The idea to organize an international workshop dedicated to glass and entropy was born during the session “Thermodynamics, Rheology, and Glass Transition” held at the XXIst International Congress on Glass, Strasbourg 2007. There, controversial viewpoints and opinions on the entropy of the glassy state surfaced in a highly emotional scientific debate. Since then, none of the controversial issues could be resolved in a satisfactory way, and more and more researchers from different fields (glass and polymer sciences, statistical mechanics, computational simulation) agreed that there is a need to meet, on a regular and long-term basis, within the frame of a series of workshops specifically dedicated to glass and its entropy. As a consequence, representatives from Corning’s European Technology Center, Avon, France spontaneously opted to sponsor the first international workshop on glass and entropy, and Profs. Lothar Wondraczek and Reinhard Conradt, both from Germany, agreed to organize and chair it. This first workshop was endorsed by the newly founded Technical Committee 08 of the International Comission on Glass “Relaxation Phenomena in Glasses” and supported locally by the Slovak Glass Society. The basis of today’s controversy is Nernst’s theorem which he presented in 1905, one day before Christmas, at a meeting of the Königliche Gesellschaft der Wissenschaften (Göttingen, Germany, ) and a year later, on December 20, 1906, at a meeting of the Königlich Preussische Akademie der Wissenschaften (Berlin, Germany, ). In 1921 the Nobel Prize in Chemistry 1920 was bestowed upon him “in recognition of his work in thermochemistry.
The eventual formulation of the third law, however, goes back to Planck , who in 1910 interpreted Nernst’s theorem: “Upon infinitely decreasing temperature, the entropy of any pure condensed substance approaches a limit which is independent of pressure, aggregate state, and chemical modification” (translated from German; the term “chemical modification” is used as a synonym of “chemical composition”). The statement is most conveniently accounted for by defining this universal limit as zero.
Since, scientists have been wrestling with the possibility of finite entropy – more precisely: of a finite positive entropy difference to the universal limit – at absolute zero temperature for certain types of materials. The debate focused on the concept of internal equilibrium and – based on pioneering experimental work by Simon on glassy glycerol and silica [5, 6], Giauque and coworkers (e.g. ), Clusius and coworkers (e.g. ) and others – led to a reformulation of the 3rd law by Simon  in 1927. Approximately 20 years later, Kauzmann published his paper on the nature of the glassy state and the behavior of liquids at low temperatures , from which the scientific world deduced the “Kauzmann Paradox”, wherein the extrapolated entropy of an undercooled liquid apparently approaches a value below the one of the isochemical crystalline state. The role of entropy in undercooled and frozen-in liquids has since been the subject of many debates, with researchers arguing from the viewpoints of thermodynamics, statistical mechanics, and kinetics.
The essence of the present controversy may be highlighted by the following questions: Does a glass possess a finite residual entropy at absolute zero? And how does the entropy of a glass forming system change, abruptly, at the glass transition? Based on the computation of energy landscapes and the concept of broken ergodicity, the glassy state is described in terms of a liquid confined to a single metabasin of the configurational phase space with an entropy loss – but no latent heat – accompanying the glass transition. In this frame of description, a glass does not appear to have any residual entropy at absolute zero. The opposite answer is derived by means of classical thermodynamics and the thermodynamics of irreversible processes. This controversy clearly shows that the statement made in the year 1995 by the 1997 Nobel laureate (physics) P.W. Anderson  still holds today:
“The deepest and most interesting unsolved problem in solid state theory is probably the theory of the nature of glass and the glass transition.”
The 1st International Workshop on Glass and Entropy was held at Trencin, Slovak Republic, from June 25 to 27, 2008. It attracted contributions from 38 outstanding scientists, most of which were recently, in April 2009, published in a special issue of the Journal of Non-Crystalline Solids . For the time being, the intention of this publication is to provide an overview of present viewpoints and the contrast between these. Together with the publication of this book, the second International Workshop on Glass and Entropy was held at Aberystwyth, United Kingdom, from April 22 to April 24, 2009, organized by G. Neville Greaves, Martin Wilding and Lothar Wondraczek and endorsed by ICG and its TC08. If was sponsored by the EU-FP7-initiative EFONGA (European Forum on New Glass Applications, and attracted 28 invited papers from scientists from all over the world. Where the fist meeting concluded with the note that further actions will need to specify a common nomenclature (e.g. characteristic temperatures, definition of entropy, etc.) and to design experiments that will be accepted as decisive by the broad community, here, it was agreed on jointly pursuing particularly three types of experiments: dissolution calorimetry (having identified model glasses); measurements of the electromotoric force in glass-crystal galvanic cells and vapor-pressure measurments. As a novel area of specific interest, “glasses under extreme conditions” was identified, with special emphasis on the role of high pressures on structure and dynamics of glass-forming systems.
Photograph: Participants of GE1 in 2007
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- W. Nernst: Über die Beziehung zwischen Wärmeentwicklung und maximaler Arbeit bei kondensierten Systemen. Ber. Kgl. Pr. Akad. Wiss. 52 (1906) 933 -940.
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- M. Planck: Vorlesungen über Thermodynamik. Veit, Leipzig, 3rd ed. (1911).
- F. Simon, F. Lange: Zur Frage der Entropie amorpher Substanzen. Z. Physik 38 (1926) 227-236.
- F. Simon: Über den Zustand der unterkühlten Flüssigkeiten und Gläser. Z. anorg. allg. Chem. 203 (1931) 219-227.
- W.F. Giauque, J.O. Clayton: The heat capacity and entropy of nitrogen. J. Am. Chem. Soc. 55 (1933) 4875-4889.
- K. Clusius, E. Bartholomé: The heat of rotation of the molecule HD and D-2 and the nuclear spin of D atoms. Z. Elektrochem. Angew. Phys. Chem. 40 (1934) 524-529.
- F. Simon: Zum Prinzip von der Unerreichbarkeit des absoluten Nullpunktes. Z. Phys. 41 (1927) 806-809.
- W. Kauzmann: The nature of the glassy state and the behavior of liquids at low temperatures. Chem. Rev. 43 (1948) 219-256.
- P. W. Anderson: Through the glass lightly. Science 267 (1995) 1616.
- L. Wondraczek, R. Conradt: Glass and Entropy. J. Non-Cryst. Solids 355 (2009) vii-viii.