DOE OSTI2020
NaCo2(MoO5)2 crystallizes in the monoclinic C2/m space group. The structure is three-dimensional. Na1+ is bonded to six O2- atoms to form distorted NaO6 octahedra that share corners with four equivalent CoO6 octahedra and corners with six equivalent MoO4 tetrahedra. The corner-sharing octahedral tilt angles are 59°. There are four shorter (2.45 Å) and two longer (2.77 Å) Na–O bond lengths. Mo6+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with three equivalent NaO6 octahedra and corners with four equivalent CoO6 octahedra. The corner-sharing octahedra tilt angles range from 46–66°. There are a spread of Mo–O bond distances ranging from 1.73–1.89 Å. Co+3.50+ is bonded to six O2- atoms to form CoO6 octahedra that share corners with two equivalent NaO6 octahedra, corners with four equivalent MoO4 tetrahedra, and edges with two equivalent CoO6 octahedra. The corner-sharing octahedral tilt angles are 59°. There is two shorter (1.82 Å) and four longer (2.10 Å) Co–O bond length. There are four inequivalent O2- sites. In the first O2- site, O2- is bonded in a water-like geometry to two equivalent Co+3.50+ atoms. In the second O2- site, O2- is bonded in a trigonal planar geometry to one Na1+, one Mo6+, and one Co+3.50+ atom. In the third O2- site, O2- is bonded in a distorted single-bond geometry to one Na1+ and one Mo6+ atom. In the fourth O2- site, O2- is bonded in a distorted T-shaped geometry to one Mo6+ and two equivalent Co+3.50+ atoms.