Materials Data on Mg5(Si4O15)2 by Materials Project

Mg5(Si2O7)4O2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional and consists of four water molecules and one Mg5(Si2O7)4 framework. In the Mg5(Si2O7)4 framework, there are three inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four equivalent SiO4 tetrahedra and edges with six MgO6 octahedra. There are two shorter (2.06 Å) and four longer (2.18 Å) Mg–O bond lengths. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with four SiO4 tetrahedra and edges with five MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.13 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 three MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.19 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 MgO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–59°. There is two shorter (1.63 Å) and two longer (1.64 Å) Si–O bond length. In the second Si site, Si is bonded to four O atoms to form SiO4 tetrahedra that share corners with two MgO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 52–55°. There are a spread of Si–O bond distances ranging from 1.61–1.65 Å. There are nine inequivalent O sites. In the first O site, O is bonded in a distorted trigonal planar geometry to two Mg and one Si atom. In the second O site, O is bonded in a single-bond geometry to one Mg and one O atom. The O–O bond length is 2.08 Å. 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 linear geometry to two equivalent Si atoms. In the fifth O site, O is bonded in a bent 150 degrees geometry to two Si atoms. In the sixth O site, O is bonded in a distorted bent 150 degrees geometry to two Si atoms. In the seventh O site, O is bonded in a 2-coordinate geometry to two equivalent O atoms. In the eighth O site, O is bonded in a trigonal non-coplanar geometry to three Mg atoms. In the ninth O site, O is bonded in a rectangular see-saw-like geometry to three Mg and one Si atom.