Materials Data on Ce8U2O21 by Materials Project

Abstract

U2Ce8O21 is alpha bismuth trifluoride-derived structured and crystallizes in the orthorhombic Cmmm space group. The structure is three-dimensional. there are two inequivalent U6+ sites. In the first U6+ site, U6+ is bonded in a distorted body-centered cubic geometry to ten O2- atoms. There are eight shorter (2.34 Å) and two longer (2.72 Å) U–O bond lengths. In the second U6+ site, U6+ is bonded in a distorted body-centered cubic geometry to ten O2- atoms. There are eight shorter (2.34 Å) and two longer (2.72 Å) U–O bond lengths. There are three inequivalent Ce+3.75+ sites. In the first Ce+3.75+ site, Ce+3.75+ is bonded in a 8-coordinate geometry to nine O2- atoms. There are a spread of Ce–O bond distances ranging from 2.39–2.63 Å. In the second Ce+3.75+ site, Ce+3.75+ is bonded in a body-centered cubic geometry to eight O2- atoms. All Ce–O bond lengths are 2.36 Å. In the third Ce+3.75+ site, Ce+3.75+ is bonded in a body-centered cubic geometry to eight O2- atoms. There are four shorter (2.32 Å) and four longer (2.34 Å) Ce–O bond lengths. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ce+3.75+ atoms to form a mixture of corner and edge-sharing OCe4 tetrahedra. In the second O2- site, O2- is bonded to four equivalent Ce+3.75+ atoms to form a mixture of corner and edge-sharing OCe4 tetrahedra. In the third O2- site, O2- is bonded to two U6+, two Ce+3.75+, and one O2- atom to form OCe2U2O tetrahedra that share corners with fourteen OCe4 tetrahedra, edges with six OCe2U2O tetrahedra, and faces with three equivalent OCe2U2O tetrahedra. The O–O bond length is 2.42 Å. In the fourth O2- site, O2- is bonded in a 2-coordinate geometry to four U6+, two equivalent Ce+3.75+, and eight equivalent O2- atoms.