Classification of mobile- and immobile-molecule timescales for the Stokes-Einstein and Stokes-Einstein-Debye relations in supercooled water

Abstract

Molecular dynamics simulations have been performed on TIP4P/2005 supercooled water to investigate the molecular diffusion and shear viscosity at various timescales and assess the Stokes-Einstein (SE) and Stokes-Einstein-Debye (SED) relations. For this purpose, we calculated various time correlation functions, such as the mean-squared displacement, stress relaxation function, density correlation function, hydrogen-bond correlation function, rotational correlation function of molecular orientation, non-Gaussian parameter, and four-point correlation function. Our study of the SE and SED relations indicates that the transport coefficients and timescales obtained using these time correlation functions may be classified into two distinct classes: those governed by either mobile or immobile molecules, due to dynamical heterogeneity. In particular, we show that the stress relaxation time, hydrogen-bond lifetime, and large-angle rotational relaxation time are coupled with translational diffusion, and are characterized by mobile molecules. In contrast, the structural $\alpha$-relaxation time, small-angle rotational relaxation time, and characteristic timescales of four-point correlation functions are decoupled with translational diffusion, and are governed by immobile molecules. This decoupling results in a violation of the SE relation. These results indicate that the identification of timescales that appropriately characterize transport coefficients, such as translational diffusion constant and shear viscosity, provides a deep insight into the violation of the SE and SED relations in glass-forming liquids.

15 pages, 5 figures

References in corpus (16)

• Fractional Stokes-Einstein and Debye-Stokes-Einstein relations in a network forming liquid
• Two-State Thermodynamics and the Possibility of a Liquid-Liquid Phase Transition in Supercooled TIP4P/2005 Water
• Identifying time scales for violation/preservation of Stokes-Einstein relation in supercooled water
• Coupling/decoupling between translational and rotational dynamics in a supercooled molecular liquid
• Viscosity and self-diffusion of supercooled and stretched water from molecular dynamics simulations
• A comprehensive scenario of the thermodynamic anomalies of water using the TIP4P/2005 model
• Computational probes of molecular motion in the Lewis and Whanstrom model for ortho-terphenyl
• Crucial role of fragmented and isolated defects in persistent relaxation of deeply supercooled water
• Relationship between bond-breakage correlations and four-point correlations in heterogeneous glassy dynamics: Configuration changes and vibration modes
• Spurious violation of the Stokes-Einstein-Debye relation in supercooled water
• Potential Energy Landscape of TIP4P/2005 water
• Length scale dependence of the Stokes-Einstein and Adam-Gibbs relations in model glass formers
• Heterogeneous diffusion, viscosity and the Stokes Einstein relation in binary liquids
• Determination of onset temperature from the entropy for fragile to strong liquids
• Fast dynamics perspective on the breakdown of the Stokes-Einstein law in fragile glassformers
• Assessment of elastic models in supercooled water: A molecular dynamics study with the TIP4P/2005f force field

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