Materials Data on K2NbO3F by Materials Project
K2NbO3F is (La,Ba)CuO4-derived structured and crystallizes in the tetragonal I4mm space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to five O2- and four equivalent F1- atoms. There are one shorter (2.85 Å) and four longer (2.86 Å) K–O bond lengths. All K–F bond lengths are 2.84 Å. In the second K1+ site, K1+ is bonded in a 9-coordinate geometry to eight O2- and one F1- atom. There are four shorter (2.84 Å) and four longer (2.99 Å) K–O bond lengths. The K–F bond length is 2.65 Å. Nb5+ is bonded to five O2- and one F1- atom to form corner-sharing NbO5F octahedra. The corner-sharing octahedral tilt angles are 13°. There is one shorter (1.84 Å) and four longer (2.02 Å) Nb–O bond length. The Nb–F bond length is 2.33 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted linear geometry to four K1+ and two equivalent Nb5+ atoms. In the second O2- site, O2- is bonded to five K1+ and one Nb5+ atom to form distorted OK5Nb octahedra that share a cornercorner with one FK5Nb octahedra, corners with four equivalent OK5Nb octahedra, edges with four equivalent OK5Nb octahedra, and edges with four equivalent FK5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–6°. F1- is bonded to five K1+ and one Nb5+ atom to form distorted FK5Nb octahedra that share a cornercorner with one OK5Nb octahedra, corners with four equivalent FK5Nb octahedra, edges with four equivalent OK5Nb octahedra, and edges with four equivalent FK5Nb octahedra. The corner-sharing octahedra tilt angles range from 0–2°.