The crystal structure described by Ca8Mn6Al2O21 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted q6 geometry to one O(3), two equivalent O(1), four equivalent O(4), and four equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a distorted q6 geometry to two equivalent O(2), four equivalent O(4), and four equivalent O(5) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra and corners with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedra are not tilted. In the second Mn site, Mn(2) is bonded to one O(3) and four equivalent O(5) atoms to form MnO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  a cornercorner with one Mn(2)O5 square pyramid. The corner-sharing octahedral tilt angles are 9°. Al(1) is bonded in a rectangular see-saw-like geometry to four equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(1) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a linear geometry to four equivalent Ca(2) and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to four equivalent Ca(1) and two equivalent Mn(2) atoms to form distorted OCa4Mn2 octahedra that share corners with sixteen equivalent O(4)Ca4MnAl octahedra and faces with eight equivalent O(5)Ca4Mn2 octahedra. The corner-sharing octahedral tilt angles are 55°. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Al(1) atom to form distorted OCa4MnAl octahedra that share corners with two equivalent O(3)Ca4Mn2 octahedra, corners with six equivalent O(4)Ca4MnAl octahedra, corners with eight equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(4)Ca4MnAl octahedra, faces with two equivalent O(5)Ca4Mn2 octahedra, and faces with two equivalent O(4)Ca4MnAl octahedra. The corner-sharing octahedral tilt angles range from 1-70°. In the fifth O site, O(5) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Mn(2) atom to form distorted OCa4Mn2 octahedra that share corners with six equivalent O(5)Ca4Mn2 octahedra, corners with eight equivalent O(4)Ca4MnAl octahedra, edges with two equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(4)Ca4MnAl octahedra,  a faceface with one O(3)Ca4Mn2 octahedra, faces with two equivalent O(5)Ca4Mn2 octahedra, and faces with two equivalent O(4)Ca4MnAl octahedra. The corner-sharing octahedral tilt angles range from 3-65°. is represented by the CIF file [CIF]
data_Ca8Mn6Al2O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.737
_cell_length_b   7.737
_cell_length_c   7.442
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   445.430
_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
  Ca  Ca0  1  0.262  0.262  0.250  1.0
  Ca  Ca1  1  0.252  0.252  0.750  1.0
  Ca  Ca2  1  0.262  0.738  0.250  1.0
  Ca  Ca3  1  0.252  0.748  0.750  1.0
  Ca  Ca4  1  0.738  0.262  0.250  1.0
  Ca  Ca5  1  0.748  0.252  0.750  1.0
  Ca  Ca6  1  0.738  0.738  0.250  1.0
  Ca  Ca7  1  0.748  0.748  0.750  1.0
  Mn  Mn8  1  0.000  0.500  0.997  1.0
  Mn  Mn9  1  0.000  0.500  0.503  1.0
  Mn  Mn10  1  0.500  0.000  0.997  1.0
  Mn  Mn11  1  0.500  0.000  0.503  1.0
  Mn  Mn12  1  0.500  0.500  0.998  1.0
  Mn  Mn13  1  0.500  0.500  0.502  1.0
  Al  Al14  1  0.000  0.000  0.004  1.0
  Al  Al15  1  0.000  0.000  0.496  1.0
  O  O16  1  0.000  0.500  0.250  1.0
  O  O17  1  0.000  0.500  0.750  1.0
  O  O18  1  0.500  0.000  0.250  1.0
  O  O19  1  0.500  0.000  0.750  1.0
  O  O20  1  0.500  0.500  0.250  1.0
  O  O21  1  0.235  0.000  0.000  1.0
  O  O22  1  0.235  0.000  0.500  1.0
  O  O23  1  0.256  0.500  0.977  1.0
  O  O24  1  0.256  0.500  0.523  1.0
  O  O25  1  0.765  0.000  0.000  1.0
  O  O26  1  0.765  0.000  0.500  1.0
  O  O27  1  0.744  0.500  0.977  1.0
  O  O28  1  0.744  0.500  0.523  1.0
  O  O29  1  0.000  0.235  0.000  1.0
  O  O30  1  0.000  0.235  0.500  1.0
  O  O31  1  0.000  0.765  0.000  1.0
  O  O32  1  0.000  0.765  0.500  1.0
  O  O33  1  0.500  0.256  0.977  1.0
  O  O34  1  0.500  0.256  0.523  1.0
  O  O35  1  0.500  0.744  0.977  1.0
  O  O36  1  0.500  0.744  0.523  1.0
[/CIF]
.
