Materials Data on K2NiF4 by Materials Project
K2NiF4 is (La,Ba)CuO4 structured and crystallizes in the tetragonal I4/mmm space group. The structure is three-dimensional. K1+ is bonded in a 9-coordinate geometry to nine F1- atoms. There are a spread of K–F bond distances ranging from 2.65–2.88 Å. Ni2+ is bonded to six F1- atoms to form corner-sharing NiF6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.03 Å) and four longer (2.04 Å) Ni–F bond lengths. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded to five equivalent K1+ and one Ni2+ atom to form distorted FK5Ni octahedra that share corners with seventeen FK5Ni octahedra, edges with eight equivalent FK5Ni octahedra, and faces with four equivalent FK4Ni2 octahedra. The corner-sharing octahedra tilt angles range from 0–57°. In the second F1- site, F1- is bonded to four equivalent K1+ and two equivalent Ni2+ atoms to form distorted FK4Ni2 octahedra that share corners with fourteen FK5Ni octahedra, edges with two equivalent FK4Ni2 octahedra, and faces with eight FK5Ni octahedra. The corner-sharing octahedra tilt angles range from 0–57°.