LOCAL-STRUCTURE CHANGES IN V2O3 BELOW AND ABOVE THE METAL-INSULATOR-TRANSITION

According to diffraction measurements of the average structure, V2O3 c hanges on heating from monoclinic to trigonal, accompanied by a 1.4% v olume decrease, where some V - V distances decrease by about 0.11 Angs trom A, favoring the Mott - Hubbard mechanism of the phase transition from insulator to metal. Our x-ray absorption fine structure measureme nts of the local structure of the single crystal V2O3 show the same de crease in volume but no change in local symmetry in the transition, in dicating that the phase transition contains a significant order-disord er component, contrary to the purely displacive model based on diffrac tion results. (C) 1997 Elsevier Science Ltd.