Materials Data on KAl4(SiO6)2 by Materials Project
KAl4(SiO6)2 crystallizes in the monoclinic C2/c space group. The structure is three-dimensional. K is bonded to six O atoms to form KO6 octahedra that share corners with six equivalent AlO4 tetrahedra and corners with six equivalent SiO4 tetrahedra. There are a spread of K–O bond distances ranging from 2.90–3.11 Å. There are two inequivalent Al sites. In the first Al site, Al is bonded to four O atoms to form AlO4 tetrahedra that share corners with three equivalent KO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 70–75°. There are a spread of Al–O bond distances ranging from 1.74–1.78 Å. In the second Al site, Al is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Al–O bond distances ranging from 1.80–2.08 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three equivalent KO6 octahedra and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 66–71°. There is three shorter (1.62 Å) and one longer (1.72 Å) Si–O bond length. There are six inequivalent O sites. In the first O site, O is bonded in a trigonal planar geometry to three Al atoms. In the second O site, O is bonded in a 2-coordinate geometry to one K, one Al, and one Si atom. In the third O site, O is bonded in a distorted bent 150 degrees geometry to one K, one Al, and one Si atom. In the fourth O site, O is bonded in a 2-coordinate geometry to one K, one Al, and one Si atom. In the fifth O site, O is bonded in a 3-coordinate geometry to two equivalent Al and one O atom. The O–O bond length is 1.39 Å. In the sixth O site, O is bonded in a distorted trigonal planar geometry to two equivalent Al and one Si atom.