Materials Data on CaMg(SiO3)2 by Materials Project

CaMgSi2O6 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. Ca2+ is bonded in a 7-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.31–3.00 Å. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent SiO4 tetrahedra, corners with two equivalent SiO5 trigonal bipyramids, edges with two equivalent MgO6 octahedra, and an edgeedge with one SiO5 trigonal bipyramid. There are a spread of Mg–O bond distances ranging from 1.94–2.19 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to five O2- atoms to form SiO5 trigonal bipyramids that share corners with two equivalent MgO6 octahedra, corners with two equivalent SiO5 trigonal bipyramids, an edgeedge with one MgO6 octahedra, and an edgeedge with one SiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 34–55°. There are a spread of Si–O bond distances ranging from 1.72–1.92 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–62°. There are a spread of Si–O bond distances ranging from 1.59–1.70 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two equivalent Mg2+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two equivalent Si4+ atoms. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Mg2+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ca2+ and two equivalent Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted see-saw-like geometry to one Ca2+, one Mg2+, and two equivalent Si4+ atoms. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Ca2+, two equivalent Mg2+, and one Si4+ atom.