Materials Data on Sr4Nb2O9 by Materials Project

Abstract

Sr4Nb2O9 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are three inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with two equivalent SrO12 cuboctahedra, faces with two equivalent SrO12 cuboctahedra, faces with two equivalent SrO6 octahedra, and faces with six NbO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.56–3.03 Å. In the second Sr2+ site, Sr2+ is bonded in a distorted q6 geometry to nine O2- atoms. There are a spread of Sr–O bond distances ranging from 2.64–3.01 Å. In the third Sr2+ site, Sr2+ is bonded to six O2- atoms to form SrO6 octahedra that share corners with six NbO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–33°. There are a spread of Sr–O bond distances ranging from 2.39–2.45 Å. There are three inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent SrO6 octahedra, and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (1.97 Å) and two longer (2.09 Å) Nb–O bond lengths. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with two equivalent NbO6 octahedra, corners with four equivalent SrO6 octahedra, and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–33°. There are a spread of Nb–O bond distances ranging from 1.90–2.34 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra and faces with four equivalent SrO12 cuboctahedra. The corner-sharing octahedral tilt angles are 0°. There are four shorter (1.98 Å) and two longer (2.06 Å) Nb–O bond lengths. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded in a 6-coordinate geometry to four Sr2+ and two Nb5+ atoms. In the second O2- site, O2- is bonded in a 5-coordinate geometry to four Sr2+ and one Nb5+ atom. In the third O2- site, O2- is bonded in a 1-coordinate geometry to four Sr2+ and two Nb5+ atoms. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to three Sr2+ and one Nb5+ atom. In the fifth O2- site, O2- is bonded in a 2-coordinate geometry to five Sr2+ and one Nb5+ atom.