Materials Data on Mg7Si2(H3O7)2 by Materials Project

Abstract

Mg7Si2H6O14 crystallizes in the hexagonal P6_3 space group. The structure is three-dimensional. there are three inequivalent Mg2+ sites. In the first 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 2.02–2.47 Å. In the second Mg2+ site, Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two SiO4 tetrahedra, edges with three MgO6 octahedra, and an edgeedge with one SiO4 tetrahedra. There are a spread of Mg–O bond distances ranging from 2.02–2.23 Å. In the third Mg2+ site, Mg2+ is bonded to six O2- atoms to form edge-sharing MgO6 octahedra. There are three shorter (2.07 Å) and three longer (2.09 Å) Mg–O bond lengths. 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 three equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There is three shorter (1.66 Å) and one longer (1.68 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent MgO6 octahedra and edges with three equivalent MgO6 octahedra. The corner-sharing octahedral tilt angles are 58°. There is one shorter (1.63 Å) and three longer (1.66 Å) Si–O bond length. There are two 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 0.98 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three Mg2+ and one H1+ atom. In the second O2- site, O2- is bonded in a 3-coordinate geometry to two Mg2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to four Mg2+ and one H1+ atom. In the fourth O2- site, O2- is bonded in a distorted tetrahedral geometry to three equivalent Mg2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three equivalent Mg2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Mg2+ and one Si4+ atom.