Materials Data on CaYNb2O7 by Materials Project
CaYNb2O7 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 YO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.30–2.64 Å. Y3+ is bonded to eight O2- atoms to form distorted YO8 hexagonal bipyramids that share edges with two equivalent YO8 hexagonal bipyramids, edges with four equivalent CaO8 hexagonal bipyramids, and edges with six NbO6 octahedra. There are two shorter (2.24 Å) and six longer (2.53 Å) Y–O bond lengths. 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 YO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 49–54°. All Nb–O bond lengths are 2.05 Å. 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 YO8 hexagonal bipyramids, and edges with four equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 43–49°. There are two shorter (2.01 Å) and four longer (2.02 Å) Nb–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to two equivalent Ca2+ and two equivalent Y3+ atoms to form OCa2Y2 tetrahedra that share corners with six OCa2Y2 tetrahedra and an edgeedge with one OY2Nb2 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Nb+4.50+ atoms. In the third O2- site, O2- is bonded to two equivalent Y3+ and two equivalent Nb+4.50+ atoms to form a mixture of distorted edge and corner-sharing OY2Nb2 tetrahedra. In the fourth O2- site, O2- is bonded in a 4-coordinate geometry to one Ca2+, one Y3+, and two Nb+4.50+ atoms.