Lu3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Lu sites. In the first Lu site, Lu(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 LuO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Lu(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Lu(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 42-49°. In the second Lu site, Lu(2) is bonded in a distorted body-centered cubic 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 Lu(1)O7 pentagonal bipyramids, and edges with four equivalent Lu(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 45°. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Lu(1) and two equivalent Ta(1) atoms to form distorted OLu2Ta2 tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Lu(1) and two equivalent Lu(2) atoms to form OLu4 tetrahedra that share corners with two equivalent O(2)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra, corners with four equivalent O(4)Lu4 tetrahedra,  an edgeedge with one O(1)Lu2Ta2 tetrahedra,  an edgeedge with one O(4)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Lu(2), two equivalent Lu(1), and one Ta(1) atom. In the fourth O site, O(4) is bonded to two equivalent Lu(1) and two equivalent Lu(2) atoms to form OLu4 tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra, corners with four equivalent O(2)Lu4 tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the fifth O site, O(5) is bonded to one Lu(2), two equivalent Lu(1), and one Ta(1) atom to form distorted OLu3Ta tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(5)Lu3Ta tetrahedra, corners with two equivalent O(2)Lu4 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra,  an edgeedge with one O(1)Lu2Ta2 tetrahedra,  an edgeedge with one O(5)Lu3Ta tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and  an edgeedge with one O(4)Lu4 tetrahedra.
Lu3TaO7 crystallizes in the orthorhombic C222_1 space group. There are two inequivalent Lu sites. In the first Lu site, Lu(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 LuO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Lu(1)O7 pentagonal bipyramid, edges with two equivalent Ta(1)O6 octahedra, and edges with three equivalent Lu(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles range from 42-49°. The Lu(1)-O(1) bond length is 2.38 Å. The Lu(1)-O(2) bond length is 2.15 Å. The Lu(1)-O(4) bond length is 2.25 Å. There is one shorter (2.19 Å) and one longer (2.39 Å) Lu(1)-O(3) bond length. There is one shorter (2.21 Å) and one longer (2.38 Å) Lu(1)-O(5) bond length. In the second Lu site, Lu(2) is bonded in a distorted body-centered cubic geometry to two equivalent O(2), two equivalent O(3), two equivalent O(4), and two equivalent O(5) atoms. Both Lu(2)-O(2) bond lengths are 2.35 Å. Both Lu(2)-O(3) bond lengths are 2.83 Å. Both Lu(2)-O(4) bond lengths are 2.28 Å. Both Lu(2)-O(5) bond lengths are 2.36 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 Lu(1)O7 pentagonal bipyramids, and edges with four equivalent Lu(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 45°. Both Ta(1)-O(1) bond lengths are 1.99 Å. Both Ta(1)-O(3) bond lengths are 1.94 Å. Both Ta(1)-O(5) bond lengths are 2.02 Å. There are five inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Lu(1) and two equivalent Ta(1) atoms to form distorted OLu2Ta2 tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the second O site, O(2) is bonded to two equivalent Lu(1) and two equivalent Lu(2) atoms to form OLu4 tetrahedra that share corners with two equivalent O(2)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra, corners with four equivalent O(4)Lu4 tetrahedra,  an edgeedge with one O(1)Lu2Ta2 tetrahedra,  an edgeedge with one O(4)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the third O site, O(3) is bonded in a 4-coordinate geometry to one Lu(2), two equivalent Lu(1), and one Ta(1) atom. In the fourth O site, O(4) is bonded to two equivalent Lu(1) and two equivalent Lu(2) atoms to form OLu4 tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra, corners with four equivalent O(5)Lu3Ta tetrahedra, corners with four equivalent O(2)Lu4 tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and edges with two equivalent O(5)Lu3Ta tetrahedra. In the fifth O site, O(5) is bonded to one Lu(2), two equivalent Lu(1), and one Ta(1) atom to form distorted OLu3Ta tetrahedra that share corners with two equivalent O(1)Lu2Ta2 tetrahedra, corners with two equivalent O(5)Lu3Ta tetrahedra, corners with two equivalent O(2)Lu4 tetrahedra, corners with two equivalent O(4)Lu4 tetrahedra,  an edgeedge with one O(1)Lu2Ta2 tetrahedra,  an edgeedge with one O(5)Lu3Ta tetrahedra,  an edgeedge with one O(2)Lu4 tetrahedra, and  an edgeedge with one O(4)Lu4 tetrahedra.