DOE OSTI2020
Sr5U5O19 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are five inequivalent Sr2+ sites. In the first Sr2+ site, Sr2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.56–2.66 Å. In the second Sr2+ site, Sr2+ is bonded to seven O2- atoms to form distorted SrO7 pentagonal bipyramids that share corners with two equivalent UO6 octahedra, an edgeedge with one UO6 octahedra, and edges with two equivalent SrO7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 56°. There are a spread of Sr–O bond distances ranging from 2.51–2.65 Å. In the third Sr2+ site, Sr2+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.51–2.90 Å. In the fourth Sr2+ site, Sr2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.54–2.65 Å. In the fifth Sr2+ site, Sr2+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are a spread of Sr–O bond distances ranging from 2.55–2.64 Å. There are five inequivalent U+5.60+ sites. In the first U+5.60+ site, U+5.60+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.00–2.36 Å. In the second U+5.60+ site, U+5.60+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.98–2.41 Å. In the third U+5.60+ site, U+5.60+ is bonded in a distorted body-centered cubic geometry to eight O2- atoms. There are a spread of U–O bond distances ranging from 2.00–2.42 Å. In the fourth U+5.60+ site, U+5.60+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of U–O bond distances ranging from 1.99–2.58 Å. In the fifth U+5.60+ site, U+5.60+ is bonded to six O2- atoms to form UO6 octahedra that share corners with two equivalent UO6 octahedra, corners with two equivalent SrO7 pentagonal bipyramids, and an edgeedge with one SrO7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 38°. There are a spread of U–O bond distances ranging from 2.05–2.20 Å. There are nineteen inequivalent O2- sites. In the first O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form distorted OSr3U tetrahedra that share corners with eleven OSr3U tetrahedra, corners with three equivalent OSrU3 trigonal pyramids, and edges with five OSr3U tetrahedra. In the second O2- site, O2- is bonded in a 4-coordinate geometry to three Sr2+ and one U+5.60+ atom. In the third O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form distorted OSr3U tetrahedra that share corners with fourteen OSr3U tetrahedra and edges with six OSrU3 tetrahedra. In the fourth O2- site, O2- is bonded in a distorted bent 150 degrees geometry to one Sr2+ and two equivalent U+5.60+ atoms. In the fifth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form a mixture of distorted edge and corner-sharing OSrU3 tetrahedra. In the sixth O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form a mixture of distorted edge and corner-sharing OSr3U tetrahedra. In the seventh O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form distorted OSr3U tetrahedra that share corners with eleven OSrU3 tetrahedra, edges with three OSr3U tetrahedra, and edges with two equivalent OSrU3 trigonal pyramids. In the eighth O2- site, O2- is bonded in a 4-coordinate geometry to one Sr2+ and three U+5.60+ atoms. In the ninth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form a mixture of distorted edge and corner-sharing OSrU3 tetrahedra. In the tenth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form distorted OSrU3 tetrahedra that share corners with thirteen OSrU3 tetrahedra, corners with two equivalent OSrU3 trigonal pyramids, and edges with six OSr3U tetrahedra. In the eleventh O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form distorted OSrU3 tetrahedra that share corners with ten OSr3U tetrahedra and edges with six OSrU3 tetrahedra. In the twelfth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form distorted OSrU3 tetrahedra that share corners with sixteen OSrU3 tetrahedra and edges with six OSr3U tetrahedra. In the thirteenth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form distorted OSrU3 trigonal pyramids that share corners with seven OSrU3 tetrahedra, corners with two equivalent OSrU3 trigonal pyramids, and edges with four OSr3U tetrahedra. In the fourteenth O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form a mixture of distorted edge and corner-sharing OSr3U tetrahedra. In the fifteenth O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form a mixture of distorted edge and corner-sharing OSr3U tetrahedra. In the sixteenth O2- site, O2- is bonded to one Sr2+ and three U+5.60+ atoms to form distorted OSrU3 tetrahedra that share corners with twelve OSrU3 tetrahedra, corners with two equivalent OSrU3 trigonal pyramids, edges with five OSr3U tetrahedra, and an edgeedge with one OSrU3 trigonal pyramid. In the seventeenth O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form a mixture of distorted edge and corner-sharing OSr3U tetrahedra. In the eighteenth O2- site, O2- is bonded to three Sr2+ and one U+5.60+ atom to form distorted OSr3U tetrahedra that share corners with seven OSr3U tetrahedra, an edgeedge with one OSr3U tetrahedra, and an edgeedge with one OSrU3 trigonal pyramid. In the nineteenth O2- site, O2- is bonded in a 4-coordinate geometry to three Sr2+ and one U+5.60+ atom.