Materials Data on Sr3Nb2CuO9 by Materials Project
Sr3CuNb2O9 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 12-coordinate geometry to twelve O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–3.20 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with two equivalent CuO6 octahedra, and faces with six equivalent NbO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.72–3.14 Å. Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with three equivalent NbO6 octahedra, corners with three equivalent CuO6 octahedra, and faces with three equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–17°. There are a spread of Nb–O bond distances ranging from 1.91–2.12 Å. Cu2+ is bonded to six O2- atoms to form CuO6 octahedra that share corners with six equivalent NbO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 13–17°. There are four shorter (1.97 Å) and two longer (2.43 Å) Cu–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Sr2+ and two equivalent Nb5+ atoms to form distorted corner-sharing OSr4Nb2 octahedra. The corner-sharing octahedral tilt angles are 0°. In the second O2- site, O2- is bonded in a 1-coordinate geometry to four Sr2+, one Nb5+, and one Cu2+ atom. In the third O2- site, O2- is bonded in a 2-coordinate geometry to four Sr2+, one Nb5+, and one Cu2+ atom. In the fourth O2- site, O2- is bonded in a distorted linear geometry to four Sr2+ and two equivalent Nb5+ atoms.