DOE OSTI2020
V4O9 crystallizes in the orthorhombic Cmcm space group. The structure is three-dimensional. there are three inequivalent V+4.50+ sites. In the first V+4.50+ site, V+4.50+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two VO6 octahedra, corners with four equivalent VO4 tetrahedra, and an edgeedge with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 3–5°. There are a spread of V–O bond distances ranging from 1.83–2.07 Å. In the second V+4.50+ site, V+4.50+ is bonded to six O2- atoms to form VO6 octahedra that share corners with two VO6 octahedra, corners with four equivalent VO4 tetrahedra, and an edgeedge with one VO6 octahedra. The corner-sharing octahedra tilt angles range from 3–7°. There are a spread of V–O bond distances ranging from 1.84–2.07 Å. In the third V+4.50+ site, V+4.50+ is bonded to four O2- atoms to form VO4 tetrahedra that share corners with four VO6 octahedra and a cornercorner with one VO4 tetrahedra. The corner-sharing octahedra tilt angles range from 26–51°. There are a spread of V–O bond distances ranging from 1.69–1.80 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent V+4.50+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent V+4.50+ atoms. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two V+4.50+ atoms. In the fourth O2- site, O2- is bonded in a bent 150 degrees geometry to two V+4.50+ atoms. In the fifth O2- site, O2- is bonded in a linear geometry to two equivalent V+4.50+ atoms. In the sixth O2- site, O2- is bonded in a linear geometry to two V+4.50+ atoms. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to three V+4.50+ atoms.