Understanding the emergence of the boson peak in molecular glasses

Gonzalez Jimenez, M. et al. (2023) Understanding the emergence of the boson peak in molecular glasses. Nature Communications, 14, 215. (doi: 10.1038/s41467-023-35878-6) (PMID:36639380) (PMCID:PMC9839737)

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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.

Item Type:Articles
Additional Information:K.W. acknowledges funding by a grant from the European Research Council (ERC) under the European Union’s Horizon 2020 research and innovation programme (grant agreement No. 832703). K.W. and H.M.S. acknowledge funding by Leverhulme Trust Research Project Grant RPG-2018-350. We thank the Diamond Light Source for access to beamline I22 to carry out SWAXS experiments (proposal numbers SM27885 and SM28529). K.W. thanks the Engineering and Physical Sciences Research Council (EPSRC) for support through grants EP/J009733/1, EP/K034995/1, EP/N508792/1, and EP/N007417/1. G.M. acknowledges financial support from the Slovenian Research Agency (research core funding No. P1-0021). T.B. thanks the EPSRC for a studentship through the Centre for Doctoral Training in Mathematics for Real-World Systems II (EP/S022244/1). T.B. and G.C.S. also gratefully acknowledge the use of SULIS, which was funded by the EPSRC (EP/T022108/1), via the HPC Midlands+ Consortium.
Glasgow Author(s) Enlighten ID:Russell, Dr Ben and Senn, Dr Hans and Gonzalez Jimenez, Dr Mario and Tukachev, Mr Nikita and Wynne, Professor Klaas and Farrell, Mr Andrew
Authors: Gonzalez Jimenez, M., Barnard, T., Russell, B. A., Tukachev, N. V., Javornik, U., Hayes, L.-A., Farrell, A. J., Guinane, S., Senn, H. M., Smith, A. J., Wilding, M., Mali, G., Nakano, M., Miyazaki, Y., McMillan, P., Sosso, G. C., and Wynne, K.
College/School:College of Science and Engineering > School of Chemistry
Journal Name:Nature Communications
Publisher:Nature Research
ISSN (Online):2041-1723
Copyright Holders:Copyright © 2023 The Authors
First Published:First published in Nature Communications 14: 215
Publisher Policy:Reproduced under a Creative Commons License
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Data DOI:10.5525/gla.researchdata.1381

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Project CodeAward NoProject NamePrincipal InvestigatorFunder's NameFunder RefLead Dept
304469CONTROLKlaas WynneEuropean Commission (EC)832703Chemistry
303917Delocalised phonon-like modes in organic and bio-moleculesKlaas WynneLeverhulme Trust (LEVERHUL)RPG-2018-350Chemistry
166776The structure and dynamics of water confined in nanoscale pools: the dynamic crossoverKlaas WynneEngineering and Physical Sciences Research Council (EPSRC)EP/J009733/1Chemistry
171920EPSRC-ISF 2015: Computational Engineering for Advanced Materials: from micro to macroChristopher PearceEngineering and Physical Sciences Research Council (EPSRC)EP/N508792/1ENG - Infrastructure & Environment
172399Mapping and controlling nucleationKlaas WynneEngineering and Physical Sciences Research Council (EPSRC)EP/N007417/1Chemistry