The material described by Na2Ba6Si4O15 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form NaO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), two equivalent O(5), and two equivalent O(6) atoms. In the third Ba site, Ba(3) is bonded in a 9-coordinate geometry to one O(1), one O(4), one O(8), two equivalent O(2), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with four equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-40°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Na(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-16°. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 6-coordinate geometry to one Na(1), one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the second O site, O(8) is bonded in a linear geometry to two equivalent Ba(1), two equivalent Ba(3), and two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a distorted single-bond geometry to one Na(1), one Ba(1), one Ba(2), one Ba(3), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the fifth O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 1-coordinate geometry to one Na(1), one Ba(1), one Ba(2), one Ba(3), and one Si(1) atom. In the seventh O site, O(5) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Ba(1), two equivalent Ba(2), and one Si(1) atom. In the eighth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Ba(1), two equivalent Ba(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ba6Na2Si4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.898
_cell_length_b   9.569
_cell_length_c   11.528
_cell_angle_alpha   72.422
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   830.493
_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
  Ba  Ba0  1  0.979  0.333  0.916  1.0
  Ba  Ba1  1  0.995  0.658  0.586  1.0
  Ba  Ba2  1  0.503  0.002  0.225  1.0
  Ba  Ba3  1  0.997  0.002  0.725  1.0
  Ba  Ba4  1  0.003  0.998  0.275  1.0
  Ba  Ba5  1  0.479  0.667  0.584  1.0
  Ba  Ba6  1  0.521  0.333  0.416  1.0
  Ba  Ba7  1  0.021  0.667  0.084  1.0
  Ba  Ba8  1  0.005  0.342  0.414  1.0
  Ba  Ba9  1  0.495  0.342  0.914  1.0
  Ba  Ba10  1  0.505  0.658  0.086  1.0
  Ba  Ba11  1  0.497  0.998  0.775  1.0
  Na  Na12  1  0.250  0.322  0.669  1.0
  Na  Na13  1  0.750  0.678  0.831  1.0
  Na  Na14  1  0.250  0.322  0.169  1.0
  Na  Na15  1  0.750  0.678  0.331  1.0
  Si  Si16  1  0.256  0.620  0.345  1.0
  Si  Si17  1  0.744  0.380  0.655  1.0
  Si  Si18  1  0.209  0.037  0.990  1.0
  Si  Si19  1  0.291  0.037  0.490  1.0
  Si  Si20  1  0.244  0.620  0.845  1.0
  Si  Si21  1  0.791  0.963  0.010  1.0
  Si  Si22  1  0.756  0.380  0.155  1.0
  Si  Si23  1  0.709  0.963  0.510  1.0
  O  O24  1  0.923  0.290  0.681  1.0
  O  O25  1  0.309  0.884  0.028  1.0
  O  O26  1  0.423  0.710  0.819  1.0
  O  O27  1  0.759  0.864  0.149  1.0
  O  O28  1  0.577  0.290  0.181  1.0
  O  O29  1  0.931  0.285  0.175  1.0
  O  O30  1  0.753  0.487  0.012  1.0
  O  O31  1  0.238  0.512  0.757  1.0
  O  O32  1  0.756  0.865  0.920  1.0
  O  O33  1  0.691  0.116  0.972  1.0
  O  O34  1  0.244  0.135  0.080  1.0
  O  O35  1  0.262  0.512  0.257  1.0
  O  O36  1  0.259  0.136  0.351  1.0
  O  O37  1  0.191  0.884  0.528  1.0
  O  O38  1  0.241  0.136  0.851  1.0
  O  O39  1  0.741  0.864  0.649  1.0
  O  O40  1  0.253  0.513  0.488  1.0
  O  O41  1  0.256  0.135  0.580  1.0
  O  O42  1  0.747  0.487  0.512  1.0
  O  O43  1  0.762  0.488  0.243  1.0
  O  O44  1  0.738  0.488  0.743  1.0
  O  O45  1  0.431  0.715  0.325  1.0
  O  O46  1  0.744  0.865  0.420  1.0
  O  O47  1  0.569  0.285  0.675  1.0
  O  O48  1  0.077  0.710  0.319  1.0
  O  O49  1  0.000  0.000  0.000  1.0
  O  O50  1  0.809  0.116  0.472  1.0
  O  O51  1  0.247  0.513  0.988  1.0
  O  O52  1  0.069  0.715  0.825  1.0
  O  O53  1  0.500  0.000  0.500  1.0
[/CIF]
.
