DOE OSTI2020
CaFe3AlO7 is beta indium sulfide-derived structured and crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two FeO4 tetrahedra, corners with four AlO4 tetrahedra, edges with two CaO6 octahedra, and edges with three FeO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.26–2.40 Å. In the second Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.92 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with two FeO6 octahedra, corners with four AlO4 tetrahedra, edges with two CaO6 octahedra, and edges with four FeO6 octahedra. The corner-sharing octahedra tilt angles range from 16–21°. There are a spread of Ca–O bond distances ranging from 2.27–2.40 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.93 Å. There are twelve inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two AlO4 tetrahedra, corners with four FeO4 tetrahedra, and edges with four FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.02–2.11 Å. In the second Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two AlO4 tetrahedra, corners with three FeO4 tetrahedra, edges with three CaO6 octahedra, and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.96–2.16 Å. In the third Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with eight FeO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–64°. There are a spread of Fe–O bond distances ranging from 1.84–1.96 Å. In the fourth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with eight FeO6 octahedra and a cornercorner with one AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–64°. There are a spread of Fe–O bond distances ranging from 1.84–1.96 Å. In the fifth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 45–61°. There are a spread of Fe–O bond distances ranging from 1.83–2.00 Å. In the sixth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one AlO4 tetrahedra, corners with four FeO4 tetrahedra, and edges with five FeO6 octahedra. The corner-sharing octahedral tilt angles are 21°. There are a spread of Fe–O bond distances ranging from 1.95–2.18 Å. In the seventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one CaO6 octahedra, a cornercorner with one AlO4 tetrahedra, corners with four FeO4 tetrahedra, and edges with five FeO6 octahedra. The corner-sharing octahedral tilt angles are 16°. There are a spread of Fe–O bond distances ranging from 1.96–2.20 Å. In the eighth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with two AlO4 tetrahedra, corners with three FeO4 tetrahedra, edges with three CaO6 octahedra, and edges with three FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.97–2.15 Å. In the ninth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.01–2.09 Å. In the tenth Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four FeO4 tetrahedra, an edgeedge with one CaO6 octahedra, and edges with six FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.99–2.09 Å. In the eleventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with six FeO4 tetrahedra and edges with five FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 2.02–2.09 Å. In the twelfth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with nine FeO6 octahedra. The corner-sharing octahedra tilt angles range from 42–61°. There are a spread of Fe–O bond distances ranging from 1.83–2.00 Å. There are four inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two equivalent CaO6 octahedra, a cornercorner with one FeO4 tetrahedra, and corners with two AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–66°. There are a spread of Al–O bond distances ranging from 1.75–1.78 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one FeO6 octahedra, corners with two CaO6 octahedra, a cornercorner with one FeO4 tetrahedra, and corners with two AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–66°. There is two shorter (1.76 Å) and two longer (1.78 Å) Al–O bond length. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two equivalent CaO6 octahedra, corners with three FeO6 octahedra, and corners with two AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–67°. There are a spread of Al–O bond distances ranging from 1.77–1.83 Å. In the fourth Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share corners with two CaO6 octahedra, corners with three FeO6 octahedra, and corners with two AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 45–70°. There is three shorter (1.76 Å) and one longer (1.82 Å) Al–O bond length. There are twenty-eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to two Ca2+, one Fe3+, and one Al3+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Fe3+ atoms. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Fe3+ atoms. In the fifth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe3+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Fe3+ atoms. In the seventh O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe3+ atoms. In the eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe3+ atoms. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe3+ atoms. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe3+, and one Al3+ atom. In the eleventh O2- site, O2- is bonded in a trigonal planar geometry to one Ca2+ and two Al3+ atoms. In the twelfth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe3+ atoms. In the thirteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe3+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted tetrahedral geometry to one Ca2+ and three Fe3+ atoms. In the fifteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca2+, one Fe3+, and one Al3+ atom. In the sixteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, two Fe3+, and one Al3+ atom. In the seventeenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ca2+ and two Al3+ atoms. In the eighteenth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four Fe3+ atoms. In the nineteenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two equivalent Ca2+, one Fe3+, and one Al3+ atom. In the twentieth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+ and three Fe3+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Fe3+ atoms. In the twenty-second O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+ and three Fe3+ atoms. In the twenty-third O2- site, O2- is bonded in a distorted see-saw-like geometry to one Ca2+ and three Fe3+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to four Fe3+ atoms. In the twenty-fifth O2- site, O2- is bonded in a distorted tetrahedral geometry to one Ca2+, two Fe3+, and one Al3+ atom. In the twenty-sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and two Al3+ atoms. In the twenty-seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+, one Fe3+, and one Al3+ atom. In the twenty-eighth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Ca2+, one Fe3+, and one Al3+ atom.