The material structure described by Ba2Si3O8 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(3), one O(4), two equivalent O(7), and three equivalent O(2) atoms to form distorted BaO8 hexagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, edges with four equivalent Ba(1)O8 hexagonal bipyramids, and edges with two equivalent Si(1)O4 tetrahedra. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(5), one O(7), one O(8), two equivalent O(4), and three equivalent O(6) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ba(1)O8 hexagonal bipyramids. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids and corners with two equivalent Si(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Si(2) atom. In the second O site, O(5) is bonded in a 2-coordinate geometry to one Ba(2), one Si(2), and one Si(3) atom. In the third O site, O(6) is bonded in a distorted single-bond geometry to three equivalent Ba(2) and one Si(3) atom. In the fourth O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Si(3) atom. In the fifth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one Si(2), and one Si(3) atom. In the sixth O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1) and two equivalent Si(1) atoms. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one Si(1) atom. In the eighth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2Si3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.707
_cell_length_b   12.528
_cell_length_c   14.025
_cell_angle_alpha   86.524
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   825.614
_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
  Ba  Ba0  1  0.752  0.856  0.468  1.0
  Ba  Ba1  1  0.252  0.144  0.032  1.0
  Ba  Ba2  1  0.248  0.144  0.532  1.0
  Ba  Ba3  1  0.748  0.856  0.968  1.0
  Ba  Ba4  1  0.272  0.582  0.389  1.0
  Ba  Ba5  1  0.772  0.418  0.111  1.0
  Ba  Ba6  1  0.728  0.418  0.611  1.0
  Ba  Ba7  1  0.228  0.582  0.889  1.0
  Si  Si8  1  0.821  0.974  0.188  1.0
  Si  Si9  1  0.321  0.026  0.312  1.0
  Si  Si10  1  0.179  0.026  0.812  1.0
  Si  Si11  1  0.679  0.974  0.688  1.0
  Si  Si12  1  0.821  0.724  0.223  1.0
  Si  Si13  1  0.321  0.276  0.277  1.0
  Si  Si14  1  0.179  0.276  0.777  1.0
  Si  Si15  1  0.679  0.724  0.723  1.0
  Si  Si16  1  0.315  0.649  0.111  1.0
  Si  Si17  1  0.815  0.351  0.389  1.0
  Si  Si18  1  0.685  0.351  0.889  1.0
  Si  Si19  1  0.185  0.649  0.611  1.0
  O  O20  1  0.151  0.001  0.214  1.0
  O  O21  1  0.651  0.999  0.286  1.0
  O  O22  1  0.849  0.999  0.786  1.0
  O  O23  1  0.349  0.001  0.714  1.0
  O  O24  1  0.736  0.035  0.090  1.0
  O  O25  1  0.236  0.965  0.410  1.0
  O  O26  1  0.264  0.965  0.910  1.0
  O  O27  1  0.764  0.035  0.590  1.0
  O  O28  1  0.796  0.845  0.173  1.0
  O  O29  1  0.296  0.155  0.327  1.0
  O  O30  1  0.204  0.155  0.827  1.0
  O  O31  1  0.704  0.845  0.673  1.0
  O  O32  1  0.739  0.713  0.332  1.0
  O  O33  1  0.239  0.287  0.168  1.0
  O  O34  1  0.261  0.287  0.668  1.0
  O  O35  1  0.761  0.713  0.832  1.0
  O  O36  1  0.148  0.682  0.209  1.0
  O  O37  1  0.648  0.318  0.291  1.0
  O  O38  1  0.852  0.318  0.791  1.0
  O  O39  1  0.352  0.682  0.709  1.0
  O  O40  1  0.248  0.529  0.584  1.0
  O  O41  1  0.748  0.471  0.916  1.0
  O  O42  1  0.752  0.471  0.416  1.0
  O  O43  1  0.252  0.529  0.084  1.0
  O  O44  1  0.233  0.734  0.522  1.0
  O  O45  1  0.733  0.266  0.978  1.0
  O  O46  1  0.767  0.266  0.478  1.0
  O  O47  1  0.267  0.734  0.022  1.0
  O  O48  1  0.852  0.649  0.650  1.0
  O  O49  1  0.352  0.351  0.850  1.0
  O  O50  1  0.148  0.351  0.350  1.0
  O  O51  1  0.648  0.649  0.150  1.0
[/CIF]
.
