Materials Data on MgSi2O5 by Materials Project

Abstract

MgSi2O5 crystallizes in the orthorhombic Pbam space group. The structure is three-dimensional. Mg2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Mg–O bond distances ranging from 2.13–2.50 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to five O2- atoms to form distorted SiO5 square pyramids that share corners with four equivalent SiO6 octahedra and an edgeedge with one SiO5 square pyramid. The corner-sharing octahedra tilt angles range from 49–51°. There are a spread of Si–O bond distances ranging from 1.70–1.78 Å. In the second Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with four equivalent SiO5 square pyramids and edges with two equivalent SiO6 octahedra. There is four shorter (1.77 Å) and two longer (1.84 Å) Si–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Mg2+ and two Si4+ atoms. In the second O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Si4+ atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 tetrahedra. In the third O2- site, O2- is bonded to two equivalent Mg2+ and two equivalent Si4+ atoms to form a mixture of distorted edge and corner-sharing OMg2Si2 trigonal pyramids. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to three Si4+ atoms.