Y2O3 crystallizes in the monoclinic P2_1/m space group. There are six inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(1), and three equivalent O(3) atoms. In the second Y site, Y(2) is bonded to one O(4), one O(5), two equivalent O(2), and three equivalent O(1) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Y(3)O6 octahedra, edges with two equivalent Y(4)O6 octahedra, and edges with four equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 52°. In the third Y site, Y(3) is bonded to one O(3), one O(8), two equivalent O(4), and two equivalent O(6) atoms to form YO6 octahedra that share corners with two equivalent Y(4)O6 octahedra, corners with two equivalent Y(2)O7 pentagonal bipyramids,  an edgeedge with one Y(4)O6 octahedra, and edges with two equivalent Y(3)O6 octahedra. The corner-sharing octahedral tilt angles are 14°. In the fourth Y site, Y(4) is bonded to one O(2), one O(7), two equivalent O(5), and two equivalent O(6) atoms to form distorted YO6 octahedra that share corners with two equivalent Y(3)O6 octahedra,  an edgeedge with one Y(3)O6 octahedra, edges with two equivalent Y(4)O6 octahedra, and edges with two equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 14°. In the fifth Y site, Y(5) is bonded in a 6-coordinate geometry to one O(5), two equivalent O(8), and three equivalent O(9) atoms. In the sixth Y site, Y(6) is bonded in a 7-coordinate geometry to one O(6), one O(9), two equivalent O(8), and three equivalent O(7) atoms. There are nine inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and three equivalent Y(2) atoms to form distorted OY5 square pyramids that share corners with two equivalent O(2)Y4 tetrahedra, corners with three equivalent O(5)Y4 tetrahedra, corners with four equivalent O(3)Y4 tetrahedra, edges with four equivalent O(1)Y5 square pyramids,  an edgeedge with one O(3)Y4 tetrahedra, and edges with three equivalent O(2)Y4 tetrahedra. In the second O site, O(2) is bonded to one Y(1), one Y(4), and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(1)Y5 square pyramids, corners with two equivalent O(6)Y5 square pyramids,  a cornercorner with one O(7)Y4 tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with three equivalent O(3)Y4 tetrahedra, edges with three equivalent O(1)Y5 square pyramids, and edges with two equivalent O(5)Y4 tetrahedra. In the third O site, O(3) is bonded to one Y(3) and three equivalent Y(1) atoms to form OY4 tetrahedra that share corners with two equivalent O(6)Y5 square pyramids, corners with four equivalent O(1)Y5 square pyramids, corners with two equivalent O(3)Y4 tetrahedra, corners with three equivalent O(2)Y4 tetrahedra,  a cornercorner with one O(8)Y5 trigonal bipyramid,  an edgeedge with one O(1)Y5 square pyramid, and edges with two equivalent O(3)Y4 tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Y(1), one Y(2), and two equivalent Y(3) atoms. In the fifth O site, O(5) is bonded to one Y(2), one Y(5), and two equivalent Y(4) atoms to form distorted OY4 tetrahedra that share corners with two equivalent O(6)Y5 square pyramids, corners with three equivalent O(1)Y5 square pyramids, corners with two equivalent O(5)Y4 tetrahedra, corners with two equivalent O(7)Y4 tetrahedra, corners with two equivalent O(8)Y5 trigonal bipyramids, corners with three equivalent O(9)Y4 trigonal pyramids,  an edgeedge with one O(6)Y5 square pyramid, and edges with two equivalent O(2)Y4 tetrahedra. In the sixth O site, O(6) is bonded to one Y(6), two equivalent Y(3), and two equivalent Y(4) atoms to form OY5 square pyramids that share  a cornercorner with one O(7)Y4 tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra,  a cornercorner with one O(9)Y4 trigonal pyramid, edges with two equivalent O(6)Y5 square pyramids,  an edgeedge with one O(5)Y4 tetrahedra, edges with two equivalent O(7)Y4 tetrahedra, and edges with two equivalent O(8)Y5 trigonal bipyramids. In the seventh O site, O(7) is bonded to one Y(4) and three equivalent Y(6) atoms to form OY4 tetrahedra that share  a cornercorner with one O(6)Y5 square pyramid,  a cornercorner with one