The material structure described by Cr2Al2O7 crystallizes in the cubic Fd-3m space group. Cr(1) is bonded to six equivalent O(2) atoms to form distorted corner-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles are 61°. Al(1) is bonded in a body-centered cubic geometry to two equivalent O(1) and six equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Al(1) atoms to form OAl4 tetrahedra that share corners with four equivalent O(1)Al4 tetrahedra, corners with twelve equivalent O(2)Al2Cr2 tetrahedra, and edges with six equivalent O(2)Al2Cr2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Cr(1) and two equivalent Al(1) atoms to form OAl2Cr2 tetrahedra that share corners with two equivalent O(1)Al4 tetrahedra, corners with twelve equivalent O(2)Al2Cr2 tetrahedra,  an edgeedge with one O(1)Al4 tetrahedra, and edges with four equivalent O(2)Al2Cr2 tetrahedra. is represented by the CIF file [CIF]
data_Al2Cr2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.714
_cell_length_b   6.714
_cell_length_c   6.714
_cell_angle_alpha   60.000
_cell_angle_beta   60.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   214.028
_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  0.125  0.125  0.125  1.0
  Al  Al1  1  0.625  0.125  0.125  1.0
  Al  Al2  1  0.125  0.125  0.625  1.0
  Al  Al3  1  0.125  0.625  0.125  1.0
  Cr  Cr4  1  0.625  0.625  0.625  1.0
  Cr  Cr5  1  0.125  0.625  0.625  1.0
  Cr  Cr6  1  0.625  0.625  0.125  1.0
  Cr  Cr7  1  0.625  0.125  0.625  1.0
  O  O8  1  0.000  0.000  0.000  1.0
  O  O9  1  0.250  0.250  0.250  1.0
  O  O10  1  0.271  0.271  0.729  1.0
  O  O11  1  0.521  0.521  0.979  1.0
  O  O12  1  0.729  0.271  0.729  1.0
  O  O13  1  0.729  0.271  0.271  1.0
  O  O14  1  0.271  0.729  0.729  1.0
  O  O15  1  0.271  0.729  0.271  1.0
  O  O16  1  0.729  0.729  0.271  1.0
  O  O17  1  0.979  0.521  0.521  1.0
  O  O18  1  0.521  0.979  0.979  1.0
  O  O19  1  0.979  0.979  0.521  1.0
  O  O20  1  0.979  0.521  0.979  1.0
  O  O21  1  0.521  0.979  0.521  1.0
[/CIF]
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The material structure described by Cr2Al2O7 crystallizes in the cubic Fd-3m space group. Cr(1) is bonded to six equivalent O(2) atoms to form distorted corner-sharing CrO6 octahedra. The corner-sharing octahedral tilt angles are 61°. Al(1) is bonded in a body-centered cubic geometry to two equivalent O(1) and six equivalent O(2) atoms. There are two inequivalent O sites. In the first O site, O(1) is bonded to four equivalent Al(1) atoms to form OAl4 tetrahedra that share corners with four equivalent O(1)Al4 tetrahedra, corners with twelve equivalent O(2)Al2Cr2 tetrahedra, and edges with six equivalent O(2)Al2Cr2 tetrahedra. In the second O site, O(2) is bonded to two equivalent Cr(1) and two equivalent Al(1) atoms to form OAl2Cr2 tetrahedra that share corners with two equivalent O(1)Al4 tetrahedra, corners with twelve equivalent O(2)Al2Cr2 tetrahedra,  an edgeedge with one O(1)Al4 tetrahedra, and edges with four equivalent O(2)Al2Cr2 tetrahedra. is represented by the CIF file [CIF]
data_Al2Cr2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.714
_cell_length_b   6.714
_cell_length_c   6.714
_cell_angle_alpha   60.000
_cell_angle_beta   60.000
_cell_angle_gamma   60.000
_symmetry_Int_Tables_number   1
_cell_volume   214.028
_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  0.125  0.125  0.125  1.0
  Al  Al1  1  0.625  0.125  0.125  1.0
  Al  Al2  1  0.125  0.125  0.625  1.0
  Al  Al3  1  0.125  0.625  0.125  1.0
  Cr  Cr4  1  0.625  0.625  0.625  1.0
  Cr  Cr5  1  0.125  0.625  0.625  1.0
  Cr  Cr6  1  0.625  0.625  0.125  1.0
  Cr  Cr7  1  0.625  0.125  0.625  1.0
  O  O8  1  0.000  0.000  0.000  1.0
  O  O9  1  0.250  0.250  0.250  1.0
  O  O10  1  0.271  0.271  0.729  1.0
  O  O11  1  0.521  0.521  0.979  1.0
  O  O12  1  0.729  0.271  0.729  1.0
  O  O13  1  0.729  0.271  0.271  1.0
  O  O14  1  0.271  0.729  0.729  1.0
  O  O15  1  0.271  0.729  0.271  1.0
  O  O16  1  0.729  0.729  0.271  1.0
  O  O17  1  0.979  0.521  0.521  1.0
  O  O18  1  0.521  0.979  0.979  1.0
  O  O19  1  0.979  0.979  0.521  1.0
  O  O20  1  0.979  0.521  0.979  1.0
  O  O21  1  0.521  0.979  0.521  1.0
[/CIF]
.