DOE OSTI2020
Eu2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Eu3+ sites. In the first Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.33–2.78 Å. In the second Eu3+ site, Eu3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Eu–O bond distances ranging from 2.31–2.59 Å. In the third Eu3+ site, Eu3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing EuO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Eu–O bond distances ranging from 2.26–2.56 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four Eu3+ atoms to form distorted OEu4 trigonal pyramids that share a cornercorner with one OEu6 octahedra, corners with two equivalent OEu5 square pyramids, corners with nine OEu4 tetrahedra, corners with two equivalent OEu4 trigonal pyramids, edges with three equivalent OEu5 square pyramids, and edges with two equivalent OEu4 trigonal pyramids. The corner-sharing octahedral tilt angles are 38°. In the second O2- site, O2- is bonded to five Eu3+ atoms to form distorted OEu5 square pyramids that share corners with seven OEu4 tetrahedra, corners with two equivalent OEu4 trigonal pyramids, edges with two equivalent OEu6 octahedra, edges with two equivalent OEu5 square pyramids, edges with three OEu4 tetrahedra, and edges with three equivalent OEu4 trigonal pyramids. In the third O2- site, O2- is bonded to six Eu3+ atoms to form OEu6 octahedra that share corners with six OEu4 tetrahedra, corners with two equivalent OEu4 trigonal pyramids, edges with two equivalent OEu6 octahedra, edges with four equivalent OEu5 square pyramids, and edges with six OEu4 tetrahedra. In the fourth O2- site, O2- is bonded to four Eu3+ atoms to form distorted OEu4 tetrahedra that share corners with two equivalent OEu6 octahedra, corners with two equivalent OEu5 square pyramids, corners with four OEu4 tetrahedra, corners with six equivalent OEu4 trigonal pyramids, an edgeedge with one OEu6 octahedra, edges with two equivalent OEu5 square pyramids, and an edgeedge with one OEu4 tetrahedra. The corner-sharing octahedral tilt angles are 11°. In the fifth O2- site, O2- is bonded to four Eu3+ atoms to form OEu4 tetrahedra that share a cornercorner with one OEu6 octahedra, corners with five equivalent OEu5 square pyramids, corners with four OEu4 tetrahedra, corners with three equivalent OEu4 trigonal pyramids, edges with two equivalent OEu6 octahedra, an edgeedge with one OEu5 square pyramid, and edges with two equivalent OEu4 tetrahedra. The corner-sharing octahedral tilt angles are 48°.