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Zhai Q, Gao XY, Lee CS, Ong CY, Yan K, Deng HY, Yang S, Lam CH. Surface mobility gradient and emergent facilitation in glassy films. SOFT MATTER 2024; 20:4389-4394. [PMID: 38757511 DOI: 10.1039/d4sm00221k] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/18/2024]
Abstract
Confining glassy polymers into films can substantially modify their local and film-averaged properties. We present a lattice model of film geometry with void-mediated facilitation behaviors but free from any elasticity effect. We analyze the spatially varying viscosity to delineate the transport properties of glassy films. The film mobility measurements reported by Yang et al., Science, 2010, 328, 1676 are successfully reproduced. The flow exhibits a crossover from a simple viscous flow to a surface-dominated regime as the temperature decreases. The propagation of a highly mobile front induced by the free surface is visualized in real space. Our approach provides a microscopic treatment of the observed glassy phenomena.
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Affiliation(s)
- Qiang Zhai
- School of Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an, Shaanxi, 710049, China.
| | - Xin-Yuan Gao
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Chun-Shing Lee
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Chin-Yuan Ong
- School of Physics, Yale University, New Haven, Connecticut, 06520, USA
| | - Ke Yan
- School of Mechanical Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi, 710049, China.
| | - Hai-Yao Deng
- School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff, CF24 3AA, Wales, UK.
| | - Sen Yang
- School of Physics, MOE Key Laboratory for Nonequilibrium Synthesis and Modulation of Condensed Matter, Xi'an, Shaanxi, 710049, China.
| | - Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China.
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Li B, Lee CS, Gao XY, Deng HY, Lam CH. The distinguishable-particle lattice model of glasses in three dimensions. SOFT MATTER 2024; 20:1009-1017. [PMID: 38197256 DOI: 10.1039/d3sm01343j] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/11/2024]
Abstract
The nature of glassy states in realistic finite dimensions is still under fierce debate. Lattice models can offer valuable insights and facilitate deeper theoretical understanding. Recently, a disordered-interacting lattice model with distinguishable particles in two dimensions (2D) has been shown to produce a wide range of dynamical properties of structural glasses, including the slow and heterogeneous characteristics of the glassy dynamics, various fragility behaviors of glasses, and so on. These findings support the usefulness of this model for modeling structural glasses. An important question is whether such properties still hold in the more realistic three dimensions. In this study, we aim to extend the distinguishable-particle lattice model (DPLM) to three dimensions (3D) and explore the corresponding glassy dynamics. Through extensive kinetic Monte Carlo simulations, we found that the 3D DPLM exhibits many typical glassy behaviors, such as plateaus in the mean square displacement of particles and the self-intermediate scattering function, dynamic heterogeneity, variability of glass fragilities, and so on, validating the effectiveness of the DPLM in a broader realistic setting. The observed glassy behaviors of the 3D DPLM appear similar to those of its 2D counterpart, in accordance with recent findings in molecular models of glasses. We further investigate the role of void-induced motions in dynamical relaxations and discuss their relation to dynamic facilitation. As lattice models tend to keep the minimal but important modeling elements, they are typically much more amenable to analysis. Therefore, we envisage that the DPLM will benefit future theoretical developments, such as the configuration tree theory, towards a more comprehensive understanding of structural glasses.
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Affiliation(s)
- Bo Li
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Chun-Shing Lee
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
- School of Science, Harbin Institute of Technology (Shenzhen), Shenzhen, 518055, China
| | - Xin-Yuan Gao
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
- Department of Physics, The Chinese University of Hong Kong, Shatin, New Territories, Hong Kong, China
| | - Hai-Yao Deng
- School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3AA, Wales, UK.
| | - Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China.
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Gopinath G, Lee CS, Gao XY, An XD, Chan CH, Yip CT, Deng HY, Lam CH. Diffusion-Coefficient Power Laws and Defect-Driven Glassy Dynamics in Swap Acceleration. PHYSICAL REVIEW LETTERS 2022; 129:168002. [PMID: 36306762 DOI: 10.1103/physrevlett.129.168002] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 09/15/2022] [Indexed: 06/16/2023]
Abstract
Particle swaps can drastically accelerate dynamics in glass. The mechanism is expected to be vital for a fundamental understanding of glassy dynamics. To extract defining features, we propose a partial swap model with a fraction ϕ_{s} of swap-initiating particles, which can only swap locally with each other or with regular particles. We focus on the swap-dominating regime. At all temperatures studied, particle diffusion coefficients scale with ϕ_{s} in unexpected power laws with temperature-dependent exponents, consistent with the kinetic picture of glassy dynamics. At small ϕ_{s}, swap initiators, becoming defect particles, induce remarkably typical glassy dynamics of regular particles. This supports defect models of glass.
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Affiliation(s)
- Gautham Gopinath
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Chun-Shing Lee
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Xin-Yuan Gao
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Xiao-Dong An
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
| | - Chor-Hoi Chan
- Department of Physics, Harbin Institute of Technology, Shenzhen 518055, China
| | - Cho-Tung Yip
- Department of Physics, Harbin Institute of Technology, Shenzhen 518055, China
| | - Hai-Yao Deng
- School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3AA, Wales, United Kingdom
| | - Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hung Hom, Hong Kong, China
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Gao XY, Deng HY, Lee CS, You JQ, Lam CH. Emergence of two-level systems in glass formers: a kinetic Monte Carlo study. SOFT MATTER 2022; 18:2211-2221. [PMID: 35226017 DOI: 10.1039/d1sm01809d] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/14/2023]
Abstract
Using a distinguishable-particle lattice model based on void-induced dynamics, we successfully reproduce the well-known linear relation between heat capacity and temperature at very low temperatures. The heat capacity is dominated by two-level systems formed due to the strong localization of voids to two neighboring sites, and can be exactly calculated in the limit of ultrastable glasses. Similar but weaker localization at higher temperatures accounts for glass transition. The result supports the conventional two-level tunneling picture by revealing how two-level systems emerge from random particle interactions, which also cause glass transition. Our approach provides a unified framework for relating microscopic dynamics of glasses at room and cryogenic temperatures.
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Affiliation(s)
- Xin-Yuan Gao
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China.
| | - Hai-Yao Deng
- School of Physics and Astronomy, Cardiff University, 5 The Parade, Cardiff CF24 3AA, Wales, UK
| | - Chun-Shing Lee
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China.
| | - J Q You
- Department of Physics, Zhejiang University, Hangzhou 310027, China
| | - Chi-Hang Lam
- Department of Applied Physics, Hong Kong Polytechnic University, Hong Kong, China.
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