DOE OSTI2019
FeNb2O6 is Brookite-derived structured and crystallizes in the triclinic P1 space group. The structure is three-dimensional. there are eight inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 12–55°. There are a spread of Nb–O bond distances ranging from 1.84–2.35 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.33 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.33 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 12–55°. There are a spread of Nb–O bond distances ranging from 1.84–2.35 Å. In the fifth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.34 Å. In the sixth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.34 Å. In the seventh Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.33 Å. In the eighth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent FeO6 octahedra, corners with four NbO6 octahedra, an edgeedge with one FeO6 octahedra, and edges with two equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 11–55°. There are a spread of Nb–O bond distances ranging from 1.83–2.33 Å. There are four inequivalent Fe2+ sites. In the first Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four NbO6 octahedra, edges with two NbO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 11–24°. There are a spread of Fe–O bond distances ranging from 2.11–2.19 Å. In the second Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four NbO6 octahedra, edges with two NbO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 11–26°. There are a spread of Fe–O bond distances ranging from 2.11–2.23 Å. In the third Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four NbO6 octahedra, edges with two NbO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 11–24°. There are a spread of Fe–O bond distances ranging from 2.11–2.19 Å. In the fourth Fe2+ site, Fe2+ is bonded to six O2- atoms to form FeO6 octahedra that share corners with four NbO6 octahedra, edges with two NbO6 octahedra, and edges with two equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 11–26°. There are a spread of Fe–O bond distances ranging from 2.11–2.23 Å. There are twenty-four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the third O2- site, O2- is bonded in a T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the fourth O2- site, O2- is bonded in a T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the sixth O2- site, O2- is bonded in a T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the seventh O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the ninth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the tenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the eleventh O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the twelfth O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the fourteenth O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the fifteenth O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the sixteenth O2- site, O2- is bonded in a distorted T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the seventeenth O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom. In the eighteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the nineteenth O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the twentieth O2- site, O2- is bonded in a distorted T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the twenty-first O2- site, O2- is bonded in a distorted T-shaped geometry to one Nb5+ and two Fe2+ atoms. In the twenty-second O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the twenty-third O2- site, O2- is bonded in a 3-coordinate geometry to three Nb5+ atoms. In the twenty-fourth O2- site, O2- is bonded in a distorted T-shaped geometry to two Nb5+ and one Fe2+ atom.