The crystal structure described by CaFe2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with three equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-67°. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with three equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-67°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(8) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the third Fe site, Fe(3) is bonded to one O(1), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form distorted FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(8) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), one Fe(1), one Fe(3), and one Fe(4) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Fe(1), one Fe(2), and one Fe(4) atom. In the third O site, O(3) is bonded to one Ca(2), one Fe(1), one Fe(2), and one Fe(3) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(1), one Fe(2), one Fe(3), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the fifth O site, O(5) is bonded to one Ca(1), one Fe(1), one Fe(2), and one Fe(3) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the sixth O site, O(6) is bonded to one Ca(1), one Fe(1), one Fe(2), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the seventh O site, O(7) is bonded to one Ca(2), one Fe(2), one Fe(3), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Fe(1), one Fe(3), and one Fe(4) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. is represented by the CIF file [CIF]
data_Ca(FeO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.225
_cell_length_b   6.233
_cell_length_c   6.313
_cell_angle_alpha   93.246
_cell_angle_beta   118.314
_cell_angle_gamma   118.853
_symmetry_Int_Tables_number   1
_cell_volume   175.451
_cell_formula_units_Z   2
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  0.257  0.137  0.878  1.0
  Ca  Ca1  1  0.743  0.862  0.122  1.0
  Fe  Fe2  1  0.500  1.000  0.500  1.0
  Fe  Fe3  1  0.498  0.500  0.499  1.0
  Fe  Fe4  1  1.000  0.500  0.001  1.0
  Fe  Fe5  1  0.001  0.500  0.499  1.0
  O  O6  1  0.033  0.720  0.262  1.0
  O  O7  1  0.468  0.753  0.699  1.0
  O  O8  1  0.440  0.705  0.251  1.0
  O  O9  1  0.950  0.714  0.699  1.0
  O  O10  1  0.560  0.295  0.749  1.0
  O  O11  1  0.532  0.247  0.300  1.0
  O  O12  1  0.052  0.288  0.303  1.0
  O  O13  1  0.967  0.279  0.737  1.0
[/CIF]
.
The crystal structure described by CaFe2O4 is Spinel structured and crystallizes in the triclinic P1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), one O(5), one O(6), and one O(8) atom to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with three equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-67°. In the second Ca site, Ca(2) is bonded to one O(1), one O(2), one O(3), and one O(7) atom to form CaO4 tetrahedra that share corners with three equivalent Fe(1)O6 octahedra, corners with three equivalent Fe(2)O6 octahedra, corners with three equivalent Fe(3)O6 octahedra, and corners with three equivalent Fe(4)O6 octahedra. The corner-sharing octahedral tilt angles range from 53-67°. There are four inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(1), one O(2), one O(3), one O(5), one O(6), and one O(8) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(2)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the second Fe site, Fe(2) is bonded to one O(2), one O(3), one O(4), one O(5), one O(6), and one O(7) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(3)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the third Fe site, Fe(3) is bonded to one O(1), one O(3), one O(4), one O(5), one O(7), and one O(8) atom to form distorted FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(4)O6 octahedra. In the fourth Fe site, Fe(4) is bonded to one O(1), one O(2), one O(4), one O(6), one O(7), and one O(8) atom to form FeO6 octahedra that share corners with three equivalent Ca(1)O4 tetrahedra, corners with three equivalent Ca(2)O4 tetrahedra, edges with two equivalent Fe(1)O6 octahedra, edges with two equivalent Fe(2)O6 octahedra, and edges with two equivalent Fe(3)O6 octahedra. There are eight inequivalent O sites. In the first O site, O(1) is bonded to one Ca(2), one Fe(1), one Fe(3), and one Fe(4) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the second O site, O(2) is bonded in a distorted rectangular see-saw-like geometry to one Ca(2), one Fe(1), one Fe(2), and one Fe(4) atom. In the third O site, O(3) is bonded to one Ca(2), one Fe(1), one Fe(2), and one Fe(3) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the fourth O site, O(4) is bonded to one Ca(1), one Fe(2), one Fe(3), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the fifth O site, O(5) is bonded to one Ca(1), one Fe(1), one Fe(2), and one Fe(3) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. In the sixth O site, O(6) is bonded to one Ca(1), one Fe(1), one Fe(2), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 tetrahedra. In the seventh O site, O(7) is bonded to one Ca(2), one Fe(2), one Fe(3), and one Fe(4) atom to form a mixture of distorted corner and edge-sharing OCaFe3 trigonal pyramids. In the eighth O site, O(8) is bonded to one Ca(1), one Fe(1), one Fe(3), and one Fe(4) atom to form a mixture of corner and edge-sharing OCaFe3 tetrahedra. is represented by the CIF file [CIF]
data_Ca(FeO2)2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   6.225
_cell_length_b   6.233
_cell_length_c   6.313
_cell_angle_alpha   93.246
_cell_angle_beta   118.314
_cell_angle_gamma   118.853
_symmetry_Int_Tables_number   1
_cell_volume   175.451
_cell_formula_units_Z   2
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  0.257  0.137  0.878  1.0
  Ca  Ca1  1  0.743  0.862  0.122  1.0
  Fe  Fe2  1  0.500  1.000  0.500  1.0
  Fe  Fe3  1  0.498  0.500  0.499  1.0
  Fe  Fe4  1  1.000  0.500  0.001  1.0
  Fe  Fe5  1  0.001  0.500  0.499  1.0
  O  O6  1  0.033  0.720  0.262  1.0
  O  O7  1  0.468  0.753  0.699  1.0
  O  O8  1  0.440  0.705  0.251  1.0
  O  O9  1  0.950  0.714  0.699  1.0
  O  O10  1  0.560  0.295  0.749  1.0
  O  O11  1  0.532  0.247  0.300  1.0
  O  O12  1  0.052  0.288  0.303  1.0
  O  O13  1  0.967  0.279  0.737  1.0
[/CIF]
.