Materials Data on Nb2Ni2O9 by Materials Project
Nb2Ni2O9 crystallizes in the hexagonal P6_3/mcm space group. The structure is three-dimensional. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six equivalent NiO6 octahedra and a faceface with one NbO6 octahedra. The corner-sharing octahedral tilt angles are 52°. There are three shorter (1.98 Å) and three longer (2.10 Å) Nb–O bond lengths. Ni4+ is bonded to six equivalent O2- atoms to form NiO6 octahedra that share corners with six equivalent NbO6 octahedra and edges with three equivalent NiO6 octahedra. The corner-sharing octahedral tilt angles are 52°. All Ni–O bond lengths are 1.87 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Nb5+ and two equivalent Ni4+ atoms. In the second O2- site, O2- is bonded in an L-shaped geometry to two equivalent Nb5+ atoms.