A NEW VIEW OF THE ELECTRONIC-STRUCTURE OF THE SPIN-PEIERLS COMPOUND ALPHA'-NAV2O5

The present understanding of the electronic and magnetic properties of alpha'-NaV2O5 is based on the hypothesis of strong charge disproporti onation into V4+ and V5+, which is assumed to lead to a spin-1/2 Heise nberg chain system. A recent structure analysis shows, however, that t he V-ions are in a mixed valence state and indistiguishable. We propos e an explanation for the insulating state, which is not based on charg e modulation, and show that strong correlations together with the Heit ler-London character of the relevant intermediate states naturally lea d to antiferromagnetic Heisenberg chains. The interchain coupling is w eak and frustrated, and its effect on the uniform susceptibility is fo und to be small.