Materials Data on K4V2O9 by Materials Project
K4V2O9 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent K sites. In the first K site, K is bonded to seven O atoms to form KO7 pentagonal bipyramids that share corners with two equivalent VO4 tetrahedra, edges with two equivalent KO7 pentagonal bipyramids, and edges with two equivalent VO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.76–2.91 Å. In the second K site, K is bonded in a 7-coordinate geometry to seven O atoms. There are a spread of K–O bond distances ranging from 2.68–3.13 Å. In the third K site, K is bonded in a 9-coordinate geometry to nine O atoms. There are a spread of K–O bond distances ranging from 2.78–3.14 Å. V is bonded to four O atoms to form VO4 tetrahedra that share a cornercorner with one KO7 pentagonal bipyramid, a cornercorner with one VO4 tetrahedra, and an edgeedge with one KO7 pentagonal bipyramid. There are a spread of V–O bond distances ranging from 1.70–1.84 Å. There are four inequivalent O sites. In the first O site, O is bonded in a distorted single-bond geometry to four K and one V atom. In the second O site, O is bonded in a distorted linear geometry to four K and two equivalent V atoms. In the third O site, O is bonded in a distorted rectangular see-saw-like geometry to four K atoms. In the fourth O site, O is bonded in a distorted single-bond geometry to three K and one V atom.