Metal-Insulator Transition and Local Structure of V2O3

According to diffraction measurements of the average structure, V 2 O 3 changes on heating from monoclinic to trigonal, accompanied by a 1.4% volume decrease, where some V - V distances decrease by about 0.11 A, 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 V 2 O 3 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 1eV in the metal, consistent with the shielding of the core hole potential by conducting electrons.