Materials Data on Mg3Si(O2F)2 by Materials Project

Mg3SiO4F2 is beta indium sulfide-derived structured and crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to four O2- and two equivalent F1- atoms to form MgO4F2 octahedra that share corners with six MgO4F2 octahedra, corners with two equivalent SiO4 tetrahedra, edges with three MgO4F2 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–59°. There are a spread of Mg–O bond distances ranging from 2.02–2.19 Å. There are one shorter (2.01 Å) and one longer (2.05 Å) Mg–F bond lengths. In the second Mg2+ site, Mg2+ is bonded to four O2- and two equivalent F1- atoms to form MgO4F2 octahedra that share corners with eight equivalent MgO4F2 octahedra, corners with two equivalent SiO4 tetrahedra, edges with two equivalent MgO4F2 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 49–57°. There are a spread of Mg–O bond distances ranging from 2.05–2.23 Å. Both Mg–F bond lengths are 2.04 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with six MgO4F2 octahedra and edges with three MgO4F2 octahedra. The corner-sharing octahedra tilt angles range from 56–60°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Mg2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Mg2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Mg2+ and one Si4+ atom. F1- is bonded in a distorted trigonal planar geometry to three Mg2+ atoms.