DOI: 10.17188/1266923
title: Materials Data on Mg7As6(HO6)4 by Materials Project

description: Mg7As6(HO6)4 crystallizes in the triclinic P-1 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 equivalent MgO6 octahedra, corners with four AsO4 tetrahedra, and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedral tilt angles are 57°. There are a spread of Mg–O bond distances ranging from 2.16–2.44 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form distorted MgO6 octahedra that share a cornercorner with one MgO6 octahedra, corners with five AsO4 tetrahedra, an edgeedge with one MgO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 57°. There are a spread of Mg–O bond distances ranging from 2.07–2.19 Å. In the third Mg2+ site, Mg2+ is bonded to five O2- atoms to form distorted MgO5 trigonal bipyramids that share a cornercorner with one MgO6 octahedra, corners with three AsO4 tetrahedra, and an edgeedge with one MgO6 octahedra. The corner-sharing octahedral tilt angles are 60°. There are a spread of Mg–O bond distances ranging from 2.00–2.20 Å. In the fourth Mg2+ site, Mg2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Mg–O bond distances ranging from 2.05–2.58 Å. There are three inequivalent As5+ sites. In the first As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with three MgO6 octahedra and corners with two equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 57–70°. There are a spread of As–O bond distances ranging from 1.70–1.81 Å. In the second As5+ site, As5+ is bonded to four O2- atoms to form AsO4 tetrahedra that share corners with four MgO6 octahedra and a cornercorner with one MgO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 25–55°. There is two shorter (1.72 Å) and two longer (1.73 Å) As–O bond length. In the third As5+ site, As5+ is bonded in a distorted trigonal non-coplanar geometry to three O2- atoms. There are a spread of As–O bond distances ranging from 1.76–1.95 Å. There are two inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a linear geometry to two O2- atoms. There is one shorter (1.05 Å) and one longer (1.47 Å) H–O bond length. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. There are twelve inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two 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 in a distorted trigonal planar geometry to two Mg2+ and one As5+ atom. In the fourth O2- site, O2- is bonded in a distorted water-like geometry to one As5+ and one O2- atom. The O–O bond length is 1.47 Å. In the fifth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Mg2+ and one As5+ atom. 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 T-shaped geometry to one Mg2+, one As5+, and one H1+ atom. In the eighth O2- site, O2- is bonded in a trigonal planar geometry to two Mg2+ and one As5+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal non-coplanar geometry to two Mg2+ and one As5+ atom. In the tenth O2- site, O2- is bonded in a distorted single-bond geometry to two Mg2+, one As5+, and one H1+ atom. In the eleventh O2- site, O2- is bonded in a distorted single-bond geometry to one Mg2+, one H1+, and one O2- atom. In the twelfth O2- site, O2- is bonded in a trigonal planar geometry to two Mg2+ and one As5+ atom.