K3NpO2F5 crystallizes in the tetragonal I4_1/a space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent F(2), two equivalent F(3), and three equivalent F(1) atoms. In the second K site, K(2) is bonded to four equivalent O(1) and four equivalent F(3) 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. In the third K site, K(3) is bonded to two equivalent F(2) and four equivalent F(1) atoms to form KF6 octahedra that share corners with six equivalent Np(1)O2F5 pentagonal bipyramids. Np(1) is bonded to two equivalent O(1), one F(2), two equivalent F(1), and two equivalent F(3) atoms to form NpO2F5 pentagonal bipyramids that share corners with two equivalent K(2)O4F4 hexagonal bipyramids, corners with three equivalent K(3)F6 octahedra, and  an edgeedge with one K(2)O4F4 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 0-35°. O(1) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Np(1) atom. There are three inequivalent F sites. In the first F site, F(1) is bonded in a 5-coordinate geometry to one K(3), three equivalent K(1), and one Np(1) atom. In the second F site, F(2) is bonded in a 6-coordinate geometry to one K(3), four equivalent K(1), and one Np(1) atom. In the third F site, F(3) is bonded to one K(2), two equivalent K(1), and one Np(1) atom to form a mixture of edge and corner-sharing FK3Np tetrahedra.
K3NpO2F5 crystallizes in the tetragonal I4_1/a space group. There are three inequivalent K sites. In the first K site, K(1) is bonded in a 9-coordinate geometry to two equivalent O(1), two equivalent F(2), two equivalent F(3), and three equivalent F(1) atoms. There is one shorter (3.07 Å) and one longer (3.16 Å) K(1)-O(1) bond length. There is one shorter (2.93 Å) and one longer (3.20 Å) K(1)-F(2) bond length. There is one shorter (2.66 Å) and one longer (2.74 Å) K(1)-F(3) bond length. There are a spread of K(1)-F(1) bond distances ranging from 2.65-3.23 Å. In the second K site, K(2) is bonded to four equivalent O(1) and four equivalent F(3) 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(2)-O(1) bond lengths are 2.90 Å. All K(2)-F(3) bond lengths are 2.75 Å. In the third K site, K(3) is bonded to two equivalent F(2) and four equivalent F(1) atoms to form KF6 octahedra that share corners with six equivalent Np(1)O2F5 pentagonal bipyramids. Both K(3)-F(2) bond lengths are 2.67 Å. All K(3)-F(1) bond lengths are 2.59 Å. Np(1) is bonded to two equivalent O(1), one F(2), two equivalent F(1), and two equivalent F(3) atoms to form NpO2F5 pentagonal bipyramids that share corners with two equivalent K(2)O4F4 hexagonal bipyramids, corners with three equivalent K(3)F6 octahedra, and  an edgeedge with one K(2)O4F4 hexagonal bipyramid. The corner-sharing octahedral tilt angles range from 0-35°. Both Np(1)-O(1) bond lengths are 1.83 Å. The Np(1)-F(2) bond length is 2.31 Å. Both Np(1)-F(1) bond lengths are 2.30 Å. Both Np(1)-F(3) bond lengths are 2.25 Å. O(1) is bonded in a distorted single-bond geometry to one K(2), two equivalent K(1), and one Np(1) atom. There are three inequivalent F sites. In the first F site, F(1) is bonded in a 5-coordinate geometry to one K(3), three equivalent K(1), and one Np(1) atom. In the second F site, F(2) is bonded in a 6-coordinate geometry to one K(3), four equivalent K(1), and one Np(1) atom. In the third F site, F(3) is bonded to one K(2), two equivalent K(1), and one Np(1) atom to form a mixture of edge and corner-sharing FK3Np tetrahedra.