The crystal structure described by BaAl2Si2O8 crystallizes in the trigonal P-3m1 space group. Ba(1) is bonded to twelve equivalent O(1) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent Al(1)O4 tetrahedra, and edges with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to one O(2) and three equivalent O(1) atoms to form AlO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with three equivalent Ba(1)O12 cuboctahedra. Si(1) is bonded to one O(2) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with four equivalent Al(1)O4 tetrahedra and edges with three equivalent Ba(1)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Al(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_BaAl2(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.419
_cell_length_b   5.419
_cell_length_c   7.919
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   201.361
_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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Al  Al1  1  0.333  0.667  0.703  1.0
  Al  Al2  1  0.667  0.333  0.297  1.0
  Si  Si3  1  0.667  0.333  0.717  1.0
  Si  Si4  1  0.333  0.667  0.283  1.0
  O  O5  1  0.991  0.495  0.795  1.0
  O  O6  1  0.505  0.495  0.795  1.0
  O  O7  1  0.505  0.009  0.795  1.0
  O  O8  1  0.009  0.505  0.205  1.0
  O  O9  1  0.495  0.505  0.205  1.0
  O  O10  1  0.495  0.991  0.205  1.0
  O  O11  1  0.333  0.667  0.486  1.0
  O  O12  1  0.667  0.333  0.514  1.0
[/CIF]
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The crystal structure described by BaAl2Si2O8 crystallizes in the trigonal P-3m1 space group. Ba(1) is bonded to twelve equivalent O(1) atoms to form BaO12 cuboctahedra that share edges with six equivalent Ba(1)O12 cuboctahedra, edges with six equivalent Al(1)O4 tetrahedra, and edges with six equivalent Si(1)O4 tetrahedra. Al(1) is bonded to one O(2) and three equivalent O(1) atoms to form AlO4 tetrahedra that share corners with four equivalent Si(1)O4 tetrahedra and edges with three equivalent Ba(1)O12 cuboctahedra. Si(1) is bonded to one O(2) and three equivalent O(1) atoms to form SiO4 tetrahedra that share corners with four equivalent Al(1)O4 tetrahedra and edges with three equivalent Ba(1)O12 cuboctahedra. There are two inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 120 degrees geometry to two equivalent Ba(1), one Al(1), and one Si(1) atom. In the second O site, O(2) is bonded in a linear geometry to one Al(1) and one Si(1) atom. is represented by the CIF file [CIF]
data_BaAl2(SiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.419
_cell_length_b   5.419
_cell_length_c   7.919
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   201.361
_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
  Ba  Ba0  1  0.000  0.000  0.000  1.0
  Al  Al1  1  0.333  0.667  0.703  1.0
  Al  Al2  1  0.667  0.333  0.297  1.0
  Si  Si3  1  0.667  0.333  0.717  1.0
  Si  Si4  1  0.333  0.667  0.283  1.0
  O  O5  1  0.991  0.495  0.795  1.0
  O  O6  1  0.505  0.495  0.795  1.0
  O  O7  1  0.505  0.009  0.795  1.0
  O  O8  1  0.009  0.505  0.205  1.0
  O  O9  1  0.495  0.505  0.205  1.0
  O  O10  1  0.495  0.991  0.205  1.0
  O  O11  1  0.333  0.667  0.486  1.0
  O  O12  1  0.667  0.333  0.514  1.0
[/CIF]
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