DOE OSTI2020
Na2Mo2O5 crystallizes in the monoclinic Cm space group. The structure is three-dimensional. there are two inequivalent Na1+ sites. In the first Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.31–2.73 Å. In the second Na1+ site, Na1+ is bonded in a 7-coordinate geometry to seven O2- atoms. There are a spread of Na–O bond distances ranging from 2.49–2.80 Å. There are three inequivalent Mo4+ sites. In the first Mo4+ site, Mo4+ is bonded to six O2- atoms to form MoO6 octahedra that share corners with four equivalent MoO6 octahedra, a cornercorner with one MoO4 tetrahedra, and a cornercorner with one MoO4 trigonal pyramid. The corner-sharing octahedra tilt angles range from 4–22°. There are a spread of Mo–O bond distances ranging from 2.00–2.16 Å. In the second Mo4+ site, Mo4+ is bonded to four O2- atoms to form distorted MoO4 trigonal pyramids that share corners with two equivalent MoO6 octahedra and corners with two equivalent MoO4 tetrahedra. The corner-sharing octahedral tilt angles are 29°. There are a spread of Mo–O bond distances ranging from 1.87–2.07 Å. In the third Mo4+ site, Mo4+ is bonded to four O2- atoms to form MoO4 tetrahedra that share corners with two equivalent MoO6 octahedra and corners with two equivalent MoO4 trigonal pyramids. The corner-sharing octahedral tilt angles are 42°. There are a spread of Mo–O bond distances ranging from 1.92–2.02 Å. There are six inequivalent O2- sites. In the first O2- site, O2- is bonded to four Na1+ and two equivalent Mo4+ atoms to form distorted ONa4Mo2 octahedra that share corners with two equivalent ONa4Mo2 octahedra, corners with two equivalent ONa2Mo2 tetrahedra, corners with two equivalent ONa2Mo2 trigonal pyramids, and edges with two equivalent ONa4Mo2 octahedra. The corner-sharing octahedral tilt angles are 2°. In the second O2- site, O2- is bonded in a 6-coordinate geometry to four Na1+ and two equivalent Mo4+ atoms. In the third O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Na1+ and two Mo4+ atoms. In the fourth O2- site, O2- is bonded in a distorted rectangular see-saw-like geometry to two Na1+ and two Mo4+ atoms. In the fifth O2- site, O2- is bonded to two equivalent Na1+ and two Mo4+ atoms to form ONa2Mo2 trigonal pyramids that share corners with four equivalent ONa4Mo2 octahedra and corners with two equivalent ONa2Mo2 tetrahedra. The corner-sharing octahedra tilt angles range from 39–68°. In the sixth O2- site, O2- is bonded to two equivalent Na1+ and two Mo4+ atoms to form distorted ONa2Mo2 tetrahedra that share corners with four equivalent ONa4Mo2 octahedra and corners with two equivalent ONa2Mo2 trigonal pyramids. The corner-sharing octahedra tilt angles range from 55–65°.