Materials Data on Ba2U2O7 by Materials Project
Ba2U2O7 crystallizes in the orthorhombic Imma space group. The structure is three-dimensional. there are two inequivalent Ba2+ sites. In the first Ba2+ site, Ba2+ is bonded to eight O2- atoms to form distorted BaO8 hexagonal bipyramids that share corners with two equivalent BaO8 hexagonal bipyramids, corners with two equivalent UO6 octahedra, and edges with six UO6 octahedra. The corner-sharing octahedral tilt angles are 55°. There are a spread of Ba–O bond distances ranging from 2.60–3.16 Å. In the second Ba2+ site, Ba2+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are four shorter (2.73 Å) and four longer (3.06 Å) Ba–O bond lengths. There are two inequivalent U5+ sites. In the first U5+ site, U5+ is bonded to six O2- atoms to form UO6 octahedra that share corners with six UO6 octahedra and edges with four equivalent BaO8 hexagonal bipyramids. The corner-sharing octahedra tilt angles range from 39–43°. There are four shorter (2.15 Å) and two longer (2.18 Å) U–O bond lengths. In the second U5+ site, U5+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent BaO8 hexagonal bipyramids, corners with four equivalent UO6 octahedra, and edges with two equivalent BaO8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. There are two shorter (2.07 Å) and four longer (2.23 Å) U–O bond lengths. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted bent 150 degrees geometry to two equivalent Ba2+ and two equivalent U5+ atoms. In the second O2- site, O2- is bonded in a 4-coordinate geometry to two Ba2+ and two U5+ atoms. In the third O2- site, O2- is bonded in a 4-coordinate geometry to three Ba2+ and one U5+ atom.