DOE OSTI2020
KB5O8 crystallizes in the orthorhombic Pbca space group. The structure is two-dimensional and consists of eight KBO2 clusters and two B2O3 sheets oriented in the (0, 0, 1) direction. In each KBO2 cluster, K1+ is bonded in a 1-coordinate geometry to one O2- atom. The K–O bond length is 2.64 Å. B3+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.26 Å) and one longer (1.28 Å) B–O bond length. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a single-bond geometry to one B3+ atom. In the second O2- site, O2- is bonded in a distorted single-bond geometry to one K1+ and one B3+ atom. In each B2O3 sheet, there are four inequivalent B3+ sites. In the first B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.34 Å) and one longer (1.52 Å) B–O bond length. In the second B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.29–1.49 Å. In the third B3+ site, B3+ is bonded in a tetrahedral geometry to four O2- atoms. There are a spread of B–O bond distances ranging from 1.44–1.49 Å. In the fourth B3+ site, B3+ is bonded in a trigonal planar geometry to three O2- atoms. There are a spread of B–O bond distances ranging from 1.32–1.49 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two B3+ atoms. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two B3+ atoms. In the third O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms. In the fourth O2- site, O2- is bonded in a water-like geometry to two B3+ atoms. In the fifth O2- site, O2- is bonded in a trigonal planar geometry to three B3+ atoms. In the sixth O2- site, O2- is bonded in a bent 120 degrees geometry to two B3+ atoms.