Materials Data on KNb4AsO13 by Materials Project

Abstract

KNb4AsO13 crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. K1+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.81–3.33 Å. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with five NbO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 20–42°. There are a spread of Nb–O bond distances ranging from 1.87–2.17 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with four equivalent NbO6 octahedra, corners with two equivalent AsO4 tetrahedra, and an edgeedge with one NbO6 octahedra. The corner-sharing octahedra tilt angles range from 20–28°. There are a spread of Nb–O bond distances ranging from 1.84–2.28 Å. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with six NbO6 octahedra. The corner-sharing octahedra tilt angles range from 45–54°. There are a spread of As–O bond distances ranging from 1.71–1.74 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Nb5+ and one As5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Nb5+ and one As5+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two Nb5+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two equivalent Nb5+ atoms. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+, one Nb5+, and one As5+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Nb5+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Nb5+ atoms.