O(2)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra, corners with two equivalent O(7)Y4 tetrahedra, corners with four equivalent O(8)Y5 trigonal bipyramids, corners with three equivalent O(9)Y4 trigonal pyramids, edges with two equivalent O(6)Y5 square pyramids, edges with two equivalent O(7)Y4 tetrahedra, and  an edgeedge with one O(8)Y5 trigonal bipyramid. In the eighth O site, O(8) is bonded to one Y(3), two equivalent Y(5), and two equivalent Y(6) atoms to form distorted OY5 trigonal bipyramids that share  a cornercorner with one O(3)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra, corners with four equivalent O(7)Y4 tetrahedra, corners with two equivalent O(9)Y4 trigonal pyramids, edges with two equivalent O(6)Y5 square pyramids,  an edgeedge with one O(7)Y4 tetrahedra, edges with two equivalent O(8)Y5 trigonal bipyramids, and edges with three equivalent O(9)Y4 trigonal pyramids. In the ninth O site, O(9) is bonded to one Y(6) and three equivalent Y(5) atoms to form distorted OY4 trigonal pyramids that share  a cornercorner with one O(6)Y5 square pyramid, corners with three equivalent O(5)Y4 tetrahedra, corners with three equivalent O(7)Y4 tetrahedra, corners with two equivalent O(8)Y5 trigonal bipyramids, corners with two equivalent O(9)Y4 trigonal pyramids, edges with three equivalent O(8)Y5 trigonal bipyramids, and edges with two equivalent O(9)Y4 trigonal pyramids.
Y2O3 crystallizes in the monoclinic P2_1/m space group. There are six inequivalent Y sites. In the first Y site, Y(1) is bonded in a 7-coordinate geometry to one O(2), one O(4), two equivalent O(1), and three equivalent O(3) atoms. The Y(1)-O(2) bond length is 2.28 Å. The Y(1)-O(4) bond length is 2.62 Å. Both Y(1)-O(1) bond lengths are 2.40 Å. There is one shorter (2.23 Å) and two longer (2.27 Å) Y(1)-O(3) bond lengths. In the second Y site, Y(2) is bonded to one O(4), one O(5), two equivalent O(2), and three equivalent O(1) atoms to form distorted YO7 pentagonal bipyramids that share corners with two equivalent Y(3)O6 octahedra, edges with two equivalent Y(4)O6 octahedra, and edges with four equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 52°. The Y(2)-O(4) bond length is 2.29 Å. The Y(2)-O(5) bond length is 2.43 Å. Both Y(2)-O(2) bond lengths are 2.27 Å. There is one shorter (2.30 Å) and two longer (2.44 Å) Y(2)-O(1) bond lengths. In the third Y site, Y(3) is bonded to one O(3), one O(8), two equivalent O(4), and two equivalent O(6) atoms to form YO6 octahedra that share corners with two equivalent Y(4)O6 octahedra, corners with two equivalent Y(2)O7 pentagonal bipyramids,  an edgeedge with one Y(4)O6 octahedra, and edges with two equivalent Y(3)O6 octahedra. The corner-sharing octahedral tilt angles are 14°. The Y(3)-O(3) bond length is 2.20 Å. The Y(3)-O(8) bond length is 2.26 Å. Both Y(3)-O(4) bond lengths are 2.20 Å. Both Y(3)-O(6) bond lengths are 2.43 Å. In the fourth Y site, Y(4) is bonded to one O(2), one O(7), two equivalent O(5), and two equivalent O(6) atoms to form distorted YO6 octahedra that share corners with two equivalent Y(3)O6 octahedra,  an edgeedge with one Y(3)O6 octahedra, edges with two equivalent Y(4)O6 octahedra, and edges with two equivalent Y(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 14°. The Y(4)-O(2) bond length is 2.24 Å. The Y(4)-O(7) bond length is 2.23 Å. Both Y(4)-O(5) bond lengths are 2.23 Å. Both Y(4)-O(6) bond lengths are 2.43 Å. In the fifth Y site, Y(5) is bonded in a 6-coordinate geometry to one O(5), two equivalent O(8), and three equivalent O(9) atoms. The Y(5)-O(5) bond length is 2.22 Å. Both Y(5)-O(8) bond lengths are 2.40 Å. There are two shorter (2.23 Å) and one longer (2.44 Å) Y(5)-O(9) bond length. In the sixth Y site, Y(6) is bonded in a 7-coordinate geometry to one O(6), one O(9), two equivalent O(8), and three equivalent O(7) atoms. The Y(6)-O(6) bond length is 2.43 Å. The Y(6)-O(9) bond length is 2.32 Å. Both Y(6)-O(8) bond lengths are 2.51 Å. There are two shorter (2.22 Å) and one longer (2.25 Å) Y(6)-O(7) bond length. There are nine inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Y(1) and