K3NpO2F5 crystallizes in the tetragonal I4_1/amd space group. There are three inequivalent K sites. In the first K site, K(1) is bonded to two equivalent F(3) and four equivalent F(2) atoms to form KF6 octahedra that share corners with six equivalent Np(1)O2F5 pentagonal bipyramids. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms. In the third K site, K(3) is bonded to four equivalent O(1) and four equivalent F(1) atoms to form distorted KO4F4 hexagonal bipyramids that share corners with four equivalent Np(1)O2F5 pentagonal bipyramids and edges with two equivalent Np(1)O2F5 pentagonal bipyramids. Np(1) is bonded to two equivalent O(1), one F(3), two equivalent F(1), and two equivalent F(2) atoms to form NpO2F5 pentagonal bipyramids that share corners with two equivalent K(3)O4F4 hexagonal bipyramids, corners with three equivalent K(1)F6 octahedra, and  an edgeedge with one K(3)O4F4 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 0-29°. O(1) is bonded in a distorted single-bond geometry to one K(3), two equivalent K(2), and one Np(1) atom. There are three inequivalent F sites. In the first F site, F(1) is bonded to one K(3), two equivalent K(2), and one Np(1) atom to form FK3Np tetrahedra that share corners with three equivalent F(3)K5Np octahedra, corners with four equivalent F(1)K3Np tetrahedra,  an edgeedge with one F(3)K5Np octahedra, and  an edgeedge with one F(1)K3Np tetrahedra. The corner-sharing octahedral tilt angles range from 13-37°. In the second F site, F(2) is bonded in a rectangular see-saw-like geometry to one K(1), two equivalent K(2), and one Np(1) atom. In the third F site, F(3) is bonded to one K(1), four equivalent K(2), and one Np(1) atom to form distorted FK5Np octahedra that share  a cornercorner with one F(3)K5Np octahedra, corners with six equivalent F(1)K3Np tetrahedra, edges with two equivalent F(3)K5Np octahedra, and edges with two equivalent F(1)K3Np tetrahedra. The corner-sharing octahedra are not tilted.
K3NpO2F5 crystallizes in the tetragonal I4_1/amd space group. There are three inequivalent K sites. In the first K site, K(1) is bonded to two equivalent F(3) and four equivalent F(2) atoms to form KF6 octahedra that share corners with six equivalent Np(1)O2F5 pentagonal bipyramids. Both K(1)-F(3) bond lengths are 2.70 Å. All K(1)-F(2) bond lengths are 2.54 Å. In the second K site, K(2) is bonded in a 8-coordinate geometry to two equivalent O(1), two equivalent F(1), two equivalent F(2), and two equivalent F(3) atoms. Both K(2)-O(1) bond lengths are 3.34 Å. Both K(2)-F(1) bond lengths are 2.70 Å. Both K(2)-F(2) bond lengths are 2.74 Å. Both K(2)-F(3) bond lengths are 3.06 Å. In the third K site, K(3) is bonded to four equivalent O(1) and four equivalent F(1) atoms to form distorted KO4F4 hexagonal bipyramids that share corners with four equivalent Np(1)O2F5 pentagonal bipyramids and edges with two equivalent Np(1)O2F5 pentagonal bipyramids. All K(3)-O(1) bond lengths are 2.87 Å. All K(3)-F(1) bond lengths are 2.76 Å. Np(1) is bonded to two equivalent O(1), one F(3), two equivalent F(1), and two equivalent F(2) atoms to form NpO2F5 pentagonal bipyramids that share corners with two equivalent K(3)O4F4 hexagonal bipyramids, corners with three equivalent K(1)F6 octahedra, and  an edgeedge with one K(3)O4F4 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 0-29°. Both Np(1)-O(1) bond lengths are 1.83 Å. The Np(1)-F(3) bond length is 2.31 Å. Both Np(1)-F(1) bond lengths are 2.26 Å. Both Np(1)-F(2) bond lengths are 2.29 Å. O(1) is bonded in a distorted single-bond geometry to one K(3), two equivalent K(2), and one Np(1) atom. There are three inequivalent F sites. In the first F site, F(1) is bonded to one K(3), two equivalent K(2), and one Np(1) atom to form FK3Np tetrahedra that share corners with three equivalent F(3)K5Np octahedra, corners with four equivalent F(1)K3Np tetrahedra,  an edgeedge with one F(3)K5Np octahedra, and  an edgeedge with one F(1)K3Np tetrahedra. The corner-sharing octahedral tilt angles range from 13-37°. In the second F site, F(2) is bonded in a rectangular see-saw-like geometry to one K(1), two equivalent K(2), and one Np(1) atom. In the third F site, F(3) is bonded to one K(1), four equivalent K(2), and one Np(1) atom to form distorted FK5Np octahedra that share  a cornercorner with one F(3)K5Np octahedra, corners with six equivalent F(1)K3Np tetrahedra, edges with two equivalent F(3)K5Np octahedra, and edges with two equivalent F(1)K3Np tetrahedra. The corner-sharing octahedra are not tilted.