Materials Data on K2Ge4O9 by Materials Project
K2Ge4O9 crystallizes in the trigonal P-3c1 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 2.78–3.00 Å. There are four inequivalent Ge4+ sites. In the first Ge4+ site, Ge4+ is bonded to six O2- atoms to form corner-sharing GeO6 octahedra. There is three shorter (1.90 Å) and three longer (1.92 Å) Ge–O bond length. In the second Ge4+ site, Ge4+ is bonded to six equivalent O2- atoms to form corner-sharing GeO6 octahedra. All Ge–O bond lengths are 1.94 Å. In the third 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 octahedral tilt angles are 56°. There is two shorter (1.77 Å) and two longer (1.82 Å) Ge–O bond length. In the fourth 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 GeO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–52°. There are a spread of Ge–O bond distances ranging from 1.75–1.81 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one K1+ and two Ge4+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent K1+ and two Ge4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent K1+ and two Ge4+ atoms. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent K1+ and two equivalent Ge4+ atoms. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to one K1+ and two Ge4+ atoms.