Dy2Ge2O7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted DyO8 hexagonal bipyramids that share corners with two equivalent Ge(1)O4 tetrahedra, edges with two equivalent Dy(1)O8 hexagonal bipyramids, edges with two equivalent Dy(2)O6 octahedra, edges with two equivalent Ge(1)O4 tetrahedra, and edges with two equivalent Ge(2)O4 tetrahedra. In the second Dy site, Dy(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form DyO6 octahedra that share corners with two equivalent Dy(2)O6 octahedra, corners with two equivalent Ge(1)O4 tetrahedra, corners with four equivalent Ge(2)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 59°. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with two equivalent Dy(1)O8 hexagonal bipyramids, corners with two equivalent Dy(2)O6 octahedra,  a cornercorner with one Ge(2)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 49°. In the second Ge site, Ge(2) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form GeO4 tetrahedra that share corners with four equivalent Dy(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-61°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Dy(1), one Ge(1), and one Ge(2) atom to form distorted corner-sharing ODy2Ge2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Dy(1), one Dy(2), and one Ge(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to two equivalent Dy(1) and one Ge(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Dy(1), one Dy(2), and one Ge(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to two equivalent Dy(2) and one Ge(2) atom.
Dy2Ge2O7 crystallizes in the monoclinic P2_1/m space group. There are two inequivalent Dy sites. In the first Dy site, Dy(1) is bonded to two equivalent O(1), two equivalent O(2), two equivalent O(3), and two equivalent O(4) atoms to form distorted DyO8 hexagonal bipyramids that share corners with two equivalent Ge(1)O4 tetrahedra, edges with two equivalent Dy(1)O8 hexagonal bipyramids, edges with two equivalent Dy(2)O6 octahedra, edges with two equivalent Ge(1)O4 tetrahedra, and edges with two equivalent Ge(2)O4 tetrahedra. Both Dy(1)-O(1) bond lengths are 2.54 Å. Both Dy(1)-O(2) bond lengths are 2.57 Å. Both Dy(1)-O(3) bond lengths are 2.33 Å. Both Dy(1)-O(4) bond lengths are 2.47 Å. In the second Dy site, Dy(2) is bonded to two equivalent O(2), two equivalent O(4), and two equivalent O(5) atoms to form DyO6 octahedra that share corners with two equivalent Dy(2)O6 octahedra, corners with two equivalent Ge(1)O4 tetrahedra, corners with four equivalent Ge(2)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 59°. Both Dy(2)-O(2) bond lengths are 2.25 Å. Both Dy(2)-O(4) bond lengths are 2.26 Å. Both Dy(2)-O(5) bond lengths are 2.33 Å. There are two inequivalent Ge sites. In the first Ge site, Ge(1) is bonded to one O(1), one O(3), and two equivalent O(2) atoms to form GeO4 tetrahedra that share corners with two equivalent Dy(1)O8 hexagonal bipyramids, corners with two equivalent Dy(2)O6 octahedra,  a cornercorner with one Ge(2)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles are 49°. The Ge(1)-O(1) bond length is 1.79 Å. The Ge(1)-O(3) bond length is 1.75 Å. Both Ge(1)-O(2) bond lengths are 1.75 Å. In the second Ge site, Ge(2) is bonded to one O(1), one O(5), and two equivalent O(4) atoms to form GeO4 tetrahedra that share corners with four equivalent Dy(2)O6 octahedra,  a cornercorner with one Ge(1)O4 tetrahedra, and edges with two equivalent Dy(1)O8 hexagonal bipyramids. The corner-sharing octahedral tilt angles range from 48-61°. The Ge(2)-O(1) bond length is 1.81 Å. The Ge(2)-O(5) bond length is 1.75 Å. Both Ge(2)-O(4) bond lengths are 1.76 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Dy(1), one Ge(1), and one Ge(2) atom to form distorted corner-sharing ODy2Ge2 tetrahedra. In the second O site, O(2) is bonded in a distorted trigonal non-coplanar geometry to one Dy(1), one Dy(2), and one Ge(1) atom. In the third O site, O(3) is bonded in a trigonal planar geometry to two equivalent Dy(1) and one Ge(1) atom. In the fourth O site, O(4) is bonded in a distorted trigonal non-coplanar geometry to one Dy(1), one Dy(2), and one Ge(2) atom. In the fifth O site, O(5) is bonded in a trigonal planar geometry to two equivalent Dy(2) and one Ge(2) atom.