GdNd3Zr4O14 crystallizes in the trigonal R-3m space group. Gd(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. Nd(1) is bonded in a distorted hexagonal planar geometry to two equivalent O(2) and four equivalent O(3) atoms. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a body-centered cubic geometry to two equivalent O(1) and six equivalent O(3) atoms. In the second Zr site, Zr(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Zr(1) and three equivalent Zr(2) atoms to form OZr4 tetrahedra that share corners with four equivalent O(1)Zr4 tetrahedra, corners with six equivalent O(3)Nd2Zr2 tetrahedra, corners with six equivalent O(2)NdGdZr2 tetrahedra, edges with three equivalent O(3)Nd2Zr2 tetrahedra, and edges with three equivalent O(2)NdGdZr2 tetrahedra. In the second O site, O(2) is bonded to one Gd(1), one Nd(1), and two equivalent Zr(2) atoms to form ONdGdZr2 tetrahedra that share corners with two equivalent O(1)Zr4 tetrahedra, corners with four equivalent O(3)Nd2Zr2 tetrahedra, corners with eight equivalent O(2)NdGdZr2 tetrahedra,  an edgeedge with one O(1)Zr4 tetrahedra, edges with two equivalent O(3)Nd2Zr2 tetrahedra, and edges with two equivalent O(2)NdGdZr2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Nd(1), one Zr(1), and one Zr(2) atom to form ONd2Zr2 tetrahedra that share corners with two equivalent O(1)Zr4 tetrahedra, corners with four equivalent O(2)NdGdZr2 tetrahedra, corners with eight equivalent O(3)Nd2Zr2 tetrahedra,  an edgeedge with one O(1)Zr4 tetrahedra, edges with two equivalent O(3)Nd2Zr2 tetrahedra, and edges with two equivalent O(2)NdGdZr2 tetrahedra.
GdNd3Zr4O14 crystallizes in the trigonal R-3m space group. Gd(1) is bonded in a 6-coordinate geometry to six equivalent O(2) atoms. All Gd(1)-O(2) bond lengths are 2.30 Å. Nd(1) is bonded in a distorted hexagonal planar geometry to two equivalent O(2) and four equivalent O(3) atoms. Both Nd(1)-O(2) bond lengths are 2.35 Å. All Nd(1)-O(3) bond lengths are 2.34 Å. There are two inequivalent Zr sites. In the first Zr site, Zr(1) is bonded in a body-centered cubic geometry to two equivalent O(1) and six equivalent O(3) atoms. Both Zr(1)-O(1) bond lengths are 2.33 Å. All Zr(1)-O(3) bond lengths are 2.26 Å. In the second Zr site, Zr(2) is bonded in a body-centered cubic geometry to two equivalent O(1), two equivalent O(3), and four equivalent O(2) atoms. Both Zr(2)-O(1) bond lengths are 2.29 Å. Both Zr(2)-O(3) bond lengths are 2.26 Å. All Zr(2)-O(2) bond lengths are 2.28 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to one Zr(1) and three equivalent Zr(2) atoms to form OZr4 tetrahedra that share corners with four equivalent O(1)Zr4 tetrahedra, corners with six equivalent O(3)Nd2Zr2 tetrahedra, corners with six equivalent O(2)NdGdZr2 tetrahedra, edges with three equivalent O(3)Nd2Zr2 tetrahedra, and edges with three equivalent O(2)NdGdZr2 tetrahedra. In the second O site, O(2) is bonded to one Gd(1), one Nd(1), and two equivalent Zr(2) atoms to form ONdGdZr2 tetrahedra that share corners with two equivalent O(1)Zr4 tetrahedra, corners with four equivalent O(3)Nd2Zr2 tetrahedra, corners with eight equivalent O(2)NdGdZr2 tetrahedra,  an edgeedge with one O(1)Zr4 tetrahedra, edges with two equivalent O(3)Nd2Zr2 tetrahedra, and edges with two equivalent O(2)NdGdZr2 tetrahedra. In the third O site, O(3) is bonded to two equivalent Nd(1), one Zr(1), and one Zr(2) atom to form ONd2Zr2 tetrahedra that share corners with two equivalent O(1)Zr4 tetrahedra, corners with four equivalent O(2)NdGdZr2 tetrahedra, corners with eight equivalent O(3)Nd2Zr2 tetrahedra,  an edgeedge with one O(1)Zr4 tetrahedra, edges with two equivalent O(3)Nd2Zr2 tetrahedra, and edges with two equivalent O(2)NdGdZr2 tetrahedra.