Direct measurement of the structural change associated with amorphous solidification using static scattering of coherent radiation

CF Petersen and P Harrowell, JOURNAL OF CHEMICAL PHYSICS, 159, 244506 (2023).

DOI: 10.1063/5.0177251

In this paper, we demonstrate that the weak temperature dependence of the structure factor of supercooled liquids, a defining feature of the glass transition, is a consequence of the averaging of the scattering intensity due to angular averaging. We show that the speckle at individual wavevectors, calculated from a simulated glass former, exhibits a Debye-Waller factor with a sufficiently large temperature dependence to represent a structural order parameter capable of distinguishing liquid from glass. We also extract from the speckle intensities a quantity proportional to the variance of the local restraint, i.e., a direct experimental measure of the amplitude of structural heterogeneity.

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