Materials Data on MgAl2SiHO7 by Materials Project

MgAl2SiHO7 crystallizes in the monoclinic C2/c 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 2.09–2.25 Å. There are three 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 equivalent AlO6 octahedra. There is two shorter (1.82 Å) and four longer (1.96 Å) Al–O bond length. 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 1.82–1.97 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 1.89–2.03 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 54–61°. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. H is bonded in a linear geometry to two O atoms. There is one shorter (1.01 Å) and one longer (1.60 Å) H–O bond length. There are seven inequivalent O sites. In the first O site, O is bonded in a 4-coordinate geometry to two equivalent Mg, one Al, and one H atom. In the second O site, O is bonded in a distorted trigonal planar geometry to two equivalent 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 distorted rectangular see-saw-like geometry to two equivalent Mg, one Al, and one Si atom. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two Al and one Si atom. 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 to three Al and one H atom to form corner-sharing OAl3H tetrahedra.