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.
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°. The Ca(1)-O(4) bond length is 2.16 Å. The Ca(1)-O(5) bond length is 2.23 Å. The Ca(1)-O(6) bond length is 2.20 Å. The Ca(1)-O(8) bond length is 2.22 Å. 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°. The Ca(2)-O(1) bond length is 2.22 Å. The Ca(2)-O(2) bond length is 2.20 Å. The Ca(2)-O(3) bond length is 2.22 Å. The Ca(2)-O(7) bond length is 2.17 Å. 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. The Fe(1)-O(1) bond length is 2.10 Å. The Fe(1)-O(2) bond length is 2.03 Å. The Fe(1)-O(3) bond length is 2.11 Å. The Fe(1)-O(5) bond length is 2.11 Å. The Fe(1)-O(6) bond length is 2.04 Å. The Fe(1)-O(8) bond length is 2.10 Å. 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. The Fe(2)-O(2) bond length is 2.10 Å. The Fe(2)-O(3) bond length is 2.09 Å. The Fe(2)-O(4) bond length is 2.02 Å. The Fe(2)-O(5) bond length is 2.09 Å. The Fe(2)-O(6) bond length is 2.11 Å. The Fe(2)-O(7) bond length is 2.00 Å. 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. The Fe(3)-O(1) bond length is 1.95 Å. The Fe(3)-O(3) bond length is 1.98 Å. The Fe(3)-O(4) bond length is 2.37 Å. The Fe(3)-O(5) bond length is 1.98 Å. The Fe(3)-O(7) bond length is 2.37 Å. The Fe(3)-O(8) bond length is 1.96 Å. 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. The Fe(4)-O(1) bond length is 2.10 Å. The Fe(4)-O(2) bond length is 2.10 Å. The Fe(4)-O(4) bond length is 2.01 Å. The Fe(4)-O(6) bond length is 2.10 Å. The Fe(4)-O(7) bond length is 2.00 Å. The Fe(4)-O(8) bond length is 2.11 Å. 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.