Materials Data on MgSi2 by Materials Project

MgSi2 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are four inequivalent Mg sites. In the first Mg site, Mg is bonded in a 4-coordinate geometry to five Si atoms. There are a spread of Mg–Si bond distances ranging from 2.71–2.99 Å. In the second Mg site, Mg is bonded to eight Si atoms to form MgSi8 hexagonal bipyramids that share corners with two equivalent MgSi5 tetrahedra and edges with eight MgSi8 hexagonal bipyramids. There are a spread of Mg–Si bond distances ranging from 2.87–3.08 Å. In the third Mg site, Mg is bonded to eight Si atoms to form distorted edge-sharing MgSi8 hexagonal bipyramids. There are a spread of Mg–Si bond distances ranging from 2.79–3.18 Å. In the fourth Mg site, Mg is bonded to five Si atoms to form distorted MgSi5 tetrahedra that share corners with two equivalent MgSi8 hexagonal bipyramids and corners with four equivalent MgSi5 tetrahedra. There are a spread of Mg–Si bond distances ranging from 2.69–3.03 Å. There are eight inequivalent Si sites. In the first Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. There are one shorter (2.37 Å) and two longer (2.38 Å) Si–Si bond lengths. In the second Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. Both Si–Si bond lengths are 2.38 Å. In the third Si site, Si is bonded in a 5-coordinate geometry to two equivalent Mg and three Si atoms. There are two shorter (2.34 Å) and one longer (2.37 Å) Si–Si bond lengths. In the fourth Si site, Si is bonded in a 5-coordinate geometry to two equivalent Mg and three Si atoms. There are two shorter (2.36 Å) and one longer (2.38 Å) Si–Si bond lengths. In the fifth Si site, Si is bonded in a 7-coordinate geometry to five Mg and two equivalent Si atoms. In the sixth Si site, Si is bonded in a 7-coordinate geometry to four Mg and three Si atoms. The Si–Si bond length is 2.42 Å. In the seventh Si site, Si is bonded in a distorted hexagonal planar geometry to two equivalent Mg and four Si atoms. In the eighth Si site, Si is bonded in a 6-coordinate geometry to three Mg and three Si atoms.