The structure described by CaFe2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(10) and three equivalent O(1) atoms to form CaO4 tetrahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Fe(4)O6 octahedra, and corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-68°. In the second Ca site, Ca(2) is bonded to one O(2) and three equivalent O(4) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-61°. In the third Ca site, Ca(3) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form CaO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with three equivalent Fe(4)O6 octahedra. In the fourth Ca site, Ca(4) is bonded to one O(6) and three equivalent O(8) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(5)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. In the fifth Ca site, Ca(5) is bonded to one O(9) and three equivalent O(3) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-64°. In the sixth Ca site, Ca(6) is bonded to one O(12) and three equivalent O(7) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(4)O6 octahedra, corners with three equivalent Fe(5)O6 octahedra, and corners with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-65°. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(2)O4 tetrahedra,  a cornercorner with one Fe(6)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ca(5)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with four equivalent Fe(1)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(6), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(4)O4 tetrahedra,  a cornercorner with one Ca(5)O4 tetrahedra, corners with two equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ca(6)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. In the third Fe site, Fe(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form FeO6 octahedra that share corners with three equivalent Ca(2)O4 tetrahedra, corners with three equivalent Ca(5)O4 tetrahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with three equivalent Fe(2)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ca(6)O4 tetrahedra, corners with two equivalent Ca(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. In the fifth Fe site, Fe(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form FeO6 octahedra that share corners with three equivalent Ca(4)O4 tetrahedra, corners with three equivalent Ca(6)O4 tetrahedra, edges with three equivalent Fe(2)O6 octahedra, and edges with three equivalent Fe(4)O6 octahedra. In the sixth Fe site, Fe(6) is bonded to one O(5) and three equivalent O(11) atoms to form FeO4 tetrahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-63°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), and two equivalent Fe(1) atoms to form OCa2Fe2 trigonal pyramids that share corners with four equivalent O(3)CaFe3 tetrahedra,  a cornercorner with one O(10)CaFe3 trigonal pyramid, corners with two equivalent O(1)Ca2Fe2 trigonal pyramids,  an edgeedge with one O(2)CaFe3 trigonal pyramid, and edges with two equivalent O(1)Ca2Fe2 trigonal pyramids. In the second O site, O(2) is bonded to one Ca(2) and three equivalent Fe(1) atoms to form distorted OCaFe3 trigonal pyramids that share corners with three equivalent O(4)CaFe3 tetrahedra, corners with six equivalent O(3)CaFe3 tetrahedra, and edges with three equivalent O(1)Ca2Fe2 trigonal pyramids. In the third O site, O(3) is bonded to one Ca(5), one Fe(3), and two equivalent