The material structure described by Ba2Si3O8 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Ba sites. In the first Ba site, Ba(1) is bonded to one O(1), one O(3), one O(4), two equivalent O(7), and three equivalent O(2) atoms to form distorted BaO8 hexagonal bipyramids that share corners with two equivalent Si(1)O4 tetrahedra, corners with two equivalent Si(2)O4 tetrahedra, corners with two equivalent Si(3)O4 tetrahedra, edges with four equivalent Ba(1)O8 hexagonal bipyramids, and edges with two equivalent Si(1)O4 tetrahedra. In the second Ba site, Ba(2) is bonded in a 8-coordinate geometry to one O(5), one O(7), one O(8), two equivalent O(4), and three equivalent O(6) atoms. There are three inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids,  a cornercorner with one Si(2)O4 tetrahedra, corners with two equivalent Si(1)O4 tetrahedra, and edges with two equivalent Ba(1)O8 hexagonal bipyramids. In the second Si site, Si(2) is bonded to one O(3), one O(4), one O(5), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids,  a cornercorner with one Si(1)O4 tetrahedra, and corners with two equivalent Si(3)O4 tetrahedra. In the third Si site, Si(3) is bonded to one O(5), one O(6), one O(7), and one O(8) atom to form SiO4 tetrahedra that share corners with two equivalent Ba(1)O8 hexagonal bipyramids and corners with two equivalent Si(2)O4 tetrahedra. There are eight inequivalent O sites. In the first O site, O(4) is bonded in a distorted single-bond geometry to one Ba(1), two equivalent Ba(2), and one Si(2) atom. In the second O site, O(5) is bonded in a 2-coordinate geometry to one Ba(2), one Si(2), and one Si(3) atom. In the third O site, O(6) is bonded in a distorted single-bond geometry to three equivalent Ba(2) and one Si(3) atom. In the fourth O site, O(7) is bonded in a distorted single-bond geometry to one Ba(2), two equivalent Ba(1), and one Si(3) atom. In the fifth O site, O(8) is bonded in a distorted bent 120 degrees geometry to one Ba(2), one Si(2), and one Si(3) atom. In the sixth O site, O(1) is bonded in a 2-coordinate geometry to one Ba(1) and two equivalent Si(1) atoms. In the seventh O site, O(2) is bonded in a distorted single-bond geometry to three equivalent Ba(1) and one Si(1) atom. In the eighth O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Ba(1), one Si(1), and one Si(2) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ba2Si3O8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.707
_cell_length_b   12.528
_cell_length_c   14.025
_cell_angle_alpha   86.524
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   825.614
_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
  Ba  Ba0  1  0.752  0.856  0.468  1.0
  Ba  Ba1  1  0.252  0.144  0.032  1.0
  Ba  Ba2  1  0.248  0.144  0.532  1.0
  Ba  Ba3  1  0.748  0.856  0.968  1.0
  Ba  Ba4  1  0.272  0.582  0.389  1.0
  Ba  Ba5  1  0.772  0.418  0.111  1.0
  Ba  Ba6  1  0.728  0.418  0.611  1.0
  Ba  Ba7  1  0.228  0.582  0.889  1.0
  Si  Si8  1  0.821  0.974  0.188  1.0
  Si  Si9  1  0.321  0.026  0.312  1.0
  Si  Si10  1  0.179  0.026  0.812  1.0
  Si  Si11  1  0.679  0.974  0.688  1.0
  Si  Si12  1  0.821  0.724  0.223  1.0
  Si  Si13  1  0.321  0.276  0.277  1.0
  Si  Si14  1  0.179  0.276  0.777  1.0
  Si  Si15  1  0.679  0.724  0.723  1.0
  Si  Si16  1  0.315  0.649  0.111  1.0
  Si  Si17  1  0.815  0.351  0.389  1.0
  Si  Si18  1  0.685  0.351  0.889  1.0
  Si  Si19  1  0.185  0.649  0.611  1.0
  O  O20  1  0.151  0.001  0.214  1.0
  O  O21  1  0.651  0.999  0.286  1.0
  O  O22  1  0.849  0.999  0.786  1.0
  O  O23  1  0.349  0.001  0.714  1.0
  O  O24  1  0.736  0.035  0.090  1.0
  O  O25  1  0.236  0.965  0.410  1.0
  O  O26  1  0.264  0.965  0.910  1.0
  O  O27  1  0.764  0.035  0.590  1.0
  O  O28  1  0.796  0.845  0.173  1.0
  O  O29  1  0.296  0.155  0.327  1.0
  O  O30  1  0.204  0.155  0.827  1.0
  O  O31  1  0.704  0.845  0.673  1.0
  O  O32  1  0.739  0.713  0.332  1.0
  O  O33  1  0.239  0.287  0.168  1.0
  O  O34  1  0.261  0.287  0.668  1.0
  O  O35  1  0.761  0.713  0.832  1.0
  O  O36  1  0.148  0.682  0.209  1.0
  O  O37  1  0.648  0.318  0.291  1.0
  O  O38  1  0.852  0.318  0.791  1.0
  O  O39  1  0.352  0.682  0.709  1.0
  O  O40  1  0.248  0.529  0.584  1.0
  O  O41  1  0.748  0.471  0.916  1.0
  O  O42  1  0.752  0.471  0.416  1.0
  O  O43  1  0.252  0.529  0.084  1.0
  O  O44  1  0.233  0.734  0.522  1.0
  O  O45  1  0.733  0.266  0.978  1.0
  O  O46  1  0.767  0.266  0.478  1.0
  O  O47  1  0.267  0.734  0.022  1.0
  O  O48  1  0.852  0.649  0.650  1.0
  O  O49  1  0.352  0.351  0.850  1.0
  O  O50  1  0.148  0.351  0.350  1.0
  O  O51  1  0.648  0.649  0.150  1.0
[/CIF]
.