Materials Data on Mg3Si2O9 by Materials Project

Mg3Si2O9 crystallizes in the hexagonal P6_3 space group. The structure is two-dimensional and consists of two Mg3Si2O9 sheets oriented in the (0, 0, 1) direction. Mg is bonded to six O atoms to form MgO6 octahedra that share corners with two 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. There are two inequivalent Si sites. In the first Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three equivalent 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. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with three equivalent 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 five 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 distorted rectangular see-saw-like geometry to three equivalent Mg and one Si atom. In the third O site, O is bonded in a trigonal non-coplanar geometry to three equivalent Mg atoms. In the fourth O site, O is bonded in a trigonal non-coplanar geometry to three equivalent Mg atoms. In the fifth O site, O is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mg and one Si atom.