Materials Data on Ca2Ta2O7 by Materials Project
Ca2Ta2O7 crystallizes in the cubic Fd-3m space group. The structure is three-dimensional. Ca2+ is bonded to eight O2- atoms to form distorted CaO8 hexagonal bipyramids that share edges with six equivalent CaO8 hexagonal bipyramids and edges with six equivalent TaO6 octahedra. There are two shorter (2.28 Å) and six longer (2.68 Å) Ca–O bond lengths. Ta5+ is bonded to six equivalent O2- atoms to form TaO6 octahedra that share corners with six equivalent TaO6 octahedra and edges with six equivalent CaO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 41°. All Ta–O bond lengths are 1.99 Å. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ca2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded to four equivalent Ca2+ atoms to form corner-sharing OCa4 tetrahedra.