DOE OSTI2020
Ni4Nb2O9 crystallizes in the orthorhombic Fdd2 space group. The structure is three-dimensional. there are four inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.85–2.32 Å. In the second Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.84–2.32 Å. In the third Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.85–2.34 Å. In the fourth Nb5+ site, Nb5+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Nb–O bond distances ranging from 1.85–2.35 Å. There are ten inequivalent Ni2+ sites. In the first Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Ni–O bond distances ranging from 2.00–2.24 Å. In the second Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–64°. There are a spread of Ni–O bond distances ranging from 2.02–2.20 Å. In the third Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–64°. There are a spread of Ni–O bond distances ranging from 2.02–2.18 Å. In the fourth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 46–48°. There are a spread of Ni–O bond distances ranging from 2.02–2.22 Å. In the fifth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 47°. There are a spread of Ni–O bond distances ranging from 2.02–2.14 Å. In the sixth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–48°. There are a spread of Ni–O bond distances ranging from 2.03–2.15 Å. In the seventh Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 46–63°. There are a spread of Ni–O bond distances ranging from 2.02–2.20 Å. In the eighth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner and edge-sharing NiO6 octahedra. The corner-sharing octahedral tilt angles are 45°. There are a spread of Ni–O bond distances ranging from 2.01–2.13 Å. In the ninth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 46–63°. There are a spread of Ni–O bond distances ranging from 2.03–2.21 Å. In the tenth Ni2+ site, Ni2+ is bonded to six O2- atoms to form a mixture of corner, edge, and face-sharing NiO6 octahedra. The corner-sharing octahedra tilt angles range from 44–47°. There are a spread of Ni–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 one Nb5+ and four Ni2+ atoms to form distorted ONbNi4 trigonal bipyramids that share corners with three ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with three ONb2Ni2 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nb5+ and two Ni2+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nb5+ and two Ni2+ atoms. In the fourth O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the fifth O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to one Nb5+ and three Ni2+ atoms. In the seventh O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the eighth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nb5+ and two Ni2+ atoms. In the ninth O2- site, O2- is bonded to one Nb5+ and four Ni2+ atoms to form distorted ONbNi4 trigonal bipyramids that share corners with two ONbNi4 trigonal bipyramids, corners with three ONb2Ni2 trigonal pyramids, edges with three ONbNi4 trigonal bipyramids, and edges with three ONb2Ni2 trigonal pyramids. In the tenth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Nb5+ and three Ni2+ atoms. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nb5+ and two Ni2+ atoms. In the twelfth O2- site, O2- is bonded to one Nb5+ and four Ni2+ atoms to form distorted ONbNi4 trigonal bipyramids that share corners with two ONbNi4 trigonal bipyramids, corners with three ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with three ONb2Ni2 trigonal pyramids. In the thirteenth O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the fourteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Nb5+ and three Ni2+ atoms. In the fifteenth O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the sixteenth O2- site, O2- is bonded to one Nb5+ and four Ni2+ atoms to form distorted ONbNi4 trigonal bipyramids that share corners with two ONbNi4 trigonal bipyramids, corners with three ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with three ONb2Ni2 trigonal pyramids. In the seventeenth O2- site, O2- is bonded to two Nb5+ and two Ni2+ atoms to form distorted ONb2Ni2 trigonal pyramids that share corners with two ONbNi4 trigonal bipyramids, corners with four ONb2Ni2 trigonal pyramids, edges with two ONbNi4 trigonal bipyramids, and edges with two ONb2Ni2 trigonal pyramids. In the eighteenth O2- site, O2- is bonded in a 4-coordinate geometry to one Nb5+ and three Ni2+ atoms.