Materials Data on MgSi2 by Materials Project

Abstract

MgSi2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are three inequivalent Mg sites. In the first Mg site, Mg is bonded to four equivalent Mg and eight Si atoms to form distorted MgMg4Si8 cuboctahedra that share corners with eight MgMg2Si10 cuboctahedra, edges with four equivalent MgMg4Si8 cuboctahedra, and faces with eight MgMg4Si8 cuboctahedra. There are two shorter (2.91 Å) and two longer (2.96 Å) Mg–Mg bond lengths. There are a spread of Mg–Si bond distances ranging from 2.80–2.99 Å. In the second Mg site, Mg is bonded to two equivalent Mg and ten Si atoms to form distorted MgMg2Si10 cuboctahedra that share corners with seven MgMg4Si8 cuboctahedra, edges with eight MgMg2Si10 cuboctahedra, and faces with seven MgMg4Si8 cuboctahedra. There are a spread of Mg–Si bond distances ranging from 2.78–3.10 Å. In the third Mg site, Mg is bonded to twelve Si atoms to form MgSi12 cuboctahedra that share corners with six MgMg4Si8 cuboctahedra, edges with eight MgMg2Si10 cuboctahedra, and faces with four MgMg2Si10 cuboctahedra. There are a spread of Mg–Si bond distances ranging from 2.77–2.92 Å. There are four inequivalent Si sites. In the first Si site, Si is bonded in a 9-coordinate geometry to five Mg and four Si atoms. There are a spread of Si–Si bond distances ranging from 2.68–2.79 Å. In the second Si site, Si is bonded in a 9-coordinate geometry to seven Mg and two equivalent Si atoms. There are one shorter (2.72 Å) and one longer (2.73 Å) Si–Si bond lengths. In the third Si site, Si is bonded in a 12-coordinate geometry to four Mg and two equivalent Si atoms. In the fourth Si site, Si is bonded in a 4-coordinate geometry to four Mg and two equivalent Si atoms.