Materials Data on UNb2O7 by Materials Project
UNb2O7 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. U4+ is bonded to seven O2- atoms to form distorted edge-sharing UO7 hexagonal pyramids. There are one shorter (2.24 Å) and six longer (2.30 Å) U–O bond lengths. There are two 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 1.84–2.45 Å. In the second Nb5+ site, Nb5+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Nb–O bond distances ranging from 1.98–2.40 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a trigonal planar geometry to two equivalent U4+ and one Nb5+ atom. In the second O2- site, O2- is bonded in a linear geometry to one U4+ and one Nb5+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to three Nb5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to three Nb5+ atoms. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to one U4+ and two equivalent Nb5+ atoms.