Materials Data on Mg7(SiO3)8 by Materials Project

Abstract

Mg7(SiO3)8 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra, edges with five MgO6 octahedra, and an edgeedge with one MgO5 square pyramid. There are a spread of Mg–O bond distances ranging from 2.06–2.12 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with six SiO4 tetrahedra, edges with three MgO6 octahedra, and edges with two equivalent MgO5 square pyramids. There are a spread of Mg–O bond distances ranging from 2.02–2.16 Å. In the third Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.07–2.11 Å. In the fourth Mg site, Mg is bonded to five O atoms to form distorted MgO5 square pyramids that share corners with four SiO4 tetrahedra, edges with three MgO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.41 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 corners with three MgO6 octahedra, a cornercorner with one MgO5 square pyramid, and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 57–62°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 58–62°. There are a spread of Si–O bond distances ranging from 1.63–1.65 Å. In the third Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra, a cornercorner with one MgO5 square pyramid, corners with two equivalent SiO4 tetrahedra, and an edgeedge with one MgO5 square pyramid. The corner-sharing octahedra tilt angles range from 32–60°. There are a spread of Si–O bond distances ranging from 1.61–1.69 Å. In the fourth Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra, corners with two equivalent MgO5 square pyramids, and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–61°. There are a spread of Si–O bond distances ranging from 1.61–1.67 Å. There are fourteen inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the third O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the fourth O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the fifth O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si trigonal pyramids. In the sixth O site, O is bonded to three Mg and one Si atom to form a mixture of distorted corner and edge-sharing OMg3Si tetrahedra. In the seventh O site, O is bonded in a rectangular see-saw-like geometry to three Mg and one Si atom. In the eighth O site, O is bonded in a rectangular see-saw-like geometry to three Mg and one Si atom. In the ninth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the tenth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the eleventh O site, O is bonded in a distorted T-shaped geometry to two Mg and one Si atom. In the twelfth O site, O is bonded in a distorted trigonal planar geometry to two Mg and one Si atom. In the thirteenth O site, O is bonded in a 3-coordinate geometry to one Mg and two Si atoms. In the fourteenth O site, O is bonded in a bent 150 degrees geometry to two Si atoms.