three equivalent Y(2) atoms to form distorted OY5 square pyramids that share corners with two equivalent O(2)Y4 tetrahedra, corners with three equivalent O(5)Y4 tetrahedra, corners with four equivalent O(3)Y4 tetrahedra, edges with four equivalent O(1)Y5 square pyramids,  an edgeedge with one O(3)Y4 tetrahedra, and edges with three equivalent O(2)Y4 tetrahedra. In the second O site, O(2) is bonded to one Y(1), one Y(4), and two equivalent Y(2) atoms to form OY4 tetrahedra that share corners with two equivalent O(1)Y5 square pyramids, corners with two equivalent O(6)Y5 square pyramids,  a cornercorner with one O(7)Y4 tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with three equivalent O(3)Y4 tetrahedra, edges with three equivalent O(1)Y5 square pyramids, and edges with two equivalent O(5)Y4 tetrahedra. In the third O site, O(3) is bonded to one Y(3) and three equivalent Y(1) atoms to form OY4 tetrahedra that share corners with two equivalent O(6)Y5 square pyramids, corners with four equivalent O(1)Y5 square pyramids, corners with two equivalent O(3)Y4 tetrahedra, corners with three equivalent O(2)Y4 tetrahedra,  a cornercorner with one O(8)Y5 trigonal bipyramid,  an edgeedge with one O(1)Y5 square pyramid, and edges with two equivalent O(3)Y4 tetrahedra. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Y(1), one Y(2), and two equivalent Y(3) atoms. In the fifth O site, O(5) is bonded to one Y(2), one Y(5), and two equivalent Y(4) atoms to form distorted OY4 tetrahedra that share corners with two equivalent O(6)Y5 square pyramids, corners with three equivalent O(1)Y5 square pyramids, corners with two equivalent O(5)Y4 tetrahedra, corners with two equivalent O(7)Y4 tetrahedra, corners with two equivalent O(8)Y5 trigonal bipyramids, corners with three equivalent O(9)Y4 trigonal pyramids,  an edgeedge with one O(6)Y5 square pyramid, and edges with two equivalent O(2)Y4 tetrahedra. In the sixth O site, O(6) is bonded to one Y(6), two equivalent Y(3), and two equivalent Y(4) atoms to form OY5 square pyramids that share  a cornercorner with one O(7)Y4 tetrahedra, corners with two equivalent O(2)Y4 tetrahedra, corners with two equivalent O(3)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra,  a cornercorner with one O(9)Y4 trigonal pyramid, edges with two equivalent O(6)Y5 square pyramids,  an edgeedge with one O(5)Y4 tetrahedra, edges with two equivalent O(7)Y4 tetrahedra, and edges with two equivalent O(8)Y5 trigonal bipyramids. In the seventh O site, O(7) is bonded to one Y(4) and three equivalent Y(6) atoms to form OY4 tetrahedra that share  a cornercorner with one O(6)Y5 square pyramid,  a cornercorner with one O(2)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra, corners with two equivalent O(7)Y4 tetrahedra, corners with four equivalent O(8)Y5 trigonal bipyramids, corners with three equivalent O(9)Y4 trigonal pyramids, edges with two equivalent O(6)Y5 square pyramids, edges with two equivalent O(7)Y4 tetrahedra, and  an edgeedge with one O(8)Y5 trigonal bipyramid. In the eighth O site, O(8) is bonded to one Y(3), two equivalent Y(5), and two equivalent Y(6) atoms to form distorted OY5 trigonal bipyramids that share  a cornercorner with one O(3)Y4 tetrahedra, corners with two equivalent O(5)Y4 tetrahedra, corners with four equivalent O(7)Y4 tetrahedra, corners with two equivalent O(9)Y4 trigonal pyramids, edges with two equivalent O(6)Y5 square pyramids,  an edgeedge with one O(7)Y4 tetrahedra, edges with two equivalent O(8)Y5 trigonal bipyramids, and edges with three equivalent O(9)Y4 trigonal pyramids. In the ninth O site, O(9) is bonded to one Y(6) and three equivalent Y(5) atoms to form distorted OY4 trigonal pyramids that share  a cornercorner with one O(6)Y5 square pyramid, corners with three equivalent O(5)Y4 tetrahedra, corners with three equivalent O(7)Y4 tetrahedra, corners with two equivalent O(8)Y5 trigonal bipyramids, corners with two equivalent O(9)Y4 trigonal pyramids, edges with three equivalent O(8)Y5 trigonal bipyramids, and edges with two equivalent O(9)Y4 trigonal pyramids.