Materials Data on K4Ge9O20 by Materials Project
K4Ge9O20 crystallizes in the tetragonal I4_1/a space group. The structure is three-dimensional. K1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of K–O bond distances ranging from 2.66–3.11 Å. There are three inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to four equivalent O2- atoms to form corner-sharing GeO4 tetrahedra. The corner-sharing octahedral tilt angles are 57°. All Ge–O bond lengths are 1.77 Å. In the second Ge4+ site, Ge4+ is bonded to four O2- atoms to form GeO4 tetrahedra that share corners with two equivalent GeO6 octahedra and corners with two equivalent GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 61–62°. There are a spread of Ge–O bond distances ranging from 1.76–1.80 Å. In the third Ge4+ site, Ge4+ is bonded to six O2- atoms to form GeO6 octahedra that share corners with three GeO4 tetrahedra and edges with three equivalent GeO6 octahedra. There are a spread of Ge–O bond distances ranging from 1.86–2.02 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two Ge4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to three equivalent Ge4+ atoms. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two equivalent Ge4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Ge4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Ge4+ atoms.