The compound described by MgFe4(NiO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(1), one Fe(2), one Ni(1), and one Ni(2) atom to form OMgFe2Ni2 square pyramids that share  a cornercorner with one O(2)MgFe3Ni square pyramid,  a cornercorner with one O(4)MgFe3Ni square pyramid, corners with four equivalent O(1)MgFe2Ni2 square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(2)MgFe3Ni square pyramids, edges with three equivalent O(4)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Ni(1) atom to form OMgFe3Ni square pyramids that share  a cornercorner with one O(1)MgFe2Ni2 square pyramid,  a cornercorner with one O(4)MgFe3Ni square pyramid, corners with four equivalent O(2)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(1)MgFe2Ni2 square pyramids, edges with three equivalent O(4)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. In the third O site, O(3) is bonded to one Fe(1), one Fe(3), one Ni(1), and one Ni(2) atom to form OFe2Ni2 tetrahedra that share corners with three equivalent O(1)MgFe2Ni2 square pyramids, corners with three equivalent O(2)MgFe3Ni square pyramids, corners with three equivalent O(4)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra,  an edgeedge with one O(1)MgFe2Ni2 square pyramid,  an edgeedge with one O(2)MgFe3Ni square pyramid, and  an edgeedge with one O(4)MgFe3Ni square pyramid. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Ni(2) atom to form OMgFe3Ni square pyramids that share  a cornercorner with one O(1)MgFe2Ni2 square pyramid,  a cornercorner with one O(2)MgFe3Ni square pyramid, corners with four equivalent O(4)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(1)MgFe2Ni2 square pyramids, edges with three equivalent O(2)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. is represented by the CIF card [CIF]
data_MgFe4(NiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.934
_cell_length_b   6.332
_cell_length_c   5.938
_cell_angle_alpha   62.017
_cell_angle_beta   59.930
_cell_angle_gamma   62.049
_symmetry_Int_Tables_number   1
_cell_volume   162.343
_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  0.125  0.625  0.125  1.0
  Fe  Fe1  1  0.971  0.098  0.964  1.0
  Fe  Fe2  1  0.279  0.152  0.286  1.0
  Fe  Fe3  1  0.625  0.125  0.625  1.0
  Fe  Fe4  1  0.625  0.625  0.625  1.0
  Ni  Ni5  1  0.125  0.625  0.625  1.0
  Ni  Ni6  1  0.625  0.625  0.125  1.0
  O  O7  1  0.385  0.369  0.385  1.0
  O  O8  1  0.382  0.382  0.870  1.0
  O  O9  1  0.403  0.798  0.402  1.0
  O  O10  1  0.871  0.381  0.381  1.0
  O  O11  1  0.379  0.869  0.869  1.0
  O  O12  1  0.847  0.452  0.848  1.0
  O  O13  1  0.868  0.868  0.380  1.0
  O  O14  1  0.865  0.881  0.865  1.0
[/CIF]
.
The compound described by MgFe4(NiO4)2 crystallizes in the triclinic P-1 space group. Mg(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form MgO6 octahedra that share corners with six equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. There are three inequivalent Fe sites. In the first Fe site, Fe(1) is bonded in a rectangular see-saw-like geometry to one O(1), one O(2), one O(3), and one O(4) atom. In the second Fe site, Fe(2) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form FeO6 octahedra that share corners with six equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-3°. In the third Fe site, Fe(3) is bonded to two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form FeO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Ni(1)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. There are two inequivalent Ni sites. In the first Ni site, Ni(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Ni(2)O6 octahedra. In the second Ni site, Ni(2) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(4) atoms to form NiO6 octahedra that share edges with two equivalent Mg(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Ni(1)O6 octahedra. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Mg(1), one Fe(1), one Fe(2), one Ni(1), and one Ni(2) atom to form OMgFe2Ni2 square pyramids that share  a cornercorner with one O(2)MgFe3Ni square pyramid,  a cornercorner with one O(4)MgFe3Ni square pyramid, corners with four equivalent O(1)MgFe2Ni2 square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(2)MgFe3Ni square pyramids, edges with three equivalent O(4)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. In the second O site, O(2) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Ni(1) atom to form OMgFe3Ni square pyramids that share  a cornercorner with one O(1)MgFe2Ni2 square pyramid,  a cornercorner with one O(4)MgFe3Ni square pyramid, corners with four equivalent O(2)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(1)MgFe2Ni2 square pyramids, edges with three equivalent O(4)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. In the third O site, O(3) is bonded to one Fe(1), one Fe(3), one Ni(1), and one Ni(2) atom to form OFe2Ni2 tetrahedra that share corners with three equivalent O(1)MgFe2Ni2 square pyramids, corners with three equivalent O(2)MgFe3Ni square pyramids, corners with three equivalent O(4)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra,  an edgeedge with one O(1)MgFe2Ni2 square pyramid,  an edgeedge with one O(2)MgFe3Ni square pyramid, and  an edgeedge with one O(4)MgFe3Ni square pyramid. In the fourth O site, O(4) is bonded to one Mg(1), one Fe(1), one Fe(2), one Fe(3), and one Ni(2) atom to form OMgFe3Ni square pyramids that share  a cornercorner with one O(1)MgFe2Ni2 square pyramid,  a cornercorner with one O(2)MgFe3Ni square pyramid, corners with four equivalent O(4)MgFe3Ni square pyramids, corners with three equivalent O(3)Fe2Ni2 tetrahedra, edges with three equivalent O(1)MgFe2Ni2 square pyramids, edges with three equivalent O(2)MgFe3Ni square pyramids, and  an edgeedge with one O(3)Fe2Ni2 tetrahedra. is represented by the CIF card [CIF]
data_MgFe4(NiO4)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   5.934
_cell_length_b   6.332
_cell_length_c   5.938
_cell_angle_alpha   62.017
_cell_angle_beta   59.930
_cell_angle_gamma   62.049
_symmetry_Int_Tables_number   1
_cell_volume   162.343
_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  0.125  0.625  0.125  1.0
  Fe  Fe1  1  0.971  0.098  0.964  1.0
  Fe  Fe2  1  0.279  0.152  0.286  1.0
  Fe  Fe3  1  0.625  0.125  0.625  1.0
  Fe  Fe4  1  0.625  0.625  0.625  1.0
  Ni  Ni5  1  0.125  0.625  0.625  1.0
  Ni  Ni6  1  0.625  0.625  0.125  1.0
  O  O7  1  0.385  0.369  0.385  1.0
  O  O8  1  0.382  0.382  0.870  1.0
  O  O9  1  0.403  0.798  0.402  1.0
  O  O10  1  0.871  0.381  0.381  1.0
  O  O11  1  0.379  0.869  0.869  1.0
  O  O12  1  0.847  0.452  0.848  1.0
  O  O13  1  0.868  0.868  0.380  1.0
  O  O14  1  0.865  0.881  0.865  1.0
[/CIF]
.