Na5NpO6 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(3)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Np(1)O6 octahedra, and edges with four equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-17°. In the second Na site, Na(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Np(1)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, edges with two equivalent Np(1)O6 octahedra, edges with four equivalent Na(1)O6 octahedra, and edges with six equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. In the third Na site, Na(3) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Np(1)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, edges with two equivalent Np(1)O6 octahedra, edges with three equivalent Na(2)O6 octahedra, edges with three equivalent Na(3)O6 octahedra, and edges with four equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-17°. Np(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NpO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(3)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with four equivalent Na(3)O6 octahedra, and edges with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Np(1) atom to form a mixture of corner and edge-sharing ONa5Np octahedra. The corner-sharing octahedral tilt angles range from 0-15°. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Np(1) atom to form a mixture of distorted corner and edge-sharing ONa5Np octahedra. The corner-sharing octahedral tilt angles range from 0-11°.
Na5NpO6 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. There are three inequivalent Na sites. In the first Na site, Na(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(3)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with three equivalent Na(1)O6 octahedra, edges with three equivalent Np(1)O6 octahedra, and edges with four equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 14-17°. Both Na(1)-O(2) bond lengths are 2.36 Å. There are two shorter (2.36 Å) and two longer (2.39 Å) Na(1)-O(1) bond lengths. In the second Na site, Na(2) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Np(1)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, edges with two equivalent Np(1)O6 octahedra, edges with four equivalent Na(1)O6 octahedra, and edges with six equivalent Na(3)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-14°. Both Na(2)-O(2) bond lengths are 2.70 Å. All Na(2)-O(1) bond lengths are 2.32 Å. In the third Na site, Na(3) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NaO6 octahedra that share corners with two equivalent Np(1)O6 octahedra, corners with four equivalent Na(1)O6 octahedra, edges with two equivalent Np(1)O6 octahedra, edges with three equivalent Na(2)O6 octahedra, edges with three equivalent Na(3)O6 octahedra, and edges with four equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 1-17°. Both Na(3)-O(2) bond lengths are 2.42 Å. There are two shorter (2.35 Å) and two longer (2.54 Å) Na(3)-O(1) bond lengths. Np(1) is bonded to two equivalent O(2) and four equivalent O(1) atoms to form NpO6 octahedra that share corners with two equivalent Na(2)O6 octahedra, corners with four equivalent Na(3)O6 octahedra, edges with two equivalent Na(2)O6 octahedra, edges with four equivalent Na(3)O6 octahedra, and edges with six equivalent Na(1)O6 octahedra. The corner-sharing octahedral tilt angles range from 0-1°. Both Np(1)-O(2) bond lengths are 2.00 Å. All Np(1)-O(1) bond lengths are 2.04 Å. There are two inequivalent O sites. In the first O site, O(1) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Np(1) atom to form a mixture of corner and edge-sharing ONa5Np octahedra. The corner-sharing octahedral tilt angles range from 0-15°. In the second O site, O(2) is bonded to one Na(2), two equivalent Na(1), two equivalent Na(3), and one Np(1) atom to form a mixture of distorted corner and edge-sharing ONa5Np octahedra. The corner-sharing octahedral tilt angles range from 0-11°.