Dy2Ce2O7 crystallizes in the orthorhombic Pmma space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. In the second Dy site, Dy(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing DyO6 octahedra. The corner-sharing octahedral tilt angles are 62°. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Dy(2) and two equivalent Ce(1) atoms to form OCe2Dy2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(1)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(2)CeDy3 tetrahedra. In the second O site, O(2) is bonded to one Dy(1), two equivalent Dy(2), and one Ce(1) atom to form distorted OCeDy3 tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with two equivalent O(5)Ce3Dy tetrahedra, corners with two equivalent O(4)Ce4 tetrahedra, corners with six equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(5)Ce3Dy tetrahedra,  an edgeedge with one O(2)CeDy3 tetrahedra, and edges with two equivalent O(1)Ce2Dy2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Dy(1) and two equivalent Ce(2) atoms to form OCe2Dy2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(5)Ce3Dy tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(1)Ce2Dy2 tetrahedra,  an edgeedge with one O(3)Ce2Dy2 tetrahedra, and edges with four equivalent O(5)Ce3Dy tetrahedra. In the fifth O site, O(5) is bonded to one Dy(1), one Ce(1), and two equivalent Ce(2) atoms to form OCe3Dy tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with two equivalent O(4)Ce4 tetrahedra, corners with two equivalent O(2)CeDy3 tetrahedra, corners with six equivalent O(5)Ce3Dy tetrahedra,  an edgeedge with one O(5)Ce3Dy tetrahedra,  an edgeedge with one O(2)CeDy3 tetrahedra, edges with two equivalent O(3)Ce2Dy2 tetrahedra, and edges with two equivalent O(4)Ce4 tetrahedra.
Dy2Ce2O7 crystallizes in the orthorhombic Pmma space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded in a 6-coordinate geometry to two equivalent O(2), two equivalent O(3), and two equivalent O(5) atoms. Both Dy(1)-O(2) bond lengths are 2.25 Å. Both Dy(1)-O(3) bond lengths are 2.19 Å. Both Dy(1)-O(5) bond lengths are 2.36 Å. In the second Dy site, Dy(2) is bonded to two equivalent O(1) and four equivalent O(2) atoms to form a mixture of distorted corner and edge-sharing DyO6 octahedra. The corner-sharing octahedral tilt angles are 62°. Both Dy(2)-O(1) bond lengths are 2.28 Å. All Dy(2)-O(2) bond lengths are 2.35 Å. There are two inequivalent Ce sites. In the first Ce site, Ce(1) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms. Both Ce(1)-O(1) bond lengths are 2.41 Å. Both Ce(1)-O(2) bond lengths are 2.63 Å. Both Ce(1)-O(4) bond lengths are 2.30 Å. Both Ce(1)-O(5) bond lengths are 2.35 Å. In the second Ce site, Ce(2) is bonded in a body-centered cubic geometry to two equivalent O(3), two equivalent O(4), and four equivalent O(5) atoms. Both Ce(2)-O(3) bond lengths are 2.40 Å. Both Ce(2)-O(4) bond lengths are 2.43 Å. All Ce(2)-O(5) bond lengths are 2.31 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Dy(2) and two equivalent Ce(1) atoms to form OCe2Dy2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(1)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(2)CeDy3 tetrahedra. In the second O site, O(2) is bonded to one Dy(1), two equivalent Dy(2), and one Ce(1) atom to form distorted OCeDy3 tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with two equivalent O(5)Ce3Dy tetrahedra, corners with two equivalent O(4)Ce4 tetrahedra, corners with six equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(5)Ce3Dy tetrahedra,  an edgeedge with one O(2)CeDy3 tetrahedra, and edges with two equivalent O(1)Ce2Dy2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Dy(1) and two equivalent Ce(2) atoms to form OCe2Dy2 tetrahedra that share corners with two equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(3)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(4)Ce4 tetrahedra, and edges with four equivalent O(5)Ce3Dy tetrahedra. In the fourth O site, O(4) is bonded to two equivalent Ce(1) and two equivalent Ce(2) atoms to form OCe4 tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with four equivalent O(5)Ce3Dy tetrahedra, corners with four equivalent O(4)Ce4 tetrahedra, corners with four equivalent O(2)CeDy3 tetrahedra,  an edgeedge with one O(1)Ce2Dy2 tetrahedra,  an edgeedge with one O(3)Ce2Dy2 tetrahedra, and edges with four equivalent O(5)Ce3Dy tetrahedra. In the fifth O site, O(5) is bonded to one Dy(1), one Ce(1), and two equivalent Ce(2) atoms to form OCe3Dy tetrahedra that share corners with two equivalent O(1)Ce2Dy2 tetrahedra, corners with two equivalent O(3)Ce2Dy2 tetrahedra, corners with two equivalent O(4)Ce4 tetrahedra, corners with two equivalent O(2)CeDy3 tetrahedra, corners with six equivalent O(5)Ce3Dy tetrahedra,  an edgeedge with one O(5)Ce3Dy tetrahedra,  an edgeedge with one O(2)CeDy3 tetrahedra, edges with two equivalent O(3)Ce2Dy2 tetrahedra, and edges with two equivalent O(4)Ce4 tetrahedra.