Gd3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 40-49°. In the second Gd site, Gd(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Ta(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Gd(1)O7 pentagonal bipyramids, and edges with four equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Ta(1) atoms to form distorted OGd2Ta2 trigonal pyramids that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(5)Gd3Ta tetrahedra, and  an edgeedge with one O(1)Gd2Ta2 trigonal pyramid. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Ta(1) atom. 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 two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with four equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Ta tetrahedra. In the fifth O site, O(5) is bonded to one Gd(2), two equivalent Gd(1), and one Ta(1) atom to form distorted OGd3Ta tetrahedra that share corners with two equivalent O(5)Gd3Ta tetrahedra, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(5)Gd3Ta tetrahedra,  an edgeedge with one O(2)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd2Ta2 trigonal pyramid.
Gd3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Gd sites. In the first Gd site, Gd(1) is bonded to one O(1), one O(2), one O(4), two equivalent O(3), and two equivalent O(5) atoms to form distorted GdO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Gd(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 40-49°. The Gd(1)-O(1) bond length is 2.52 Å. The Gd(1)-O(2) bond length is 2.24 Å. The Gd(1)-O(4) bond length is 2.30 Å. There is one shorter (2.31 Å) and one longer (2.44 Å) Gd(1)-O(3) bond length. There is one shorter (2.31 Å) and one longer (2.44 Å) Gd(1)-O(5) bond length. In the second Gd site, Gd(2) is bonded in a 8-coordinate geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Gd(2)-O(2) bond lengths are 2.40 Å. Both Gd(2)-O(3) bond lengths are 2.99 Å. Both Gd(2)-O(4) bond lengths are 2.34 Å. Both Gd(2)-O(5) bond lengths are 2.42 Å. Ta(1) is bonded to two equivalent O(1), two equivalent O(3), and two equivalent O(5) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Gd(1)O7 pentagonal bipyramids, and edges with four equivalent Gd(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 39°. Both Ta(1)-O(1) bond lengths are 2.00 Å. Both Ta(1)-O(3) bond lengths are 1.94 Å. Both Ta(1)-O(5) bond lengths are 2.03 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Gd(1) and two equivalent Ta(1) atoms to form distorted OGd2Ta2 trigonal pyramids that share corners with two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Gd(1) and two equivalent Gd(2) atoms to form OGd4 tetrahedra that share corners with two equivalent O(2)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with four equivalent O(4)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, edges with two equivalent O(5)Gd3Ta tetrahedra, and  an edgeedge with one O(1)Gd2Ta2 trigonal pyramid. In the third O site, O(3) is bonded in a 3-coordinate geometry to one Gd(2), two equivalent Gd(1), and one Ta(1) atom. 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 two equivalent O(4)Gd4 tetrahedra, corners with four equivalent O(5)Gd3Ta tetrahedra, corners with four equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(2)Gd4 tetrahedra, and edges with two equivalent O(5)Gd3Ta tetrahedra. In the fifth O site, O(5) is bonded to one Gd(2), two equivalent Gd(1), and one Ta(1) atom to form distorted OGd3Ta tetrahedra that share corners with two equivalent O(5)Gd3Ta tetrahedra, corners with two equivalent O(2)Gd4 tetrahedra, corners with two equivalent O(4)Gd4 tetrahedra, corners with two equivalent O(1)Gd2Ta2 trigonal pyramids,  an edgeedge with one O(5)Gd3Ta tetrahedra,  an edgeedge with one O(2)Gd4 tetrahedra,  an edgeedge with one O(4)Gd4 tetrahedra, and  an edgeedge with one O(1)Gd2Ta2 trigonal pyramid.