The crystal structure described by CrAl7(Bi2O9)2 crystallizes in the monoclinic P2 space group. Cr(1) is bonded to two equivalent O(1), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. There are five inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(4), two equivalent O(7), and two equivalent O(9) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(3)O6 octahedra. In the second Al site, Al(2) is bonded to two equivalent O(10), two equivalent O(3), and two equivalent O(8) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. In the third Al site, Al(3) is bonded to two equivalent O(2), two equivalent O(7), and two equivalent O(9) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. In the fourth Al site, Al(4) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra,  a cornercorner with one Al(2)O6 octahedra,  a cornercorner with one Al(3)O6 octahedra, and  a cornercorner with one Al(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-58°. In the fifth Al site, Al(5) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra,  a cornercorner with one Al(2)O6 octahedra,  a cornercorner with one Al(3)O6 octahedra, and  a cornercorner with one Al(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-58°. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(10), one O(3), and one O(9) atom. In the second Bi site, Bi(2) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(2), one O(4), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(1), one Al(4), and one Bi(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Al(3), one Al(5), and one Bi(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Al(2), one Al(4), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(5), and one Bi(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Al(4) atoms. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Al(5) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(3), and one Al(4) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Cr(1), one Al(2), and one Al(5) atom. In the ninth O site, O(9) is bonded to one Al(1), one Al(3), one Bi(1), and one Bi(2) atom to form distorted edge-sharing OAl2Bi2 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Cr(1), one Al(2), one Bi(1), and one Bi(2) atom. is represented by the CIF file [CIF]
data_Al7Cr(Bi2O9)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.823
_cell_length_b   7.800
_cell_length_c   8.243
_cell_angle_alpha   89.874
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   374.432
_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
  Al  Al0  1  0.262  0.000  0.000  1.0
  Al  Al1  1  0.739  0.500  0.500  1.0
  Al  Al2  1  0.738  0.000  0.000  1.0
  Al  Al3  1  0.502  0.350  0.160  1.0
  Al  Al4  1  0.502  0.650  0.840  1.0
  Al  Al5  1  0.502  0.854  0.337  1.0
  Al  Al6  1  0.502  0.146  0.663  1.0
  Cr  Cr7  1  0.258  0.500  0.500  1.0
  Bi  Bi8  1  0.997  0.169  0.330  1.0
  Bi  Bi9  1  0.997  0.831  0.670  1.0
  Bi  Bi10  1  0.998  0.672  0.168  1.0
  Bi  Bi11  1  0.998  0.328  0.832  1.0
  O  O12  1  0.250  0.371  0.285  1.0
  O  O13  1  0.250  0.629  0.715  1.0
  O  O14  1  0.748  0.877  0.206  1.0
  O  O15  1  0.748  0.123  0.794  1.0
  O  O16  1  0.748  0.626  0.709  1.0
  O  O17  1  0.748  0.374  0.291  1.0
  O  O18  1  0.253  0.125  0.792  1.0
  O  O19  1  0.253  0.875  0.208  1.0
  O  O20  1  0.502  0.500  0.000  1.0
  O  O21  1  0.500  0.000  0.500  1.0
  O  O22  1  0.501  0.137  0.085  1.0
  O  O23  1  0.501  0.863  0.915  1.0
  O  O24  1  0.512  0.641  0.411  1.0
  O  O25  1  0.512  0.359  0.589  1.0
  O  O26  1  0.000  0.143  0.065  1.0
  O  O27  1  0.000  0.857  0.935  1.0
  O  O28  1  0.989  0.648  0.433  1.0
  O  O29  1  0.989  0.352  0.567  1.0
[/CIF]
.
