Materials Data on UNb4O12 by Materials Project

UNb4O12 crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. U4+ is bonded to twelve O2- atoms to form UO12 cuboctahedra that share corners with four equivalent UO12 cuboctahedra and faces with eight equivalent NbO6 octahedra. There are eight shorter (2.56 Å) and four longer (2.80 Å) U–O bond lengths. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six equivalent NbO6 octahedra and faces with two equivalent UO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Nb–O bond distances ranging from 1.95–2.02 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to one U4+ and two equivalent Nb5+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent U4+ and two equivalent Nb5+ atoms.