Materials Data on Mg2As2O9 by Materials Project
Mg2As2O9 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Mg sites. In the first Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with five AsO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.14 Å. In the second Mg site, Mg is bonded to six O atoms to form MgO6 octahedra that share corners with five AsO4 tetrahedra and edges with two equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.01–2.14 Å. There are two inequivalent As sites. In the first As site, As is bonded to four O atoms to form AsO4 tetrahedra that share corners with five MgO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 46–59°. There are a spread of As–O bond distances ranging from 1.68–1.80 Å. In the second As site, As is bonded to four O atoms to form AsO4 tetrahedra that share corners with five MgO6 octahedra and a cornercorner with one AsO4 tetrahedra. The corner-sharing octahedra tilt angles range from 38–60°. There are a spread of As–O bond distances ranging from 1.66–1.80 Å. There are nine inequivalent O sites. In the first O site, O is bonded in a bent 150 degrees geometry to one Mg and one As atom. In the second O site, O is bonded in a distorted trigonal planar geometry to two Mg and one As atom. In the third O site, O is bonded in a trigonal planar geometry to two Mg and one As atom. In the fourth O site, O is bonded in a single-bond geometry to one Mg atom. In the fifth O site, O is bonded in a distorted trigonal planar geometry to two Mg and one As atom. In the sixth O site, O is bonded in a single-bond geometry to one Mg atom. In the seventh O site, O is bonded in a bent 120 degrees geometry to one Mg and one As atom. In the eighth O site, O is bonded in a distorted trigonal planar geometry to two Mg and one As atom. In the ninth O site, O is bonded in a bent 120 degrees geometry to two As atoms.