Y2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(4), and three equivalent O(3) atoms. In the second Y site, Y(2) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing YO6 octahedra. The corner-sharing octahedra are not tilted. In the third Y site, Y(3) is bonded in a 7-coordinate geometry to one O(3), one O(5), two equivalent O(1), and three equivalent O(2) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(2), two equivalent Y(1), and two equivalent Y(3) atoms to form distorted OY5 square pyramids that share corners with two equivalent O(4)Y4 tetrahedra, corners with five equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra, edges with two equivalent O(1)Y5 square pyramids,  an edgeedge with one O(2)Y4 tetrahedra, edges with two equivalent O(4)Y4 tetrahedra, and edges with three equivalent O(3)Y4 trigonal pyramids. In the second O site, O(2) is bonded to one Y(2) and three equivalent Y(3) atoms to form OY4 tetrahedra that share  a cornercorner with one O(5)Y6 octahedra, corners with five equivalent O(1)Y5 square pyramids, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(4)Y4 tetrahedra, corners with three equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra,  an edgeedge with one O(1)Y5 square pyramid, and edges with two equivalent O(2)Y4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the third O site, O(3) is bonded to one Y(3) and three equivalent Y(1) atoms to form distorted OY4 trigonal pyramids that share  a cornercorner with one O(5)Y6 octahedra, corners with two equivalent O(1)Y5 square pyramids, corners with three equivalent O(2)Y4 tetrahedra, corners with six equivalent O(4)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with three equivalent O(1)Y5 square pyramids, and edges with two equivalent O(3)Y4 trigonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(5)Y6 octahedra, corners with two equivalent O(1)Y5 square pyramids, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(4)Y4 tetrahedra, corners with six equivalent O(3)Y4 trigonal pyramids,  an edgeedge with one O(5)Y6 octahedra, edges with two equivalent O(1)Y5 square pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the fifth O site, O(5) is bonded to two equivalent Y(3) and four equivalent Y(2) atoms to form OY6 octahedra that share corners with two equivalent O(2)Y4 tetrahedra, corners with four equivalent O(4)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra, edges with four equivalent O(1)Y5 square pyramids, edges with two equivalent O(4)Y4 tetrahedra, and edges with four equivalent O(2)Y4 tetrahedra.
Y2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(4), and three equivalent O(3) atoms. Both Y(1)-O(1) bond lengths are 2.47 Å. There is one shorter (2.26 Å) and one longer (2.41 Å) Y(1)-O(4) bond length. There are two shorter (2.23 Å) and one longer (2.55 Å) Y(1)-O(3) bond length. In the second Y site, Y(2) is bonded to one O(1), one O(2), two equivalent O(4), and two equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing YO6 octahedra. The corner-sharing octahedra are not tilted. The Y(2)-O(1) bond length is 2.25 Å. The Y(2)-O(2) bond length is 2.18 Å. Both Y(2)-O(4) bond lengths are 2.20 Å. Both Y(2)-O(5) bond lengths are 2.47 Å. In the third Y site, Y(3) is bonded in a 7-coordinate geometry to one O(3), one O(5), two equivalent O(1), and three equivalent O(2) atoms. The Y(3)-O(3) bond length is 2.29 Å. The Y(3)-O(5) bond length is 2.71 Å. Both Y(3)-O(1) bond lengths are 2.40 Å. There is one shorter (2.23 Å) and two longer (2.25 Å) Y(3)-O(2) bond lengths. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Y(2), two equivalent Y(1), and two equivalent Y(3) atoms to form distorted OY5 square pyramids that share corners with two equivalent O(4)Y4 tetrahedra, corners with five equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra, edges with two equivalent O(1)Y5 square pyramids,  an edgeedge with one O(2)Y4 tetrahedra, edges with two equivalent O(4)Y4 tetrahedra, and edges with three equivalent O(3)Y4 trigonal pyramids. In the second O site, O(2) is bonded to one Y(2) and three equivalent Y(3) atoms to form OY4 tetrahedra that share  a cornercorner with one O(5)Y6 octahedra, corners with five equivalent O(1)Y5 square pyramids, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(4)Y4 tetrahedra, corners with three equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra,  an edgeedge with one O(1)Y5 square pyramid, and edges with two equivalent O(2)Y4 tetrahedra. The corner-sharing octahedral tilt angles are 49°. In the third O site, O(3) is bonded to one Y(3) and three equivalent Y(1) atoms to form distorted OY4 trigonal pyramids that share  a cornercorner with one O(5)Y6 octahedra, corners with two equivalent O(1)Y5 square pyramids, corners with three equivalent O(2)Y4 tetrahedra, corners with six equivalent O(4)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with three equivalent O(1)Y5 square pyramids, and edges with two equivalent O(3)Y4 trigonal pyramids. The corner-sharing octahedral tilt angles are 37°. In the fourth O site, O(4) is bonded to two equivalent Y(1) and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(5)Y6 octahedra, corners with two equivalent O(1)Y5 square pyramids, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(4)Y4 tetrahedra, corners with six equivalent O(3)Y4 trigonal pyramids,  an edgeedge with one O(5)Y6 octahedra, edges with two equivalent O(1)Y5 square pyramids, and  an edgeedge with one O(4)Y4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the fifth O site, O(5) is bonded to two equivalent Y(3) and four equivalent Y(2) atoms to form OY6 octahedra that share corners with two equivalent O(2)Y4 tetrahedra, corners with four equivalent O(4)Y4 tetrahedra, corners with two equivalent O(3)Y4 trigonal pyramids, edges with two equivalent O(5)Y6 octahedra, edges with four equivalent O(1)Y5 square pyramids, edges with two equivalent O(4)Y4 tetrahedra, and edges with four equivalent O(2)Y4 tetrahedra.