The material described by MgCr(SiO3)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(4), and one O(6) atom. Cr(1) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(4) atoms to form CrO6 octahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-64°. In the second Si site, Si(2) is bonded to one O(4), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-66°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one Si(2) atom. In the third O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cr(1), and one Si(1) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the sixth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cr(1), and one Si(2) 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   9.375
_cell_length_b   5.382
_cell_length_c   9.546
_cell_angle_alpha   79.809
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   473.993
_cell_formula_units_Z   4
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  0.002  0.488  0.248  1.0
  Mg  Mg1  1  0.998  0.512  0.752  1.0
  Mg  Mg2  1  0.502  0.012  0.752  1.0
  Mg  Mg3  1  0.498  0.988  0.248  1.0
  Cr  Cr4  1  0.352  0.488  0.252  1.0
  Cr  Cr5  1  0.648  0.512  0.748  1.0
  Cr  Cr6  1  0.852  0.012  0.748  1.0
  Cr  Cr7  1  0.148  0.988  0.252  1.0
  Si  Si8  1  0.838  0.239  0.045  1.0
  Si  Si9  1  0.162  0.761  0.955  1.0
  Si  Si10  1  0.338  0.261  0.955  1.0
  Si  Si11  1  0.662  0.739  0.045  1.0
  Si  Si12  1  0.163  0.219  0.546  1.0
  Si  Si13  1  0.837  0.781  0.454  1.0
  Si  Si14  1  0.663  0.281  0.454  1.0
  Si  Si15  1  0.337  0.719  0.546  1.0
  O  O16  1  0.990  0.226  0.126  1.0
  O  O17  1  0.010  0.774  0.874  1.0
  O  O18  1  0.490  0.274  0.874  1.0
  O  O19  1  0.510  0.726  0.126  1.0
  O  O20  1  0.347  0.209  0.129  1.0
  O  O21  1  0.653  0.791  0.871  1.0
  O  O22  1  0.847  0.291  0.871  1.0
  O  O23  1  0.153  0.709  0.129  1.0
  O  O24  1  0.278  0.425  0.593  1.0
  O  O25  1  0.722  0.575  0.407  1.0
  O  O26  1  0.778  0.075  0.407  1.0
  O  O27  1  0.222  0.925  0.593  1.0
  O  O28  1  0.150  0.273  0.371  1.0
  O  O29  1  0.850  0.727  0.629  1.0
  O  O30  1  0.650  0.227  0.629  1.0
  O  O31  1  0.350  0.773  0.371  1.0
  O  O32  1  0.759  0.483  0.099  1.0
  O  O33  1  0.241  0.517  0.901  1.0
  O  O34  1  0.259  0.017  0.901  1.0
  O  O35  1  0.741  0.983  0.099  1.0
  O  O36  1  0.518  0.247  0.368  1.0
  O  O37  1  0.482  0.753  0.632  1.0
  O  O38  1  0.018  0.253  0.632  1.0
  O  O39  1  0.982  0.747  0.368  1.0
[/CIF]
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The material described by MgCr(SiO3)2 crystallizes in the monoclinic P2_1/c space group. Mg(1) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(4), and one O(6) atom. Cr(1) is bonded to one O(1), one O(6), two equivalent O(2), and two equivalent O(4) atoms to form CrO6 octahedra that share corners with three equivalent Si(1)O4 tetrahedra, corners with three equivalent Si(2)O4 tetrahedra, and edges with two equivalent Cr(1)O6 octahedra. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), and two equivalent O(5) atoms to form SiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and corners with two equivalent Si(1)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 33-64°. In the second Si site, Si(2) is bonded to one O(4), one O(6), and two equivalent O(3) atoms to form SiO4 tetrahedra that share corners with three equivalent Cr(1)O6 octahedra and corners with two equivalent Si(2)O4 tetrahedra. The corner-sharing octahedral tilt angles range from 42-66°. There are six inequivalent O sites. In the first O site, O(5) is bonded in a distorted bent 150 degrees geometry to two equivalent Si(1) atoms. In the second O site, O(6) is bonded in a distorted trigonal planar geometry to one Mg(1), one Cr(1), and one Si(2) atom. In the third O site, O(1) is bonded in a distorted T-shaped geometry to one Mg(1), one Cr(1), and one Si(1) atom. In the fourth O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cr(1), and one Si(1) atom. In the fifth O site, O(3) is bonded in a bent 150 degrees geometry to two equivalent Si(2) atoms. In the sixth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to one Mg(1), two equivalent Cr(1), and one Si(2) 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   9.375
_cell_length_b   5.382
_cell_length_c   9.546
_cell_angle_alpha   79.809
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   473.993
_cell_formula_units_Z   4
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  0.002  0.488  0.248  1.0
  Mg  Mg1  1  0.998  0.512  0.752  1.0
  Mg  Mg2  1  0.502  0.012  0.752  1.0
  Mg  Mg3  1  0.498  0.988  0.248  1.0
  Cr  Cr4  1  0.352  0.488  0.252  1.0
  Cr  Cr5  1  0.648  0.512  0.748  1.0
  Cr  Cr6  1  0.852  0.012  0.748  1.0
  Cr  Cr7  1  0.148  0.988  0.252  1.0
  Si  Si8  1  0.838  0.239  0.045  1.0
  Si  Si9  1  0.162  0.761  0.955  1.0
  Si  Si10  1  0.338  0.261  0.955  1.0
  Si  Si11  1  0.662  0.739  0.045  1.0
  Si  Si12  1  0.163  0.219  0.546  1.0
  Si  Si13  1  0.837  0.781  0.454  1.0
  Si  Si14  1  0.663  0.281  0.454  1.0
  Si  Si15  1  0.337  0.719  0.546  1.0
  O  O16  1  0.990  0.226  0.126  1.0
  O  O17  1  0.010  0.774  0.874  1.0
  O  O18  1  0.490  0.274  0.874  1.0
  O  O19  1  0.510  0.726  0.126  1.0
  O  O20  1  0.347  0.209  0.129  1.0
  O  O21  1  0.653  0.791  0.871  1.0
  O  O22  1  0.847  0.291  0.871  1.0
  O  O23  1  0.153  0.709  0.129  1.0
  O  O24  1  0.278  0.425  0.593  1.0
  O  O25  1  0.722  0.575  0.407  1.0
  O  O26  1  0.778  0.075  0.407  1.0
  O  O27  1  0.222  0.925  0.593  1.0
  O  O28  1  0.150  0.273  0.371  1.0
  O  O29  1  0.850  0.727  0.629  1.0
  O  O30  1  0.650  0.227  0.629  1.0
  O  O31  1  0.350  0.773  0.371  1.0
  O  O32  1  0.759  0.483  0.099  1.0
  O  O33  1  0.241  0.517  0.901  1.0
  O  O34  1  0.259  0.017  0.901  1.0
  O  O35  1  0.741  0.983  0.099  1.0
  O  O36  1  0.518  0.247  0.368  1.0
  O  O37  1  0.482  0.753  0.632  1.0
  O  O38  1  0.018  0.253  0.632  1.0
  O  O39  1  0.982  0.747  0.368  1.0
[/CIF]
.