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Probing excitations and cooperatively rearranging regions in deeply supercooled liquids

Ortlieb, L., Ingebrigtsen, T. S., Hallett, J. E. ORCID:, Turci, F. and Royall, C. P. (2023) Probing excitations and cooperatively rearranging regions in deeply supercooled liquids. Nature Communications, 14. 2621. ISSN 2041-1723

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To link to this item DOI: 10.1038/s41467-023-37793-2


Upon approaching the glass transition, the relaxation of supercooled liquids is controlled by activated processes, which become dominant at temperatures below the so-called dynamical crossover predicted by Mode Coupling theory (MCT). Two of the main frameworks rationalising this behaviour are dynamic facilitation theory (DF) and the thermodynamic scenario which give equally good descriptions of the available data. Only particle-resolved data from liquids supercooled below the MCT crossover can reveal the microscopic mechanism of relaxation. By employing state-of-the-art GPU simulations and nano-particle resolved colloidal experiments, we identify the elementary units of relaxation in deeply supercooled liquids. Focusing on the excitations of DF and cooperatively rearranging regions (CRRs) implied by the thermodynamic scenario, we find that several predictions of both hold well below the MCT crossover: for the elementary excitations, their density follows a Boltzmann law, and their timescales converge at low temperatures. For CRRs, the decrease in bulk configurational entropy is accompanied by the increase of their fractal dimension. While the timescale of excitations remains microscopic, that of CRRs tracks a timescale associated with dynamic heterogeneity, t* ∼τ0:8. This timescale separation of excitations and CRRs opens the possibility of accumulation of excitations giving rise to cooperative behaviour leading to CRRs.

Item Type:Article
Divisions:Life Sciences > School of Chemistry, Food and Pharmacy > Department of Chemistry
ID Code:111897
Publisher:Nature Publishing Group


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