Fe(1) atoms to form OCaFe3 tetrahedra that share  a cornercorner with one O(9)CaFe3 tetrahedra, corners with two equivalent O(3)CaFe3 tetrahedra, corners with three equivalent O(4)CaFe3 tetrahedra, corners with two equivalent O(2)CaFe3 trigonal pyramids, corners with four equivalent O(1)Ca2Fe2 trigonal pyramids, and edges with two equivalent O(3)CaFe3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(2), one Fe(3), and two equivalent Fe(2) atoms to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(6) and three equivalent Fe(1) atoms. In the sixth O site, O(6) is bonded to one Ca(4) and three equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(6), one Fe(5), and two equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the eighth O site, O(8) is bonded to one Ca(4), one Fe(5), and two equivalent Fe(4) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the ninth O site, O(9) is bonded to one Ca(5) and three equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the tenth O site, O(10) is bonded to one Ca(1) and three equivalent Fe(4) atoms to form distorted OCaFe3 trigonal pyramids that share corners with three equivalent O(12)CaFe3 tetrahedra, corners with three equivalent O(1)Ca2Fe2 trigonal pyramids, and edges with three equivalent O(8)CaFe3 tetrahedra. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Fe(6), and two equivalent Fe(4) atoms. In the twelfth O site, O(12) is bonded to one Ca(6) and three equivalent Fe(4) atoms to form corner-sharing OCaFe3 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca(FeO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.283
_cell_length_b   6.283
_cell_length_c   15.451
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   528.274
_cell_formula_units_Z   6
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
  Ca  Ca0  1  0.333  0.667  0.043  1.0
  Ca  Ca1  1  0.667  0.333  0.379  1.0
  Ca  Ca2  1  0.667  0.333  0.002  1.0
  Ca  Ca3  1  0.000  0.000  0.712  1.0
  Ca  Ca4  1  0.333  0.667  0.286  1.0
  Ca  Ca5  1  0.667  0.333  0.627  1.0
  Fe  Fe6  1  0.831  0.661  0.169  1.0
  Fe  Fe7  1  0.831  0.169  0.169  1.0
  Fe  Fe8  1  0.166  0.332  0.500  1.0
  Fe  Fe9  1  0.339  0.169  0.169  1.0
  Fe  Fe10  1  0.000  0.000  0.333  1.0
  Fe  Fe11  1  0.166  0.834  0.500  1.0
  Fe  Fe12  1  0.495  0.990  0.830  1.0
  Fe  Fe13  1  0.668  0.834  0.500  1.0
  Fe  Fe14  1  0.010  0.505  0.830  1.0
  Fe  Fe15  1  0.333  0.667  0.662  1.0
  Fe  Fe16  1  0.495  0.505  0.830  1.0
  Fe  Fe17  1  0.000  0.000  0.953  1.0
  O  O18  1  0.515  0.485  0.103  1.0
  O  O19  1  0.667  0.333  0.238  1.0
  O  O20  1  0.970  0.485  0.103  1.0
  O  O21  1  0.515  0.030  0.103  1.0
  O  O22  1  0.139  0.278  0.245  1.0
  O  O23  1  0.857  0.143  0.425  1.0
  O  O24  1  0.722  0.861  0.245  1.0
  O  O25  1  0.000  0.000  0.080  1.0
  O  O26  1  0.285  0.143  0.425  1.0
  O  O27  1  0.000  0.000  0.568  1.0
  O  O28  1  0.139  0.861  0.245  1.0
  O  O29  1  0.857  0.715  0.425  1.0
  O  O30  1  0.477  0.954  0.577  1.0
  O  O31  1  0.193  0.807  0.753  1.0
  O  O32  1  0.046  0.523  0.577  1.0
  O  O33  1  0.333  0.667  0.432  1.0
  O  O34  1  0.333  0.667  0.898  1.0
  O  O35  1  0.615  0.807  0.753  1.0
  O  O36  1  0.477  0.523  0.577  1.0
  O  O37  1  0.193  0.385  0.753  1.0
  O  O38  1  0.833  0.666  0.903  1.0
  O  O39  1  0.667  0.333  0.773  1.0
  O  O40  1  0.334  0.167  0.903  1.0
  O  O41  1  0.833  0.167  0.903  1.0
[/CIF]
.
