DOI: 10.17188/1270102
title: Materials Data on Ba2Ti2Si2O9F2 by Materials Project

description: Ba2Ti2Si2O9F2 crystallizes in the orthorhombic Pbca space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 11-coordinate geometry to eight O2- and three F1- atoms. There are a spread of Ba–O bond distances ranging from 2.88–3.28 Å. There are a spread of Ba–F bond distances ranging from 2.67–3.04 Å. In the second Ba2+ site, Ba2+ is bonded in a 11-coordinate geometry to eight O2- and three F1- atoms. There are a spread of Ba–O bond distances ranging from 2.80–3.30 Å. There are a spread of Ba–F bond distances ranging from 2.72–3.20 Å. There are two inequivalent Ti4+ sites. In the first Ti4+ site, Ti4+ is bonded to five O2- and one F1- atom to form TiO5F octahedra that share corners with three SiO4 tetrahedra and an edgeedge with one TiO5F octahedra. There are a spread of Ti–O bond distances ranging from 1.86–2.06 Å. The Ti–F bond length is 2.03 Å. In the second Ti4+ site, Ti4+ is bonded to five O2- and one F1- atom to form TiO5F octahedra that share corners with three SiO4 tetrahedra and an edgeedge with one TiO5F octahedra. There are a spread of Ti–O bond distances ranging from 1.87–2.04 Å. The Ti–F bond length is 2.07 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 TiO5F octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 25–53°. There are a spread of Si–O bond distances ranging from 1.62–1.66 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form SiO4 tetrahedra that share corners with three TiO5F octahedra and a cornercorner with one SiO4 tetrahedra. The corner-sharing octahedra tilt angles range from 24–46°. There are a spread of Si–O bond distances ranging from 1.62–1.68 Å. There are nine inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two Ti4+ atoms. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ba2+, one Ti4+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ti4+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to two Ba2+, one Ti4+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ti4+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+, one Ti4+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two equivalent Ba2+ and two Ti4+ atoms. In the eighth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Ba2+, one Ti4+, and one Si4+ atom. In the ninth O2- site, O2- is bonded in a distorted bent 120 degrees geometry to two equivalent Ba2+ and two Si4+ atoms. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to three Ba2+ and one Ti4+ atom. In the second F1- site, F1- is bonded in a 1-coordinate geometry to three Ba2+ and one Ti4+ atom.