Acta Crystallographica Section B

Structural Science

Volume 57, Part 3 (June 2001)

research papers

Acta Cryst. (2001). B57, 244-250 [ doi:10.1107/S0108768101002038 ]

Electron density in the sodium vanadium oxide bronze -Na_xV₂O₅ at 9 K

R. P. Ozerov, V. A. Streltsov, A. N. Sobolev, B. N. Figgis and V. L. Volkov

Abstract: The crystal structure and electron density in sodium vanadium oxide bronze, [beta] -Na_xV₂O₅ [x = 0.282 (3)], have been studied by accurate Mo K [alpha] X-ray diffraction measurements at 9.6 (3) K. No noticeable difference in the crystal structures at room temperature and 9.6 K has been observed. No superstructure reflections, previously found by Kanai, Kagoshima & Nagasawa [(1982), J. Phys. Soc. Jpn, 51, 697-698], have been detected at low temperature. Analysis of the deformation electron density has revealed the presence of the quasi-two-dimensional sheets of the -V-O-V-O- bonds in the structure. The electron density in the different chemical bonds within each of the three crystallographically independent VO₆ polyhedra noticeably varies, although there is no clear evidence that the three crystallographically independent V atoms have different valence states.

Keywords: electron density; bronze; valence states.