Revisiting the breakdown of Stokes-Einstein relation in glass-forming liquids with machine learning
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ly 2020 Vol. 63 No. 7: 276111 https://doi.org/10.1007/s11433-020-1539-4
Revisiting the breakdown of Stokes-Einstein relation in glassforming liquids with machine learning 1*†
2†
ZhenWei Wu , and Renzhong Li 1
2
School of Systems Science, Beijing Normal University, Beijing 100875, China; International Center for Quantum Materials and School of Physics, Peking University, Beijing 100871, China Received January 16, 2020; accepted March 5, 2020; published online March 25, 2020
The Stokes-Einstein (SE) relation has been considered as one of the hallmarks of dynamics in liquids. It describes that the –1 diffusion constant D is proportional to (τ/T) , where τ is the structural relaxation time and T is the temperature. In many glassforming liquids, the breakdown of SE relation often occurred when the dynamics of the liquids becomes glassy, and its origin is still debated among many scientists. Using molecular dynamics simulations and support-vector machine method, it is found that the scaling between diffusion and relaxation fails when the total population of solid-like clusters shrinks at the maximal rate with decreasing temperature, which implies a dramatic unification of clusters into an extensive dominant one occurs at the time of breakdown of the SE relation. Our data leads to an interpretation that the SE violation in metallic glass-forming liquids can be attributed to a specific change in the atomic structures. metallic glass-forming liquid, machine learning, Stokes-Einstein relation PACS number(s): 64.70.pe, 61.20.Ja, 66.20.Cy Citation:
1
Z. W. Wu, and R. Li, Revisiting the breakdown of Stokes-Einstein relation in glass-forming liquids with machine learning, Sci. China-Phys. Mech. Astron. 63, 276111 (2020), https://doi.org/10.1007/s11433-020-1539-4
Introduction
The understanding of the dynamic properties of supercooled liquids for metallic alloys is of crucial importance in condensed matter physics and material science [1-3]. When a liquid is supercooled below its melting temperature, the characteristic timescales of its dynamics become obviously rich, bridging the gap between microscopic oscillation times and macroscopic relaxation times [4-7]. Many interesting phenomena occur during the vitrification process, such as dynamic heterogeneity, super Arrhenius behavior and a breakdown of Stokes-Einstein (SE) relation. The SE relation expresses the transport coefficient D in relation to the
*Corresponding author (email: [email protected]) †These authors contributed equally to this work.
structural relaxation time τ and temperature T, which is represented as D ( / T ) 1. The SE relation is valid for most liquids at a broad range of high temperatures but in contrast, at supercooled temperatures, especially near glass transition temperature, the SE relation is not observed [8-11]. As one of the most important anomalies that has been reported in different types of supercooled liquids, the origin of the breakdown of the SE relation has attracted a lot of attentions [8-16]. No conclusion has been reached in this rega
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