DOI: 10.17188/1709761
title: Materials Data on Mg2Al2SiH4O9 by Materials Project

description: Mg2Al2SiH4O9 crystallizes in the triclinic P1 space group. The structure is two-dimensional and consists of two Mg2Al2SiH4O9 sheets oriented in the (0, 0, 1) direction. there are two inequivalent Mg2+ sites. In the first Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.09–2.18 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, edges with three equivalent MgO6 octahedra, and edges with three equivalent AlO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.08–2.18 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- atoms to form AlO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 55–64°. All Al–O bond lengths are 1.76 Å. In the second Al3+ site, Al3+ is bonded to six O2- atoms to form AlO6 octahedra that share a cornercorner with one AlO4 tetrahedra, a cornercorner with one SiO4 tetrahedra, and edges with six MgO6 octahedra. There are a spread of Al–O bond distances ranging from 1.91–2.01 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO6 octahedra, corners with two MgO6 octahedra, and corners with three equivalent AlO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–61°. There is three shorter (1.64 Å) and one longer (1.67 Å) Si–O bond length. There are four inequivalent H1+ sites. In the first H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the second H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. In the third H1+ site, H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.99 Å. In the fourth 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 nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Al3+ and one Si4+ atom. In the second O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Al3+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+, one Al3+, and one H1+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two Mg2+, one Al3+, and one H1+ atom. In the fifth O2- site, O2- is bonded in a distorted tetrahedral geometry to two Mg2+ and two Al3+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+, one Al3+, and one H1+ atom. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Mg2+, one Al3+, and one Si4+ atom. In the eighth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Al3+ and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Mg2+, one Al3+, and one H1+ atom.