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Understanding the emergence of the boson peak in molecular glasses

DOI: 10.1038/s41467-023-35878-6 DOI Help

Authors: Mario Gonzalez-Jimenez (University of Glasgow) , Trent Barnard (University of Warwick) , Ben A. Russell (University of Glasgow) , Nikita V. Tukachev (University of Glasgow) , Uroš Javornik (Slovenian NMR Centre, National Institute of Chemistry) , Laure-Anne Hayes (University of Glasgow) , Andrew J. Farrell (University of Glasgow) , Sarah Guinane (University of Glasgow) , Hans M. Senn (University of Glasgow) , Andrew J. Smith (Diamond Light Source) , Martin Wilding (University of Cardiff) , Gregor Mali (National Institute of Chemistry (Slovenia)) , Motohiro Nakano (Osaka University) , Yuji Miyazaki (Osaka University) , Paul Mcmillan (University College London) , Gabriele C. Sosso (University of Warwick) , Klaas Wynne (University of Glasgow)
Co-authored by industrial partner: No

Type: Journal Paper
Journal: Nature Communications , VOL 14

State: Published (Approved)
Published: January 2023
Diamond Proposal Number(s): 28529

Open Access Open Access

Abstract: A common feature of glasses is the “boson peak”, observed as an excess in the heat capacity over the crystal or as an additional peak in the terahertz vibrational spectrum. The microscopic origins of this peak are not well understood; the emergence of locally ordered structures has been put forward as a possible candidate. Here, we show that depolarised Raman scattering in liquids consisting of highly symmetric molecules can be used to isolate the boson peak, allowing its detailed observation from the liquid into the glass. The boson peak in the vibrational spectrum matches the excess heat capacity. As the boson peak intensifies on cooling, wide-angle x-ray scattering shows the simultaneous appearance of a pre-peak due to molecular clusters consisting of circa 20 molecules. Atomistic molecular dynamics simulations indicate that these are caused by over-coordinated molecules. These findings represent an essential step toward our understanding of the physics of vitrification.

Subject Areas: Materials, Chemistry

Instruments: I22-Small angle scattering & Diffraction

Added On: 16/01/2023 11:18


Discipline Tags:

Physical Chemistry Chemistry Materials Science

Technical Tags:

Scattering Small Angle X-ray Scattering (SAXS) Wide Angle X-ray Scattering (WAXS)