Materials Data on Na5NpO6 by Materials Project
Na5NpO6 is Caswellsilverite-like structured and crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with six NaO6 octahedra, edges with three equivalent NpO6 octahedra, and edges with nine NaO6 octahedra. The corner-sharing octahedra tilt angles range from 15–18°. There are four shorter (2.41 Å) and two longer (2.45 Å) Na–O bond lengths. In the second Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with two equivalent NpO6 octahedra, corners with four equivalent NaO6 octahedra, edges with two equivalent NpO6 octahedra, and edges with ten NaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–15°. There are four shorter (2.37 Å) and two longer (2.79 Å) Na–O bond lengths. In the third Na1+ site, Na1+ is bonded to six O2- atoms to form NaO6 octahedra that share corners with two equivalent NpO6 octahedra, corners with four equivalent NaO6 octahedra, edges with two equivalent NpO6 octahedra, and edges with ten NaO6 octahedra. The corner-sharing octahedra tilt angles range from 1–18°. There are a spread of Na–O bond distances ranging from 2.40–2.65 Å. Np7+ is bonded to six O2- atoms to form NpO6 octahedra that share corners with six NaO6 octahedra and edges with twelve NaO6 octahedra. The corner-sharing octahedra tilt angles range from 0–1°. There are two shorter (2.02 Å) and four longer (2.06 Å) Np–O bond lengths. There are two inequivalent O2- sites. In the first O2- site, O2- is bonded to five Na1+ and one Np7+ atom to form a mixture of distorted corner and edge-sharing ONa5Np octahedra. The corner-sharing octahedra tilt angles range from 0–13°. In the second O2- site, O2- is bonded in a 6-coordinate geometry to five Na1+ and one Np7+ atom.