DOI > 10.5291/ILL-DATA.6-05-961

This proposal is publicly available since 07/27/2020


The connection between fast and slow dynamics in glass-forming liquids: atest of the 'isomorph theory' of simple liquids


The molecules in a liquid close to the glass transition move on a range of timescales. Vibrations take place on the picosecond timescale while relaxations can be as slow as minutes or hours. It has several times been suggested that there is a close connection between the fast and slow dynamics, even though they differ in time scales by ten or more orders of magnitude. The recently developed isomorph theory rationalizes this connection. The aim of this experiment is to measure fast dynamics (~ nanosecond) at different state points (T-P) along lines in the phase diagram where the slow alpha relaxation is constant (so called isochrones), because the isomorph theory predicts that the fast relaxation should be invariant along these lines. The experiment requires measurements at elevated pressure, which is in itself interesting because relatively little INS/QENS high pressure data is available on glass-forming liquids. Two prototypical liquids will be studied: a van der Waals molecular liquid and an hydrogen bonded one, showing opposite trends for the pressure dependance of fragility.

Experimental Report

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Data Citation

The recommended format for citing this dataset in a research publication is in the following format:

Kristine Niss; ALBA SIMIONESCO Christiane; Simone Capaccioli; CIAMPALINI GAIA; Bernhard Frick; HANSEN Henriette Wase; PETERS Judith and SANZ Alejandro. (2015). The connection between fast and slow dynamics in glass-forming liquids: atest of the 'isomorph theory' of simple liquids. Institut Laue-Langevin (ILL) doi:10.5291/ILL-DATA.6-05-961

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Experiment Parameters

  • Environment temperature

    1.5 - 300 K
  • Experiment energy

    2.23 , 6.3
  • Experiment moment

    0.2 - 2
  • Experiment res energy

    0.3 mueV, 8 mueV
  • Experiment res moment


Sample Parameters

  • Formula

    • Dibutylphthalate (C16H22O4)
    • Dipropylene glycol (C6H14O3)