Materials Data on KAlSi3O8 by Materials Project

Abstract

KAlSi3O8 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. K1+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of K–O bond distances ranging from 2.75–2.86 Å. Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with four SiO6 octahedra, edges with two equivalent AlO6 octahedra, and edges with two equivalent SiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–51°. There are a spread of Al–O bond distances ranging from 1.86–2.01 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with four SiO6 octahedra, edges with two equivalent AlO6 octahedra, and edges with two equivalent SiO6 octahedra. The corner-sharing octahedra tilt angles range from 49–50°. There are a spread of Si–O bond distances ranging from 1.79–1.84 Å. In the second Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with two equivalent AlO6 octahedra, corners with two equivalent SiO6 octahedra, and edges with four SiO6 octahedra. The corner-sharing octahedra tilt angles range from 49–51°. There are a spread of Si–O bond distances ranging from 1.78–1.86 Å. In the third Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with two equivalent AlO6 octahedra, corners with two equivalent SiO6 octahedra, and edges with four SiO6 octahedra. The corner-sharing octahedra tilt angles range from 48–50°. There are a spread of Si–O bond distances ranging from 1.70–1.88 Å. There are eight inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to one Al3+ and two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to three Si4+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to three Si4+ atoms. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent K1+, one Al3+, and two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent K1+, two equivalent Al3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent K1+ and three Si4+ atoms. In the eighth O2- site, O2- is bonded in a 5-coordinate geometry to two equivalent K1+ and three Si4+ atoms.