The crystal structure described by MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(4), and two equivalent F(1) atoms to form MgO3F3 octahedra that share corners with two equivalent Fe(2)O5 square pyramids,  a cornercorner with one Fe(3)O3F tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. In the second Fe site, Fe(2) is bonded to one O(7), two equivalent O(1), and two equivalent O(8) atoms to form distorted FeO5 square pyramids that share corners with two equivalent Mg(1)O3F3 octahedra, corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 52-76°. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(3), and one F(3) atom to form FeO3F tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and corners with two equivalent Fe(3)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 49-77°. In the fourth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form FeF6 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-48°. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), one F(8), and two equivalent F(6) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and edges with two equivalent Fe(7)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-55°. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form corner-sharing OMgFe3 tetrahedra. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(7) and two equivalent Fe(5) atoms. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(8) and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(5) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(4), and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a 3-coordinate geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(7) atoms. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted T-shaped geometry to one Fe(7) and two equivalent Fe(1) atoms. is represented by the CIF card [CIF]
data_MgFe8(OF)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.913
_cell_length_b   9.871
_cell_length_c   3.066
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   86.749
_symmetry_Int_Tables_number   1
_cell_volume   299.517
_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  0.263  0.507  0.500  1.0
  Fe  Fe1  1  0.996  0.982  0.000  1.0
  Fe  Fe2  1  0.982  0.474  0.000  1.0
  Fe  Fe3  1  0.190  0.207  0.500  1.0
  Fe  Fe4  1  0.235  0.773  0.500  1.0
  Fe  Fe5  1  0.552  0.506  0.000  1.0
  Fe  Fe6  1  0.501  0.010  0.000  1.0
  Fe  Fe7  1  0.758  0.263  0.500  1.0
  Fe  Fe8  1  0.763  0.721  0.500  1.0
  O  O9  1  0.106  0.393  0.500  1.0
  O  O10  1  0.071  0.890  0.500  1.0
  O  O11  1  0.119  0.125  0.000  1.0
  O  O12  1  0.202  0.640  0.000  1.0
  O  O13  1  0.612  0.402  0.500  1.0
  O  O14  1  0.668  0.653  0.000  1.0
  O  O15  1  0.854  0.332  0.000  1.0
  O  O16  1  0.911  0.586  0.500  1.0
  F  F17  1  0.362  0.405  0.000  1.0
  F  F18  1  0.342  0.872  0.000  1.0
  F  F19  1  0.387  0.120  0.500  1.0
  F  F20  1  0.437  0.610  0.500  1.0
  F  F21  1  0.601  0.906  0.500  1.0
  F  F22  1  0.655  0.159  0.000  1.0
  F  F23  1  0.837  0.844  0.000  1.0
  F  F24  1  0.879  0.082  0.500  1.0
[/CIF]
.
The crystal structure described by MgFe8(OF)8 crystallizes in the monoclinic Pm space group. Mg(1) is bonded to one O(1), two equivalent O(4), one F(4), and two equivalent F(1) atoms to form MgO3F3 octahedra that share corners with two equivalent Fe(2)O5 square pyramids,  a cornercorner with one Fe(3)O3F tetrahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. There are eight inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(3), two equivalent O(2), one F(7), and two equivalent F(8) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(1)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 48-49°. In the second Fe site, Fe(2) is bonded to one O(7), two equivalent O(1), and two equivalent O(8) atoms to form distorted FeO5 square pyramids that share corners with two equivalent Mg(1)O3F3 octahedra, corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(2)O5 square pyramids. The corner-sharing octahedral tilt angles range from 52-76°. In the third Fe site, Fe(3) is bonded to one O(1), two equivalent O(3), and one F(3) atom to form FeO3F tetrahedra that share  a cornercorner with one Mg(1)O3F3 octahedra, corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and corners with two equivalent Fe(3)O3F tetrahedra. The corner-sharing octahedral tilt angles range from 49-77°. In the fourth Fe site, Fe(4) is bonded in a 6-coordinate geometry to one O(2), two equivalent O(4), one F(4), and two equivalent F(2) atoms. In the fifth Fe site, Fe(5) is bonded to