DOI: 10.17188/1730706
title: Materials Data on Al2Si2O9 by Materials Project

description: Al2Si2O9 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of one Al2Si2O9 sheet oriented in the (0, 1, 0) direction. there are four inequivalent Al sites. In the first Al site, Al is bonded in a 5-coordinate geometry to five O atoms. There are a spread of Al–O bond distances ranging from 1.77–1.95 Å. In the second Al site, Al is bonded to six O atoms to form distorted AlO6 octahedra that share corners with two SiO4 tetrahedra and edges with two equivalent AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.81–2.02 Å. In the third Al site, Al is bonded to six O atoms to form distorted AlO6 octahedra that share corners with two SiO4 tetrahedra and edges with three AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.81–2.19 Å. In the fourth Al site, Al is bonded to six O atoms to form distorted AlO6 octahedra that share corners with two SiO4 tetrahedra and an edgeedge with one AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.79–1.99 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 44°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 63°. There is three shorter (1.62 Å) and one longer (1.70 Å) Si–O bond length. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–59°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two AlO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–54°. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. There are eighteen inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to two Al and one Si atom. In the second O site, O is bonded in a trigonal planar geometry to two Al and one Si atom. In the third O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the fifth O site, O is bonded in a distorted bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a trigonal planar geometry to two Al and one Si atom. In the seventh O site, O is bonded in a distorted trigonal planar geometry to two Al and one Si atom. In the eighth O site, O is bonded in a bent 120 degrees geometry to two Si atoms. In the ninth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the tenth O site, O is bonded in a bent 120 degrees geometry to two Si atoms. In the eleventh O site, O is bonded in a water-like geometry to two Al atoms. In the twelfth O site, O is bonded in a water-like geometry to two Al atoms. In the thirteenth O site, O is bonded in a water-like geometry to two Al atoms. In the fourteenth O site, O is bonded in a water-like geometry to two Al atoms. In the fifteenth O site, O is bonded in a 2-coordinate geometry to two Al and one O atom. The O–O bond length is 1.51 Å. In the sixteenth O site, O is bonded in a 1-coordinate geometry to one Al and one O atom. The O–O bond length is 1.37 Å. In the seventeenth O site, O is bonded in a 3-coordinate geometry to two Al and one O atom. In the eighteenth O site, O is bonded in a 2-coordinate geometry to two Al and one O atom.