Metal-insulator transition and local structure of V2O3

According to diffraction measurements of the average structure, V2O3 changes on heating from monoclinic to trigonal, accompanied by a 1.4% volume decrease, where some V-V distances decrease by about O.11 Angstrom, favoring the Mott-Hubbard mechanism of the phase transition from insulator to metal. Our polarized XAFS measurements of the local structure of the single crystal V2O3 show the same decrease in volume but no change in local symmetry in the transition, indicating that the phase transition contains a significant order-disorder component, contrary to the purely displacive model based on diffraction results. XANES measurements found that the onset of the 1s --> ''3d'' transition in the insulator shifts towards lower energies by about leV in the metal, consistent with the shielding of the core hole potential by conducting electrons.