Materials Data on Ca2Nb2O7 by Materials Project
Ca2Nb2O7 crystallizes in the monoclinic P2_1 space group. The structure is three-dimensional. there are four inequivalent Ca2+ sites. In the first 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 2.33–2.80 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 2.32–2.52 Å. In the third 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 2.31–2.60 Å. In the fourth 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 2.41–3.01 Å. There are four inequivalent Nb5+ sites. In the first Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 22–45°. There are a spread of Nb–O bond distances ranging from 1.87–2.33 Å. In the second Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 27–45°. There are a spread of Nb–O bond distances ranging from 1.83–2.34 Å. In the third Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 22–42°. There are a spread of Nb–O bond distances ranging from 1.87–2.29 Å. In the fourth Nb5+ site, Nb5+ is bonded to six O2- atoms to form distorted corner-sharing NbO6 octahedra. The corner-sharing octahedra tilt angles range from 27–42°. There are a spread of Nb–O bond distances ranging from 1.87–2.31 Å. There are fourteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Ca2+ and one Nb5+ atom to form a mixture of distorted corner and edge-sharing OCa3Nb tetrahedra. In the second O2- site, O2- is bonded to two Ca2+ and two Nb5+ atoms to form a mixture of distorted corner and edge-sharing OCa2Nb2 tetrahedra. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two Ca2+ and two Nb5+ atoms. In the fourth O2- site, O2- is bonded to two Ca2+ and two Nb5+ atoms to form a mixture of distorted corner and edge-sharing OCa2Nb2 tetrahedra. In the fifth O2- site, O2- is bonded to three Ca2+ and one Nb5+ atom to form a mixture of distorted corner and edge-sharing OCa3Nb tetrahedra. In the sixth O2- site, O2- is bonded in a 1-coordinate geometry to two Ca2+ and two Nb5+ atoms. In the seventh O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+ and two equivalent Nb5+ atoms. In the eighth O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one Nb5+ atom. In the ninth O2- site, O2- is bonded in a 5-coordinate geometry to three Ca2+ and two equivalent Nb5+ atoms. In the tenth O2- site, O2- is bonded in a 1-coordinate geometry to two Ca2+ and two Nb5+ atoms. In the eleventh O2- site, O2- is bonded to three Ca2+ and one Nb5+ atom to form a mixture of distorted corner and edge-sharing OCa3Nb tetrahedra. In the twelfth O2- site, O2- is bonded in a distorted T-shaped geometry to one Ca2+ and two Nb5+ atoms. In the thirteenth O2- site, O2- is bonded in a 3-coordinate geometry to one Ca2+ and two Nb5+ atoms. In the fourteenth O2- site, O2- is bonded to two Ca2+ and two Nb5+ atoms to form distorted OCa2Nb2 tetrahedra that share corners with four OCa3Nb tetrahedra and an edgeedge with one OCa2Nb2 tetrahedra.