Materials Data on KNaMg2F6 by Materials Project

Abstract

KNaMg2F6 is (Cubic) Perovskite-derived structured and crystallizes in the tetragonal P4/mmm space group. The structure is three-dimensional. K1+ is bonded to twelve F1- atoms to form KF12 cuboctahedra that share corners with four equivalent KF12 cuboctahedra, corners with eight equivalent NaF12 cuboctahedra, faces with two equivalent NaF12 cuboctahedra, faces with four equivalent KF12 cuboctahedra, and faces with eight equivalent MgF6 octahedra. There are four shorter (2.83 Å) and eight longer (2.87 Å) K–F bond lengths. Na1+ is bonded to twelve F1- atoms to form NaF12 cuboctahedra that share corners with four equivalent NaF12 cuboctahedra, corners with eight equivalent KF12 cuboctahedra, faces with two equivalent KF12 cuboctahedra, faces with four equivalent NaF12 cuboctahedra, and faces with eight equivalent MgF6 octahedra. There are eight shorter (2.79 Å) and four longer (2.83 Å) Na–F bond lengths. Mg2+ is bonded to six F1- atoms to form MgF6 octahedra that share corners with six equivalent MgF6 octahedra, faces with four equivalent KF12 cuboctahedra, and faces with four equivalent NaF12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are a spread of Mg–F bond distances ranging from 1.97–2.03 Å. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a distorted linear geometry to two equivalent K1+, two equivalent Na1+, and two equivalent Mg2+ atoms. In the second F1- site, F1- is bonded in a distorted linear geometry to four equivalent Na1+ and two equivalent Mg2+ atoms. In the third F1- site, F1- is bonded in a distorted linear geometry to four equivalent K1+ and two equivalent Mg2+ atoms.