Materials Data on K8Al2O7 by Materials Project
K8Al2O7 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are eight inequivalent K1+ sites. In the first K1+ site, K1+ is bonded to four O2- atoms to form KO4 tetrahedra that share a cornercorner with one KO4 tetrahedra, corners with four AlO4 tetrahedra, and edges with two KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.62–2.74 Å. In the second K1+ site, K1+ is bonded in a 2-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.59–3.25 Å. In the third K1+ site, K1+ is bonded in a distorted hexagonal planar geometry to six O2- atoms. There are a spread of K–O bond distances ranging from 2.80–2.87 Å. In the fourth K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.55–3.05 Å. In the fifth K1+ site, K1+ is bonded in a 5-coordinate geometry to five O2- atoms. There are a spread of K–O bond distances ranging from 2.65–3.08 Å. In the sixth K1+ site, K1+ is bonded to four O2- atoms to form distorted KO4 tetrahedra that share a cornercorner with one KO4 tetrahedra, corners with two AlO4 tetrahedra, an edgeedge with one AlO4 tetrahedra, and edges with two KO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.53–2.75 Å. In the seventh K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.61–3.17 Å. In the eighth K1+ site, K1+ is bonded in a 4-coordinate geometry to four O2- atoms. There are a spread of K–O bond distances ranging from 2.59–2.75 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra and corners with four KO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.80–1.88 Å. In the second Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one AlO4 tetrahedra, corners with two KO4 tetrahedra, and an edgeedge with one KO4 tetrahedra. There are a spread of Al–O bond distances ranging from 1.82–1.87 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to four K1+ and two Al3+ atoms. In the third O2- site, O2- is bonded in a 6-coordinate geometry to five K1+ and one Al3+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to six K1+ and one Al3+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to five K1+ and one Al3+ atom. In the seventh O2- site, O2- is bonded in a 1-coordinate geometry to six K1+ and one Al3+ atom.