The structure described by MgCr2O7 crystallizes in the monoclinic P2_1 space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Cr(2)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra and corners with three equivalent Mg(1)O5 trigonal bipyramids. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O4 tetrahedra and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Cr(1) atom. is represented by the CIF file [CIF]
data_MgCr2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.588
_cell_length_b   6.400
_cell_length_c   7.717
_cell_angle_alpha   70.857
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   307.395
_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  0.121  0.110  0.349  1.0
  Mg  Mg1  1  0.621  0.890  0.651  1.0
  Cr  Cr2  1  0.140  0.897  0.790  1.0
  Cr  Cr3  1  0.640  0.103  0.210  1.0
  Cr  Cr4  1  0.681  0.349  0.782  1.0
  Cr  Cr5  1  0.181  0.651  0.218  1.0
  O  O6  1  0.370  0.590  0.354  1.0
  O  O7  1  0.870  0.410  0.646  1.0
  O  O8  1  0.770  0.058  0.409  1.0
  O  O9  1  0.270  0.942  0.591  1.0
  O  O10  1  0.031  0.432  0.266  1.0
  O  O11  1  0.531  0.568  0.734  1.0
  O  O12  1  0.408  0.186  0.234  1.0
  O  O13  1  0.908  0.814  0.766  1.0
  O  O14  1  0.066  0.874  0.234  1.0
  O  O15  1  0.566  0.126  0.766  1.0
  O  O16  1  0.263  0.713  0.983  1.0
  O  O17  1  0.763  0.287  0.017  1.0
  O  O18  1  0.125  0.126  0.831  1.0
  O  O19  1  0.625  0.874  0.169  1.0
[/CIF]
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The structure described by MgCr2O7 crystallizes in the monoclinic P2_1 space group. Mg(1) is bonded to one O(3), one O(4), one O(5), and two equivalent O(2) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Cr(2)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to one O(2), one O(4), one O(6), and one O(7) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(2)O4 tetrahedra and corners with three equivalent Mg(1)O5 trigonal bipyramids. In the second Cr site, Cr(2) is bonded to one O(1), one O(3), one O(5), and one O(6) atom to form CrO4 tetrahedra that share  a cornercorner with one Cr(1)O4 tetrahedra and corners with two equivalent Mg(1)O5 trigonal bipyramids. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a single-bond geometry to one Cr(2) atom. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to two equivalent Mg(1) and one Cr(1) atom. In the third O site, O(3) is bonded in a bent 120 degrees geometry to one Mg(1) and one Cr(2) atom. In the fourth O site, O(4) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(1) atom. In the fifth O site, O(5) is bonded in a bent 150 degrees geometry to one Mg(1) and one Cr(2) atom. In the sixth O site, O(6) is bonded in a bent 120 degrees geometry to one Cr(1) and one Cr(2) atom. In the seventh O site, O(7) is bonded in a single-bond geometry to one Cr(1) atom. is represented by the CIF file [CIF]
data_MgCr2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.588
_cell_length_b   6.400
_cell_length_c   7.717
_cell_angle_alpha   70.857
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   307.395
_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  0.121  0.110  0.349  1.0
  Mg  Mg1  1  0.621  0.890  0.651  1.0
  Cr  Cr2  1  0.140  0.897  0.790  1.0
  Cr  Cr3  1  0.640  0.103  0.210  1.0
  Cr  Cr4  1  0.681  0.349  0.782  1.0
  Cr  Cr5  1  0.181  0.651  0.218  1.0
  O  O6  1  0.370  0.590  0.354  1.0
  O  O7  1  0.870  0.410  0.646  1.0
  O  O8  1  0.770  0.058  0.409  1.0
  O  O9  1  0.270  0.942  0.591  1.0
  O  O10  1  0.031  0.432  0.266  1.0
  O  O11  1  0.531  0.568  0.734  1.0
  O  O12  1  0.408  0.186  0.234  1.0
  O  O13  1  0.908  0.814  0.766  1.0
  O  O14  1  0.066  0.874  0.234  1.0
  O  O15  1  0.566  0.126  0.766  1.0
  O  O16  1  0.263  0.713  0.983  1.0
  O  O17  1  0.763  0.287  0.017  1.0
  O  O18  1  0.125  0.126  0.831  1.0
  O  O19  1  0.625  0.874  0.169  1.0
[/CIF]
.