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Dynamic phase coexistence in glass-forming liquids
Raffaele Pastore1, Antonio Coniglio1, Massimo Pica Ciamarra2
1CNR-SPIN, Dipartimento di Scienze Fisiche, Universitá di Napoli Federico II, Italy.
Scientific Reports
|July 10, 2015
Summary
This study directly observes two distinct dynamic phases coexisting in supercooled liquids, revealing a transient bimodal distribution of single-particle diffusivities. This finding supports controversial hypotheses about glass dynamics and heterogeneous dynamics.
Area of Science:
- Condensed Matter Physics
- Materials Science
- Physical Chemistry
Background:
- The dynamics of supercooled liquids and glasses are often heterogeneous.
- A controversial hypothesis suggests this heterogeneity arises from the temporary coexistence of two phases with differing diffusivities.
- Directly observing and measuring these distinct dynamical phases has been challenging.
Purpose of the Study:
- To provide the first direct observation of the dynamical coexistence of two phases with different diffusivities in supercooled liquids.
- To test the hypothesis of phase coexistence as an explanation for heterogeneous dynamics.
- To relate the observed dynamical behavior to the breakdown of the Stokes-Einstein relation.
Main Methods:
- Analysis of the distribution of single-particle diffusivities in the deeply supercooled regime.
- Utilizing simulations to observe the transient bimodal shape of the diffusivity distribution.
- Investigating the timescale of phase coexistence relative to the relaxation time.
Main Results:
- Direct observation of a transient bimodal distribution in single-particle diffusivities, indicating the coexistence of two dynamical phases.
- This bimodal distribution is linked to the heterogeneity of dynamics and the breakdown of the Stokes-Einstein relation.
- The coexistence of these two dynamical phases persists up to a timescale that grows faster than the relaxation time upon cooling for certain models.
Conclusions:
- The study provides the first direct evidence for the dynamical coexistence of two distinct phases in supercooled liquids.
- This observation supports hypotheses explaining heterogeneous dynamics in glasses.
- The findings offer a framework for understanding the relationship between structural and dynamical properties of supercooled liquids.
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