Materials Data on Mg3(AsO4)2 by Materials Project

Abstract

Mg3(AsO4)2 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent AsO4 tetrahedra and edges with four MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.20 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six equivalent AsO4 tetrahedra and edges with four equivalent MgO6 octahedra. There are two shorter (2.08 Å) and four longer (2.13 Å) Mg–O bond lengths. As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with nine MgO6 octahedra. The corner-sharing octahedra tilt angles range from 50–56°. There is three shorter (1.72 Å) and one longer (1.78 Å) As–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Mg2+ and one As5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one As5+ atom.