Materials Data on Ca4Si2O7F2 by Materials Project
Ca4Si2O7F2 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to four O2- and three F1- atoms. There are a spread of Ca–O bond distances ranging from 2.29–2.84 Å. There are a spread of Ca–F bond distances ranging from 2.37–2.41 Å. In the second Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to six O2- and one F1- atom. There are a spread of Ca–O bond distances ranging from 2.34–2.65 Å. The Ca–F bond length is 2.34 Å. In the third Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to five O2- and three F1- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.92 Å. There are a spread of Ca–F bond distances ranging from 2.36–2.40 Å. In the fourth Ca2+ site, Ca2+ is bonded to five O2- and one F1- atom to form CaO5F octahedra that share corners with five SiO4 tetrahedra. There are a spread of Ca–O bond distances ranging from 2.31–2.43 Å. The Ca–F bond length is 2.39 Å. 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 CaO5F octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 42–62°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with two equivalent CaO5F octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 34–48°. There are a spread of Si–O bond distances ranging from 1.63–1.69 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate 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 2-coordinate geometry to two Ca2+ and two Si4+ atoms. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded to four Ca2+ atoms to form a mixture of edge and corner-sharing FCa4 tetrahedra. In the second F1- site, F1- is bonded to four Ca2+ atoms to form a mixture of edge and corner-sharing FCa4 tetrahedra.