DOE OSTI2020
Na3(WO3)4 crystallizes in the orthorhombic Immm space group. The structure is three-dimensional. there are three inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with eight NaO12 cuboctahedra, faces with four NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are a spread of Na–O bond distances ranging from 2.66–2.88 Å. In the second Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with eight NaO12 cuboctahedra, faces with four NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are a spread of Na–O bond distances ranging from 2.69–2.90 Å. In the third Na1+ site, Na1+ is bonded to twelve O2- atoms to form NaO12 cuboctahedra that share corners with eight NaO12 cuboctahedra, faces with four NaO12 cuboctahedra, and faces with eight equivalent WO6 octahedra. There are a spread of Na–O bond distances ranging from 2.67–2.87 Å. W+5.25+ is bonded to six O2- atoms to form WO6 octahedra that share corners with six equivalent WO6 octahedra and faces with six NaO12 cuboctahedra. The corner-sharing octahedra tilt angles range from 3–10°. There is four shorter (1.97 Å) and two longer (1.98 Å) W–O bond length. There are three inequivalent O2- sites. In the first O2- site, O2- is bonded to three Na1+ and two equivalent W+5.25+ atoms to form a mixture of distorted edge and corner-sharing ONa3W2 square pyramids. In the second O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two equivalent W+5.25+ atoms. In the third O2- site, O2- is bonded in a 5-coordinate geometry to three Na1+ and two equivalent W+5.25+ atoms.