Article Discovery of collective nonjumping motions leading to Johari–Goldstein process of stress relaxation in model ionic glass

Makina Saito ; Takeaki Araki ; Yohei Onodera SAMURAI ORCID (National Institute for Materials Science) ; Koji Ohara ; Makoto Seto ; Yoshitaka Yoda ; Yusuke Wakabayashi

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Makina Saito, Takeaki Araki, Yohei Onodera, Koji Ohara, Makoto Seto, Yoshitaka Yoda, Yusuke Wakabayashi. Discovery of collective nonjumping motions leading to Johari–Goldstein process of stress relaxation in model ionic glass. Acta Materialia. 2024, 284 (), 120536. https://doi.org/10.1016/j.actamat.2024.120536
SAMURAI

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(abstract)

The slow β, or Johari–Goldstein (JG) relaxation process, has been widely observed in glasses and is known to induce the stress relaxation associated with mechanical properties. So far, jumping motions of only a fraction of the particles were believed to contribute to the JG process in glass. However, there is no direct experimental evidence of the atomic-scale images due to the difficulties in microscopic observation. In this study, atomic motions in the quasi-spherical model ionic-glass-former Ca0.4K0.6(NO3)1.4 were microscopically observed with one-angstrom resolution, the highest resolution to date, using X-ray time-domain interferometry. The microscopic experiment directly indicated that most particles underwent angstrom-scale motions in the time scale of the JG relaxation. This result was further supported by molecular dynamics (MD) simulations. A combined study of experiments and MD simulations revealed that most particles contributed to the JG process through unexpected collective nonjumping motions with angstrom-scale displacement, activated by jumping motions of a fraction of particles. The discovery of nonjumping motions by our atomic-scale dynamic observations has considerably advanced our understanding of the puzzling mechanism of the JG process.

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Keyword: Ionic glass, Molecular dynamics simulation, Johari–Goldstein relaxation, Stress relaxation

Date published: 2024-11-04

Publisher: Elsevier BV

Journal:

  • Acta Materialia (ISSN: 13596454) vol. 284 120536

Funding:

  • Core Research for Evolutional Science and Technology JPMJCR2095
  • Japan Society for the Promotion of Science 21K03486
  • Japan Society for the Promotion of Science 24K00592
  • University of Tokyo
  • Toyo University 2016A1084
  • Toyo University 2020A1329
  • Toyo University 2019B2100
  • Toyo University 2016A1461
  • Toyo University 2020A0694
  • Japan Science and Technology Corporation
  • Iwatani Naoji Foundation
  • Japan Society for the Promotion of Science London

Manuscript type: Publisher's version (Version of record)

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First published URL: https://doi.org/10.1016/j.actamat.2024.120536

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Updated at: 2025-01-08 16:30:54 +0900

Published on MDR: 2025-01-08 16:30:54 +0900

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