ThTa2O7 crystallizes in the monoclinic C2/m space group. Th(1) is bonded in a 10-coordinate geometry to one O(3), one O(4), one O(7), two equivalent O(2), two equivalent O(6), and three equivalent O(5) atoms. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(6), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form distorted TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O7 pentagonal bipyramid,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 22°. In the second Ta site, Ta(2) is bonded to one O(1), one O(5), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form TaO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra, corners with two equivalent Ta(2)O7 pentagonal bipyramids,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 39°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(2) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent Th(1) and two equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Th(1) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Th(1) and two equivalent Ta(2) atoms. In the fifth O site, O(5) is bonded to three equivalent Th(1) and one Ta(2) atom to form a mixture of edge and corner-sharing OTh3Ta tetrahedra. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Th(1) and one Ta(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Th(1), one Ta(1), and one Ta(2) atom.
ThTa2O7 crystallizes in the monoclinic C2/m space group. Th(1) is bonded in a 10-coordinate geometry to one O(3), one O(4), one O(7), two equivalent O(2), two equivalent O(6), and three equivalent O(5) atoms. The Th(1)-O(3) bond length is 2.67 Å. The Th(1)-O(4) bond length is 2.67 Å. The Th(1)-O(7) bond length is 2.42 Å. Both Th(1)-O(2) bond lengths are 2.81 Å. Both Th(1)-O(6) bond lengths are 2.39 Å. There is one shorter (2.39 Å) and two longer (2.42 Å) Th(1)-O(5) bond lengths. There are two inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(6), one O(7), two equivalent O(1), and two equivalent O(3) atoms to form distorted TaO6 octahedra that share corners with two equivalent Ta(1)O6 octahedra,  a cornercorner with one Ta(2)O7 pentagonal bipyramid,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 22°. The Ta(1)-O(6) bond length is 1.93 Å. The Ta(1)-O(7) bond length is 1.92 Å. There is one shorter (2.03 Å) and one longer (2.11 Å) Ta(1)-O(1) bond length. Both Ta(1)-O(3) bond lengths are 1.98 Å. In the second Ta site, Ta(2) is bonded to one O(1), one O(5), one O(7), two equivalent O(2), and two equivalent O(4) atoms to form TaO7 pentagonal bipyramids that share  a cornercorner with one Ta(1)O6 octahedra, corners with two equivalent Ta(2)O7 pentagonal bipyramids,  an edgeedge with one Ta(1)O6 octahedra, and  an edgeedge with one Ta(2)O7 pentagonal bipyramid. The corner-sharing octahedral tilt angles are 39°. The Ta(2)-O(1) bond length is 2.00 Å. The Ta(2)-O(5) bond length is 2.11 Å. The Ta(2)-O(7) bond length is 2.19 Å. There is one shorter (2.01 Å) and one longer (2.06 Å) Ta(2)-O(2) bond length. Both Ta(2)-O(4) bond lengths are 1.96 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a distorted trigonal planar geometry to one Ta(2) and two equivalent Ta(1) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to two equivalent Th(1) and two equivalent Ta(2) atoms. In the third O site, O(3) is bonded in a distorted bent 150 degrees geometry to one Th(1) and two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a 2-coordinate geometry to one Th(1) and two equivalent Ta(2) atoms. In the fifth O site, O(5) is bonded to three equivalent Th(1) and one Ta(2) atom to form a mixture of edge and corner-sharing OTh3Ta tetrahedra. In the sixth O site, O(6) is bonded in a trigonal non-coplanar geometry to two equivalent Th(1) and one Ta(1) atom. In the seventh O site, O(7) is bonded in a 3-coordinate geometry to one Th(1), one Ta(1), and one Ta(2) atom.