DOI: 10.17188/1263291
title: Materials Data on Ca4Nb2O9 by Materials Project

description: Ca4Nb2O9 crystallizes in the triclinic P-1 space group. The structure is three-dimensional. there are nine inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six NbO6 octahedra. The corner-sharing octahedra tilt angles range from 31–44°. There are a spread of Ca–O bond distances ranging from 2.28–2.35 Å. In the second Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.32–2.78 Å. In the third Ca2+ site, Ca2+ is bonded in a 6-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.29–2.60 Å. In the fourth Ca2+ site, Ca2+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ca–O bond distances ranging from 2.30–2.83 Å. In the fifth Ca2+ site, Ca2+ is bonded in a 5-coordinate geometry to six O2- atoms. There are a spread of Ca–O bond distances ranging from 2.33–2.87 Å. In the sixth Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six NbO6 octahedra. The corner-sharing octahedra tilt angles range from 41–43°. There are a spread of Ca–O bond distances ranging from 2.30–2.36 Å. In the seventh Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six NbO6 octahedra. The corner-sharing octahedra tilt angles range from 34–47°. There are a spread of Ca–O bond distances ranging from 2.28–2.33 Å. In the eighth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.28–2.84 Å. In the ninth Ca2+ site, Ca2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ca–O bond distances ranging from 2.29–2.86 Å. There are five inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 28–42°. There are a spread of Nb–O bond distances ranging from 1.91–2.28 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share a cornercorner with one NbO6 octahedra and corners with five CaO6 octahedra. The corner-sharing octahedra tilt angles range from 31–47°. There are a spread of Nb–O bond distances ranging from 1.91–2.46 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted NbO6 octahedra that share corners with three CaO6 octahedra and corners with three equivalent NbO6 octahedra. The corner-sharing octahedra tilt angles range from 28–41°. There are a spread of Nb–O bond distances ranging from 1.90–2.36 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent NbO6 octahedra and corners with four CaO6 octahedra. The corner-sharing octahedra tilt angles range from 31–44°. There are a spread of Nb–O bond distances ranging from 1.99–2.13 Å. In the fifth Nb5+ site, Nb5+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with two equivalent NbO6 octahedra and corners with four CaO6 octahedra. The corner-sharing octahedra tilt angles range from 28–38°. There are a spread of Nb–O bond distances ranging from 1.98–2.11 Å. There are eighteen inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Nb5+ atom. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Nb5+ atoms. In the third O2- site, O2- is bonded in a 5-coordinate geometry to four Ca2+ and one Nb5+ atom. In the fourth O2- site, O2- is bonded to two Ca2+ and two Nb5+ atoms to form distorted OCa2Nb2 trigonal pyramids that share a cornercorner with one OCa3Nb tetrahedra, corners with two OCa2Nb2 trigonal pyramids, and an edgeedge with one OCa3Nb trigonal pyramid. In the fifth O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Nb5+ atoms. In the sixth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Nb5+ atom. In the seventh O2- site, O2- is bonded in a distorted see-saw-like geometry to three Ca2+ and one Nb5+ atom. In the eighth O2- site, O2- is bonded to three Ca2+ and one Nb5+ atom to form distorted OCa3Nb trigonal pyramids that share a cornercorner with one OCa3Nb tetrahedra, corners with three OCa2Nb2 trigonal pyramids, and an edgeedge with one OCa2Nb2 trigonal pyramid. In the ninth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Nb5+ atom. In the tenth O2- site, O2- is bonded in a 5-coordinate geometry to four Ca2+ and one Nb5+ atom. In the eleventh O2- site, O2- is bonded in a 5-coordinate geometry to four Ca2+ and one Nb5+ atom. In the twelfth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Nb5+ atom. In the thirteenth O2- site, O2- is bonded in a 5-coordinate geometry to four Ca2+ and one Nb5+ atom. In the fourteenth O2- site, O2- is bonded in a distorted see-saw-like geometry to two Ca2+ and two Nb5+ atoms. In the fifteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Ca2+ and one Nb5+ atom. In the sixteenth O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+ and two Nb5+ atoms. In the seventeenth O2- site, O2- is bonded in a 1-coordinate geometry to three Ca2+ and two Nb5+ atoms. In the eighteenth O2- site, O2- is bonded to three Ca2+ and one Nb5+ atom to form distorted OCa3Nb tetrahedra that share a cornercorner with one OCa3Nb tetrahedra and corners with two OCa2Nb2 trigonal pyramids.