Materials Data on CaSi2O5 by Materials Project
CaSi2O5 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are two 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 2.32–2.62 Å. In the second 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 2.32–2.52 Å. There are five inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two SiO6 octahedra and a cornercorner with one SiO5 trigonal bipyramid. The corner-sharing octahedra tilt angles range from 43–55°. There are a spread of Si–O bond distances ranging from 1.61–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two SiO6 octahedra and corners with two equivalent SiO5 trigonal bipyramids. The corner-sharing octahedra tilt angles range from 36–57°. There are a spread of Si–O bond distances ranging from 1.63–1.66 Å. In the third Si4+ site, Si4+ is bonded to five O2- atoms to form SiO5 trigonal bipyramids that share corners with two SiO6 octahedra and corners with three SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 36°. There are a spread of Si–O bond distances ranging from 1.69–1.84 Å. In the fourth Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with four SiO4 tetrahedra and corners with two equivalent SiO5 trigonal bipyramids. There are a spread of Si–O bond distances ranging from 1.78–1.88 Å. In the fifth Si4+ site, Si4+ is bonded to six O2- atoms to form SiO6 octahedra that share corners with four SiO4 tetrahedra and corners with two equivalent SiO5 trigonal bipyramids. There are a spread of Si–O bond distances ranging from 1.76–1.86 Å. There are ten inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the second O2- site, O2- is bonded to two Ca2+ and two Si4+ atoms to form distorted corner-sharing OCa2Si2 tetrahedra. In the third O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Ca2+ and two Si4+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ca2+ and two Si4+ atoms. In the sixth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Si4+ atoms. In the seventh O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two Si4+ atoms. In the eighth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ca2+ and two Si4+ atoms. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Si4+ atoms. In the tenth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one Si4+ atom.