Materials Data on Ba2Hf7O16 by Materials Project
Ba2Hf7O16 crystallizes in the trigonal R-3 space group. The structure is three-dimensional. Ba2+ is bonded in a 8-coordinate geometry to eight O2- atoms. There are a spread of Ba–O bond distances ranging from 2.69–2.73 Å. There are two inequivalent Hf4+ sites. In the first Hf4+ site, Hf4+ is bonded to six equivalent O2- atoms to form corner-sharing HfO6 octahedra. All Hf–O bond lengths are 2.10 Å. In the second Hf4+ site, Hf4+ is bonded to seven O2- atoms to form distorted HfO7 pentagonal bipyramids that share a cornercorner with one HfO6 octahedra, corners with two equivalent HfO7 pentagonal bipyramids, and edges with seven equivalent HfO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 35°. There are a spread of Hf–O bond distances ranging from 2.04–2.36 Å. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to one Ba2+ and three equivalent Hf4+ atoms to form a mixture of distorted corner and edge-sharing OBaHf3 tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to one Ba2+ and three equivalent Hf4+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to two equivalent Ba2+ and two Hf4+ atoms. In the fourth O2- site, O2- is bonded to four equivalent Hf4+ atoms to form a mixture of distorted corner and edge-sharing OHf4 tetrahedra.