The crystal structure described by Ca8Mn6Al2O21 crystallizes in the tetragonal P4/mmm space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded in a distorted q6 geometry to one O(3), two equivalent O(1), four equivalent O(4), and four equivalent O(5) atoms. In the second Ca site, Ca(2) is bonded in a distorted q6 geometry to two equivalent O(2), four equivalent O(4), and four equivalent O(5) atoms. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form MnO6 octahedra that share corners with two equivalent Mn(1)O6 octahedra and corners with two equivalent Mn(2)O5 square pyramids. The corner-sharing octahedra are not tilted. In the second Mn site, Mn(2) is bonded to one O(3) and four equivalent O(5) atoms to form MnO5 square pyramids that share corners with four equivalent Mn(1)O6 octahedra and  a cornercorner with one Mn(2)O5 square pyramid. The corner-sharing octahedral tilt angles are 9°. Al(1) is bonded in a rectangular see-saw-like geometry to four equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded in a distorted linear geometry to four equivalent Ca(1) and two equivalent Mn(1) atoms. In the second O site, O(2) is bonded in a linear geometry to four equivalent Ca(2) and two equivalent Mn(1) atoms. In the third O site, O(3) is bonded to four equivalent Ca(1) and two equivalent Mn(2) atoms to form distorted OCa4Mn2 octahedra that share corners with sixteen equivalent O(4)Ca4MnAl octahedra and faces with eight equivalent O(5)Ca4Mn2 octahedra. The corner-sharing octahedral tilt angles are 55°. In the fourth O site, O(4) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Al(1) atom to form distorted OCa4MnAl octahedra that share corners with two equivalent O(3)Ca4Mn2 octahedra, corners with six equivalent O(4)Ca4MnAl octahedra, corners with eight equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(4)Ca4MnAl octahedra, faces with two equivalent O(5)Ca4Mn2 octahedra, and faces with two equivalent O(4)Ca4MnAl octahedra. The corner-sharing octahedral tilt angles range from 1-70°. In the fifth O site, O(5) is bonded to two equivalent Ca(1), two equivalent Ca(2), one Mn(1), and one Mn(2) atom to form distorted OCa4Mn2 octahedra that share corners with six equivalent O(5)Ca4Mn2 octahedra, corners with eight equivalent O(4)Ca4MnAl octahedra, edges with two equivalent O(5)Ca4Mn2 octahedra, edges with two equivalent O(4)Ca4MnAl octahedra,  a faceface with one O(3)Ca4Mn2 octahedra, faces with two equivalent O(5)Ca4Mn2 octahedra, and faces with two equivalent O(4)Ca4MnAl octahedra. The corner-sharing octahedral tilt angles range from 3-65°. is represented by the CIF file [CIF]
data_Ca8Mn6Al2O21
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   7.737
_cell_length_b   7.737
_cell_length_c   7.442
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   445.430
_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
  Ca  Ca0  1  0.262  0.262  0.250  1.0
  Ca  Ca1  1  0.252  0.252  0.750  1.0
  Ca  Ca2  1  0.262  0.738  0.250  1.0
  Ca  Ca3  1  0.252  0.748  0.750  1.0
  Ca  Ca4  1  0.738  0.262  0.250  1.0
  Ca  Ca5  1  0.748  0.252  0.750  1.0
  Ca  Ca6  1  0.738  0.738  0.250  1.0
  Ca  Ca7  1  0.748  0.748  0.750  1.0
  Mn  Mn8  1  0.000  0.500  0.997  1.0
  Mn  Mn9  1  0.000  0.500  0.503  1.0
  Mn  Mn10  1  0.500  0.000  0.997  1.0
  Mn  Mn11  1  0.500  0.000  0.503  1.0
  Mn  Mn12  1  0.500  0.500  0.998  1.0
  Mn  Mn13  1  0.500  0.500  0.502  1.0
  Al  Al14  1  0.000  0.000  0.004  1.0
  Al  Al15  1  0.000  0.000  0.496  1.0
  O  O16  1  0.000  0.500  0.250  1.0
  O  O17  1  0.000  0.500  0.750  1.0
  O  O18  1  0.500  0.000  0.250  1.0
  O  O19  1  0.500  0.000  0.750  1.0
  O  O20  1  0.500  0.500  0.250  1.0
  O  O21  1  0.235  0.000  0.000  1.0
  O  O22  1  0.235  0.000  0.500  1.0
  O  O23  1  0.256  0.500  0.977  1.0
  O  O24  1  0.256  0.500  0.523  1.0
  O  O25  1  0.765  0.000  0.000  1.0
  O  O26  1  0.765  0.000  0.500  1.0
  O  O27  1  0.744  0.500  0.977  1.0
  O  O28  1  0.744  0.500  0.523  1.0
  O  O29  1  0.000  0.235  0.000  1.0
  O  O30  1  0.000  0.235  0.500  1.0
  O  O31  1  0.000  0.765  0.000  1.0
  O  O32  1  0.000  0.765  0.500  1.0
  O  O33  1  0.500  0.256  0.977  1.0
  O  O34  1  0.500  0.256  0.523  1.0
  O  O35  1  0.500  0.744  0.977  1.0
  O  O36  1  0.500  0.744  0.523  1.0
[/CIF]
.