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Intermediate-range order governs dynamics in dense colloidal liquids.

Navneet SinghZhen ZhangAjay K SoodWalter KobRajesh Ganapathy
Published in: Proceedings of the National Academy of Sciences of the United States of America (2023)
The conventional wisdom is that liquids are completely disordered and lack nontrivial structure beyond nearest-neighbor distances. Recent observations have upended this view and demonstrated that the microstructure in liquids is surprisingly rich and plays a critical role in numerous physical, biological, and industrial processes. However, approaches to uncover this structure are either system-specific or yield results that are not physically intuitive. Here, through single-particle resolved three-dimensional confocal microscope imaging and the use of a recently introduced four-point correlation function, we show that bidisperse colloidal liquids have a highly nontrivial structure comprising alternating layers with icosahedral and dodecahedral order, which extends well beyond nearest-neighbor distances and grows with supercooling. By quantifying the dynamics of the system on the particle level, we establish that it is this intermediate-range order, and not the short-range order, which has a one-to-one correlation with dynamical heterogeneities, a property directly related to the relaxation dynamics of glassy liquids. Our experimental findings provide a direct and much sought-after link between the structure and dynamics of liquids and pave the way for probing the consequences of this intermediate-range order in other liquid state processes.
Keyphrases
  • single molecule
  • physical activity
  • ionic liquid
  • wastewater treatment
  • heavy metals
  • molecular dynamics simulations
  • white matter
  • optical coherence tomography
  • photodynamic therapy
  • mass spectrometry