Materials Data on KFeS2O9 by Materials Project
KFeS2O9 crystallizes in the monoclinic P2_1/m space group. The structure is three-dimensional. K is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of K–O bond distances ranging from 2.82–3.11 Å. Fe is bonded to six O atoms to form FeO6 octahedra that share corners with five SO4 tetrahedra. There are a spread of Fe–O bond distances ranging from 2.00–2.08 Å. There are two inequivalent S sites. In the first S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with two equivalent FeO6 octahedra. The corner-sharing octahedral tilt angles are 40°. There are a spread of S–O bond distances ranging from 1.46–1.52 Å. In the second S site, S is bonded to four O atoms to form SO4 tetrahedra that share corners with three equivalent FeO6 octahedra. The corner-sharing octahedra tilt angles range from 35–45°. There are a spread of S–O bond distances ranging from 1.46–1.50 Å. There are seven inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to one K and one S atom. In the second O site, O is bonded in a single-bond geometry to two equivalent K and one S atom. In the third O site, O is bonded in a 2-coordinate geometry to one K, one Fe, and one S atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Fe and one S atom. In the fifth O site, O is bonded in a distorted single-bond geometry to three equivalent K and one S atom. In the sixth O site, O is bonded in a 3-coordinate geometry to one K, one Fe, and one S atom. In the seventh O site, O is bonded in a single-bond geometry to one Fe atom.