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Published November 2, 2007 | public
Journal Article

4D Visualization of Transitional Structures in Phase Transformations by Electron Diffraction


Complex systems in condensed phases involve a multidimensional energy landscape, and knowledge of transitional structures and separation of time scales for atomic movements is critical to understanding their dynamical behavior. Here, we report, using four-dimensional (4D) femtosecond electron diffraction, the visualization of transitional structures from the initial monoclinic to the final tetragonal phase in crystalline vanadium dioxide; the change was initiated by a near-infrared excitation. By revealing the spatiotemporal behavior from all observed Bragg diffractions in 3D, the femtosecond primary vanadium–vanadium bond dilation, the displacements of atoms in picoseconds, and the sound wave shear motion on hundreds of picoseconds were resolved, elucidating the nature of the structural pathways and the nonconcerted mechanism of the transformation.

Additional Information

© 2007 American Association for the Advancement of Science. Received 12 July 2007; accepted 19 September 2007. We are grateful to J. Weissenrieder for helpful discussions, L. H. Tjeng for generously providing some crystals, G. R. Rossman for the crystal-cutting equipment, and L. M. Henling for help with the x-ray measurements. This work was supported by the NSF, by the Air Force Office of Scientific Research, and by the Gordon and Betty Moore Center for Physical Biology at Caltech. P.B. was partially supported by the Alexander von Humboldt Foundation.

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August 19, 2023
October 18, 2023