Materials Data on MgCr(SiO3)2 by Materials Project

MgCr(SiO3)2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Mg2+ is bonded in a distorted rectangular see-saw-like geometry to four O2- atoms. There are a spread of Mg–O bond distances ranging from 1.97–2.05 Å. Cr2+ is bonded to six O2- atoms to form CrO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent CrO6 octahedra. There are a spread of Cr–O bond distances ranging from 2.06–2.40 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 33–64°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent CrO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–66°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Cr2+, and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted T-shaped geometry to one Mg2+, one Cr2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Cr2+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Mg2+, two equivalent Cr2+, and one Si4+ atom.