The structure described by MgCr(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Mg(1)O6 octahedra. Cr(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-60°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1), one Cr(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgCr(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.391
_cell_length_b   6.736
_cell_length_c   6.736
_cell_angle_alpha   84.362
_cell_angle_beta   74.698
_cell_angle_gamma   74.698
_symmetry_Int_Tables_number   1
_cell_volume   227.438
_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  0.250  0.597  0.403  1.0
  Mg  Mg1  1  0.750  0.403  0.597  1.0
  Cr  Cr2  1  0.750  0.767  0.233  1.0
  Cr  Cr3  1  0.250  0.233  0.767  1.0
  Si  Si4  1  0.274  0.117  0.294  1.0
  Si  Si5  1  0.726  0.883  0.706  1.0
  Si  Si6  1  0.226  0.706  0.883  1.0
  Si  Si7  1  0.774  0.294  0.117  1.0
  O  O8  1  0.935  0.853  0.855  1.0
  O  O9  1  0.065  0.147  0.145  1.0
  O  O10  1  0.565  0.145  0.147  1.0
  O  O11  1  0.435  0.855  0.853  1.0
  O  O12  1  0.152  0.294  0.467  1.0
  O  O13  1  0.848  0.706  0.533  1.0
  O  O14  1  0.348  0.533  0.706  1.0
  O  O15  1  0.652  0.467  0.294  1.0
  O  O16  1  0.350  0.878  0.372  1.0
  O  O17  1  0.650  0.122  0.628  1.0
  O  O18  1  0.150  0.628  0.122  1.0
  O  O19  1  0.850  0.372  0.878  1.0
[/CIF]
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The structure described by MgCr(SiO3)2 is Esseneite structured and crystallizes in the monoclinic C2/c space group. Mg(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form MgO6 octahedra that share corners with six equivalent Si(1)O4 tetrahedra and edges with two equivalent Mg(1)O6 octahedra. Cr(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms. Si(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form SiO4 tetrahedra that share corners with three equivalent Mg(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 35-60°. There are three inequivalent O sites. In the first O site, O(1) is bonded in a distorted bent 150 degrees geometry to one Cr(1) and two equivalent Si(1) atoms. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Mg(1), one Cr(1), and one Si(1) atom. In the third O site, O(3) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one Si(1) atom. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgCr(SiO3)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.391
_cell_length_b   6.736
_cell_length_c   6.736
_cell_angle_alpha   84.362
_cell_angle_beta   74.698
_cell_angle_gamma   74.698
_symmetry_Int_Tables_number   1
_cell_volume   227.438
_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  0.250  0.597  0.403  1.0
  Mg  Mg1  1  0.750  0.403  0.597  1.0
  Cr  Cr2  1  0.750  0.767  0.233  1.0
  Cr  Cr3  1  0.250  0.233  0.767  1.0
  Si  Si4  1  0.274  0.117  0.294  1.0
  Si  Si5  1  0.726  0.883  0.706  1.0
  Si  Si6  1  0.226  0.706  0.883  1.0
  Si  Si7  1  0.774  0.294  0.117  1.0
  O  O8  1  0.935  0.853  0.855  1.0
  O  O9  1  0.065  0.147  0.145  1.0
  O  O10  1  0.565  0.145  0.147  1.0
  O  O11  1  0.435  0.855  0.853  1.0
  O  O12  1  0.152  0.294  0.467  1.0
  O  O13  1  0.848  0.706  0.533  1.0
  O  O14  1  0.348  0.533  0.706  1.0
  O  O15  1  0.652  0.467  0.294  1.0
  O  O16  1  0.350  0.878  0.372  1.0
  O  O17  1  0.650  0.122  0.628  1.0
  O  O18  1  0.150  0.628  0.122  1.0
  O  O19  1  0.850  0.372  0.878  1.0
[/CIF]
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