The material described by MgCr4O9 crystallizes in the tetragonal P4/n space group. Mg(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 edge and corner-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 distorted bent 120 degrees geometry to one Mg(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1) and three equivalent Cr(1) atoms. is represented by the CIF file [CIF]
data_MgCr4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.890
_cell_length_b   8.327
_cell_length_c   8.327
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   339.118
_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
  Mg  Mg0  1  0.120  0.250  0.250  1.0
  Mg  Mg1  1  0.880  0.750  0.750  1.0
  Cr  Cr2  1  0.616  0.535  0.341  1.0
  Cr  Cr3  1  0.384  0.841  0.465  1.0
  Cr  Cr4  1  0.616  0.341  0.965  1.0
  Cr  Cr5  1  0.384  0.035  0.841  1.0
  Cr  Cr6  1  0.616  0.965  0.159  1.0
  Cr  Cr7  1  0.616  0.159  0.535  1.0
  Cr  Cr8  1  0.384  0.465  0.659  1.0
  Cr  Cr9  1  0.384  0.659  0.035  1.0
  O  O10  1  0.500  0.750  0.250  1.0
  O  O11  1  0.500  0.250  0.750  1.0
  O  O12  1  0.059  0.685  0.971  1.0
  O  O13  1  0.059  0.529  0.685  1.0
  O  O14  1  0.059  0.971  0.815  1.0
  O  O15  1  0.059  0.815  0.529  1.0
  O  O16  1  0.941  0.315  0.029  1.0
  O  O17  1  0.941  0.471  0.315  1.0
  O  O18  1  0.941  0.029  0.185  1.0
  O  O19  1  0.941  0.185  0.471  1.0
  O  O20  1  0.452  0.043  0.355  1.0
  O  O21  1  0.452  0.145  0.043  1.0
  O  O22  1  0.452  0.355  0.457  1.0
  O  O23  1  0.452  0.457  0.145  1.0
  O  O24  1  0.548  0.543  0.855  1.0
  O  O25  1  0.548  0.855  0.957  1.0
  O  O26  1  0.548  0.645  0.543  1.0
  O  O27  1  0.548  0.957  0.645  1.0
[/CIF]
.
The material described by MgCr4O9 crystallizes in the tetragonal P4/n space group. Mg(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 edge and corner-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 distorted bent 120 degrees geometry to one Mg(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Mg(1) and three equivalent Cr(1) atoms. is represented by the CIF file [CIF]
data_MgCr4O9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   4.890
_cell_length_b   8.327
_cell_length_c   8.327
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   339.118
_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
  Mg  Mg0  1  0.120  0.250  0.250  1.0
  Mg  Mg1  1  0.880  0.750  0.750  1.0
  Cr  Cr2  1  0.616  0.535  0.341  1.0
  Cr  Cr3  1  0.384  0.841  0.465  1.0
  Cr  Cr4  1  0.616  0.341  0.965  1.0
  Cr  Cr5  1  0.384  0.035  0.841  1.0
  Cr  Cr6  1  0.616  0.965  0.159  1.0
  Cr  Cr7  1  0.616  0.159  0.535  1.0
  Cr  Cr8  1  0.384  0.465  0.659  1.0
  Cr  Cr9  1  0.384  0.659  0.035  1.0
  O  O10  1  0.500  0.750  0.250  1.0
  O  O11  1  0.500  0.250  0.750  1.0
  O  O12  1  0.059  0.685  0.971  1.0
  O  O13  1  0.059  0.529  0.685  1.0
  O  O14  1  0.059  0.971  0.815  1.0
  O  O15  1  0.059  0.815  0.529  1.0
  O  O16  1  0.941  0.315  0.029  1.0
  O  O17  1  0.941  0.471  0.315  1.0
  O  O18  1  0.941  0.029  0.185  1.0
  O  O19  1  0.941  0.185  0.471  1.0
  O  O20  1  0.452  0.043  0.355  1.0
  O  O21  1  0.452  0.145  0.043  1.0
  O  O22  1  0.452  0.355  0.457  1.0
  O  O23  1  0.452  0.457  0.145  1.0
  O  O24  1  0.548  0.543  0.855  1.0
  O  O25  1  0.548  0.855  0.957  1.0
  O  O26  1  0.548  0.645  0.543  1.0
  O  O27  1  0.548  0.957  0.645  1.0
[/CIF]
.