Materials Data on Ca4Nb6O21 by Materials Project

Abstract

(Ca2Nb3O10)4O2 crystallizes in the orthorhombic Cmm2 space group. The structure is two-dimensional and consists of two water molecules and one Ca2Nb3O10 sheet oriented in the (0, 0, 1) direction. In the Ca2Nb3O10 sheet, there are three inequivalent Ca sites. In the first Ca site, Ca is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ca–O bond distances ranging from 2.39–2.78 Å. In the second Ca site, Ca is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ca–O bond distances ranging from 2.40–2.78 Å. In the third Ca site, Ca is bonded in a 10-coordinate geometry to ten O atoms. There are a spread of Ca–O bond distances ranging from 2.41–2.78 Å. There are three inequivalent Nb sites. In the first Nb site, Nb is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Nb–O bond distances ranging from 1.76–2.43 Å. In the second Nb site, Nb is bonded in a 6-coordinate geometry to six O atoms. There are a spread of Nb–O bond distances ranging from 1.78–2.40 Å. In the third Nb site, Nb is bonded to six O atoms to form corner-sharing NbO6 octahedra. The corner-sharing octahedral tilt angles are 33°. There are a spread of Nb–O bond distances ranging from 1.94–2.04 Å. There are eight inequivalent O sites. In the first O site, O is bonded to two equivalent Ca and two equivalent Nb atoms to form a mixture of distorted edge and corner-sharing OCa2Nb2 trigonal pyramids. In the second O site, O is bonded to two Ca and two equivalent Nb atoms to form a mixture of distorted edge and corner-sharing OCa2Nb2 trigonal pyramids. In the third O site, O is bonded to two Ca and two equivalent Nb atoms to form a mixture of distorted edge and corner-sharing OCa2Nb2 trigonal pyramids. In the fourth O site, O is bonded in a single-bond geometry to one Nb atom. In the fifth O site, O is bonded in a single-bond geometry to one Nb atom. In the sixth O site, O is bonded in a distorted single-bond geometry to four equivalent Ca and two Nb atoms. In the seventh O site, O is bonded in a distorted single-bond geometry to four Ca and two Nb atoms. In the eighth O site, O is bonded in a 2-coordinate geometry to two Ca and two equivalent Nb atoms.