Materials Data on Mg3Si2O9 by Materials Project

Mg3Si2O9 crystallizes in the monoclinic Cm space group. The structure is two-dimensional and consists of one Mg3Si2O9 sheet oriented in the (0, 0, 1) direction. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Mg–O bond distances ranging from 1.98–2.46 Å. In the second Mg site, Mg is bonded to six O atoms to form distorted MgO6 octahedra that share corners with two equivalent SiO4 tetrahedra and edges with three equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 1.93–2.21 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two equivalent MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–57°. There are a spread of Si–O bond distances ranging from 1.65–1.67 Å. There are six inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the second O site, O is bonded in a bent 150 degrees geometry to two equivalent Si atoms. In the third O site, O is bonded in a rectangular see-saw-like geometry to three Mg and one Si atom. In the fourth O site, O is bonded in a 4-coordinate geometry to three Mg and one O atom. The O–O bond length is 1.44 Å. In the fifth O site, O is bonded in a 4-coordinate geometry to three Mg and one O atom. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms.