The material structure described by MgCr2(HgO4)2 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-67°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-59°. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form CrO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-55°. Hg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form HgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Hg(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Cr(2), and two equivalent Hg(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(1) and two equivalent Hg(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cr(2) and one Hg(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Hg(1) atom. is represented by the CIF card [CIF]
data_MgCr2(HgO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.534
_cell_length_b   5.534
_cell_length_c   6.785
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   110.800
_symmetry_Int_Tables_number   1
_cell_volume   194.266
_cell_formula_units_Z   1
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  0.665  0.335  0.750  1.0
  Cr  Cr1  1  0.642  0.358  0.250  1.0
  Cr  Cr2  1  0.362  0.638  0.750  1.0
  Hg  Hg3  1  0.996  0.004  0.481  1.0
  Hg  Hg4  1  0.996  0.004  0.019  1.0
  O  O5  1  0.694  0.729  0.750  1.0
  O  O6  1  0.302  0.235  0.250  1.0
  O  O7  1  0.765  0.698  0.250  1.0
  O  O8  1  0.271  0.306  0.750  1.0
  O  O9  1  0.257  0.743  0.945  1.0
  O  O10  1  0.747  0.253  0.484  1.0
  O  O11  1  0.747  0.253  0.016  1.0
  O  O12  1  0.257  0.743  0.555  1.0
[/CIF]
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The material structure described by MgCr2(HgO4)2 crystallizes in the orthorhombic Amm2 space group. Mg(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form distorted MgO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra, corners with two equivalent Cr(1)O4 tetrahedra, and  an edgeedge with one Cr(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 66-67°. There are two inequivalent Cr sites. In the first Cr site, Cr(1) is bonded to two equivalent O(2) and two equivalent O(4) atoms to form CrO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra and corners with two equivalent Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 47-59°. In the second Cr site, Cr(2) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form CrO4 tetrahedra that share corners with six equivalent Hg(1)O6 octahedra and  an edgeedge with one Mg(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-55°. Hg(1) is bonded to one O(3), one O(4), two equivalent O(1), and two equivalent O(2) atoms to form HgO6 octahedra that share corners with three equivalent Mg(1)O4 tetrahedra, corners with three equivalent Cr(1)O4 tetrahedra, corners with three equivalent Cr(2)O4 tetrahedra, and edges with two equivalent Hg(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded in a 4-coordinate geometry to one Mg(1), one Cr(2), and two equivalent Hg(1) atoms. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Cr(1) and two equivalent Hg(1) atoms. In the third O site, O(3) is bonded in a distorted single-bond geometry to one Cr(2) and one Hg(1) atom. In the fourth O site, O(4) is bonded in a trigonal planar geometry to one Mg(1), one Cr(1), and one Hg(1) atom. is represented by the CIF card [CIF]
data_MgCr2(HgO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.534
_cell_length_b   5.534
_cell_length_c   6.785
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   110.800
_symmetry_Int_Tables_number   1
_cell_volume   194.266
_cell_formula_units_Z   1
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  0.665  0.335  0.750  1.0
  Cr  Cr1  1  0.642  0.358  0.250  1.0
  Cr  Cr2  1  0.362  0.638  0.750  1.0
  Hg  Hg3  1  0.996  0.004  0.481  1.0
  Hg  Hg4  1  0.996  0.004  0.019  1.0
  O  O5  1  0.694  0.729  0.750  1.0
  O  O6  1  0.302  0.235  0.250  1.0
  O  O7  1  0.765  0.698  0.250  1.0
  O  O8  1  0.271  0.306  0.750  1.0
  O  O9  1  0.257  0.743  0.945  1.0
  O  O10  1  0.747  0.253  0.484  1.0
  O  O11  1  0.747  0.253  0.016  1.0
  O  O12  1  0.257  0.743  0.555  1.0
[/CIF]
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