DOI: 10.17188/1692681
title: Materials Data on Ca6Si6H2O19 by Materials Project

description: Ca6Si6O17(OH)2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.35–2.81 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six SiO4 tetrahedra and edges with two equivalent CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.33–2.46 Å. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with four SiO4 tetrahedra and edges with two equivalent CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.34–2.43 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.34–2.80 Å. There are three inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one CaO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 55°. There is two shorter (1.61 Å) and two longer (1.64 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 two CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–60°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two CaO6 octahedra and corners with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 40–61°. There are a spread of Si–O bond distances ranging from 1.62–1.67 Å. H1+ is bonded in a single-bond geometry to one O2- atom. The H–O bond length is 0.97 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two equivalent Si4+ atoms. In the second O2- site, O2- is bonded in a distorted single-bond geometry to three Ca2+ and one H1+ atom. In the third O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form a mixture of distorted edge and corner-sharing OCa3Si tetrahedra. In the fourth O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form a mixture of distorted edge and corner-sharing OCa3Si trigonal pyramids. In the fifth O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form a mixture of distorted edge and corner-sharing OCa3Si trigonal pyramids. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the ninth O2- site, O2- is bonded to three Ca2+ and one Si4+ atom to form a mixture of distorted edge and corner-sharing OCa3Si trigonal pyramids. In the tenth O2- site, O2- is bonded in a bent 150 degrees geometry to two Si4+ atoms.