What is it about?
The phenomenon of decompression amorphization of crystalline dense ice was investigated using time-resolved synchrotron x-ray diffraction. The transformation process is found to go through two intermediate amorphous structures and is governed by kinetics. The formation and kinetic of the intermediate high and low-density amorphous ices were identified and characterized. In particular, the transitions exhibit different thermally-activated mechanism above and below 110 K. Molecular-dynamics simulations show the transition involves a large change in density and substantial displacements of water at the nanoscale.
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Why is it important?
The time resolution captures events that were not observed previously and reveals a complex kinetic pathway with three distinctive transitions, The results present insight into the metastability and complexity of the energy landscape in temperature/time-dependent structural evolution in amorphous ices. The intermediate amorphous - amorphous processes compete against each other. The end result is a juxtaposition of these processes.
Perspectives
The inter-conversion between compressed amorphous is driven by kinetics and determined by the temperature and the rate of pressure increase 9or decrease). Displacements of the water during the amorphous-amorphous transformation are not diffusive and in the order of nano-meter.
John Tse
University of Saskatchewan
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This page is a summary of: Temperature-dependent kinetic pathways featuring distinctive thermal-activation mechanisms in structural evolution of ice VII, Proceedings of the National Academy of Sciences, June 2020, Proceedings of the National Academy of Sciences,
DOI: 10.1073/pnas.2007959117.
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