Materials Data on Mg3(AsO4)2 by Materials Project

Abstract

Mg3(AsO4)2 crystallizes in the tetragonal I-4 space group. The structure is three-dimensional. there are four inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two MgO6 octahedra, corners with four AsO4 tetrahedra, edges with two MgO6 octahedra, and an edgeedge with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–60°. There are a spread of Mg–O bond distances ranging from 2.03–2.21 Å. In the second Mg2+ site, Mg2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are four shorter (2.16 Å) and four longer (2.66 Å) Mg–O bond lengths. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with six AsO4 tetrahedra, and edges with two equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Mg–O bond distances ranging from 2.08–2.15 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent MgO6 octahedra, corners with six AsO4 tetrahedra, and edges with two equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Mg–O bond distances ranging from 2.07–2.23 Å. There are three inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four equivalent O2- atoms to form AsO4 tetrahedra that share corners with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 49–51°. All As–O bond lengths are 1.72 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with six MgO6 octahedra and an edgeedge with one MgO6 octahedra. The corner-sharing octahedra tilt angles range from 43–53°. There are a spread of As–O bond distances ranging from 1.70–1.78 Å. In the third As5+ site, As5+ is bonded to four equivalent O2- atoms to form AsO4 tetrahedra that share corners with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 48–51°. All As–O bond lengths are 1.72 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Mg2+ and one As5+ atom. In the second O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the third O2- site, O2- is bonded to three Mg2+ and one As5+ atom to form corner-sharing OMg3As tetrahedra. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two Mg2+ and one As5+ atom.