Materials Data on K6Na2Fe7O38 by Materials Project
K6Na2Fe7O38 crystallizes in the trigonal R32 space group. The structure is three-dimensional. K is bonded in a 6-coordinate geometry to six O atoms. There are a spread of K–O bond distances ranging from 2.64–3.09 Å. Na is bonded in a 6-coordinate geometry to six O atoms. There are three shorter (2.40 Å) and three longer (2.73 Å) Na–O bond lengths. There are three inequivalent Fe sites. In the first Fe site, Fe is bonded to six O atoms to form distorted edge-sharing FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.75–2.22 Å. In the second Fe site, Fe is bonded to six equivalent O atoms to form distorted edge-sharing FeO6 octahedra. All Fe–O bond lengths are 2.06 Å. In the third Fe site, Fe is bonded to six O atoms to form distorted edge-sharing FeO6 octahedra. There are a spread of Fe–O bond distances ranging from 1.71–2.16 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to two equivalent K and one Fe atom. In the second O site, O is bonded in a 3-coordinate geometry to one K and three Fe atoms. In the third O site, O is bonded in a distorted trigonal planar geometry to two Fe and one O atom. The O–O bond length is 1.28 Å. In the fourth O site, O is bonded in a distorted bent 150 degrees geometry to one Na and one O atom. In the fifth O site, O is bonded in a 1-coordinate geometry to two equivalent K and one Fe atom. In the sixth O site, O is bonded in a 3-coordinate geometry to one K, one Na, and one O atom. The O–O bond length is 1.44 Å. In the seventh O site, O is bonded in a trigonal non-coplanar geometry to three equivalent O atoms.