Gd3AsO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. In the second Gd site, Gd(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent As(1)O6 octahedra, corners with three equivalent Gd(2)O7 pentagonal bipyramids, edges with two equivalent As(1)O6 octahedra, and edges with two equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 34-38°. As(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form AsO6 octahedra that share corners with two equivalent As(1)O6 octahedra, corners with four equivalent Gd(2)O7 pentagonal bipyramids, and edges with four equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and one As(1) atom to form distorted OGd3As trigonal pyramids that share corners with four equivalent O(4)Gd4 tetrahedra, edges with two equivalent O(4)Gd4 tetrahedra, and edges with two equivalent O(1)Gd3As trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Gd(1), two equivalent Gd(2), and one As(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Gd(2) and two equivalent As(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with six equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(1)Gd3As trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with two equivalent O(1)Gd3As trigonal pyramids.
Gd3AsO7 crystallizes in the orthorhombic Pnma space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded in a distorted body-centered cubic geometry to two equivalent O(1), two equivalent O(2), and four equivalent O(4) atoms. Both Gd(1)-O(1) bond lengths are 2.52 Å. Both Gd(1)-O(2) bond lengths are 2.92 Å. There are two shorter (2.32 Å) and two longer (2.33 Å) Gd(1)-O(4) bond lengths. In the second Gd site, Gd(2) is bonded to one O(3), two equivalent O(1), two equivalent O(2), and two equivalent O(4) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent As(1)O6 octahedra, corners with three equivalent Gd(2)O7 pentagonal bipyramids, edges with two equivalent As(1)O6 octahedra, and edges with two equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 34-38°. The Gd(2)-O(3) bond length is 2.54 Å. There is one shorter (2.37 Å) and one longer (2.45 Å) Gd(2)-O(1) bond length. There is one shorter (2.35 Å) and one longer (2.40 Å) Gd(2)-O(2) bond length. Both Gd(2)-O(4) bond lengths are 2.24 Å. As(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form AsO6 octahedra that share corners with two equivalent As(1)O6 octahedra, corners with four equivalent Gd(2)O7 pentagonal bipyramids, and edges with four equivalent Gd(2)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 34°. Both As(1)-O(1) bond lengths are 1.88 Å. Both As(1)-O(2) bond lengths are 1.84 Å. Both As(1)-O(3) bond lengths are 1.93 Å. There are four inequivalent O sites. In the first O site, O(1) is bonded to one Gd(1), two equivalent Gd(2), and one As(1) atom to form distorted OGd3As trigonal pyramids that share corners with four equivalent O(4)Gd4 tetrahedra, edges with two equivalent O(4)Gd4 tetrahedra, and edges with two equivalent O(1)Gd3As trigonal pyramids. In the second O site, O(2) is bonded in a 3-coordinate geometry to one Gd(1), two equivalent Gd(2), and one As(1) atom. In the third O site, O(3) is bonded in a 4-coordinate geometry to two equivalent Gd(2) and two equivalent As(1) atoms. In the fourth O site, O(4) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with six equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(1)Gd3As trigonal pyramids,  an edgeedge with one O(4)Gd4 tetrahedra, and edges with two equivalent O(1)Gd3As trigonal pyramids.