Ho2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing HoO6 octahedra. The corner-sharing octahedra are not tilted. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(3), and three equivalent O(1) atoms. In the third Ho site, Ho(3) is bonded in a 7-coordinate geometry to two equivalent O(3), two equivalent O(5), and three equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Ho(1) and three equivalent Ho(2) atoms to form OHo4 tetrahedra that share  a cornercorner with one O(2)Ho6 octahedra, corners with five equivalent O(3)Ho5 square pyramids, corners with two equivalent O(1)Ho4 tetrahedra, corners with two equivalent O(5)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra,  an edgeedge with one O(3)Ho5 square pyramid, and edges with two equivalent O(1)Ho4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the second O site, O(2) is bonded to two equivalent Ho(2) and four equivalent Ho(1) atoms to form OHo6 octahedra that share corners with two equivalent O(1)Ho4 tetrahedra, corners with four equivalent O(5)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra, edges with four equivalent O(3)Ho5 square pyramids, edges with two equivalent O(5)Ho4 tetrahedra, and edges with four equivalent O(1)Ho4 tetrahedra. In the third O site, O(3) is bonded to one Ho(1), two equivalent Ho(2), and two equivalent Ho(3) atoms to form distorted OHo5 square pyramids that share corners with two equivalent O(5)Ho4 tetrahedra, corners with five equivalent O(1)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra, edges with two equivalent O(3)Ho5 square pyramids,  an edgeedge with one O(1)Ho4 tetrahedra, and edges with two equivalent O(5)Ho4 tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ho(2) and three equivalent Ho(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Ho(1) and two equivalent Ho(3) atoms to form OHo4 tetrahedra that share corners with two equivalent O(2)Ho6 octahedra, corners with two equivalent O(3)Ho5 square pyramids, corners with two equivalent O(1)Ho4 tetrahedra, corners with two equivalent O(5)Ho4 tetrahedra,  an edgeedge with one O(2)Ho6 octahedra, edges with two equivalent O(3)Ho5 square pyramids, and  an edgeedge with one O(5)Ho4 tetrahedra. The corner-sharing octahedral tilt angles are 14°.
Ho2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Ho sites. In the first Ho site, Ho(1) is bonded to one O(1), one O(3), two equivalent O(2), and two equivalent O(5) atoms to form a mixture of distorted edge and corner-sharing HoO6 octahedra. The corner-sharing octahedra are not tilted. The Ho(1)-O(1) bond length is 2.17 Å. The Ho(1)-O(3) bond length is 2.23 Å. Both Ho(1)-O(2) bond lengths are 2.45 Å. Both Ho(1)-O(5) bond lengths are 2.18 Å. In the second Ho site, Ho(2) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(3), and three equivalent O(1) atoms. The Ho(2)-O(2) bond length is 2.70 Å. The Ho(2)-O(4) bond length is 2.27 Å. Both Ho(2)-O(3) bond lengths are 2.38 Å. There is one shorter (2.21 Å) and two longer (2.23 Å) Ho(2)-O(1) bond lengths. In the third Ho site, Ho(3) is bonded in a 7-coordinate geometry to two equivalent O(3), two equivalent O(5), and three equivalent O(4) atoms. Both Ho(3)-O(3) bond lengths are 2.45 Å. There is one shorter (2.23 Å) and one longer (2.39 Å) Ho(3)-O(5) bond length. There are two shorter (2.21 Å) and one longer (2.55 Å) Ho(3)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Ho(1) and three equivalent Ho(2) atoms to form OHo4 tetrahedra that share  a cornercorner with one O(2)Ho6 octahedra, corners with five equivalent O(3)Ho5 square pyramids, corners with two equivalent O(1)Ho4 tetrahedra, corners with two equivalent O(5)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra,  an edgeedge with one O(3)Ho5 square pyramid, and edges with two equivalent O(1)Ho4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the second O site, O(2) is bonded to two equivalent Ho(2) and four equivalent Ho(1) atoms to form OHo6 octahedra that share corners with two equivalent O(1)Ho4 tetrahedra, corners with four equivalent O(5)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra, edges with four equivalent O(3)Ho5 square pyramids, edges with two equivalent O(5)Ho4 tetrahedra, and edges with four equivalent O(1)Ho4 tetrahedra. In the third O site, O(3) is bonded to one Ho(1), two equivalent Ho(2), and two equivalent Ho(3) atoms to form distorted OHo5 square pyramids that share corners with two equivalent O(5)Ho4 tetrahedra, corners with five equivalent O(1)Ho4 tetrahedra, edges with two equivalent O(2)Ho6 octahedra, edges with two equivalent O(3)Ho5 square pyramids,  an edgeedge with one O(1)Ho4 tetrahedra, and edges with two equivalent O(5)Ho4 tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Ho(2) and three equivalent Ho(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Ho(1) and two equivalent Ho(3) atoms to form OHo4 tetrahedra that share corners with two equivalent O(2)Ho6 octahedra, corners with two equivalent O(3)Ho5 square pyramids, corners with two equivalent O(1)Ho4 tetrahedra, corners with two equivalent O(5)Ho4 tetrahedra,  an edgeedge with one O(2)Ho6 octahedra, edges with two equivalent O(3)Ho5 square pyramids, and  an edgeedge with one O(5)Ho4 tetrahedra. The corner-sharing octahedral tilt angles are 14°.