The crystal structure described by CaCr4O9 crystallizes in the tetragonal P4/n space group. Ca(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Cr(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing CrO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted square co-planar geometry to four equivalent Cr(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Cr(1) atoms. is represented by the CIF file [CIF]
data_CaCr4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.457
_cell_length_b   8.457
_cell_length_c   5.186
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   370.944
_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
  Ca  Ca0  1  0.500  0.000  0.139  1.0
  Ca  Ca1  1  0.000  0.500  0.861  1.0
  Cr  Cr2  1  0.591  0.288  0.610  1.0
  Cr  Cr3  1  0.712  0.591  0.390  1.0
  Cr  Cr4  1  0.212  0.091  0.610  1.0
  Cr  Cr5  1  0.091  0.788  0.390  1.0
  Cr  Cr6  1  0.409  0.712  0.610  1.0
  Cr  Cr7  1  0.788  0.909  0.610  1.0
  Cr  Cr8  1  0.909  0.212  0.390  1.0
  Cr  Cr9  1  0.288  0.409  0.390  1.0
  O  O10  1  0.500  0.500  0.500  1.0
  O  O11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.237  0.429  0.078  1.0
  O  O13  1  0.929  0.263  0.078  1.0
  O  O14  1  0.071  0.737  0.078  1.0
  O  O15  1  0.763  0.571  0.078  1.0
  O  O16  1  0.263  0.071  0.922  1.0
  O  O17  1  0.571  0.237  0.922  1.0
  O  O18  1  0.429  0.763  0.922  1.0
  O  O19  1  0.737  0.929  0.922  1.0
  O  O20  1  0.604  0.789  0.464  1.0
  O  O21  1  0.289  0.896  0.464  1.0
  O  O22  1  0.711  0.104  0.464  1.0
  O  O23  1  0.396  0.211  0.464  1.0
  O  O24  1  0.104  0.289  0.536  1.0
  O  O25  1  0.211  0.604  0.536  1.0
  O  O26  1  0.789  0.396  0.536  1.0
  O  O27  1  0.896  0.711  0.536  1.0
[/CIF]
.
The crystal structure described by CaCr4O9 crystallizes in the tetragonal P4/n space group. Ca(1) is bonded in a 8-coordinate geometry to four equivalent O(2) and four equivalent O(3) atoms. Cr(1) is bonded to one O(1), one O(2), and three equivalent O(3) atoms to form a mixture of distorted corner and edge-sharing CrO5 trigonal bipyramids. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted square co-planar geometry to four equivalent Cr(1) atoms. In the second O site, O(2) is bonded in a 2-coordinate geometry to one Ca(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Ca(1) and three equivalent Cr(1) atoms. is represented by the CIF file [CIF]
data_CaCr4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   8.457
_cell_length_b   8.457
_cell_length_c   5.186
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   370.944
_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
  Ca  Ca0  1  0.500  0.000  0.139  1.0
  Ca  Ca1  1  0.000  0.500  0.861  1.0
  Cr  Cr2  1  0.591  0.288  0.610  1.0
  Cr  Cr3  1  0.712  0.591  0.390  1.0
  Cr  Cr4  1  0.212  0.091  0.610  1.0
  Cr  Cr5  1  0.091  0.788  0.390  1.0
  Cr  Cr6  1  0.409  0.712  0.610  1.0
  Cr  Cr7  1  0.788  0.909  0.610  1.0
  Cr  Cr8  1  0.909  0.212  0.390  1.0
  Cr  Cr9  1  0.288  0.409  0.390  1.0
  O  O10  1  0.500  0.500  0.500  1.0
  O  O11  1  0.000  0.000  0.500  1.0
  O  O12  1  0.237  0.429  0.078  1.0
  O  O13  1  0.929  0.263  0.078  1.0
  O  O14  1  0.071  0.737  0.078  1.0
  O  O15  1  0.763  0.571  0.078  1.0
  O  O16  1  0.263  0.071  0.922  1.0
  O  O17  1  0.571  0.237  0.922  1.0
  O  O18  1  0.429  0.763  0.922  1.0
  O  O19  1  0.737  0.929  0.922  1.0
  O  O20  1  0.604  0.789  0.464  1.0
  O  O21  1  0.289  0.896  0.464  1.0
  O  O22  1  0.711  0.104  0.464  1.0
  O  O23  1  0.396  0.211  0.464  1.0
  O  O24  1  0.104  0.289  0.536  1.0
  O  O25  1  0.211  0.604  0.536  1.0
  O  O26  1  0.789  0.396  0.536  1.0
  O  O27  1  0.896  0.711  0.536  1.0
[/CIF]
.