The boson peak in structural and orientational glasses of simple alcohols: Specific heat at low temperatures

We review in this work specific-heat experiments, that we have conducted on different hydrogen-bonded glasses during last years. Specifically, we have measured the low-temperature specific heat Cp for a set of glassy alcohols: normal and fully-deuterated ethanol, 1- and 2- propanol, and glycerol. Et...

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Bibliographic Details
Published in:arXiv.org 2002-01
Main Authors: Ramos, Miguel A, Talon, Cesar, Vieira, Sebastian
Format: Article
Language:English
Subjects:
Alcohol
Alcohols
Crystal structure
Deuteration
Ethanol
Glass
Glycerol
Heat
Hydrogen bonding
Isomers
Polymorphism
Scaling laws
Solid phases
Specific heat
Temperature
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Summary:We review in this work specific-heat experiments, that we have conducted on different hydrogen-bonded glasses during last years. Specifically, we have measured the low-temperature specific heat Cp for a set of glassy alcohols: normal and fully-deuterated ethanol, 1- and 2- propanol, and glycerol. Ethanol exhibits a very interesting polymorphism presenting three different solid phases at low temperature: a fully-ordered (monoclinic) crystal, an orientationally-disordered (cubic) crystal or 'orientational glass', and the ordinary structural glass. By measuring and comparing the low-temperature specific heat of the three phases, in the 'boson peak' range 2-10 K as well as in the tunneling-states range below 1K, we are able to provide a quantitative confirmation that ''glassy behavior'' is not an exclusive property of amorphous solids. On the other hand, propanol is the simplest monoalcohol with two different stereoisomers (1- and 2-propanol), what allows us to study directly the influence of the spatial rearrangement of atoms on the universal properties of glasses. We have measured the specific heat of both isomers, finding a noteworthy quantitative difference between them. Finally, low-temperature specific-heat data of glassy glycerol have also been obtained. Here we propose a simple method based upon the soft-potential model to analyze low-temperature specific-heat measurements, and we use this method for a quantitative comparison of all these data of glassy alcohols and as a stringent test of several universal correlations and scaling laws suggested in the literature. In particular, we find that the interstitialcy model for the boson peak [A. V. Granato, Phys. Rev. Lett. 68 (1992) 974] gives a very good account of the temperature at which the maximum in Cp/T^3 occurs.
ISSN:2331-8422
DOI:10.48550/arxiv.0201560