ORIGIN OF THE METAL-TO-INSULATOR TRANSITION IN H0.33MOO3

The electronic structure of the double octahedral layers present in H0 .33MoO3 has been studied. It is shown that, depending on structural de tails, three bands, two of them having a two-dimensional character and one having a one-dimensional character, can be in competition at the bottom of the t(2g)-block bandstructure. Both qualitative arguments an d detailed computations show that the Fermi surface of the double octa hedral layers has a two-dimensional character and does not exhibit nes ting vectors. Consequently, the metal-to-insulator transition exhibite d by H0.33MoO3 cannot be a Fermi surface driven electronic instability , as recently proposed. An order-disorder transition of the protons is suggested as a more likely origin of this resistivity anomaly.