The crystal structure described by CrAl7(Bi2O9)2 crystallizes in the monoclinic P2 space group. Cr(1) is bonded to two equivalent O(1), two equivalent O(10), and two equivalent O(8) atoms to form CrO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(2)O6 octahedra. There are five inequivalent Al sites. In the first Al site, Al(1) is bonded to two equivalent O(4), two equivalent O(7), and two equivalent O(9) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(3)O6 octahedra. In the second Al site, Al(2) is bonded to two equivalent O(10), two equivalent O(3), and two equivalent O(8) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. In the third Al site, Al(3) is bonded to two equivalent O(2), two equivalent O(7), and two equivalent O(9) atoms to form AlO6 octahedra that share corners with two equivalent Al(4)O4 tetrahedra, corners with two equivalent Al(5)O4 tetrahedra, and edges with two equivalent Al(1)O6 octahedra. In the fourth Al site, Al(4) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form AlO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra,  a cornercorner with one Al(2)O6 octahedra,  a cornercorner with one Al(3)O6 octahedra, and  a cornercorner with one Al(4)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 48-58°. In the fifth Al site, Al(5) is bonded to one O(2), one O(4), one O(6), and one O(8) atom to form AlO4 tetrahedra that share  a cornercorner with one Cr(1)O6 octahedra,  a cornercorner with one Al(1)O6 octahedra,  a cornercorner with one Al(2)O6 octahedra,  a cornercorner with one Al(3)O6 octahedra, and  a cornercorner with one Al(5)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 45-58°. There are two inequivalent Bi sites. In the first Bi site, Bi(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(10), one O(3), and one O(9) atom. In the second Bi site, Bi(2) is bonded in a distorted rectangular see-saw-like geometry to one O(10), one O(2), one O(4), and one O(9) atom. There are ten inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Cr(1), one Al(4), and one Bi(1) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Al(3), one Al(5), and one Bi(2) atom. In the third O site, O(3) is bonded in a distorted trigonal planar geometry to one Al(2), one Al(4), and one Bi(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(5), and one Bi(2) atom. In the fifth O site, O(5) is bonded in a linear geometry to two equivalent Al(4) atoms. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Al(5) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal planar geometry to one Al(1), one Al(3), and one Al(4) atom. In the eighth O site, O(8) is bonded in a distorted trigonal planar geometry to one Cr(1), one Al(2), and one Al(5) atom. In the ninth O site, O(9) is bonded to one Al(1), one Al(3), one Bi(1), and one Bi(2) atom to form distorted edge-sharing OAl2Bi2 tetrahedra. In the tenth O site, O(10) is bonded in a 4-coordinate geometry to one Cr(1), one Al(2), one Bi(1), and one Bi(2) atom. is represented by the CIF file [CIF]
data_Al7Cr(Bi2O9)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.823
_cell_length_b   7.800
_cell_length_c   8.243
_cell_angle_alpha   89.874
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   374.432
_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
  Al  Al0  1  0.262  0.000  0.000  1.0
  Al  Al1  1  0.739  0.500  0.500  1.0
  Al  Al2  1  0.738  0.000  0.000  1.0
  Al  Al3  1  0.502  0.350  0.160  1.0
  Al  Al4  1  0.502  0.650  0.840  1.0
  Al  Al5  1  0.502  0.854  0.337  1.0
  Al  Al6  1  0.502  0.146  0.663  1.0
  Cr  Cr7  1  0.258  0.500  0.500  1.0
  Bi  Bi8  1  0.997  0.169  0.330  1.0
  Bi  Bi9  1  0.997  0.831  0.670  1.0
  Bi  Bi10  1  0.998  0.672  0.168  1.0
  Bi  Bi11  1  0.998  0.328  0.832  1.0
  O  O12  1  0.250  0.371  0.285  1.0
  O  O13  1  0.250  0.629  0.715  1.0
  O  O14  1  0.748  0.877  0.206  1.0
  O  O15  1  0.748  0.123  0.794  1.0
  O  O16  1  0.748  0.626  0.709  1.0
  O  O17  1  0.748  0.374  0.291  1.0
  O  O18  1  0.253  0.125  0.792  1.0
  O  O19  1  0.253  0.875  0.208  1.0
  O  O20  1  0.502  0.500  0.000  1.0
  O  O21  1  0.500  0.000  0.500  1.0
  O  O22  1  0.501  0.137  0.085  1.0
  O  O23  1  0.501  0.863  0.915  1.0
  O  O24  1  0.512  0.641  0.411  1.0
  O  O25  1  0.512  0.359  0.589  1.0
  O  O26  1  0.000  0.143  0.065  1.0
  O  O27  1  0.000  0.857  0.935  1.0
  O  O28  1  0.989  0.648  0.433  1.0
  O  O29  1  0.989  0.352  0.567  1.0
[/CIF]
.