Materials Data on CsTiNb(O2F)2 by Materials Project
CsTiNb(O2F)2 crystallizes in the monoclinic C2 space group. The structure is three-dimensional. there are two inequivalent Cs1+ sites. In the first Cs1+ site, Cs1+ is bonded to five O2- and one F1- atom to form distorted CsO5F octahedra that share corners with six equivalent TiO3F3 octahedra and corners with six equivalent NbO5F octahedra. The corner-sharing octahedra tilt angles range from 67–70°. There are a spread of Cs–O bond distances ranging from 3.20–3.48 Å. The Cs–F bond length is 3.28 Å. In the second Cs1+ site, Cs1+ is bonded to three O2- and three F1- atoms to form distorted CsO3F3 octahedra that share corners with six equivalent TiO3F3 octahedra and corners with six equivalent NbO5F octahedra. The corner-sharing octahedra tilt angles range from 68–77°. There are one shorter (3.24 Å) and two longer (3.53 Å) Cs–O bond lengths. There are two shorter (3.16 Å) and one longer (3.27 Å) Cs–F bond lengths. Ti4+ is bonded to three O2- and three F1- atoms to form TiO3F3 octahedra that share corners with two equivalent TiO3F3 octahedra, corners with four equivalent NbO5F octahedra, and corners with six CsO5F octahedra. The corner-sharing octahedra tilt angles range from 28–76°. There are a spread of Ti–O bond distances ranging from 1.85–1.89 Å. There are a spread of Ti–F bond distances ranging from 2.01–2.09 Å. Nb5+ is bonded to five O2- and one F1- atom to form NbO5F octahedra that share corners with two equivalent NbO5F octahedra, corners with four equivalent TiO3F3 octahedra, and corners with six CsO5F octahedra. The corner-sharing octahedra tilt angles range from 28–77°. There are a spread of Nb–O bond distances ranging from 1.94–2.00 Å. The Nb–F bond length is 2.20 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one Ti4+, and one Nb5+ atom. In the second O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+, one Ti4+, and one Nb5+ atom. In the third O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Cs1+ and two equivalent Nb5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to one Cs1+ and two equivalent Nb5+ atoms. In the fifth O2- site, O2- is bonded in a bent 150 degrees geometry to one Cs1+, one Ti4+, and one Nb5+ atom. There are three inequivalent F1- sites. In the first F1- site, F1- is bonded in a 2-coordinate geometry to one Cs1+ and two equivalent Ti4+ atoms. In the second F1- site, F1- is bonded in a 2-coordinate geometry to one Cs1+, one Ti4+, and one Nb5+ atom. In the third F1- site, F1- is bonded in a distorted bent 150 degrees geometry to one Cs1+ and two equivalent Ti4+ atoms.