Neutron and X-ray diffraction experiments have shown that NaV2O5 consi
sts of zig-zag V chains of average valence 4.5 rather than a charge or
dered state at room temperature. Both these experiments revealed super
lattice reflections below the phase transition temperature T-SP approx
imate to 34 K. The modulation below T-SP is due to displacements predo
minantly of V atoms for which we propose a model. (C) 1998 Elsevier Sc
ience Ltd. All rights reserved.