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 to six O atoms to form MgO6 octahedra that share corners with two equivalent SiO4 tetrahedra and edges with six equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.11 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two equivalent SiO4 tetrahedra and edges with six MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.10 Å. Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. All Si–O bond lengths are 1.65 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 distorted rectangular see-saw-like geometry to three Mg and one Si atom. In the fourth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the fifth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the sixth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms.