Materials Data on Sr2Nb2O7 by Materials Project
Sr2Nb2O7 is Pb (Zr_0.50 Ti_0.48) O_3-like structured and crystallizes in the orthorhombic Cmc2_1 space group. The structure is three-dimensional. there are two inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sr–O bond distances ranging from 2.49–2.96 Å. In the second Sr2+ site, Sr2+ is bonded to twelve O2- atoms to form distorted SrO12 cuboctahedra that share corners with six equivalent SrO12 cuboctahedra, faces with four equivalent SrO12 cuboctahedra, and faces with eight NbO6 octahedra. There are a spread of Sr–O bond distances ranging from 2.54–3.14 Å. There are two inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with four NbO6 octahedra and faces with two equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 16–37°. There are a spread of Nb–O bond distances ranging from 1.85–2.37 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with six NbO6 octahedra and faces with six equivalent SrO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 7–37°. There are a spread of Nb–O bond distances ranging from 1.85–2.36 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a 2-coordinate geometry to three equivalent Sr2+ and two equivalent Nb5+ atoms. In the second O2- site, O2- is bonded to two equivalent Sr2+ and two Nb5+ atoms to form distorted corner-sharing OSr2Nb2 tetrahedra. In the third O2- site, O2- is bonded in a 1-coordinate geometry to three equivalent Sr2+ and one Nb5+ atom. In the fourth O2- site, O2- is bonded to three equivalent Sr2+ and one Nb5+ atom to form distorted corner-sharing OSr3Nb tetrahedra. In the fifth O2- site, O2- is bonded in a 1-coordinate geometry to four equivalent Sr2+ and two equivalent Nb5+ atoms. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two equivalent Sr2+ and two Nb5+ atoms. In the seventh O2- site, O2- is bonded in a 2-coordinate geometry to two Sr2+ and two equivalent Nb5+ atoms.