Materials Data on K2Al2B2O7 by Materials Project
K2Al2B2O7 crystallizes in the trigonal P321 space group. The structure is three-dimensional. there are two inequivalent K1+ sites. In the first K1+ site, K1+ is bonded in a 9-coordinate geometry to nine O2- atoms. There are a spread of K–O bond distances ranging from 2.74–3.29 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to ten O2- atoms. There are a spread of K–O bond distances ranging from 2.73–3.38 Å. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. There is one shorter (1.73 Å) and three longer (1.78 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. There is one shorter (1.74 Å) and three longer (1.77 Å) Al–O bond length. In the third Al3+ site, Al3+ is bonded to four O2- atoms to form corner-sharing AlO4 tetrahedra. There is one shorter (1.74 Å) and three longer (1.77 Å) Al–O bond length. B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is two shorter (1.38 Å) and one longer (1.39 Å) B–O bond length. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to three equivalent K1+ and two equivalent Al3+ atoms. In the second O2- site, O2- is bonded in a 2-coordinate geometry to three K1+, one Al3+, and one B3+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to three K1+, one Al3+, and one B3+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two K1+, one Al3+, and one B3+ atom. In the fifth O2- site, O2- is bonded in a linear geometry to three equivalent K1+ and two Al3+ atoms.