DOI: 10.17188/1350708
title: Materials Data on Ca8Si5O18 by Materials Project

description: Ca8Si5O18 crystallizes in the orthorhombic Pbcn space group. The structure is three-dimensional. there are five inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with eight CaO6 octahedra, corners with four SiO4 tetrahedra, edges with two CaO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–68°. There are a spread of Ca–O bond distances ranging from 2.33–2.52 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with four equivalent CaO6 octahedra, corners with two equivalent SiO4 tetrahedra, edges with four CaO6 octahedra, and edges with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 64–68°. There are two shorter (2.34 Å) and four longer (2.41 Å) Ca–O bond lengths. In the third Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with four CaO6 octahedra, corners with two SiO4 tetrahedra, edges with three CaO6 octahedra, and edges with two SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 60–75°. There are a spread of Ca–O bond distances ranging from 2.33–2.50 Å. In the fourth Ca2+ site, Ca2+ is bonded to six O2- atoms to form distorted CaO6 octahedra that share corners with four CaO6 octahedra, corners with five SiO4 tetrahedra, an edgeedge with one CaO6 octahedra, and an edgeedge with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 54–75°. There are a spread of Ca–O bond distances ranging from 2.24–2.52 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.37–2.65 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 corners with six CaO6 octahedra and edges with three CaO6 octahedra. The corner-sharing octahedra tilt angles range from 50–60°. There are a spread of Si–O bond distances ranging from 1.64–1.67 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four CaO6 octahedra, a cornercorner with one SiO4 tetrahedra, and edges with two CaO6 octahedra. The corner-sharing octahedra tilt angles range from 52–63°. There are a spread of Si–O bond distances ranging from 1.63–1.73 Å. In the third Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with four equivalent CaO6 octahedra and corners with two equivalent SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 53–69°. There is two shorter (1.61 Å) and two longer (1.68 Å) Si–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 2-coordinate geometry to two Ca2+ and two Si4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to three Ca2+ and one Si4+ atom. 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 in a 3-coordinate geometry to two Ca2+ and one Si4+ atom.