Materials Data on CaNdNb2O7 by Materials Project
CaNdNb2O7 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share edges with two equivalent CaO8 hexagonal bipyramids, edges with four equivalent NdO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are two shorter (2.29 Å) and six longer (2.68 Å) Ca–O bond lengths. Nd3+ is bonded to eight O2- atoms to form distorted NdO8 hexagonal bipyramids that share edges with two equivalent NdO8 hexagonal bipyramids, edges with four equivalent CaO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are a spread of Nd–O bond distances ranging from 2.31–2.62 Å. There are two inequivalent Nb+4.50+ sites. In the first Nb+4.50+ site, Nb+4.50+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent CaO8 hexagonal bipyramids, and edges with four equivalent NdO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 46–49°. There are four shorter (2.04 Å) and two longer (2.05 Å) Nb–O bond lengths. In the second Nb+4.50+ site, Nb+4.50+ is bonded to six O2- atoms to form NbO6 octahedra that share corners with six NbO6 octahedra, edges with two equivalent NdO8 hexagonal bipyramids, and edges with four equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 42–46°. There are two shorter (2.03 Å) and four longer (2.04 Å) Nb–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Nb+4.50+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Nd3+ and two equivalent Nb+4.50+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Nd3+, and two Nb+4.50+ atoms. In the fourth O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Nd3+ atoms to form corner-sharing OCa2Nd2 tetrahedra.