The structure described by MgFeO2 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(4), two equivalent O(6), and two equivalent O(7) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Fe(2)O5 trigonal bipyramids, edges with two equivalent Mg(1)O5 trigonal bipyramids, and  a faceface with one Fe(2)O5 trigonal bipyramid. In the second Mg site, Mg(2) is bonded to one O(1), two equivalent O(5), and two equivalent O(8) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids, edges with two equivalent Mg(2)O5 trigonal bipyramids, and  a faceface with one Fe(3)O5 trigonal bipyramid. In the third Mg site, Mg(3) is bonded to one O(7), one O(8), and two equivalent O(3) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Fe(2)O5 trigonal bipyramids, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O5 trigonal bipyramid. In the fourth Mg site, Mg(4) is bonded to one O(5), one O(6), and two equivalent O(2) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Fe(2)O5 trigonal bipyramids, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(3), and two equivalent O(6) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Mg(3)O4 tetrahedra, edges with two equivalent Fe(2)O5 trigonal bipyramids, and  a faceface with one Mg(1)O5 trigonal bipyramid. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(2), and two equivalent O(8) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(2)O5 trigonal bipyramids,  an edgeedge with one Mg(4)O4 tetrahedra, edges with two equivalent Fe(3)O5 trigonal bipyramids, and  a faceface with one Mg(2)O5 trigonal bipyramid. In the fourth Fe site, Fe(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(7) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), one Fe(3), and two equivalent Fe(4) atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(5)Mg3Fe2 trigonal bipyramids, corners with two equivalent O(7)Mg3Fe2 trigonal bipyramids, and  an edgeedge with one O(7)Mg3Fe2 trigonal bipyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(4) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(3) and two equivalent Fe(2) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent O(4)MgFe3 tetrahedra, corners with two equivalent O(5)Mg3Fe2 trigonal bipyramids, corners with two equivalent O(7)Mg3Fe2 trigonal bipyramids, and  an edgeedge with one O(5)Mg3Fe2 trigonal bipyramid. In the fifth O site, O(5) is bonded to one Mg(4), two equivalent Mg(2), and two equivalent Fe(1) atoms to form distorted OMg3Fe2 trigonal bipyramids that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(4)MgFe3 tetrahedra,  an edgeedge with one O(4)MgFe3 tetrahedra, and edges with two equivalent O(5)Mg3Fe2 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(4), two equivalent Mg(1), and two equivalent Fe(2) atoms. In the seventh O site, O(7) is bonded to one Mg(3), two equivalent Mg(1), and two equivalent Fe(4) atoms to form distorted OMg3Fe2 trigonal bipyramids that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(4)MgFe3 tetrahedra,  an edgeedge with one O(1)MgFe3 tetrahedra, and edges with two equivalent O(7)Mg3Fe2 trigonal bipyramids. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(3), two equivalent Mg(2), and two equivalent Fe(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgFeO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.976
_cell_length_b   8.429
_cell_length_c   8.530
_cell_angle_alpha   85.388
_cell_angle_beta   79.750
_cell_angle_gamma   79.843
_symmetry_Int_Tables_number   1
_cell_volume   207.008
_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  0.358  0.063  0.231  1.0
  Mg  Mg1  1  0.638  0.917  0.797  1.0
  Mg  Mg2  1  0.080  0.707  0.135  1.0
  Mg  Mg3  1  0.916  0.274  0.893  1.0
  Fe  Fe4  1  0.623  0.184  0.568  1.0
  Fe  Fe5  1  0.203  0.378  0.216  1.0
  Fe  Fe6  1  0.794  0.603  0.811  1.0
  Fe  Fe7  1  0.375  0.793  0.459  1.0
  O  O8  1  0.815  0.756  0.613  1.0
  O  O9  1  0.365  0.424  0.847  1.0
  O  O10  1  0.628  0.558  0.186  1.0
  O  O11  1  0.182  0.222  0.415  1.0
  O  O12  1  0.079  0.096  0.738  1.0
  O  O13  1  0.847  0.198  0.117  1.0
  O  O14  1  0.917  0.884  0.290  1.0
  O  O15  1  0.148  0.782  0.911  1.0
[/CIF]
.
