YTa3O9 crystallizes in the monoclinic C2/m space group. Y(1) is bonded to one O(6), two equivalent O(1), two equivalent O(5), three equivalent O(2), and four equivalent O(4) atoms to form distorted YO12 cuboctahedra that share corners with three equivalent Y(1)O12 cuboctahedra, faces with two equivalent Y(1)O12 cuboctahedra, faces with two equivalent Ta(3)O6 octahedra, faces with three equivalent Ta(1)O6 octahedra, and faces with three equivalent Ta(2)O6 octahedra. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with three equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-22°. In the second Ta site, Ta(2) is bonded to one O(2), one O(7), two equivalent O(1), and two equivalent O(4) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(3)O6 octahedra, and faces with three equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-22°. In the third Ta site, Ta(3) is bonded to one O(6), one O(7), two equivalent O(1), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with two equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-14°. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Y(1), one Ta(2), and one Ta(3) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to three equivalent Y(1), one Ta(1), and one Ta(2) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Y(1), one Ta(1), and one Ta(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Y(1), one Ta(1), and one Ta(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Y(1) and two equivalent Ta(3) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Ta(2) and one Ta(3) atom.
YTa3O9 crystallizes in the monoclinic C2/m space group. Y(1) is bonded to one O(6), two equivalent O(1), two equivalent O(5), three equivalent O(2), and four equivalent O(4) atoms to form distorted YO12 cuboctahedra that share corners with three equivalent Y(1)O12 cuboctahedra, faces with two equivalent Y(1)O12 cuboctahedra, faces with two equivalent Ta(3)O6 octahedra, faces with three equivalent Ta(1)O6 octahedra, and faces with three equivalent Ta(2)O6 octahedra. The Y(1)-O(6) bond length is 3.06 Å. Both Y(1)-O(1) bond lengths are 2.70 Å. Both Y(1)-O(5) bond lengths are 2.86 Å. There is one shorter (2.45 Å) and two longer (2.80 Å) Y(1)-O(2) bond lengths. There are two shorter (2.43 Å) and two longer (2.47 Å) Y(1)-O(4) bond lengths. There are three inequivalent Ta sites. In the first Ta site, Ta(1) is bonded to one O(2), one O(3), two equivalent O(4), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(1)O6 octahedra, corners with two equivalent Ta(3)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with three equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-22°. The Ta(1)-O(2) bond length is 2.05 Å. The Ta(1)-O(3) bond length is 1.93 Å. Both Ta(1)-O(4) bond lengths are 2.09 Å. Both Ta(1)-O(5) bond lengths are 1.91 Å. In the second Ta site, Ta(2) is bonded to one O(2), one O(7), two equivalent O(1), and two equivalent O(4) atoms to form distorted TaO6 octahedra that share corners with three equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(3)O6 octahedra, and faces with three equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 5-22°. The Ta(2)-O(2) bond length is 2.09 Å. The Ta(2)-O(7) bond length is 1.89 Å. Both Ta(2)-O(1) bond lengths are 1.92 Å. Both Ta(2)-O(4) bond lengths are 2.09 Å. In the third Ta site, Ta(3) is bonded to one O(6), one O(7), two equivalent O(1), and two equivalent O(5) atoms to form TaO6 octahedra that share  a cornercorner with one Ta(3)O6 octahedra, corners with two equivalent Ta(1)O6 octahedra, corners with three equivalent Ta(2)O6 octahedra, and faces with two equivalent Y(1)O12 cuboctahedra. The corner-sharing octahedral tilt angles range from 0-14°. The Ta(3)-O(6) bond length is 1.96 Å. The Ta(3)-O(7) bond length is 1.98 Å. Both Ta(3)-O(1) bond lengths are 2.00 Å. Both Ta(3)-O(5) bond lengths are 1.97 Å. There are seven inequivalent O sites. In the first O site, O(1) is bonded in a 2-coordinate geometry to one Y(1), one Ta(2), and one Ta(3) atom. In the second O site, O(2) is bonded in a 5-coordinate geometry to three equivalent Y(1), one Ta(1), and one Ta(2) atom. In the third O site, O(3) is bonded in a linear geometry to two equivalent Ta(1) atoms. In the fourth O site, O(4) is bonded in a distorted rectangular see-saw-like geometry to two equivalent Y(1), one Ta(1), and one Ta(2) atom. In the fifth O site, O(5) is bonded in a distorted linear geometry to one Y(1), one Ta(1), and one Ta(3) atom. In the sixth O site, O(6) is bonded in a linear geometry to two equivalent Y(1) and two equivalent Ta(3) atoms. In the seventh O site, O(7) is bonded in a linear geometry to one Ta(2) and one Ta(3) atom.