The structure described by Na4Mg(FeO2)4 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the third Na site, Na(3) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share corners with two equivalent Fe(3)O4 tetrahedra and  an edgeedge with one Fe(1)O4 tetrahedra. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form FeO4 tetrahedra that share  an edgeedge with one Na(3)O4 tetrahedra. In the second Fe site, Fe(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the third Fe site, Fe(3) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form FeO4 tetrahedra that share corners with two equivalent Na(3)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one Na(3), one Mg(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgFe2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Fe(2), and one Fe(3) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Fe(2), and one Fe(3) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Mg(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgFe2 trigonal bipyramids. is represented by the CIF file [CIF]
data_Na4Mg(FeO2)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.808
_cell_length_b   5.808
_cell_length_c   7.268
_cell_angle_alpha   90.234
_cell_angle_beta   89.766
_cell_angle_gamma   87.899
_symmetry_Int_Tables_number   1
_cell_volume   245.040
_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
  Na  Na0  1  0.786  0.786  0.000  1.0
  Na  Na1  1  0.284  0.719  0.770  1.0
  Na  Na2  1  0.719  0.284  0.230  1.0
  Na  Na3  1  0.149  0.149  0.500  1.0
  Mg  Mg4  1  0.469  0.469  0.500  1.0
  Fe  Fe5  1  0.808  0.808  0.500  1.0
  Fe  Fe6  1  0.707  0.286  0.770  1.0
  Fe  Fe7  1  0.286  0.707  0.230  1.0
  Fe  Fe8  1  0.223  0.223  0.000  1.0
  O  O9  1  0.140  0.745  0.481  1.0
  O  O10  1  0.900  0.251  0.978  1.0
  O  O11  1  0.745  0.140  0.519  1.0
  O  O12  1  0.313  0.344  0.244  1.0
  O  O13  1  0.672  0.643  0.695  1.0
  O  O14  1  0.251  0.900  0.022  1.0
  O  O15  1  0.643  0.672  0.305  1.0
  O  O16  1  0.344  0.313  0.756  1.0
[/CIF]
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The structure described by Na4Mg(FeO2)4 crystallizes in the monoclinic C2 space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded in a 4-coordinate geometry to two equivalent O(2) and two equivalent O(4) atoms. In the second Na site, Na(2) is bonded in a 4-coordinate geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the third Na site, Na(3) is bonded to two equivalent O(1) and two equivalent O(3) atoms to form distorted NaO4 tetrahedra that share corners with two equivalent Fe(3)O4 tetrahedra and  an edgeedge with one Fe(1)O4 tetrahedra. Mg(1) is bonded in a 6-coordinate geometry to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to two equivalent O(1) and two equivalent O(4) atoms to form FeO4 tetrahedra that share  an edgeedge with one Na(3)O4 tetrahedra. In the second Fe site, Fe(2) is bonded in a distorted rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the third Fe site, Fe(3) is bonded to two equivalent O(2) and two equivalent O(3) atoms to form FeO4 tetrahedra that share corners with two equivalent Na(3)O4 tetrahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), one Na(3), one Mg(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgFe2 trigonal bipyramids. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Fe(2), and one Fe(3) atom. In the third O site, O(3) is bonded in a 5-coordinate geometry to one Na(2), one Na(3), one Mg(1), one Fe(2), and one Fe(3) atom. In the fourth O site, O(4) is bonded to one Na(1), one Na(2), one Mg(1), one Fe(1), and one Fe(2) atom to form a mixture of distorted edge and corner-sharing ONa2MgFe2 trigonal bipyramids. is represented by the CIF file [CIF]
data_Na4Mg(FeO2)4
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.808
_cell_length_b   5.808
_cell_length_c   7.268
_cell_angle_alpha   90.234
_cell_angle_beta   89.766
_cell_angle_gamma   87.899
_symmetry_Int_Tables_number   1
_cell_volume   245.040
_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
  Na  Na0  1  0.786  0.786  0.000  1.0
  Na  Na1  1  0.284  0.719  0.770  1.0
  Na  Na2  1  0.719  0.284  0.230  1.0
  Na  Na3  1  0.149  0.149  0.500  1.0
  Mg  Mg4  1  0.469  0.469  0.500  1.0
  Fe  Fe5  1  0.808  0.808  0.500  1.0
  Fe  Fe6  1  0.707  0.286  0.770  1.0
  Fe  Fe7  1  0.286  0.707  0.230  1.0
  Fe  Fe8  1  0.223  0.223  0.000  1.0
  O  O9  1  0.140  0.745  0.481  1.0
  O  O10  1  0.900  0.251  0.978  1.0
  O  O11  1  0.745  0.140  0.519  1.0
  O  O12  1  0.313  0.344  0.244  1.0
  O  O13  1  0.672  0.643  0.695  1.0
  O  O14  1  0.251  0.900  0.022  1.0
  O  O15  1  0.643  0.672  0.305  1.0
  O  O16  1  0.344  0.313  0.756  1.0
[/CIF]
.