Gd2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing GdO6 octahedra. The corner-sharing octahedra are not tilted. In the second Gd site, Gd(2) is bonded in a 7-coordinate geometry to one O(4), one O(5), two equivalent O(1), and three equivalent O(2) atoms. In the third Gd site, Gd(3) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(4) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and two equivalent Gd(3) atoms to form distorted OGd5 square pyramids that share corners with two equivalent O(3)Gd4 tetrahedra, corners with five equivalent O(2)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra, edges with two equivalent O(1)Gd5 square pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(3)Gd4 tetrahedra. In the second O site, O(2) is bonded to one Gd(1) and three equivalent Gd(2) atoms to form OGd4 tetrahedra that share  a cornercorner with one O(5)Gd6 octahedra, corners with five equivalent O(1)Gd5 square pyramids, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(3)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra,  an edgeedge with one O(1)Gd5 square pyramid, and edges with two equivalent O(2)Gd4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. In the third O site, O(3) is bonded to two equivalent Gd(1) and two equivalent Gd(3) atoms to form OGd4 tetrahedra that share corners with two equivalent O(5)Gd6 octahedra, corners with two equivalent O(1)Gd5 square pyramids, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(3)Gd4 tetrahedra,  an edgeedge with one O(5)Gd6 octahedra, edges with two equivalent O(1)Gd5 square pyramids, and  an edgeedge with one O(3)Gd4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Gd(2) and three equivalent Gd(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Gd(2) and four equivalent Gd(1) atoms to form OGd6 octahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(3)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra, edges with four equivalent O(1)Gd5 square pyramids, edges with two equivalent O(3)Gd4 tetrahedra, and edges with four equivalent O(2)Gd4 tetrahedra.
Gd2O3 crystallizes in the monoclinic C2/m space group. There are three inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), two equivalent O(3), and two equivalent O(5) atoms to form a mixture of distorted corner and edge-sharing GdO6 octahedra. The corner-sharing octahedra are not tilted. The Gd(1)-O(1) bond length is 2.29 Å. The Gd(1)-O(2) bond length is 2.23 Å. Both Gd(1)-O(3) bond lengths are 2.24 Å. Both Gd(1)-O(5) bond lengths are 2.52 Å. In the second Gd site, Gd(2) is bonded in a 7-coordinate geometry to one O(4), one O(5), two equivalent O(1), and three equivalent O(2) atoms. The Gd(2)-O(4) bond length is 2.33 Å. The Gd(2)-O(5) bond length is 2.75 Å. Both Gd(2)-O(1) bond lengths are 2.44 Å. There is one shorter (2.27 Å) and two longer (2.29 Å) Gd(2)-O(2) bond lengths. In the third Gd site, Gd(3) is bonded in a 7-coordinate geometry to two equivalent O(1), two equivalent O(3), and three equivalent O(4) atoms. Both Gd(3)-O(1) bond lengths are 2.52 Å. There is one shorter (2.29 Å) and one longer (2.43 Å) Gd(3)-O(3) bond length. There are two shorter (2.27 Å) and one longer (2.61 Å) Gd(3)-O(4) bond length. There are five inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and two equivalent Gd(3) atoms to form distorted OGd5 square pyramids that share corners with two equivalent O(3)Gd4 tetrahedra, corners with five equivalent O(2)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra, edges with two equivalent O(1)Gd5 square pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(3)Gd4 tetrahedra. In the second O site, O(2) is bonded to one Gd(1) and three equivalent Gd(2) atoms to form OGd4 tetrahedra that share  a cornercorner with one O(5)Gd6 octahedra, corners with five equivalent O(1)Gd5 square pyramids, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(3)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra,  an edgeedge with one O(1)Gd5 square pyramid, and edges with two equivalent O(2)Gd4 tetrahedra. The corner-sharing octahedral tilt angles are 50°. In the third O site, O(3) is bonded to two equivalent Gd(1) and two equivalent Gd(3) atoms to form OGd4 tetrahedra that share corners with two equivalent O(5)Gd6 octahedra, corners with two equivalent O(1)Gd5 square pyramids, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(3)Gd4 tetrahedra,  an edgeedge with one O(5)Gd6 octahedra, edges with two equivalent O(1)Gd5 square pyramids, and  an edgeedge with one O(3)Gd4 tetrahedra. The corner-sharing octahedral tilt angles are 14°. In the fourth O site, O(4) is bonded in a 4-coordinate geometry to one Gd(2) and three equivalent Gd(3) atoms. In the fifth O site, O(5) is bonded to two equivalent Gd(2) and four equivalent Gd(1) atoms to form OGd6 octahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(3)Gd4 tetrahedra, edges with two equivalent O(5)Gd6 octahedra, edges with four equivalent O(1)Gd5 square pyramids, edges with two equivalent O(3)Gd4 tetrahedra, and edges with four equivalent O(2)Gd4 tetrahedra.