Materials Data on MgAl2SiO7 by Materials Project

Abstract

MgAl2SiO7 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Mg is bonded to six O atoms to form distorted MgO6 octahedra that share corners with two equivalent 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 2.08–2.16 Å. There are four inequivalent Al sites. In the first Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.81–1.98 Å. In the second Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.81–1.99 Å. In the third Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with two equivalent SiO4 tetrahedra and edges with six equivalent MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.87–2.07 Å. In the fourth Al site, Al is bonded to six O atoms to form AlO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with four AlO6 octahedra. There are a spread of Al–O bond distances ranging from 1.82–1.97 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with seven AlO6 octahedra. The corner-sharing octahedra tilt angles range from 53–60°. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. There are seven inequivalent O sites. In the first O site, O is bonded to two equivalent Mg, one Al, and one Si atom to form a mixture of distorted corner and edge-sharing OMg2AlSi tetrahedra. In the second O site, O is bonded in a distorted trigonal planar geometry to two Al and one Si atom. In the third O site, O is bonded in a trigonal non-coplanar geometry to two equivalent Mg and one Al atom. In the fourth O site, O is bonded in a trigonal non-coplanar geometry to two equivalent Mg and one Al atom. In the fifth O site, O is bonded in a distorted trigonal non-coplanar geometry to three Al atoms. In the sixth O site, O is bonded in a distorted 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.