Our research: ENTROPY MATTERS!
The scientific team of Prof. Šob from our Department of Chemistry and Prof. Lejček from the Academy of Sciences of the Czech Republic has made a fundamental contribution to the research of the accumulation of impurities at the interface between crystals. This phenomenon, for example, in the 1960s caused a series of accidents at nuclear power plants in Great Britain. The study published in the prestigious journal Progress in Materials Science opens up new possibilities for the development of more durable alloys or new technological processes for their production.
A series of disasters occurred at nuclear power stations through the United Kingdom in the 1960s. During these disasters, turbine rotors made of a steel fractured intergranularly. The primary reason for this destruction was accumulation of phosphorus at the interfaces among the crystals, so called ‘grain boundaries’. This grain boundary segregation then caused reduction of material cohesion in these regions and thus to cracking of the turbines which brought catastrophic consequences
Since that time, a huge amount of experimental data on grain boundary segregation have been gathered, followed by a boom of theoretical approaches to this phenomenon, mainly using the ab-initio calculations. In the very recent time, machine learning and artificial intelligence contribute substantially to these calculations.
However, there is a very important problem: Theoretical results and experimental data are not always immediately comparable. In the recent paper published in the prestigious research journal Progress in Materials Science prof. Pavel Lejček of the Department of Functional Materials, Institute of Physics of the Czech Academy of Sciences, and prof. Mojmír Šob of Masaryk University in Brno compared a series of the results of both approaches obtained by themselves as well as published in literature, and showed that the agreement between experiment and theory can be obtained exclusively in the case of considering the value of the thermodynamic function of entropy in theoretical calculations. Let us mention that its contribution is frequently neglected in theoretical calculations.
An important item in the mentioned paper is the fact, that it predicts existence of a new phenomenon – the entropy-driven grain boundary segregation – which has been unknown till now. At present, prof. Lejček carries out the first experiments related to this phenomenon. The preliminary (unpublished) results suggest the existence of this phenomenon!
The research of properties and effects of entropy thus opens new ways not only in the field of grain boundary segregation but also brings further possibilities in chemistry and solid state physics at all. This is important, for example, for the development of progressive alloys and new technologies.
The above-mentioned paper is one of few fully domestic contributions in highly impacted journals such as Progress in Materials Science. There are two Czech authors having Czech affiliations, and the complete research presented in that paper has been performed in Czechia. The authors did also not need any ‘door opener’ of an eminent foreign institution as it is frequently applied in the case of such papers. In opposite, the door to writing this paper were opened on basis of their own scientific prestige. This success is therefore all the more valuable as it represents the results of the Czech science only. It is worth noting that the mentioned paper is the second one of these authors published in the Progress in Materials Science, which documents indisputable qualities as well as the respect to the work of these Czech scientists.
Lejček, M. Šob, Entropy: A Controversy between Experiment and Calculations in Grain Boundary Segregation, Progress in Materials Science 151 (2025) 101431 (38 pp.).