Materials Data on Mg3Si2H4O9 by Materials Project
Mg3Si2O5(OH)4 crystallizes in the trigonal P31m space group. The structure is two-dimensional and consists of one Mg3Si2O5(OH)4 sheet oriented in the (0, 0, 1) direction. Mg2+ is bonded to six O2- atoms to form MgO6 octahedra that share corners with two equivalent SiO4 tetrahedra and edges with six equivalent MgO6 octahedra. There are a spread of Mg–O bond distances ranging from 2.04–2.16 Å. Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three equivalent MgO6 octahedra and corners with three equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 56°. There is one shorter (1.61 Å) and three longer (1.67 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 0.97 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. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted single-bond geometry to three equivalent Mg2+ and one H1+ atom. In the second O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three equivalent Mg2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Si4+ atoms. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Mg2+ and one H1+ atom.