Conference Presentation (Invited)

FZJ-2024-01687

http://join2-wiki.gsi.de/foswiki/pub/Main/Artwork/join2_logo100x88.png Microscopic Dynamics of Structural Glasses Investigated by Quasielastic Neutron Scattering

Zorn, R. (Corresponding author)FZJ*

2022

Abstract: In this presentation I will give a short introduction into quasielastic neutron scattering (QENS) and its application to glass-forming systems. QENS operates on time scales from picoseconds to a microsecond and at the same time has a spatial resolution in the Ångström range. Therefore, it is well suited for the study of molecular and polymeric glass-formers.The dynamics of glass-formers is still poorly understood, but certain universal features can be found which a theory has to explain. Foremost, there is the α relaxation, which governs what is usually called ‘glass transition’. Its temperature-dependence is highly non-Arrhenius and the shape of correlation functions non-exponential. In addition, faster relaxations may be present, among which the universal ‘fast β relaxation’ in the picosecond range is strongly related to the α relaxation in mode-coupling theory. As the fastest universal process, glasses show an excess of the vibrational density of states above the Debye model in the low frequency range, the so-called ‘boson peak’.All these phenomena can be observed by QENS with the additional information of a length scale. In addition, it is possible to study them in confined glass-formers in order to access their system-size-dependence. Selected QENS experiments will be presented and discussed.

Keyword(s): Basic research (1st) ; Soft Condensed Matter (2nd)

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Contributing Institute(s):

1. Neutronenstreuung (JCNS-1)
2. Neutronenstreuung und biologische Materie (IBI-8)

Research Program(s):

1. 6G4 - Jülich Centre for Neutron Research (JCNS) (FZJ) (POF4-6G4) (POF4-6G4)
2. 5241 - Molecular Information Processing in Cellular Systems (POF4-524) (POF4-524)
3. 5251 - Multilevel Brain Organization and Variability (POF4-525) (POF4-525)

Experiment(s):

1. J-NSE: Neutron spin-echo spectrometer (NL2ao)

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