DOE OSTI2020
CuFe2O4 is Spinel-like structured and crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are nine inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with three CuO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–58°. There are a spread of Fe–O bond distances ranging from 1.91–1.98 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two equivalent CuO4 tetrahedra, corners with four FeO4 tetrahedra, edges with three FeO6 octahedra, and edges with three CuO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.02–2.08 Å. In the third Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with three equivalent FeO4 tetrahedra, corners with three equivalent CuO4 tetrahedra, edges with two CuO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.13 Å. In the fourth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 53–60°. There are a spread of Fe–O bond distances ranging from 1.92–1.94 Å. In the fifth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra, edges with two equivalent FeO6 octahedra, and edges with four CuO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.03–2.09 Å. In the sixth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 53–59°. There are a spread of Fe–O bond distances ranging from 1.91–1.93 Å. In the seventh Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Fe–O bond distances ranging from 1.91–1.94 Å. In the eighth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one CuO4 tetrahedra, corners with five FeO4 tetrahedra, edges with three FeO6 octahedra, and edges with three CuO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.08 Å. In the ninth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with six FeO6 octahedra and corners with six CuO6 octahedra. The corner-sharing octahedra tilt angles range from 53–59°. There are a spread of Fe–O bond distances ranging from 1.91–1.96 Å. There are six inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded to four O2- atoms to form CuO4 tetrahedra that share corners with three CuO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 56–59°. There are a spread of Cu–O bond distances ranging from 1.99–2.03 Å. In the second Cu2+ site, Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with two equivalent CuO4 tetrahedra, corners with four FeO4 tetrahedra, an edgeedge with one CuO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.03–2.21 Å. In the third Cu2+ site, Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six FeO4 tetrahedra, edges with two CuO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.01–2.34 Å. In the fourth Cu2+ site, Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six FeO4 tetrahedra, edges with two CuO6 octahedra, and edges with four equivalent FeO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.02–2.28 Å. In the fifth Cu2+ site, Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six FeO4 tetrahedra, edges with two CuO6 octahedra, and edges with four FeO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.00–2.34 Å. In the sixth Cu2+ site, Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share a cornercorner with one CuO4 tetrahedra, corners with five FeO4 tetrahedra, an edgeedge with one CuO6 octahedra, and edges with five FeO6 octahedra. There are a spread of Cu–O bond distances ranging from 2.07–2.18 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Fe3+ and one Cu2+ atom to form a mixture of distorted corner and edge-sharing OFe3Cu trigonal pyramids. In the second O2- site, O2- is bonded to two Fe3+ and two Cu2+ atoms to form a mixture of distorted corner and edge-sharing OFe2Cu2 trigonal pyramids. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the fourth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Cu2+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the seventh O2- site, O2- is bonded to two Fe3+ and two Cu2+ atoms to form a mixture of distorted corner and edge-sharing OFe2Cu2 trigonal pyramids. In the eighth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the tenth O2- site, O2- is bonded to two Fe3+ and two Cu2+ atoms to form a mixture of distorted corner and edge-sharing OFe2Cu2 trigonal pyramids. In the eleventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the twelfth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Fe3+ and two Cu2+ atoms. In the fourteenth O2- site, O2- is bonded to two equivalent Fe3+ and two Cu2+ atoms to form distorted corner-sharing OFe2Cu2 trigonal pyramids. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the sixteenth O2- site, O2- is bonded to three Fe3+ and one Cu2+ atom to form a mixture of distorted corner and edge-sharing OFe3Cu trigonal pyramids. In the seventeenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Fe3+ and one Cu2+ atom. In the eighteenth O2- site, O2- is bonded to four Fe3+ atoms to form a mixture of distorted corner and edge-sharing OFe4 trigonal pyramids.