one O(6), two equivalent O(5), one F(1), and two equivalent F(4) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, edges with two equivalent Mg(1)O3F3 octahedra, and edges with two equivalent Fe(5)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 54-55°. In the sixth Fe site, Fe(6) is bonded to one F(2), one F(6), two equivalent F(3), and two equivalent F(5) atoms to form FeF6 octahedra that share corners with two equivalent Fe(7)O3F3 octahedra, corners with two equivalent Fe(8)O3F3 octahedra, corners with two equivalent Fe(3)O3F tetrahedra, and edges with two equivalent Fe(6)F6 octahedra. The corner-sharing octahedral tilt angles range from 46-48°. In the seventh Fe site, Fe(7) is bonded to one O(5), two equivalent O(7), one F(8), and two equivalent F(6) atoms to form FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and edges with two equivalent Fe(7)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 46-55°. In the eighth Fe site, Fe(8) is bonded to one O(8), two equivalent O(6), one F(5), and two equivalent F(7) atoms to form distorted FeO3F3 octahedra that share corners with two equivalent Fe(6)F6 octahedra, corners with two equivalent Fe(1)O3F3 octahedra, corners with two equivalent Fe(5)O3F3 octahedra, corners with two equivalent Fe(2)O5 square pyramids, and edges with two equivalent Fe(8)O3F3 octahedra. The corner-sharing octahedral tilt angles range from 48-54°. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(3), and two equivalent Fe(2) atoms to form corner-sharing OMgFe3 tetrahedra. In the second O site, O(2) is bonded in a trigonal planar geometry to one Fe(4) and two equivalent Fe(1) atoms. In the third O site, O(3) is bonded in a trigonal planar geometry to one Fe(1) and two equivalent Fe(3) atoms. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to two equivalent Mg(1) and two equivalent Fe(4) atoms. In the fifth O site, O(5) is bonded in a trigonal planar geometry to one Fe(7) and two equivalent Fe(5) atoms. In the sixth O site, O(6) is bonded in a trigonal planar geometry to one Fe(5) and two equivalent Fe(8) atoms. In the seventh O site, O(7) is bonded in a trigonal planar geometry to one Fe(2) and two equivalent Fe(7) atoms. In the eighth O site, O(8) is bonded in a trigonal planar geometry to one Fe(8) and two equivalent Fe(2) atoms. There are eight inequivalent F sites. In the first F site, F(1) is bonded in a distorted trigonal non-coplanar geometry to two equivalent Mg(1) and one Fe(5) atom. In the second F site, F(2) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(4) atoms. In the third F site, F(3) is bonded in a distorted T-shaped geometry to one Fe(3) and two equivalent Fe(6) atoms. In the fourth F site, F(4) is bonded in a 4-coordinate geometry to one Mg(1), one Fe(4), and two equivalent Fe(5) atoms. In the fifth F site, F(5) is bonded in a 3-coordinate geometry to one Fe(8) and two equivalent Fe(6) atoms. In the sixth F site, F(6) is bonded in a distorted T-shaped geometry to one Fe(6) and two equivalent Fe(7) atoms. In the seventh F site, F(7) is bonded in a distorted trigonal planar geometry to one Fe(1) and two equivalent Fe(8) atoms. In the eighth F site, F(8) is bonded in a distorted T-shaped geometry to one Fe(7) and two equivalent Fe(1) atoms. is represented by the CIF card [CIF]
data_MgFe8(OF)8
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   9.913
_cell_length_b   9.871
_cell_length_c   3.066
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   86.749
_symmetry_Int_Tables_number   1
_cell_volume   299.517
_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  0.263  0.507  0.500  1.0
  Fe  Fe1  1  0.996  0.982  0.000  1.0
  Fe  Fe2  1  0.982  0.474  0.000  1.0
  Fe  Fe3  1  0.190  0.207  0.500  1.0
  Fe  Fe4  1  0.235  0.773  0.500  1.0
  Fe  Fe5  1  0.552  0.506  0.000  1.0
  Fe  Fe6  1  0.501  0.010  0.000  1.0
  Fe  Fe7  1  0.758  0.263  0.500  1.0
  Fe  Fe8  1  0.763  0.721  0.500  1.0
  O  O9  1  0.106  0.393  0.500  1.0
  O  O10  1  0.071  0.890  0.500  1.0
  O  O11  1  0.119  0.125  0.000  1.0
  O  O12  1  0.202  0.640  0.000  1.0
  O  O13  1  0.612  0.402  0.500  1.0
  O  O14  1  0.668  0.653  0.000  1.0
  O  O15  1  0.854  0.332  0.000  1.0
  O  O16  1  0.911  0.586  0.500  1.0
  F  F17  1  0.362  0.405  0.000  1.0
  F  F18  1  0.342  0.872  0.000  1.0
  F  F19  1  0.387  0.120  0.500  1.0
  F  F20  1  0.437  0.610  0.500  1.0
  F  F21  1  0.601  0.906  0.500  1.0
  F  F22  1  0.655  0.159  0.000  1.0
  F  F23  1  0.837  0.844  0.000  1.0
  F  F24  1  0.879  0.082  0.500  1.0
[/CIF]
.