The structure described by CaFe2O4 is Spinel-like structured and crystallizes in the trigonal P3m1 space group. There are six inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(10) and three equivalent O(1) atoms to form CaO4 tetrahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Fe(4)O6 octahedra, and corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 56-68°. In the second Ca site, Ca(2) is bonded to one O(2) and three equivalent O(4) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 59-61°. In the third Ca site, Ca(3) is bonded to three equivalent O(1) and three equivalent O(11) atoms to form CaO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Fe(6)O4 tetrahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with three equivalent Fe(4)O6 octahedra. In the fourth Ca site, Ca(4) is bonded to one O(6) and three equivalent O(8) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(5)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-62°. In the fifth Ca site, Ca(5) is bonded to one O(9) and three equivalent O(3) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with six equivalent Fe(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 58-64°. In the sixth Ca site, Ca(6) is bonded to one O(12) and three equivalent O(7) atoms to form CaO4 tetrahedra that share corners with three equivalent Fe(4)O6 octahedra, corners with three equivalent Fe(5)O6 octahedra, and corners with six equivalent Fe(2)O6 octahedra. The corner-sharing octahedral tilt angles range from 60-65°. There are six inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(5), two equivalent O(1), and two equivalent O(3) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(2)O4 tetrahedra,  a cornercorner with one Fe(6)O4 tetrahedra, corners with two equivalent Ca(1)O4 tetrahedra, corners with two equivalent Ca(5)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Fe(3)O6 octahedra, and edges with four equivalent Fe(1)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(6), one O(9), two equivalent O(4), and two equivalent O(7) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(4)O4 tetrahedra,  a cornercorner with one Ca(5)O4 tetrahedra, corners with two equivalent Ca(2)O4 tetrahedra, corners with two equivalent Ca(6)O4 tetrahedra,  an edgeedge with one Fe(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra, and edges with four equivalent Fe(2)O6 octahedra. In the third Fe site, Fe(3) is bonded to three equivalent O(3) and three equivalent O(4) atoms to form FeO6 octahedra that share corners with three equivalent Ca(2)O4 tetrahedra, corners with three equivalent Ca(5)O4 tetrahedra, edges with three equivalent Fe(1)O6 octahedra, and edges with three equivalent Fe(2)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(10), one O(12), two equivalent O(11), and two equivalent O(8) atoms to form FeO6 octahedra that share  a cornercorner with one Ca(1)O4 tetrahedra,  a cornercorner with one Ca(6)O4 tetrahedra, corners with two equivalent Ca(4)O4 tetrahedra, corners with two equivalent Fe(6)O4 tetrahedra,  an edgeedge with one Ca(3)O6 octahedra,  an edgeedge with one Fe(5)O6 octahedra, and edges with four equivalent Fe(4)O6 octahedra. In the fifth Fe site, Fe(5) is bonded to three equivalent O(7) and three equivalent O(8) atoms to form FeO6 octahedra that share corners with three equivalent Ca(4)O4 tetrahedra, corners with three equivalent Ca(6)O4 tetrahedra, edges with three equivalent Fe(2)O6 octahedra, and edges with three equivalent Fe(4)O6 octahedra. In the sixth Fe site, Fe(6) is bonded to one O(5) and three equivalent O(11) atoms to form FeO4 tetrahedra that share corners with three equivalent Ca(3)O6 octahedra, corners with three equivalent Fe(1)O6 octahedra, and corners with six equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-63°. There are twelve inequivalent O sites. In the first O site, O(1) is bonded to one Ca(1), one Ca(3), and two equivalent Fe(1) atoms to form OCa2Fe2 trigonal pyramids that share corners with four equivalent O(3)CaFe3 tetrahedra,  a cornercorner with one O(10)CaFe3 trigonal pyramid, corners with two equivalent O(1)Ca2Fe2 trigonal pyramids,  an edgeedge with one O(2)CaFe3 trigonal