Atomic displacements in High-Entropy Alloys examined
The supercell is randomly filled with the five elements on the fcc-lattice positions; In the starting configuration, all layers are precisely on top of each other. The displacements of all elements in the final configuration have been revealed by a simultaneous fit of the independent experimental spectra with a use of Reverse Monte Carlo simulations. © A.Kuzmin / University of Latvia and A. Smekhova / HZB
High-entropy alloys of 3d metals have intriguing properties that are interesting for applications in the energy sector. An international team at BESSY II has now investigated the local order on an atomic scale in a so-called high-entropy Cantor alloy of chromium, manganese, iron, cobalt and nickel. The results from combined spectroscopic studies and statistical simulations expand the understanding of this group of materials.
High-entropy alloys are under discussion for very different applications: Some materials from this group are suitable for hydrogen storage, others for noble metal-free electrocatalysis, radiation shielding or as supercapacitors.
The microscopic structure of high-entropy alloys is very diverse and changeable; in particular, the local ordering and the presence of different secondary phases affect significantly the macroscopic properties such as hardness, corrosion resistance and also magnetism. The so-called Cantor alloy, which consists of the elements chromium, manganese, iron, cobalt and nickel mixed in an equimolar proportion, can be considered as a suitable model system for the whole class of these materials.
Local structure studied at BESSY II
Scientists from the Federal Institute for Materials Research (BAM, Berlin), the University of Latvia in Riga, Latvia, the Ruhr University in Bochum and the HZB have now studied the local structure of this model system in detail. Using X-ray absorption spectroscopy (EXAFS) at BESSY II, they were able to precisely track each individual element and their displacements from the ideal lattice positions for this system in the most unbiased manner with the help of statistical calculations and the reverse Monte Carlo method.
Chromium shows larger displacements
In this way, they uncovered peculiarities in the local environment of each element: Despite all five elements of the alloy are distributed at the nodes of the face-centred cubic lattice and have very close statistically averaged interatomic distances (2.54 - 2.55 Å) with their nearest neighbours, larger structural relaxations were found solely for chromium atoms. Besides, no evidence of secondary phases was detected at the atomic scale. The macroscopic magnetic properties studied with conventional magnetometry at HZB CoreLab were correlated with the revealed structural relaxations of Chromium.
"The results describe the arrangement of individual atoms at the atomic scale and how the complex magnetic order that we revealed may occur," explains HZB physicist Dr. Alevtina Smekhova, who supervised the experiments at HZB.
- AI agents deliver results – but do they reason scientifically?A research team co-led by Kevin Maik Jablonka from the Helmholtz Institute for Polymers in Energy Applications Jena (HIPOLE Jena) and N. M. Anoop Krishnan from the Indian Institute of Technology Delhi has developed Corral, a new benchmark for AI agents in science. The preprint “AI scientists produce results without reasoning scientifically” has been published on arXiv (https://doi.org/10.48550/arXiv.2604.18805). The analysis shows that current systems can execute scientific workflows and deliver results; however, they often do not follow the basic principles of scientific testing and reasoning.
- Magnetic field during catalyst synthesis triples ammonia yieldApplying an external magnetic field during the synthesis of CoFe₂O₄ electrocatalysts triples the ammonia yield during electrocatalytic conversion. The magnetic field alters the surface states of the spinel oxide thin films, making catalytically active sites more accessible. In the journal 'Advanced Functional Materials', a team led by Marcel Risch at HZB and Sanjay Mathur at University of Cologne demonstrates a scalable strategy for developing next-generation electrocatalysts for efficient and sustainable chemical production.
- Materials chemistry shapes the future of catalysisThe synthesis of materials can serve as a tool for developing smart, adaptive electrocatalysts. This rapidly evolving field of research involves in-situ analytics, data-driven discoveries and autonomous robotics. These new approaches could accelerate the discovery of long-lasting and efficient catalysts for future energy conversion and the decarbonisation of the chemical industry. A recent article by Dr Prashanth Menezes and his team in the renowned journal Angewandte Chemie provides an overview of this research.