Materials Data on Mg2Al2SiO9 by Materials Project

Abstract

Mg2Al2SiO9 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of two Mg2Al2SiO9 sheets oriented in the (0, 0, 1) direction. In one of the Mg2Al2SiO9 sheets, there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.24 Å. In the second Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.21 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 a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–63°. There are a spread of Al–O bond distances ranging from 1.73–1.80 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, and edges with six MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.02 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–60°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. There are nine inequivalent O sites. In the first O site, O is bonded in a distorted rectangular see-saw-like geometry to two Mg and two Al atoms. In the second O site, O is bonded in a distorted bent 120 degrees geometry to one Al and one Si atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the fourth O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the fifth O site, O is bonded in a rectangular see-saw-like geometry to two Mg, one Al, and one Si atom. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the seventh O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the eighth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the ninth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In one of the Mg2Al2SiO9 sheets, there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.24 Å. In the second Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.05–2.23 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 a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 56–63°. There is three shorter (1.74 Å) and one longer (1.79 Å) Al–O bond length. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, and edges with six MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.86–2.01 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–60°. There is three shorter (1.62 Å) and one longer (1.69 Å) Si–O bond length. There are nine inequivalent O sites. In the first O site, O is bonded in a distorted bent 150 degrees geometry to one Al and one Si atom. In the second O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the third O site, O is bonded in a bent 150 degrees geometry to one Al and one Si atom. In the fourth O site, O is bonded in a distorted rectangular see-saw-like geometry to two Mg and two Al atoms. In the fifth O site, O is bonded in a rectangular see-saw-like geometry to two Mg, one Al, and one Si atom. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the seventh O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the eighth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom. In the ninth O site, O is bonded in a trigonal non-coplanar geometry to two Mg and one Al atom.