Materials Data on Nb3Pb2O7F5 by Materials Project

Abstract

Pb2Nb3O7F5 crystallizes in the orthorhombic Imm2 space group. The structure is three-dimensional. there are three inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to five O2- and one F1- atom to form distorted NbO5F octahedra that share corners with five NbO5F octahedra and faces with four equivalent PbO4F8 cuboctahedra. The corner-sharing octahedra tilt angles range from 0–25°. There are a spread of Nb–O bond distances ranging from 1.86–2.02 Å. The Nb–F bond length is 2.29 Å. In the second Nb5+ site, Nb5+ is bonded to three O2- and three F1- atoms to form distorted corner-sharing NbO3F3 octahedra. The corner-sharing octahedra tilt angles range from 0–23°. There is one shorter (1.77 Å) and two longer (1.97 Å) Nb–O bond length. There are two shorter (2.02 Å) and one longer (2.26 Å) Nb–F bond lengths. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 0–16°. There are a spread of Nb–O bond distances ranging from 1.96–2.26 Å. There are two inequivalent Pb2+ sites. In the first Pb2+ site, Pb2+ is bonded in a 4-coordinate geometry to eight F1- atoms. There are a spread of Pb–F bond distances ranging from 2.39–2.92 Å. In the second Pb2+ site, Pb2+ is bonded to four O2- and eight F1- atoms to form PbO4F8 cuboctahedra that share corners with four equivalent PbO4F8 cuboctahedra, faces with four equivalent PbO4F8 cuboctahedra, and faces with four equivalent NbO5F octahedra. All Pb–O bond lengths are 2.89 Å. There are a spread of Pb–F bond distances ranging from 2.65–2.78 Å. There are seven inequivalent O2- sites. In the first O2- site, O2- is bonded in a linear geometry to two Nb5+ atoms. In the second O2- site, O2- is bonded in a distorted linear geometry to two Nb5+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent Nb5+ atoms. In the fifth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Nb5+ atoms. In the sixth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Nb5+ and two equivalent Pb2+ atoms. In the seventh O2- site, O2- is bonded in a bent 150 degrees geometry to two equivalent Nb5+ and two equivalent Pb2+ atoms. There are five inequivalent F1- sites. In the first F1- site, F1- is bonded in a 1-coordinate geometry to one Nb5+ and four equivalent Pb2+ atoms. In the second F1- site, F1- is bonded in a distorted single-bond geometry to one Nb5+ and four equivalent Pb2+ atoms. In the third F1- site, F1- is bonded to four Pb2+ atoms to form a mixture of distorted edge and corner-sharing FPb4 tetrahedra. In the fourth F1- site, F1- is bonded to four Pb2+ atoms to form a mixture of distorted edge and corner-sharing FPb4 tetrahedra. In the fifth F1- site, F1- is bonded in a bent 150 degrees geometry to two equivalent Nb5+ atoms.