  0.149  0.137  1.0
  O  O31  1  0.566  0.854  0.864  1.0
  O  O32  1  0.439  0.151  0.861  1.0
  O  O33  1  0.441  0.853  0.143  1.0
  O  O34  1  0.359  0.348  0.064  1.0
  O  O35  1  0.366  0.649  0.941  1.0
  O  O36  1  0.348  0.064  0.359  1.0
  O  O37  1  0.357  0.938  0.637  1.0
  O  O38  1  0.149  0.137  0.568  1.0
  O  O39  1  0.151  0.861  0.439  1.0
  O  O40  1  0.137  0.568  0.149  1.0
  O  O41  1  0.143  0.441  0.853  1.0
  O  O42  1  0.064  0.359  0.348  1.0
  O  O43  1  0.066  0.644  0.654  1.0
  O  O44  1  0.031  0.031  0.031  1.0
[/CIF]
.