Materials Data on KNb3CuO9 by Materials Project
KCuNb3O9 crystallizes in the orthorhombic Pnc2 space group. The structure is three-dimensional. K1+ is bonded in a 11-coordinate geometry to eleven O2- atoms. There are a spread of K–O bond distances ranging from 2.72–3.29 Å. There are three 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 22–47°. There are a spread of Nb–O bond distances ranging from 1.95–2.12 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 27–39°. There are a spread of Nb–O bond distances ranging from 1.85–2.28 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 27–47°. There are a spread of Nb–O bond distances ranging from 1.95–2.17 Å. There are two inequivalent Cu2+ sites. In the first Cu2+ site, Cu2+ is bonded in a rectangular see-saw-like geometry to four O2- atoms. There are two shorter (1.96 Å) and two longer (2.07 Å) Cu–O bond lengths. In the second Cu2+ site, Cu2+ is bonded in a square co-planar geometry to four O2- atoms. All Cu–O bond lengths are 1.98 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Nb5+ and one Cu2+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Nb5+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Nb5+ and one Cu2+ atom. In the fourth O2- site, O2- is bonded in a trigonal planar geometry to two Nb5+ and one Cu2+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one K1+, two equivalent Nb5+, and one Cu2+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Nb5+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two equivalent Nb5+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two equivalent Nb5+ atoms. In the ninth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Nb5+ atoms. In the tenth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent K1+ and two Nb5+ atoms.