DOE OSTI2020
Ho2O3 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Ho3+ sites. In the first Ho3+ site, Ho3+ is bonded to six O2- atoms to form a mixture of edge and corner-sharing HoO6 octahedra. The corner-sharing octahedral tilt angles are 0°. There are a spread of Ho–O bond distances ranging from 2.19–2.46 Å. In the second Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.23–2.73 Å. In the third Ho3+ site, Ho3+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Ho–O bond distances ranging from 2.23–2.57 Å. There are five inequivalent O2- sites. In the first O2- site, O2- is bonded to four Ho3+ atoms to form OHo4 tetrahedra that share a cornercorner with one OHo6 octahedra, corners with five equivalent OHo5 square pyramids, corners with four OHo4 tetrahedra, corners with three equivalent OHo4 trigonal pyramids, edges with two equivalent OHo6 octahedra, an edgeedge with one OHo5 square pyramid, and edges with two equivalent OHo4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the second O2- site, O2- is bonded to six Ho3+ atoms to form OHo6 octahedra that share corners with six OHo4 tetrahedra, corners with two equivalent OHo4 trigonal pyramids, edges with two equivalent OHo6 octahedra, edges with four equivalent OHo5 square pyramids, and edges with six OHo4 tetrahedra. In the third O2- site, O2- is bonded to five Ho3+ atoms to form distorted OHo5 square pyramids that share corners with seven OHo4 tetrahedra, corners with two equivalent OHo4 trigonal pyramids, edges with two equivalent OHo6 octahedra, edges with two equivalent OHo5 square pyramids, edges with three OHo4 tetrahedra, and edges with three equivalent OHo4 trigonal pyramids. In the fourth O2- site, O2- is bonded to four Ho3+ atoms to form distorted OHo4 trigonal pyramids that share a cornercorner with one OHo6 octahedra, corners with two equivalent OHo5 square pyramids, corners with nine OHo4 tetrahedra, corners with two equivalent OHo4 trigonal pyramids, edges with three equivalent OHo5 square pyramids, and edges with two equivalent OHo4 trigonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the fifth O2- site, O2- is bonded to four Ho3+ atoms to form distorted OHo4 tetrahedra that share corners with two equivalent OHo6 octahedra, corners with two equivalent OHo5 square pyramids, corners with four OHo4 tetrahedra, corners with six equivalent OHo4 trigonal pyramids, an edgeedge with one OHo6 octahedra, edges with two equivalent OHo5 square pyramids, and an edgeedge with one OHo4 tetrahedra. The corner-sharing octahedral tilt angles are 13°.