Materials Data on K2NaNb(OF2)2 by Materials Project

Abstract

K2NaNbO2F4 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4_2/mnm space group. The structure is three-dimensional. K1+ is bonded to four equivalent O2- and eight F1- atoms to form KO4F8 cuboctahedra that share corners with twelve equivalent KO4F8 cuboctahedra, faces with six equivalent KO4F8 cuboctahedra, faces with four equivalent NaO2F4 octahedra, and faces with four equivalent NbO2F4 octahedra. All K–O bond lengths are 3.06 Å. All K–F bond lengths are 3.05 Å. Na1+ is bonded to two equivalent O2- and four F1- atoms to form NaO2F4 octahedra that share corners with six equivalent NbO2F4 octahedra and faces with eight equivalent KO4F8 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. Both Na–O bond lengths are 2.41 Å. There are two shorter (2.27 Å) and two longer (2.29 Å) Na–F bond lengths. Nb5+ is bonded to two equivalent O2- and four F1- atoms to form NbO2F4 octahedra that share corners with six equivalent NaO2F4 octahedra and faces with eight equivalent KO4F8 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. Both Nb–O bond lengths are 1.90 Å. All Nb–F bond lengths are 2.04 Å. O2- is bonded in a distorted linear geometry to four equivalent K1+, one Na1+, and one Nb5+ atom. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted linear geometry to four equivalent K1+, one Na1+, and one Nb5+ atom. In the second F1- site, F1- is bonded in a distorted linear geometry to four equivalent K1+, one Na1+, and one Nb5+ atom.