Materials Data on Ba4Ta2O9 by Materials Project

Abstract

Ba4Ta2O9 is Ilmenite-like structured and crystallizes in the trigonal P-3c1 space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded in a 6-coordinate geometry to six equivalent O2- atoms. There are three shorter (2.66 Å) and three longer (2.97 Å) Ba–O bond lengths. In the second Ba2+ site, Ba2+ is bonded to six O2- atoms to form distorted BaO6 pentagonal pyramids that share corners with three equivalent TaO6 octahedra, corners with three equivalent BaO6 pentagonal pyramids, and edges with three equivalent TaO6 octahedra. The corner-sharing octahedral tilt angles are 50°. There are three shorter (2.56 Å) and three longer (2.74 Å) Ba–O bond lengths. Ta5+ is bonded to six O2- atoms to form distorted TaO6 octahedra that share corners with three equivalent BaO6 pentagonal pyramids, edges with three equivalent BaO6 pentagonal pyramids, and a faceface with one TaO6 octahedra. There are three shorter (1.95 Å) and three longer (2.14 Å) Ta–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+ and two equivalent Ta5+ atoms. In the second O2- site, O2- is bonded in a 1-coordinate geometry to three Ba2+ and one Ta5+ atom.