The structure described by Mg(FeO2)8 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(6) atoms to form MgO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Fe(4)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-49°. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), two equivalent O(7), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the third Fe site, Fe(3) is bonded to one O(5), one O(8), two equivalent O(1), and two equivalent O(2) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the fourth Fe site, Fe(4) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(2) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), and two equivalent Fe(4) atoms to form distorted corner-sharing OMgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(1) atoms. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(4), and two equivalent Fe(1) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Fe(4) and two equivalent Fe(2) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg(FeO2)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.952
_cell_length_b   10.691
_cell_length_c   10.578
_cell_angle_alpha   89.371
_cell_angle_beta   89.993
_cell_angle_gamma   90.016
_symmetry_Int_Tables_number   1
_cell_volume   333.824
_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  0.010  0.975  0.503  1.0
  Fe  Fe1  1  0.009  0.137  0.316  1.0
  Fe  Fe2  1  0.009  0.635  0.145  1.0
  Fe  Fe3  1  0.509  0.617  0.839  1.0
  Fe  Fe4  1  0.509  0.146  0.682  1.0
  Fe  Fe5  1  0.009  0.812  0.691  1.0
  Fe  Fe6  1  0.009  0.314  0.862  1.0
  Fe  Fe7  1  0.509  0.332  0.167  1.0
  Fe  Fe8  1  0.509  0.803  0.325  1.0
  O  O9  1  0.009  0.326  0.287  1.0
  O  O10  1  0.009  0.327  0.049  1.0
  O  O11  1  0.009  0.688  0.337  1.0
  O  O12  1  0.009  0.926  0.321  1.0
  O  O13  1  0.509  0.804  0.808  1.0
  O  O14  1  0.510  0.842  0.552  1.0
  O  O15  1  0.509  0.196  0.867  1.0
  O  O16  1  0.509  0.431  0.843  1.0
  O  O17  1  0.009  0.623  0.719  1.0
  O  O18  1  0.009  0.622  0.958  1.0
  O  O19  1  0.009  0.261  0.670  1.0
  O  O20  1  0.010  0.023  0.686  1.0
  O  O21  1  0.509  0.145  0.198  1.0
  O  O22  1  0.510  0.107  0.455  1.0
  O  O23  1  0.509  0.753  0.140  1.0
  O  O24  1  0.509  0.518  0.164  1.0
[/CIF]
.
The structure described by Mg(FeO2)8 crystallizes in the monoclinic P2/m space group. Mg(1) is bonded to two equivalent O(4) and four equivalent O(6) atoms to form MgO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with four equivalent Fe(4)O6 octahedra, and faces with two equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles are 41°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(4), two equivalent O(5), and two equivalent O(6) atoms to form distorted FeO6 octahedra that share corners with two equivalent Mg(1)O6 octahedra, corners with four equivalent Fe(4)O6 octahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and  a faceface with one Mg(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 41-49°. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), two equivalent O(7), and two equivalent O(8) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the third Fe site, Fe(3) is bonded to one O(5), one O(8), two equivalent O(1), and two equivalent O(2) atoms to form a mixture of corner and edge-sharing FeO6 octahedra. The corner-sharing octahedral tilt angles are 50°. In the fourth Fe site, Fe(4) is bonded to one O(6), one O(7), two equivalent O(3), and two equivalent O(4) atoms to form distorted FeO6 octahedra that share corners with four equivalent Fe(1)O6 octahedra, edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. There are eight inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal non-coplanar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the second O site, O(2) is bonded in a distorted trigonal planar geometry to one Fe(2) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a distorted trigonal non-coplanar geometry to one Fe(2) and two equivalent Fe(4) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), and two equivalent Fe(4) atoms to form distorted corner-sharing OMgFe3 trigonal pyramids. In the fifth O site, O(5) is bonded in a distorted trigonal non-coplanar geometry to one Fe(3) and two equivalent Fe(1) atoms. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to two equivalent Mg(1), one Fe(4), and two equivalent Fe(1) atoms. In the seventh O site, O(7) is bonded in a distorted trigonal non-coplanar geometry to one Fe(4) and two equivalent Fe(2) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(3) and two equivalent Fe(2) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_Mg(FeO2)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.952
_cell_length_b   10.691
_cell_length_c   10.578
_cell_angle_alpha   89.371
_cell_angle_beta   89.993
_cell_angle_gamma   90.016
_symmetry_Int_Tables_number   1
_cell_volume   333.824
_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  0.010  0.975  0.503  1.0
  Fe  Fe1  1  0.009  0.137  0.316  1.0
  Fe  Fe2  1  0.009  0.635  0.145  1.0
  Fe  Fe3  1  0.509  0.617  0.839  1.0
  Fe  Fe4  1  0.509  0.146  0.682  1.0
  Fe  Fe5  1  0.009  0.812  0.691  1.0
  Fe  Fe6  1  0.009  0.314  0.862  1.0
  Fe  Fe7  1  0.509  0.332  0.167  1.0
  Fe  Fe8  1  0.509  0.803  0.325  1.0
  O  O9  1  0.009  0.326  0.287  1.0
  O  O10  1  0.009  0.327  0.049  1.0
  O  O11  1  0.009  0.688  0.337  1.0
  O  O12  1  0.009  0.926  0.321  1.0
  O  O13  1  0.509  0.804  0.808  1.0
  O  O14  1  0.510  0.842  0.552  1.0
  O  O15  1  0.509  0.196  0.867  1.0
  O  O16  1  0.509  0.431  0.843  1.0
  O  O17  1  0.009  0.623  0.719  1.0
  O  O18  1  0.009  0.622  0.958  1.0
  O  O19  1  0.009  0.261  0.670  1.0
  O  O20  1  0.010  0.023  0.686  1.0
  O  O21  1  0.509  0.145  0.198  1.0
  O  O22  1  0.510  0.107  0.455  1.0
  O  O23  1  0.509  0.753  0.140  1.0
  O  O24  1  0.509  0.518  0.164  1.0
[/CIF]
.