Materials Data on U2Nb6O21 by Materials Project
U2Nb6O21 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. U6+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.80–2.56 Å. There are four inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 24–58°. There are a spread of Nb–O bond distances ranging from 1.89–2.25 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 39–50°. There are a spread of Nb–O bond distances ranging from 1.96–2.08 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 24–63°. There are a spread of Nb–O bond distances ranging from 1.86–2.13 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 35–50°. There are a spread of Nb–O bond distances ranging from 1.96–2.05 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two Nb5+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two Nb5+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one U6+ and two Nb5+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one U6+ and two Nb5+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Nb5+ atoms. In the eighth O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the ninth O2- site, O2- is bonded in a single-bond geometry to one U6+ atom. In the tenth O2- site, O2- is bonded in a bent 120 degrees geometry to two equivalent U6+ atoms. In the eleventh O2- site, O2- is bonded in a distorted tetrahedral geometry to two equivalent U6+ and two equivalent Nb5+ atoms. In the twelfth O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms.