Structure determination of low-dimensional conductor sodium molybdenum purple bronze Na 0.9Mo 6O 17

Abstract

Structure determination of the molybdenum purple bronze Na 0.9Mo 6O 17 is carried out by single-crystal X-ray diffraction. The crystal is monoclinic with space group A2 and the lattice constants are a = 12.983(2), b = 5.518(1), c = 9.591(2) Å, β = 89.94(1)°, Z = 2. Full-matrix least-squares refinement gives the final values of R(F) = 0.028 and R w(F) = 0.040 for 1484 independent reflections, in which the occupancy factor of the sodium atom becomes 0.899(12). The present structure is built up of the linkage of the MoO 4 and MoO 6 polyhedra. There are slabs which consist of four layers of distorted MoO 6 octahedra sharing corners. Both the structure and the molybdenum valence distribution estimated from the MoO bond lengths are considered to lead to the two-dimensional electronic transport. This structure is compared with those of other members of molybdenum purple bronzes, K 0.9Mo 6O 17 and Li 0.9Mo 6O 17. The difference of the electronic properties among these compounds can be well understood on the basis of their structural characteristics.