DOI: 10.17188/1284873
title: Materials Data on Ca2TiAlSi2O9F by Materials Project

description: Ca2TiAlSi2O9F 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 six O2- and one F1- atom. There are a spread of Ca–O bond distances ranging from 2.37–2.64 Å. The Ca–F bond length is 2.31 Å. In the second 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 2.29–2.64 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra and corners with four SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Ti–O bond distances ranging from 1.88–2.03 Å. In the second Ti4+ site, Ti4+ is bonded to six O2- atoms to form TiO6 octahedra that share corners with two equivalent TiO6 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 38°. There are a spread of Ti–O bond distances ranging from 1.87–2.03 Å. There are two inequivalent Al3+ sites. In the first Al3+ site, Al3+ is bonded to four O2- and two equivalent F1- atoms to form AlO4F2 octahedra that share corners with two equivalent AlO4F2 octahedra and corners with four SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There is two shorter (1.90 Å) and two longer (1.92 Å) Al–O bond length. Both Al–F bond lengths are 1.86 Å. In the second Al3+ site, Al3+ is bonded to four O2- and two equivalent F1- atoms to form AlO4F2 octahedra that share corners with two equivalent AlO4F2 octahedra and corners with four equivalent SiO4 tetrahedra. The corner-sharing octahedral tilt angles are 37°. There is two shorter (1.90 Å) and two longer (1.92 Å) Al–O bond length. Both Al–F bond lengths are 1.87 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 a cornercorner with one TiO6 octahedra and corners with three AlO4F2 octahedra. The corner-sharing octahedra tilt angles range from 35–52°. There is two shorter (1.65 Å) and two longer (1.66 Å) Si–O bond length. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share a cornercorner with one AlO4F2 octahedra and corners with three TiO6 octahedra. The corner-sharing octahedra tilt angles range from 37–54°. There is one shorter (1.64 Å) and three longer (1.65 Å) Si–O bond length. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Al3+, and one Si4+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one Al3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Ti4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Al3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Al3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+, one Ti4+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a distorted trigonal planar geometry to one Ca2+ and two Ti4+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+, one Ti4+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+, one Ti4+, and one Si4+ atom. F1- is bonded in a 3-coordinate geometry to one Ca2+ and two Al3+ atoms.