Materials Data on K3Nb8(O5F2)2 by Materials Project
K3Nb8(O5F2)2 crystallizes in the tetragonal P4mm space group. The structure is three-dimensional. there are three inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to four equivalent O2- and five F1- atoms. All K–O bond lengths are 2.87 Å. There are one shorter (2.64 Å) and four longer (2.97 Å) K–F bond lengths. In the second K1+ site, K1+ is bonded in a 1-coordinate geometry to four equivalent O2- and five F1- atoms. All K–O bond lengths are 3.03 Å. There are one shorter (2.48 Å) and four longer (2.97 Å) K–F bond lengths. In the third K1+ site, K1+ is bonded in a 9-coordinate geometry to four equivalent O2- and five F1- atoms. All K–O bond lengths are 2.86 Å. There are one shorter (2.63 Å) and four longer (2.97 Å) K–F bond lengths. There are six inequivalent Nb+2.62+ sites. In the first Nb+2.62+ site, Nb+2.62+ is bonded to four equivalent O2- and one F1- atom to form corner-sharing NbO4F square pyramids. All Nb–O bond lengths are 2.10 Å. The Nb–F bond length is 2.23 Å. In the second Nb+2.62+ site, Nb+2.62+ is bonded to four equivalent O2- and one F1- atom to form corner-sharing NbO4F square pyramids. All Nb–O bond lengths are 2.10 Å. The Nb–F bond length is 2.10 Å. In the third Nb+2.62+ site, Nb+2.62+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Nb–O bond distances ranging from 2.08–2.15 Å. In the fourth Nb+2.62+ site, Nb+2.62+ is bonded to four equivalent O2- and one F1- atom to form corner-sharing NbO4F square pyramids. All Nb–O bond lengths are 2.10 Å. The Nb–F bond length is 2.23 Å. In the fifth Nb+2.62+ site, Nb+2.62+ is bonded to four equivalent O2- and one F1- atom to form corner-sharing NbO4F square pyramids. All Nb–O bond lengths are 2.10 Å. The Nb–F bond length is 2.00 Å. In the sixth Nb+2.62+ site, Nb+2.62+ is bonded in a square co-planar geometry to four O2- atoms. There are a spread of Nb–O bond distances ranging from 2.10–2.14 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent K1+ and three Nb+2.62+ atoms. In the second O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent K1+ and three Nb+2.62+ atoms. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to four equivalent Nb+2.62+ atoms. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to two equivalent K1+ and three Nb+2.62+ atoms. In the fifth O2- site, O2- is bonded in a T-shaped geometry to three Nb+2.62+ atoms. In the sixth O2- site, O2- is bonded in a rectangular see-saw-like geometry to four equivalent Nb+2.62+ atoms. There are four inequivalent F1- sites. In the first F1- site, F1- is bonded to five K1+ and one Nb+2.62+ atom to form a mixture of distorted edge and corner-sharing FK5Nb octahedra. The corner-sharing octahedral tilt angles are 7°. In the second F1- site, F1- is bonded in a distorted single-bond geometry to four equivalent K1+ and one Nb+2.62+ atom. In the third F1- site, F1- is bonded to five K1+ and one Nb+2.62+ atom to form a mixture of distorted edge and corner-sharing FK5Nb octahedra. The corner-sharing octahedral tilt angles are 6°. In the fourth F1- site, F1- is bonded in a linear geometry to one K1+ and one Nb+2.62+ atom.