DOE OSTI2019
Ba2Fe2O5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are seven inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.57–3.10 Å. In the second Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.59–3.18 Å. In the third Ba2+ site, Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.79–3.06 Å. In the fourth Ba2+ site, Ba2+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of Ba–O bond distances ranging from 2.79–3.27 Å. In the fifth Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.74–3.09 Å. In the sixth Ba2+ site, Ba2+ is bonded in a 10-coordinate geometry to ten O2- atoms. There are a spread of Ba–O bond distances ranging from 2.77–3.32 Å. In the seventh Ba2+ site, Ba2+ is bonded in a 12-coordinate geometry to eleven O2- atoms. There are a spread of Ba–O bond distances ranging from 2.80–3.16 Å. There are seven inequivalent Fe3+ sites. In the first Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and corners with two FeO4 tetrahedra. The corner-sharing octahedral tilt angles are 18°. There are a spread of Fe–O bond distances ranging from 1.89–1.94 Å. In the second Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one FeO5 square pyramid and corners with two FeO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.85–1.96 Å. In the third Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share corners with two FeO5 square pyramids and a cornercorner with one FeO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 1.84–1.94 Å. In the fourth Fe3+ site, Fe3+ is bonded to four O2- atoms to form FeO4 tetrahedra that share a cornercorner with one FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and a cornercorner with one FeO4 tetrahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of Fe–O bond distances ranging from 1.83–1.93 Å. In the fifth Fe3+ site, Fe3+ is bonded to five O2- atoms to form FeO5 square pyramids that share corners with two equivalent FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and corners with two FeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 3–7°. There are a spread of Fe–O bond distances ranging from 1.95–2.09 Å. In the sixth Fe3+ site, Fe3+ is bonded to five O2- atoms to form FeO5 square pyramids that share a cornercorner with one FeO6 octahedra, a cornercorner with one FeO5 square pyramid, and corners with three FeO4 tetrahedra. The corner-sharing octahedral tilt angles are 9°. There are a spread of Fe–O bond distances ranging from 1.93–2.10 Å. In the seventh Fe3+ site, Fe3+ is bonded to six O2- atoms to form FeO6 octahedra that share a cornercorner with one FeO6 octahedra, corners with three FeO5 square pyramids, and corners with two FeO4 tetrahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Fe–O bond distances ranging from 2.04–2.25 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ba2+ and two equivalent Fe3+ atoms to form a mixture of distorted face and corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 55–56°. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three Ba2+ and one Fe3+ atom. In the third O2- site, O2- is bonded to four Ba2+ and one Fe3+ atom to form distorted corner-sharing OBa4Fe trigonal bipyramids. The corner-sharing octahedral tilt angles are 37°. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one Fe3+ atom. In the fifth O2- site, O2- is bonded in a 6-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the sixth O2- site, O2- is bonded to four Ba2+ and two Fe3+ atoms to form distorted OBa4Fe2 octahedra that share corners with two OBa4Fe2 octahedra, a cornercorner with one OBa4Fe trigonal bipyramid, an edgeedge with one OBa4Fe2 octahedra, and faces with three OBa4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 54–55°. In the seventh O2- site, O2- is bonded in a 6-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the eighth O2- site, O2- is bonded in a 6-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the tenth O2- site, O2- is bonded in a 6-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the eleventh O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the twelfth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the thirteenth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the fourteenth O2- site, O2- is bonded in a 2-coordinate geometry to three Ba2+ and two Fe3+ atoms. In the fifteenth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the sixteenth O2- site, O2- is bonded in a 2-coordinate geometry to three Ba2+ and two Fe3+ atoms. In the seventeenth O2- site, O2- is bonded in a 2-coordinate geometry to four Ba2+ and two Fe3+ atoms. In the eighteenth O2- site, O2- is bonded to four Ba2+ and two Fe3+ atoms to form a mixture of distorted edge, face, and corner-sharing OBa4Fe2 octahedra. The corner-sharing octahedra tilt angles range from 54–56°.