The material described by Na2Ba6Si4O15 crystallizes in the monoclinic P2_1/c space group. Na(1) is bonded to one O(1), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form NaO6 octahedra that share corners with two equivalent Si(2)O4 tetrahedra and corners with four equivalent Si(1)O4 tetrahedra. There are three inequivalent Ba sites. In the first Ba site, Ba(1) is bonded in a 10-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), one O(8), two equivalent O(5), and two equivalent O(6) atoms. In the second Ba site, Ba(2) is bonded in a 9-coordinate geometry to one O(1), one O(2), one O(3), one O(4), one O(7), two equivalent O(5), and two equivalent O(6) atoms. In the third Ba site, Ba(3) is bonded in a 9-coordinate geometry to one O(1), one O(4), one O(8), two equivalent O(2), two equivalent O(3), and two equivalent O(7) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(4), one O(5), and one O(6) atom to form SiO4 tetrahedra that share corners with four equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 12-40°. In the second Si site, Si(2) is bonded to one O(2), one O(3), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Na(1)O6 octahedra and  a cornercorner with one Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 15-16°. There are eight inequivalent O sites. In the first O site, O(7) is bonded in a 6-coordinate geometry to one Na(1), one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the second O site, O(8) is bonded in a linear geometry to two equivalent Ba(1), two equivalent Ba(3), and two equivalent Si(2) atoms. In the third O site, O(1) is bonded in a distorted single-bond geometry to one Na(1), one Ba(1), one Ba(2), one Ba(3), and one Si(1) atom. In the fourth O site, O(2) is bonded in a 1-coordinate geometry to one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the fifth O site, O(3) is bonded in a 6-coordinate geometry to one Na(1), one Ba(1), one Ba(2), two equivalent Ba(3), and one Si(2) atom. In the sixth O site, O(4) is bonded in a 1-coordinate geometry to one Na(1), one Ba(1), one Ba(2), one Ba(3), and one Si(1) atom. In the seventh O site, O(5) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Ba(1), two equivalent Ba(2), and one Si(1) atom. In the eighth O site, O(6) is bonded in a 6-coordinate geometry to one Na(1), two equivalent Ba(1), two equivalent Ba(2), and one Si(1) atom. is represented by the CIF card [CIF]
data_Ba6Na2Si4O15
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.898
_cell_length_b   9.569
_cell_length_c   11.528
_cell_angle_alpha   72.422
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   830.493
_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
  Ba  Ba0  1  0.979  0.333  0.916  1.0
  Ba  Ba1  1  0.995  0.658  0.586  1.0
  Ba  Ba2  1  0.503  0.002  0.225  1.0
  Ba  Ba3  1  0.997  0.002  0.725  1.0
  Ba  Ba4  1  0.003  0.998  0.275  1.0
  Ba  Ba5  1  0.479  0.667  0.584  1.0
  Ba  Ba6  1  0.521  0.333  0.416  1.0
  Ba  Ba7  1  0.021  0.667  0.084  1.0
  Ba  Ba8  1  0.005  0.342  0.414  1.0
  Ba  Ba9  1  0.495  0.342  0.914  1.0
  Ba  Ba10  1  0.505  0.658  0.086  1.0
  Ba  Ba11  1  0.497  0.998  0.775  1.0
  Na  Na12  1  0.250  0.322  0.669  1.0
  Na  Na13  1  0.750  0.678  0.831  1.0
  Na  Na14  1  0.250  0.322  0.169  1.0
  Na  Na15  1  0.750  0.678  0.331  1.0
  Si  Si16  1  0.256  0.620  0.345  1.0
  Si  Si17  1  0.744  0.380  0.655  1.0
  Si  Si18  1  0.209  0.037  0.990  1.0
  Si  Si19  1  0.291  0.037  0.490  1.0
  Si  Si20  1  0.244  0.620  0.845  1.0
  Si  Si21  1  0.791  0.963  0.010  1.0
  Si  Si22  1  0.756  0.380  0.155  1.0
  Si  Si23  1  0.709  0.963  0.510  1.0
  O  O24  1  0.923  0.290  0.681  1.0
  O  O25  1  0.309  0.884  0.028  1.0
  O  O26  1  0.423  0.710  0.819  1.0
  O  O27  1  0.759  0.864  0.149  1.0
  O  O28  1  0.577  0.290  0.181  1.0
  O  O29  1  0.931  0.285  0.175  1.0
  O  O30  1  0.753  0.487  0.012  1.0
  O  O31  1  0.238  0.512  0.757  1.0
  O  O32  1  0.756  0.865  0.920  1.0
  O  O33  1  0.691  0.116  0.972  1.0
  O  O34  1  0.244  0.135  0.080  1.0
  O  O35  1  0.262  0.512  0.257  1.0
  O  O36  1  0.259  0.136  0.351  1.0
  O  O37  1  0.191  0.884  0.528  1.0
  O  O38  1  0.241  0.136  0.851  1.0
  O  O39  1  0.741  0.864  0.649  1.0
  O  O40  1  0.253  0.513  0.488  1.0
  O  O41  1  0.256  0.135  0.580  1.0
  O  O42  1  0.747  0.487  0.512  1.0
  O  O43  1  0.762  0.488  0.243  1.0
  O  O44  1  0.738  0.488  0.743  1.0
  O  O45  1  0.431  0.715  0.325  1.0
  O  O46  1  0.744  0.865  0.420  1.0
  O  O47  1  0.569  0.285  0.675  1.0
  O  O48  1  0.077  0.710  0.319  1.0
  O  O49  1  0.000  0.000  0.000  1.0
  O  O50  1  0.809  0.116  0.472  1.0
  O  O51  1  0.247  0.513  0.988  1.0
  O  O52  1  0.069  0.715  0.825  1.0
  O  O53  1  0.500  0.000  0.500  1.0
[/CIF]
.