Tb3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Tb(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 42°. In the second Tb site, Tb(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Tb(1)O7 pentagonal bipyramids, and edges with four equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 33°. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form a mixture of edge and corner-sharing OTb4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Tb(1) and two equivalent Ta(1) atoms.
Tb3TaO7 crystallizes in the orthorhombic Cmcm space group. There are two inequivalent Tb sites. In the first Tb site, Tb(1) is bonded to one O(3), two equivalent O(1), and four equivalent O(2) atoms to form distorted TbO7 pentagonal bipyramids that share corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Tb(1)O7 pentagonal bipyramids, edges with two equivalent Ta(1)O6 octahedra, and edges with two equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 42°. The Tb(1)-O(3) bond length is 2.66 Å. There is one shorter (2.23 Å) and one longer (2.27 Å) Tb(1)-O(1) bond length. There are two shorter (2.32 Å) and two longer (2.41 Å) Tb(1)-O(2) bond lengths. In the second Tb site, Tb(2) is bonded in a body-centered cubic geometry to four equivalent O(1) and four equivalent O(2) atoms. All Tb(2)-O(1) bond lengths are 2.36 Å. All Tb(2)-O(2) bond lengths are 2.68 Å. Ta(1) is bonded to two equivalent O(3) and four equivalent O(2) atoms to form TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra, corners with four equivalent Tb(1)O7 pentagonal bipyramids, and edges with four equivalent Tb(1)O7 pentagonal bipyramids. The corner-sharing octahedral tilt angles are 33°. Both Ta(1)-O(3) bond lengths are 1.97 Å. All Ta(1)-O(2) bond lengths are 2.00 Å. There are three inequivalent O sites. In the first O site, O(1) is bonded to two equivalent Tb(1) and two equivalent Tb(2) atoms to form a mixture of edge and corner-sharing OTb4 tetrahedra. In the second O site, O(2) is bonded in a 4-coordinate geometry to one Tb(2), two equivalent Tb(1), and one Ta(1) atom. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to two equivalent Tb(1) and two equivalent Ta(1) atoms.