NpYb6O12 crystallizes in the triclinic P-1 space group. Np(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NpO6 octahedra that share corners with two equivalent Yb(2)O5 square pyramids. There are three inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(5), and two equivalent O(6) atoms. In the second Yb site, Yb(2) is bonded to one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted YbO5 square pyramids that share  a cornercorner with one Np(1)O6 octahedra and  an edgeedge with one Yb(2)O5 square pyramid. The corner-sharing octahedral tilt angles are 4°. In the third Yb site, Yb(3) is bonded in a distorted pentagonal planar geometry to one O(3), one O(4), one O(5), and two equivalent O(1) atoms. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Np(1) and two equivalent Yb(3) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to one Np(1) and one Yb(1) atom. In the third O site, O(3) is bonded in a see-saw-like geometry to one Np(1), one Yb(1), one Yb(2), and one Yb(3) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Yb(3) and two equivalent Yb(2) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Yb(1), one Yb(2), and one Yb(3) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Yb(2) and two equivalent Yb(1) atoms.
NpYb6O12 crystallizes in the triclinic P-1 space group. Np(1) is bonded to two equivalent O(1), two equivalent O(2), and two equivalent O(3) atoms to form NpO6 octahedra that share corners with two equivalent Yb(2)O5 square pyramids. Both Np(1)-O(1) bond lengths are 2.01 Å. Both Np(1)-O(2) bond lengths are 1.91 Å. Both Np(1)-O(3) bond lengths are 2.12 Å. There are three inequivalent Yb sites. In the first Yb site, Yb(1) is bonded in a 5-coordinate geometry to one O(2), one O(3), one O(5), and two equivalent O(6) atoms. The Yb(1)-O(2) bond length is 2.34 Å. The Yb(1)-O(3) bond length is 2.50 Å. The Yb(1)-O(5) bond length is 2.22 Å. Both Yb(1)-O(6) bond lengths are 2.26 Å. In the second Yb site, Yb(2) is bonded to one O(3), one O(5), one O(6), and two equivalent O(4) atoms to form distorted YbO5 square pyramids that share  a cornercorner with one Np(1)O6 octahedra and  an edgeedge with one Yb(2)O5 square pyramid. The corner-sharing octahedral tilt angles are 4°. The Yb(2)-O(3) bond length is 2.26 Å. The Yb(2)-O(5) bond length is 2.28 Å. The Yb(2)-O(6) bond length is 2.27 Å. There is one shorter (2.28 Å) and one longer (2.32 Å) Yb(2)-O(4) bond length. In the third Yb site, Yb(3) is bonded in a distorted pentagonal planar geometry to one O(3), one O(4), one O(5), and two equivalent O(1) atoms. The Yb(3)-O(3) bond length is 2.33 Å. The Yb(3)-O(4) bond length is 2.22 Å. The Yb(3)-O(5) bond length is 2.27 Å. There is one shorter (2.26 Å) and one longer (2.40 Å) Yb(3)-O(1) bond length. There are six inequivalent O sites. In the first O site, O(1) is bonded in a 3-coordinate geometry to one Np(1) and two equivalent Yb(3) atoms. In the second O site, O(2) is bonded in a distorted water-like geometry to one Np(1) and one Yb(1) atom. In the third O site, O(3) is bonded in a see-saw-like geometry to one Np(1), one Yb(1), one Yb(2), and one Yb(3) atom. In the fourth O site, O(4) is bonded in a T-shaped geometry to one Yb(3) and two equivalent Yb(2) atoms. In the fifth O site, O(5) is bonded in a 3-coordinate geometry to one Yb(1), one Yb(2), and one Yb(3) atom. In the sixth O site, O(6) is bonded in a T-shaped geometry to one Yb(2) and two equivalent Yb(1) atoms.