Materials Data on BaY2Si2O7F2 by Materials Project
BaY2(Si2O7)F2 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. Ba2+ is bonded in a 9-coordinate geometry to seven O2- and two F1- atoms. There are a spread of Ba–O bond distances ranging from 2.72–3.07 Å. There are one shorter (2.64 Å) and one longer (2.74 Å) Ba–F bond lengths. There are two inequivalent Y3+ sites. In the first Y3+ site, Y3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Y–O bond distances ranging from 2.25–2.69 Å. In the second Y3+ site, Y3+ is bonded in a 8-coordinate geometry to four O2- and four F1- atoms. There are a spread of Y–O bond distances ranging from 2.32–2.46 Å. There are a spread of Y–F bond distances ranging from 2.22–2.48 Å. There are two inequivalent Si4+ sites. In the first Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.63–1.69 Å. In the second Si4+ site, Si4+ is bonded to four O2- atoms to form corner-sharing SiO4 tetrahedra. There are a spread of Si–O bond distances ranging from 1.62–1.71 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 120 degrees geometry to one Ba2+, one Y3+, and two Si4+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Y3+, and one Si4+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, one Y3+, and one Si4+ atom. In the fourth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Ba2+, one Y3+, and one Si4+ atom. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two Y3+, and one Si4+ atom. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to one Ba2+, two equivalent Y3+, and one Si4+ atom. In the seventh O2- site, O2- is bonded in a 3-coordinate geometry to two Y3+ and one Si4+ atom. There are two inequivalent F1- sites. In the first F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+ and two equivalent Y3+ atoms. In the second F1- site, F1- is bonded in a 3-coordinate geometry to one Ba2+ and two equivalent Y3+ atoms.