arXiv subjects

Dong-Xu Yu

Publications and source records attributed to Dong-Xu Yu.

3 recordsLinked to original sources

arXiv2026

A quantitative approach to flowing supercooled liquids: From microscopic heterogeneities to rheology

Soft glassy materials display rich and complex flow behaviors across both macroscopic and molecular scales, and a fundamental understanding of these phenomena remains an outstanding challenge. Here, we propose a theoretical model for the flow of supercooled liquids -- a typical class of glassy fluids -- based on a two-state paradigm that conceptualizes the flow as a dynamic coexistence of transient solid-like and liquid-like regions. The model rests on two essential physical ingredients: a correlation length that captures medium-range structural order, and a localized elasticity-mediated interaction that restricts stress propagation within solid-like regions. Remarkably, with all parameters determined solely from equilibrium state, the model quantitatively reproduces rheological responses -- including both steady-state and start-up shear -- for a broad range of shear rates. Furthermore, it simultaneously captures the evolution of molecular dynamic heterogeneity. This dual success -- spanning macroscopic rheology and microscopic spatiotemporal fluctuations -- underscores the pivotal role of structural and dynamic heterogeneities in governing the rheological response. Moreover, it provides a direct understanding of how the flow behaviors of a supercooled liquid are embedded in its equilibrium properties.

cond-mat.soft↗

arXiv2025

Understanding Flow Behaviors of Supercooled Liquids by Embodying Solid-Liquid Duality at Particle Level

Understanding the flow behaviors of supercooled liquids presents a major challenge in liquid-state physics due to the strong nonlinearity and rich phenomena. To unravel this complexity, we introduce the concept of local configurational relaxation time $\tau_\rm{LC}$, which allows us to embody the solid-liquid duality, proposed by Maxwell for phenomenologically describing materials' response to external load, at the particle level. The spatial distribution of $\tau_\rm{LC}$ in flow is heterogeneous. Depending on the comparison between the local mobility measured by $\tau_\rm{LC}$ and the external shear rate, the shear response of local regions is either solid-like or liquid-like. In this way, $\tau_\rm{LC}$ plays a role similar to the Maxwell time. By applying this microscopic solid-liquid duality to different conditions of shear flow with a wide range of shear rates, we describe the emergence of shear thinning in steady shear, and predict the major characteristics of the transient response to start-up shear. Furthermore, we reveal a clear structural foundation for $\tau_\rm{LC}$ and the solid-liquid duality associated with it by introducing an order parameter extracted from local configuration. Thus, we establish a framework that connects microscopic structure, dynamics, local mechanical response, and flow behaviors for supercooled liquids. Finally, we rationalize our framework in terms of activations from energy basins that are facilitated by shear. This model illustrates how local structure, convection and thermal activation collectively determine $\tau_\rm{LC}$. Notably, it predicts two distinct response groups, which well correspond to the microscopic solid-liquid duality.

cond-mat.soft↗

arXiv2025

Connecting Shear Thinning and Dynamic Heterogeneity in Supercooled Liquids by Localized Elasticity

Supercooled liquids exhibit complicated dynamical behaviors: At the microscopic level, the dynamics is heterogeneous spatially, known as dynamic heterogeneity. At the macroscopic level, the shear viscosity $\eta$ decreases as shear rate $\dot{\gamma}$ increases with a power law $\eta\sim\dot{\gamma}^{-\lambda}$, known as shear thinning. The relation between these two universal dynamical phenomena remains elusive. With simulations of several model liquids in two and three dimensions, we show that they are quantitatively bridged by localized elasticity embodied as transient clusters that elastically respond to shear. Prominent dynamic heterogeneity emerges right after the massive yielding of these clusters, which is initiated by shear transformation zones and facilitated by elasticity-mediated interaction. With this picture, a scaling law relating shear thinning to the characteristic length of dynamic heterogeneity is found.

cond-mat.soft↗