DOI: 10.17188/1290762
title: Materials Data on Mg17(As3O16)2 by Materials Project

description: Mg17(As3O16)2 crystallizes in the monoclinic P2/m space group. The structure is three-dimensional. there are six inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO6 octahedra, corners with three AsO4 tetrahedra, an edgeedge with one AsO6 octahedra, and edges with six MgO6 octahedra. The corner-sharing octahedra tilt angles range from 3–17°. There are a spread of Mg–O bond distances ranging from 2.05–2.18 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one MgO6 octahedra, corners with three AsO4 tetrahedra, an edgeedge with one AsO6 octahedra, and edges with six MgO6 octahedra. The corner-sharing octahedral tilt angles are 1°. There are a spread of Mg–O bond distances ranging from 2.08–2.16 Å. 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 three AsO4 tetrahedra, an edgeedge with one AsO6 octahedra, and edges with six MgO6 octahedra. The corner-sharing octahedral tilt angles are 16°. There are a spread of Mg–O bond distances ranging from 2.00–2.20 Å. In the fourth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with three equivalent MgO6 octahedra, corners with three AsO4 tetrahedra, an edgeedge with one AsO6 octahedra, and edges with five MgO6 octahedra. The corner-sharing octahedra tilt angles range from 8–18°. There are a spread of Mg–O bond distances ranging from 2.06–2.17 Å. In the fifth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, edges with two AsO6 octahedra, and edges with seven MgO6 octahedra. The corner-sharing octahedra tilt angles range from 3–18°. There are a spread of Mg–O bond distances ranging from 2.08–2.28 Å. In the sixth Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with six MgO6 octahedra, edges with two equivalent AsO6 octahedra, and edges with eight MgO6 octahedra. The corner-sharing octahedra tilt angles range from 1–16°. There are two shorter (2.13 Å) and four longer (2.17 Å) Mg–O bond lengths. There are four inequivalent As5+ sites. In the first As5+ site, 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 52–59°. There are a spread of As–O bond distances ranging from 1.70–1.77 Å. In the second As5+ site, 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 51–56°. There are a spread of As–O bond distances ranging from 1.70–1.75 Å. In the third As5+ site, As5+ is bonded to six O2- atoms to form AsO6 octahedra that share edges with ten MgO6 octahedra. There is four shorter (1.87 Å) and two longer (1.90 Å) As–O bond length. In the fourth As5+ site, As5+ is bonded to six O2- atoms to form AsO6 octahedra that share edges with twelve MgO6 octahedra. There is four shorter (1.87 Å) and two longer (1.89 Å) As–O bond length. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded to four Mg2+ and one As5+ atom to form OMg4As square pyramids that share corners with three OMg4As square pyramids, corners with two equivalent OMg3As trigonal pyramids, edges with two equivalent OMg6 octahedra, edges with five OMg5 square pyramids, and an edgeedge with one OMg3As trigonal pyramid. In the second O2- site, O2- is bonded to three Mg2+ and one As5+ atom to form distorted OMg3As trigonal pyramids that share corners with two equivalent OMg6 octahedra, a cornercorner with one OMg5 square pyramid, and edges with three OMg4As square pyramids. The corner-sharing octahedral tilt angles are 3°. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the fourth O2- site, O2- is bonded to six Mg2+ atoms to form OMg6 octahedra that share a cornercorner with one OMg6 octahedra, corners with two equivalent OMg5 square pyramids, corners with two equivalent OMg3As trigonal pyramids, edges with seven OMg4As square pyramids, and edges with two equivalent OMg3As trigonal pyramids. The corner-sharing octahedral tilt angles are 0°. In the fifth O2- site, O2- is bonded to four Mg2+ and one As5+ atom to form OMg4As square pyramids that share corners with four OMg4As square pyramids, a cornercorner with one OMg3As trigonal pyramid, edges with two equivalent OMg6 octahedra, edges with five OMg5 square pyramids, and an edgeedge with one OMg3As trigonal pyramid. In the sixth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one As5+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one As5+ atom. In the eighth O2- site, O2- is bonded to three Mg2+ and one As5+ atom to form OMg3As trigonal pyramids that share corners with four OMg5 square pyramids, corners with two equivalent OMg3As trigonal pyramids, an edgeedge with one OMg6 octahedra, edges with two equivalent OMg4As square pyramids, and an edgeedge with one OMg3As trigonal pyramid. In the ninth O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Mg2+ and one As5+ atom. In the tenth O2- site, O2- is bonded to five Mg2+ atoms to form OMg5 square pyramids that share corners with two equivalent OMg6 octahedra, corners with five OMg3As trigonal pyramids, and edges with five OMg4As square pyramids. The corner-sharing octahedral tilt angles are 10°. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the twelfth O2- site, O2- is bonded to four Mg2+ and one As5+ atom to form OMg4As square pyramids that share corners with five OMg4As square pyramids, an edgeedge with one OMg6 octahedra, edges with two equivalent OMg5 square pyramids, and edges with four equivalent OMg3As trigonal pyramids.