The material described by MgCrO9 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra. In the second Mg site, Mg(2) is bonded in a distorted square co-planar geometry to two equivalent O(2), two equivalent O(7), and two equivalent O(8) atoms. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 31°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one O(8) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one O(9) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Mg(1) and one O(9) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one O(7) atom. In the eighth O site, O(8) is bonded in a trigonal non-coplanar geometry to one Mg(2), one O(3), and one O(8) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one O(5) and one O(6) atom. is represented by the CIF file [CIF]
data_MgCrO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.309
_cell_length_b   11.819
_cell_length_c   4.752
_cell_angle_alpha   88.605
_cell_angle_beta   103.179
_cell_angle_gamma   105.056
_symmetry_Int_Tables_number   1
_cell_volume   332.950
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.500  0.500  0.000  1.0
  Cr  Cr2  1  0.976  0.719  0.304  1.0
  Cr  Cr3  1  0.024  0.281  0.696  1.0
  O  O4  1  0.068  0.850  0.184  1.0
  O  O5  1  0.932  0.150  0.816  1.0
  O  O6  1  0.716  0.653  0.132  1.0
  O  O7  1  0.284  0.347  0.868  1.0
  O  O8  1  0.151  0.611  0.294  1.0
  O  O9  1  0.849  0.389  0.706  1.0
  O  O10  1  0.997  0.726  0.645  1.0
  O  O11  1  0.003  0.274  0.355  1.0
  O  O12  1  0.241  0.004  0.734  1.0
  O  O13  1  0.759  0.996  0.266  1.0
  O  O14  1  0.732  0.894  0.674  1.0
  O  O15  1  0.268  0.106  0.326  1.0
  O  O16  1  0.523  0.546  0.588  1.0
  O  O17  1  0.477  0.454  0.412  1.0
  O  O18  1  0.129  0.563  0.034  1.0
  O  O19  1  0.871  0.437  0.966  1.0
  O  O20  1  0.640  0.911  0.400  1.0
  O  O21  1  0.360  0.089  0.600  1.0
[/CIF]
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The material described by MgCrO9 crystallizes in the triclinic P-1 space group. There are two inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to two equivalent O(1), two equivalent O(5), and two equivalent O(6) atoms to form MgO6 octahedra that share corners with two equivalent Cr(1)O4 tetrahedra. In the second Mg site, Mg(2) is bonded in a distorted square co-planar geometry to two equivalent O(2), two equivalent O(7), and two equivalent O(8) atoms. Cr(1) is bonded to one O(1), one O(2), one O(3), and one O(4) atom to form CrO4 tetrahedra that share  a cornercorner with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles are 31°. There are nine inequivalent O sites. In the first O site, O(1) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the second O site, O(2) is bonded in a bent 150 degrees geometry to one Mg(2) and one Cr(1) atom. In the third O site, O(3) is bonded in a distorted bent 120 degrees geometry to one Cr(1) and one O(8) atom. In the fourth O site, O(4) is bonded in a single-bond geometry to one Cr(1) atom. In the fifth O site, O(5) is bonded in a distorted bent 120 degrees geometry to one Mg(1) and one O(9) atom. In the sixth O site, O(6) is bonded in a 2-coordinate geometry to one Mg(1) and one O(9) atom. In the seventh O site, O(7) is bonded in a distorted bent 120 degrees geometry to one Mg(2) and one O(7) atom. In the eighth O site, O(8) is bonded in a trigonal non-coplanar geometry to one Mg(2), one O(3), and one O(8) atom. In the ninth O site, O(9) is bonded in a bent 120 degrees geometry to one O(5) and one O(6) atom. is represented by the CIF file [CIF]
data_MgCrO9
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.309
_cell_length_b   11.819
_cell_length_c   4.752
_cell_angle_alpha   88.605
_cell_angle_beta   103.179
_cell_angle_gamma   105.056
_symmetry_Int_Tables_number   1
_cell_volume   332.950
_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  0.000  0.000  0.000  1.0
  Mg  Mg1  1  0.500  0.500  0.000  1.0
  Cr  Cr2  1  0.976  0.719  0.304  1.0
  Cr  Cr3  1  0.024  0.281  0.696  1.0
  O  O4  1  0.068  0.850  0.184  1.0
  O  O5  1  0.932  0.150  0.816  1.0
  O  O6  1  0.716  0.653  0.132  1.0
  O  O7  1  0.284  0.347  0.868  1.0
  O  O8  1  0.151  0.611  0.294  1.0
  O  O9  1  0.849  0.389  0.706  1.0
  O  O10  1  0.997  0.726  0.645  1.0
  O  O11  1  0.003  0.274  0.355  1.0
  O  O12  1  0.241  0.004  0.734  1.0
  O  O13  1  0.759  0.996  0.266  1.0
  O  O14  1  0.732  0.894  0.674  1.0
  O  O15  1  0.268  0.106  0.326  1.0
  O  O16  1  0.523  0.546  0.588  1.0
  O  O17  1  0.477  0.454  0.412  1.0
  O  O18  1  0.129  0.563  0.034  1.0
  O  O19  1  0.871  0.437  0.966  1.0
  O  O20  1  0.640  0.911  0.400  1.0
  O  O21  1  0.360  0.089  0.600  1.0
[/CIF]
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