Breakdown of the Stokes-Einstein relation above the melting temperature in a liquid phase-change material.
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Univ Arizona, Dept Mat Sci & EngnIssue Date
2018-11-01
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AMER ASSOC ADVANCEMENT SCIENCECitation
Wei, S., Evenson, Z., Stolpe, M., Lucas, P., & Angell, C. A. (2018). Breakdown of the Stokes-Einstein relation above the melting temperature in a liquid phase-change material. Science advances, 4(11), eaat8632.Journal
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Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).Collection Information
This item from the UA Faculty Publications collection is made available by the University of Arizona with support from the University of Arizona Libraries. If you have questions, please contact us at repository@u.library.arizona.edu.Abstract
The dynamic properties of liquid phase-change materials (PCMs), such as viscosity η and the atomic self-diffusion coefficient D, play an essential role in the ultrafast phase switching behavior of novel nonvolatile phase-change memory applications. To connect η to D, the Stokes-Einstein relation (SER) is commonly assumed to be valid at high temperatures near or above the melting temperature Tm and is often used for assessing liquid fragility (or crystal growth velocity) of technologically important PCMs. However, using quasi-elastic neutron scattering, we provide experimental evidence for a breakdown of the SER even at temperatures above Tm in the high-atomic mobility state of a PCM, Ge1Sb2Te4. This implies that although viscosity may have strongly increased during cooling, diffusivity can remain high owing to early decoupling, being a favorable feature for the fast phase switching behavior of the high-fluidity PCM. We discuss the origin of the observation and propose the possible connection to a metal-semiconductor and fragile-strong transition hidden below Tm.Note
Open access journalISSN
2375-2548PubMed ID
30515453Version
Final published versionSponsors
FRM II; Feodor Lynen Postdoctoral Research Fellowship of the Alexander von Humboldt Foundation; Place-to-be RWTH Start-Up fund; DFG [SFB917]; NSF-EFRI award [1640860]; National Science Foundation Research [CHE-1213265]Additional Links
https://advances.sciencemag.org/content/4/11/eaat8632ae974a485f413a2113503eed53cd6c53
10.1126/sciadv.aat8632
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Except where otherwise noted, this item's license is described as Copyright © 2018 The Authors, some rights reserved; exclusive licensee American Association for the Advancement of Science. No claim to original U.S. Government Works. Distributed under a Creative Commons Attribution NonCommercial License 4.0 (CC BY-NC).
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