The structure described by MgFeO2 crystallizes in the triclinic P1 space group. There are four inequivalent Mg sites. In the first Mg site, Mg(1) is bonded to one O(4), two equivalent O(6), and two equivalent O(7) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Fe(2)O5 trigonal bipyramids, edges with two equivalent Mg(1)O5 trigonal bipyramids, and  a faceface with one Fe(2)O5 trigonal bipyramid. In the second Mg site, Mg(2) is bonded to one O(1), two equivalent O(5), and two equivalent O(8) atoms to form MgO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Fe(3)O5 trigonal bipyramids, edges with two equivalent Mg(2)O5 trigonal bipyramids, and  a faceface with one Fe(3)O5 trigonal bipyramid. In the third Mg site, Mg(3) is bonded to one O(7), one O(8), and two equivalent O(3) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Fe(2)O5 trigonal bipyramids, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(2)O5 trigonal bipyramid. In the fourth Mg site, Mg(4) is bonded to one O(5), one O(6), and two equivalent O(2) atoms to form MgO4 tetrahedra that share corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids, corners with two equivalent Mg(2)O5 trigonal bipyramids, corners with two equivalent Fe(2)O5 trigonal bipyramids, corners with two equivalent Fe(3)O5 trigonal bipyramids, and  an edgeedge with one Fe(3)O5 trigonal bipyramid. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a square co-planar geometry to two equivalent O(4) and two equivalent O(5) atoms. In the second Fe site, Fe(2) is bonded to one O(4), two equivalent O(3), and two equivalent O(6) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(1)O5 trigonal bipyramids,  an edgeedge with one Mg(3)O4 tetrahedra, edges with two equivalent Fe(2)O5 trigonal bipyramids, and  a faceface with one Mg(1)O5 trigonal bipyramid. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(2), and two equivalent O(8) atoms to form distorted FeO5 trigonal bipyramids that share corners with two equivalent Mg(3)O4 tetrahedra, corners with two equivalent Mg(4)O4 tetrahedra, corners with two equivalent Mg(2)O5 trigonal bipyramids,  an edgeedge with one Mg(4)O4 tetrahedra, edges with two equivalent Fe(3)O5 trigonal bipyramids, and  a faceface with one Mg(2)O5 trigonal bipyramid. In the fourth Fe site, Fe(4) is bonded in a square co-planar geometry to two equivalent O(1) and two equivalent O(7) atoms. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(2), one Fe(3), and two equivalent Fe(4) atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(5)Mg3Fe2 trigonal bipyramids, corners with two equivalent O(7)Mg3Fe2 trigonal bipyramids, and  an edgeedge with one O(7)Mg3Fe2 trigonal bipyramid. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(4) and two equivalent Fe(3) atoms. In the third O site, O(3) is bonded in a rectangular see-saw-like geometry to two equivalent Mg(3) and two equivalent Fe(2) atoms. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(2), and two equivalent Fe(1) atoms to form distorted OMgFe3 tetrahedra that share corners with two equivalent O(4)MgFe3 tetrahedra, corners with two equivalent O(5)Mg3Fe2 trigonal bipyramids, corners with two equivalent O(7)Mg3Fe2 trigonal bipyramids, and  an edgeedge with one O(5)Mg3Fe2 trigonal bipyramid. In the fifth O site, O(5) is bonded to one Mg(4), two equivalent Mg(2), and two equivalent Fe(1) atoms to form distorted OMg3Fe2 trigonal bipyramids that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(4)MgFe3 tetrahedra,  an edgeedge with one O(4)MgFe3 tetrahedra, and edges with two equivalent O(5)Mg3Fe2 trigonal bipyramids. In the sixth O site, O(6) is bonded in a 5-coordinate geometry to one Mg(4), two equivalent Mg(1), and two equivalent Fe(2) atoms. In the seventh O site, O(7) is bonded to one Mg(3), two equivalent Mg(1), and two equivalent Fe(4) atoms to form distorted OMg3Fe2 trigonal bipyramids that share corners with two equivalent O(1)MgFe3 tetrahedra, corners with two equivalent O(4)MgFe3 tetrahedra,  an edgeedge with one O(1)MgFe3 tetrahedra, and edges with two equivalent O(7)Mg3Fe2 trigonal bipyramids. In the eighth O site, O(8) is bonded in a 5-coordinate geometry to one Mg(3), two equivalent Mg(2), and two equivalent Fe(3) atoms. is represented by the Crystallographic Information File (CIF) [CIF]
data_MgFeO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   2.976
_cell_length_b   8.429
_cell_length_c   8.530
_cell_angle_alpha   85.388
_cell_angle_beta   79.750
_cell_angle_gamma   79.843
_symmetry_Int_Tables_number   1
_cell_volume   207.008
_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  0.358  0.063  0.231  1.0
  Mg  Mg1  1  0.638  0.917  0.797  1.0
  Mg  Mg2  1  0.080  0.707  0.135  1.0
  Mg  Mg3  1  0.916  0.274  0.893  1.0
  Fe  Fe4  1  0.623  0.184  0.568  1.0
  Fe  Fe5  1  0.203  0.378  0.216  1.0
  Fe  Fe6  1  0.794  0.603  0.811  1.0
  Fe  Fe7  1  0.375  0.793  0.459  1.0
  O  O8  1  0.815  0.756  0.613  1.0
  O  O9  1  0.365  0.424  0.847  1.0
  O  O10  1  0.628  0.558  0.186  1.0
  O  O11  1  0.182  0.222  0.415  1.0
  O  O12  1  0.079  0.096  0.738  1.0
  O  O13  1  0.847  0.198  0.117  1.0
  O  O14  1  0.917  0.884  0.290  1.0
  O  O15  1  0.148  0.782  0.911  1.0
[/CIF]
.