The crystal structure described by CaFeO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form CaO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 trigonal pyramids, edges with four equivalent Ca(1)O6 octahedra, edges with two equivalent Fe(2)O4 tetrahedra, and edges with three equivalent Fe(1)O4 trigonal pyramids. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form FeO4 trigonal pyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with three equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 trigonal pyramids, and edges with three equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-11°. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form distorted FeO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with three equivalent Fe(1)O4 trigonal pyramids, and edges with two equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Fe(2), and two equivalent Fe(1) atoms to form OCa3Fe3 octahedra that share corners with two equivalent O(3)Ca4Fe square pyramids,  a cornercorner with one O(4)Ca2Fe2 tetrahedra, edges with four equivalent O(1)Ca3Fe3 octahedra, edges with three equivalent O(3)Ca4Fe square pyramids, and edges with two equivalent O(4)Ca2Fe2 tetrahedra. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Fe(1) atom to form OCa4Fe square pyramids that share corners with two equivalent O(1)Ca3Fe3 octahedra, corners with four equivalent O(4)Ca2Fe2 tetrahedra, edges with three equivalent O(1)Ca3Fe3 octahedra, and edges with two equivalent O(3)Ca4Fe square pyramids. The corner-sharing octahedral tilt angles range from 11-13°. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), and two equivalent Fe(2) atoms to form distorted OCa2Fe2 tetrahedra that share  a cornercorner with one O(1)Ca3Fe3 octahedra, corners with four equivalent O(3)Ca4Fe square pyramids, corners with two equivalent O(4)Ca2Fe2 tetrahedra, and edges with two equivalent O(1)Ca3Fe3 octahedra. The corner-sharing octahedral tilt angles are 17°. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaFeO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.327
_cell_length_b   8.259
_cell_length_c   8.800
_cell_angle_alpha   85.378
_cell_angle_beta   89.363
_cell_angle_gamma   84.198
_symmetry_Int_Tables_number   1
_cell_volume   239.759
_cell_formula_units_Z   4
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  0.186  0.198  0.961  1.0
  Ca  Ca1  1  0.814  0.802  0.039  1.0
  Ca  Ca2  1  0.129  0.400  0.272  1.0
  Ca  Ca3  1  0.871  0.600  0.728  1.0
  Fe  Fe4  1  0.317  0.915  0.731  1.0
  Fe  Fe5  1  0.655  0.240  0.639  1.0
  Fe  Fe6  1  0.345  0.760  0.361  1.0
  Fe  Fe7  1  0.683  0.085  0.269  1.0
  O  O8  1  0.248  0.966  0.178  1.0
  O  O9  1  0.320  0.751  0.581  1.0
  O  O10  1  0.680  0.249  0.419  1.0
  O  O11  1  0.752  0.034  0.822  1.0
  O  O12  1  0.339  0.706  0.893  1.0
  O  O13  1  0.153  0.341  0.725  1.0
  O  O14  1  0.661  0.294  0.107  1.0
  O  O15  1  0.847  0.659  0.275  1.0
[/CIF]
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The crystal structure described by CaFeO2 crystallizes in the triclinic P-1 space group. There are two inequivalent Ca sites. In the first Ca site, Ca(1) is bonded to one O(4), two equivalent O(3), and three equivalent O(1) atoms to form CaO6 octahedra that share  a cornercorner with one Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 trigonal pyramids, edges with four equivalent Ca(1)O6 octahedra, edges with two equivalent Fe(2)O4 tetrahedra, and edges with three equivalent Fe(1)O4 trigonal pyramids. In the second Ca site, Ca(2) is bonded in a 5-coordinate geometry to one O(4), two equivalent O(2), and two equivalent O(3) atoms. There are two inequivalent Fe sites. In the first Fe site, Fe(1) is bonded to one O(2), one O(3), and two equivalent O(1) atoms to form FeO4 trigonal pyramids that share corners with two equivalent Ca(1)O6 octahedra, corners with three equivalent Fe(2)O4 tetrahedra, corners with two equivalent Fe(1)O4 trigonal pyramids, and edges with three equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 10-11°. In the second Fe site, Fe(2) is bonded to one O(1), one O(2), and two equivalent O(4) atoms to form distorted FeO4 tetrahedra that share  a cornercorner with one Ca(1)O6 octahedra, corners with two equivalent Fe(2)O4 tetrahedra, corners with three equivalent Fe(1)O4 trigonal pyramids, and edges with two equivalent Ca(1)O6 octahedra. The corner-sharing octahedral tilt angles are 4°. There are four inequivalent O sites. In the first O site, O(1) is bonded to three equivalent Ca(1), one Fe(2), and two equivalent Fe(1) atoms to form OCa3Fe3 octahedra that share corners with two equivalent O(3)Ca4Fe square pyramids,  a cornercorner with one O(4)Ca2Fe2 tetrahedra, edges with four equivalent O(1)Ca3Fe3 octahedra, edges with three equivalent O(3)Ca4Fe square pyramids, and edges with two equivalent O(4)Ca2Fe2 tetrahedra. In the second O site, O(2) is bonded in a rectangular see-saw-like geometry to two equivalent Ca(2), one Fe(1), and one Fe(2) atom. In the third O site, O(3) is bonded to two equivalent Ca(1), two equivalent Ca(2), and one Fe(1) atom to form OCa4Fe square pyramids that share corners with two equivalent O(1)Ca3Fe3 octahedra, corners with four equivalent O(4)Ca2Fe2 tetrahedra, edges with three equivalent O(1)Ca3Fe3 octahedra, and edges with two equivalent O(3)Ca4Fe square pyramids. The corner-sharing octahedral tilt angles range from 11-13°. In the fourth O site, O(4) is bonded to one Ca(1), one Ca(2), and two equivalent Fe(2) atoms to form distorted OCa2Fe2 tetrahedra that share  a cornercorner with one O(1)Ca3Fe3 octahedra, corners with four equivalent O(3)Ca4Fe square pyramids, corners with two equivalent O(4)Ca2Fe2 tetrahedra, and edges with two equivalent O(1)Ca3Fe3 octahedra. The corner-sharing octahedral tilt angles are 17°. is represented by the Crystallographic Information File (CIF) [CIF]
data_CaFeO2
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   3.327
_cell_length_b   8.259
_cell_length_c   8.800
_cell_angle_alpha   85.378
_cell_angle_beta   89.363
_cell_angle_gamma   84.198
_symmetry_Int_Tables_number   1
_cell_volume   239.759
_cell_formula_units_Z   4
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  0.186  0.198  0.961  1.0
  Ca  Ca1  1  0.814  0.802  0.039  1.0
  Ca  Ca2  1  0.129  0.400  0.272  1.0
  Ca  Ca3  1  0.871  0.600  0.728  1.0
  Fe  Fe4  1  0.317  0.915  0.731  1.0
  Fe  Fe5  1  0.655  0.240  0.639  1.0
  Fe  Fe6  1  0.345  0.760  0.361  1.0
  Fe  Fe7  1  0.683  0.085  0.269  1.0
  O  O8  1  0.248  0.966  0.178  1.0
  O  O9  1  0.320  0.751  0.581  1.0
  O  O10  1  0.680  0.249  0.419  1.0
  O  O11  1  0.752  0.034  0.822  1.0
  O  O12  1  0.339  0.706  0.893  1.0
  O  O13  1  0.153  0.341  0.725  1.0
  O  O14  1  0.661  0.294  0.107  1.0
  O  O15  1  0.847  0.659  0.275  1.0
[/CIF]
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