The crystal structure described by Bi2Al4O9 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with four equivalent Al(2)O6 octahedra and  a cornercorner with one Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-57°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form AlO6 octahedra that share corners with four equivalent Al(1)O4 tetrahedra and edges with two equivalent Al(2)O6 octahedra. Bi(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(2) and two equivalent Bi(1) atoms to form a mixture of distorted corner and edge-sharing OAl2Bi2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Al(1) and two equivalent Al(2) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(2), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_Al4Bi2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.692
_cell_length_b   7.704
_cell_length_c   8.135
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   356.748
_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
  Al  Al0  1  0.500  0.148  0.839  1.0
  Al  Al1  1  0.500  0.852  0.161  1.0
  Al  Al2  1  0.500  0.648  0.661  1.0
  Al  Al3  1  0.500  0.352  0.339  1.0
  Al  Al4  1  0.261  0.000  0.500  1.0
  Al  Al5  1  0.739  0.500  0.000  1.0
  Al  Al6  1  0.739  0.000  0.500  1.0
  Al  Al7  1  0.261  0.500  0.000  1.0
  Bi  Bi8  1  0.000  0.332  0.667  1.0
  Bi  Bi9  1  0.000  0.668  0.333  1.0
  Bi  Bi10  1  0.000  0.832  0.833  1.0
  Bi  Bi11  1  0.000  0.168  0.167  1.0
  O  O12  1  0.000  0.356  0.933  1.0
  O  O13  1  0.000  0.644  0.067  1.0
  O  O14  1  0.000  0.856  0.567  1.0
  O  O15  1  0.000  0.144  0.433  1.0
  O  O16  1  0.500  0.362  0.914  1.0
  O  O17  1  0.500  0.638  0.086  1.0
  O  O18  1  0.500  0.862  0.586  1.0
  O  O19  1  0.500  0.138  0.414  1.0
  O  O20  1  0.251  0.875  0.293  1.0
  O  O21  1  0.251  0.125  0.707  1.0
  O  O22  1  0.749  0.375  0.207  1.0
  O  O23  1  0.749  0.625  0.793  1.0
  O  O24  1  0.500  0.000  0.000  1.0
  O  O25  1  0.500  0.500  0.500  1.0
  O  O26  1  0.251  0.375  0.207  1.0
  O  O27  1  0.251  0.625  0.793  1.0
  O  O28  1  0.749  0.875  0.293  1.0
  O  O29  1  0.749  0.125  0.707  1.0
[/CIF]
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The crystal structure described by Bi2Al4O9 crystallizes in the orthorhombic Pbam space group. There are two inequivalent Al sites. In the first Al site, Al(1) is bonded to one O(2), one O(4), and two equivalent O(3) atoms to form AlO4 tetrahedra that share corners with four equivalent Al(2)O6 octahedra and  a cornercorner with one Al(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-57°. In the second Al site, Al(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form AlO6 octahedra that share corners with four equivalent Al(1)O4 tetrahedra and edges with two equivalent Al(2)O6 octahedra. Bi(1) is bonded in a 4-coordinate geometry to two equivalent O(1) and two equivalent O(3) atoms. There are four inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Al(2) and two equivalent Bi(1) atoms to form a mixture of distorted corner and edge-sharing OAl2Bi2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Al(1) and two equivalent Al(2) atoms. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(2), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a linear geometry to two equivalent Al(1) atoms. is represented by the CIF card [CIF]
data_Al4Bi2O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.692
_cell_length_b   7.704
_cell_length_c   8.135
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   356.748
_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
  Al  Al0  1  0.500  0.148  0.839  1.0
  Al  Al1  1  0.500  0.852  0.161  1.0
  Al  Al2  1  0.500  0.648  0.661  1.0
  Al  Al3  1  0.500  0.352  0.339  1.0
  Al  Al4  1  0.261  0.000  0.500  1.0
  Al  Al5  1  0.739  0.500  0.000  1.0
  Al  Al6  1  0.739  0.000  0.500  1.0
  Al  Al7  1  0.261  0.500  0.000  1.0
  Bi  Bi8  1  0.000  0.332  0.667  1.0
  Bi  Bi9  1  0.000  0.668  0.333  1.0
  Bi  Bi10  1  0.000  0.832  0.833  1.0
  Bi  Bi11  1  0.000  0.168  0.167  1.0
  O  O12  1  0.000  0.356  0.933  1.0
  O  O13  1  0.000  0.644  0.067  1.0
  O  O14  1  0.000  0.856  0.567  1.0
  O  O15  1  0.000  0.144  0.433  1.0
  O  O16  1  0.500  0.362  0.914  1.0
  O  O17  1  0.500  0.638  0.086  1.0
  O  O18  1  0.500  0.862  0.586  1.0
  O  O19  1  0.500  0.138  0.414  1.0
  O  O20  1  0.251  0.875  0.293  1.0
  O  O21  1  0.251  0.125  0.707  1.0
  O  O22  1  0.749  0.375  0.207  1.0
  O  O23  1  0.749  0.625  0.793  1.0
  O  O24  1  0.500  0.000  0.000  1.0
  O  O25  1  0.500  0.500  0.500  1.0
  O  O26  1  0.251  0.375  0.207  1.0
  O  O27  1  0.251  0.625  0.793  1.0
  O  O28  1  0.749  0.875  0.293  1.0
  O  O29  1  0.749  0.125  0.707  1.0
[/CIF]
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