DOE OSTI2020
Ce2Sb2Se5 crystallizes in the monoclinic P2_1/c space group. The structure is three-dimensional. there are two inequivalent Ce3+ sites. In the first Ce3+ site, Ce3+ is bonded to seven Se2- atoms to form distorted CeSe7 pentagonal bipyramids that share corners with six equivalent CeSe7 pentagonal bipyramids, edges with two equivalent CeSe6 octahedra, and edges with two equivalent SbSe5 square pyramids. There are a spread of Ce–Se bond distances ranging from 3.01–3.19 Å. In the second Ce3+ site, Ce3+ is bonded to six Se2- atoms to form CeSe6 octahedra that share corners with four equivalent CeSe6 octahedra, corners with two equivalent SbSe5 square pyramids, edges with two equivalent CeSe6 octahedra, edges with two equivalent CeSe7 pentagonal bipyramids, and edges with four equivalent SbSe5 square pyramids. The corner-sharing octahedra tilt angles range from 10–12°. There are a spread of Ce–Se bond distances ranging from 2.84–3.06 Å. There are two inequivalent Sb2+ sites. In the first Sb2+ site, Sb2+ is bonded in a 4-coordinate geometry to four Se2- atoms. There are a spread of Sb–Se bond distances ranging from 2.82–3.37 Å. In the second Sb2+ site, Sb2+ is bonded to five Se2- atoms to form SbSe5 square pyramids that share corners with two equivalent CeSe6 octahedra, corners with four equivalent SbSe5 square pyramids, edges with four equivalent CeSe6 octahedra, and edges with two equivalent CeSe7 pentagonal bipyramids. The corner-sharing octahedra tilt angles range from 81–85°. There are a spread of Sb–Se bond distances ranging from 2.61–3.02 Å. There are five inequivalent Se2- sites. In the first Se2- site, Se2- is bonded in a 3-coordinate geometry to two equivalent Ce3+ and two Sb2+ atoms. In the second Se2- site, Se2- is bonded to three equivalent Ce3+ and two equivalent Sb2+ atoms to form a mixture of corner and edge-sharing SeCe3Sb2 square pyramids. In the third Se2- site, Se2- is bonded to two equivalent Ce3+ and two equivalent Sb2+ atoms to form distorted SeCe2Sb2 tetrahedra that share corners with two equivalent SeCe3Sb2 square pyramids, corners with two equivalent SeCe2Sb2 tetrahedra, and an edgeedge with one SeCe2Sb2 tetrahedra. In the fourth Se2- site, Se2- is bonded in a 4-coordinate geometry to three Ce3+ and one Sb2+ atom. In the fifth Se2- site, Se2- is bonded to three Ce3+ and two equivalent Sb2+ atoms to form SeCe3Sb2 square pyramids that share corners with six SeCe3Sb2 square pyramids, corners with two equivalent SeCe2Sb2 tetrahedra, and edges with four equivalent SeCe3Sb2 square pyramids.