Materials Data on U3O8 by Materials Project

Abstract

U3O8 crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are two inequivalent U+5.33+ sites. In the first U+5.33+ site, U+5.33+ is bonded to seven O2- atoms to form UO7 pentagonal bipyramids that share corners with two equivalent UO6 octahedra, corners with three equivalent UO7 pentagonal bipyramids, an edgeedge with one UO6 octahedra, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 43°. There are a spread of U–O bond distances ranging from 2.08–2.38 Å. In the second U+5.33+ site, U+5.33+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent UO6 octahedra, corners with four equivalent UO7 pentagonal bipyramids, and edges with two equivalent UO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 0°. There are two shorter (2.08 Å) and four longer (2.14 Å) U–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a distorted trigonal planar geometry to three U+5.33+ atoms. In the second O2- site, O2- is bonded in a linear geometry to two equivalent U+5.33+ atoms. In the third O2- site, O2- is bonded in a linear geometry to two equivalent U+5.33+ atoms. In the fourth O2- site, O2- is bonded in a linear geometry to two equivalent U+5.33+ atoms.