pyramid, and edges with two equivalent O(1)Ca2Fe2 trigonal pyramids. In the second O site, O(2) is bonded to one Ca(2) and three equivalent Fe(1) atoms to form distorted OCaFe3 trigonal pyramids that share corners with three equivalent O(4)CaFe3 tetrahedra, corners with six equivalent O(3)CaFe3 tetrahedra, and edges with three equivalent O(1)Ca2Fe2 trigonal pyramids. In the third O site, O(3) is bonded to one Ca(5), one Fe(3), and two equivalent Fe(1) atoms to form OCaFe3 tetrahedra that share  a cornercorner with one O(9)CaFe3 tetrahedra, corners with two equivalent O(3)CaFe3 tetrahedra, corners with three equivalent O(4)CaFe3 tetrahedra, corners with two equivalent O(2)CaFe3 trigonal pyramids, corners with four equivalent O(1)Ca2Fe2 trigonal pyramids, and edges with two equivalent O(3)CaFe3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(2), one Fe(3), and two equivalent Fe(2) atoms to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the fifth O site, O(5) is bonded in a rectangular see-saw-like geometry to one Fe(6) and three equivalent Fe(1) atoms. In the sixth O site, O(6) is bonded to one Ca(4) and three equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the seventh O site, O(7) is bonded to one Ca(6), one Fe(5), and two equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the eighth O site, O(8) is bonded to one Ca(4), one Fe(5), and two equivalent Fe(4) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the ninth O site, O(9) is bonded to one Ca(5) and three equivalent Fe(2) atoms to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the tenth O site, O(10) is bonded to one Ca(1) and three equivalent Fe(4) atoms to form distorted OCaFe3 trigonal pyramids that share corners with three equivalent O(12)CaFe3 tetrahedra, corners with three equivalent O(1)Ca2Fe2 trigonal pyramids, and edges with three equivalent O(8)CaFe3 tetrahedra. In the eleventh O site, O(11) is bonded in a rectangular see-saw-like geometry to one Ca(3), one Fe(6), and two equivalent Fe(4) atoms. In the twelfth O site, O(12) is bonded to one Ca(6) and three equivalent Fe(4) atoms to form corner-sharing OCaFe3 tetrahedra. is represented by the Crystallographic Information File (CIF) [CIF]
data_Ca(FeO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.283
_cell_length_b   6.283
_cell_length_c   15.451
_cell_angle_alpha   90.000
_cell_angle_beta   90.000
_cell_angle_gamma   120.000
_symmetry_Int_Tables_number   1
_cell_volume   528.274
_cell_formula_units_Z   6
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
  Ca  Ca0  1  0.333  0.667  0.043  1.0
  Ca  Ca1  1  0.667  0.333  0.379  1.0
  Ca  Ca2  1  0.667  0.333  0.002  1.0
  Ca  Ca3  1  0.000  0.000  0.712  1.0
  Ca  Ca4  1  0.333  0.667  0.286  1.0
  Ca  Ca5  1  0.667  0.333  0.627  1.0
  Fe  Fe6  1  0.831  0.661  0.169  1.0
  Fe  Fe7  1  0.831  0.169  0.169  1.0
  Fe  Fe8  1  0.166  0.332  0.500  1.0
  Fe  Fe9  1  0.339  0.169  0.169  1.0
  Fe  Fe10  1  0.000  0.000  0.333  1.0
  Fe  Fe11  1  0.166  0.834  0.500  1.0
  Fe  Fe12  1  0.495  0.990  0.830  1.0
  Fe  Fe13  1  0.668  0.834  0.500  1.0
  Fe  Fe14  1  0.010  0.505  0.830  1.0
  Fe  Fe15  1  0.333  0.667  0.662  1.0
  Fe  Fe16  1  0.495  0.505  0.830  1.0
  Fe  Fe17  1  0.000  0.000  0.953  1.0
  O  O18  1  0.515  0.485  0.103  1.0
  O  O19  1  0.667  0.333  0.238  1.0
  O  O20  1  0.970  0.485  0.103  1.0
  O  O21  1  0.515  0.030  0.103  1.0
  O  O22  1  0.139  0.278  0.245  1.0
  O  O23  1  0.857  0.143  0.425  1.0
  O  O24  1  0.722  0.861  0.245  1.0
  O  O25  1  0.000  0.000  0.080  1.0
  O  O26  1  0.285  0.143  0.425  1.0
  O  O27  1  0.000  0.000  0.568  1.0
  O  O28  1  0.139  0.861  0.245  1.0
  O  O29  1  0.857  0.715  0.425  1.0
  O  O30  1  0.477  0.954  0.577  1.0
  O  O31  1  0.193  0.807  0.753  1.0
  O  O32  1  0.046  0.523  0.577  1.0
  O  O33  1  0.333  0.667  0.432  1.0
  O  O34  1  0.333  0.667  0.898  1.0
  O  O35  1  0.615  0.807  0.753  1.0
  O  O36  1  0.477  0.523  0.577  1.0
  O  O37  1  0.193  0.385  0.753  1.0
  O  O38  1  0.833  0.666  0.903  1.0
  O  O39  1  0.667  0.333  0.773  1.0
  O  O40  1  0.334  0.167  0.903  1.0
  O  O41  1  0.833  0.167  0.903  1.0
[/CIF]
.