DOI: 10.17188/1653059
title: Materials Data on MgAl6FeSi2(BO9)2 by Materials Project

description: MgFeAl6Si2(BO9)2 crystallizes in the orthorhombic Pmc2_1 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 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 1.97–2.22 Å. Fe2+ is bonded to five O2- atoms to form FeO5 trigonal bipyramids that share corners with two equivalent AlO6 octahedra, corners with three 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 52°. There are a spread of Fe–O bond distances ranging from 1.99–2.24 Å. There are four inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two SiO4 tetrahedra, corners with two AlO5 trigonal bipyramids, edges with two equivalent AlO6 octahedra, an edgeedge with one MgO5 trigonal bipyramid, and an edgeedge with one FeO5 trigonal bipyramid. There are a spread of Al–O bond distances ranging from 1.90–1.93 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share corners with two SiO4 tetrahedra, a cornercorner with one MgO5 trigonal bipyramid, a cornercorner with one FeO5 trigonal bipyramid, edges with two equivalent AlO6 octahedra, and edges with two AlO5 trigonal bipyramids. There are a spread of Al–O bond distances ranging from 1.88–2.01 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 1.82–1.94 Å. In the fourth 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 FeO5 trigonal bipyramid, edges with two equivalent AlO6 octahedra, and an edgeedge with one FeO5 trigonal bipyramid. The corner-sharing octahedral tilt angles are 59°. There are a spread of Al–O bond distances ranging from 1.82–1.94 Å. There are two inequivalent B3+ sites. In the first B3+ site, 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. In the second B3+ site, 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. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra, a cornercorner with one MgO5 trigonal bipyramid, a cornercorner with one AlO5 trigonal bipyramid, and corners with two equivalent FeO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 47–58°. There are a spread of Si–O bond distances ranging from 1.63–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four AlO6 octahedra, a cornercorner with one FeO5 trigonal bipyramid, a cornercorner with one AlO5 trigonal bipyramid, and corners with two 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 1.63–1.67 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form distorted corner-sharing OMgAl3 trigonal pyramids. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to one Fe2+ and three Al3+ atoms. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to one Mg2+, one Al3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted trigonal planar geometry to one Fe2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded to one Fe2+ and three Al3+ atoms to form corner-sharing OAl3Fe trigonal pyramids. In the sixth O2- site, O2- is bonded to one Mg2+ and three Al3+ atoms to form corner-sharing OMgAl3 trigonal pyramids. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Al3+ and one Si4+ atom. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two equivalent Al3+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one B3+ atom. In the tenth O2- site, O2- is bonded in a distorted trigonal planar geometry to two Al3+ and one B3+ atom. In the eleventh O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the twelfth O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Al3+ and one B3+ atom. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Mg2+, one Al3+, and one Si4+ atom. In the fourteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Fe2+, one Al3+, and one Si4+ atom.