Materials Data on Ca3Ta2O8 by Materials Project
Ca3Ta2O8 crystallizes in the orthorhombic Cmce space group. The structure is three-dimensional. there are two inequivalent Ca2+ sites. In the first Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six equivalent TaO4 tetrahedra and edges with four CaO6 octahedra. There are a spread of Ca–O bond distances ranging from 2.28–2.47 Å. In the second Ca2+ site, Ca2+ is bonded to six O2- atoms to form CaO6 octahedra that share corners with six equivalent TaO4 tetrahedra and edges with four equivalent CaO6 octahedra. There are two shorter (2.34 Å) and four longer (2.41 Å) Ca–O bond lengths. Ta5+ is bonded to four O2- atoms to form TaO4 tetrahedra that share corners with nine CaO6 octahedra. The corner-sharing octahedra tilt angles range from 49–56°. There are a spread of Ta–O bond distances ranging from 1.86–1.92 Å. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a 3-coordinate geometry to two Ca2+ and one Ta5+ atom. In the second O2- site, O2- is bonded in a rectangular see-saw-like geometry to three Ca2+ and one Ta5+ atom. In the third O2- site, O2- is bonded in a distorted trigonal planar geometry to two equivalent Ca2+ and one Ta5+ atom.