DOE OSTI2020
Sm2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Sm3+ sites. In the first Sm3+ site, Sm3+ is bonded to six O2- atoms to form a mixture of distorted edge and corner-sharing SmO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Sm–O bond distances ranging from 2.28–2.57 Å. In the second Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.31–2.81 Å. In the third Sm3+ site, Sm3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Sm–O bond distances ranging from 2.31–2.69 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to six Sm3+ atoms to form OSm6 octahedra that share corners with six OSm4 tetrahedra, corners with two equivalent OSm4 trigonal pyramids, edges with two equivalent OSm6 octahedra, edges with four equivalent OSm5 square pyramids, and edges with six OSm4 tetrahedra. In the second O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share corners with two equivalent OSm6 octahedra, corners with two equivalent OSm5 square pyramids, corners with four OSm4 tetrahedra, corners with six equivalent OSm4 trigonal pyramids, an edgeedge with one OSm6 octahedra, edges with two equivalent OSm5 square pyramids, and an edgeedge with one OSm4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the third O2- site, O2- is bonded to four Sm3+ atoms to form distorted OSm4 trigonal pyramids that share a cornercorner with one OSm6 octahedra, corners with two equivalent OSm5 square pyramids, corners with nine OSm4 tetrahedra, corners with two equivalent OSm4 trigonal pyramids, edges with three equivalent OSm5 square pyramids, and edges with two equivalent OSm4 trigonal pyramids. The corner-sharing octahedral tilt angles are 36°. In the fourth O2- site, O2- is bonded to four Sm3+ atoms to form OSm4 tetrahedra that share a cornercorner with one OSm6 octahedra, corners with five equivalent OSm5 square pyramids, corners with four OSm4 tetrahedra, corners with three equivalent OSm4 trigonal pyramids, edges with two equivalent OSm6 octahedra, an edgeedge with one OSm5 square pyramid, and edges with two equivalent OSm4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. In the fifth O2- site, O2- is bonded to five Sm3+ atoms to form distorted OSm5 square pyramids that share corners with seven OSm4 tetrahedra, corners with two equivalent OSm4 trigonal pyramids, edges with two equivalent OSm6 octahedra, edges with two equivalent OSm5 square pyramids, edges with three OSm4 tetrahedra, and edges with three equivalent OSm4 trigonal pyramids.