Materials Data on MgAl3SiBO9 by Materials Project

Abstract

MgAl3BSiO9 crystallizes in the orthorhombic Pnma space group. The structure is three-dimensional. Mg2+ is bonded to five O2- atoms to form MgO5 trigonal bipyramids that share corners with two equivalent AlO6 octahedra, corners with three equivalent SiO4 tetrahedra, a cornercorner with one AlO5 trigonal bipyramid, edges with two equivalent AlO6 octahedra, and an edgeedge with one AlO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 51°. There are a spread of Mg–O bond distances ranging from 1.97–2.20 Å. There are three inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent SiO4 tetrahedra, corners with two equivalent AlO5 trigonal bipyramids, edges with two equivalent AlO6 octahedra, and edges with two equivalent MgO5 trigonal bipyramids. There is two shorter (1.90 Å) and four longer (1.93 Å) Al–O bond length. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two equivalent SiO4 tetrahedra, corners with two equivalent MgO5 trigonal bipyramids, edges with two equivalent AlO6 octahedra, and edges with two equivalent AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.89–1.99 Å. In the third Al3+ site, Al3+ is bonded to five O2- atoms to form AlO5 trigonal bipyramids that share corners with two equivalent AlO6 octahedra, a cornercorner with one SiO4 tetrahedra, a cornercorner with one MgO5 trigonal bipyramid, edges with two equivalent AlO6 octahedra, and an edgeedge with one MgO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 59°. There are a spread of Al–O bond distances ranging from 1.82–1.95 Å. B3+ is bonded in a trigonal planar geometry to three O2- atoms. There is one shorter (1.35 Å) and two longer (1.39 Å) B–O bond length. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra, a cornercorner with one AlO5 trigonal bipyramid, and corners with three equivalent MgO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 47–59°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form corner-sharing OMgAl3 trigonal pyramids. In the second O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Al3+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one B3+ atom.