News

New publication:
Energy Storage Applications using Machine Learning: Hydrogen diffusion in Magnesium

Understanding the dynamics of hydrogen atoms in materials is crucial for the development of efficient hydrogen storage systems, a key component of the green energy transition. In a recent study published in npj Computational Materials, A. Angeletti and C. Franchini from the University of Vienna, in collaboration with L. Leoni and L. Pasquini from the University of Bologna and D. Massa from the NOMATEN Centre of Excellence in Poland, introduced an innovative machine learning strategy to accelerate and accurately model the diffusion of hydrogen in magnesium.

The research employed a hybrid approach that integrates Density Functional Theory calculations with Machine Learning Force Fields using the Vienna ab initio simulation package. By implementing an active learning procedure, the model was trained on-the-fly through the collection of a diverse dataset of sparsified atomic configurations generated during the simulation. This dataset was then used to fine-tune advanced neural network-based interatomic potentials, achieving an exceptional balance between computational efficiency and predictive accuracy, particularly with the use of the MACE framework.

The machine learning model demonstrated excellent agreement with experimental observations, accurately predicting hydrogen diffusion coefficients over a range of temperatures and correctly identifying the activation energy barrier. A systematic investigation of varying hydrogen concentrations also provided novel insights into hydrogen pair formation and clarified key aspects of hydrogen content in earlier experimental studies.

These results validate the proposed methodological framework and offer new perspectives on the kinetic behavior of hydrogen in magnesium, paving the way for the development of next-generation hydrogen storage technologies.

Beyond its immediate findings, the study highlights the transformative potential of machine learning in materials science, especially for investigating complex atomic dynamics in defective or otherwise challenging systems that have remained elusive due to computational or experimental limitations.

This work was developed within the “Doctoral College Advanced Functional Materials – Hierarchical Design of Hybrid Systems DOC 85 doc.funds” funded by the Austrian Science Fund (FWF).

Andrea Angeletti, Luca Leoni, Dario Massa, Luca Pasquini, Stefanos Papanikolaou & Cesare Franchini, npj Computational Materials volume 11, Article number: 85 (2025)New publication: Unconventional
Charge Transport in Energy Materials
https://www.nature.com/articles/s41524-025-01555-z

New publication:
Unconventional Charge Transport in
Energy Materials

The discovery and optimization of new forms of sustainable energy represent a crucial effort to meet rising global energy demands and address associated environmental risks. Fundamental research plays a key role in uncovering the mechanisms that enable efficient and clean energy conversion within suitable materials. Such energy materials are essential for energy transformation and storage and are invaluable assets in developing next-generation energy solutions.

In a recent collaborative study, published in Science Advances, the authors present unconventional polaronic charge transport in hematite—one of the most promising semiconductor materials for solar energy conversion.

Polarons are charged quasiparticles, typically generated through chemical doping or light exposure, that often inhibit charge transport and efficient energy conversion. This inhibition occurs because polarons tend to become immobilized within lattice traps in the material, preventing the generation of a charged current. However, using an advanced technique that probes local electric fields near the hematite surface, experimental work at Charles University in Prague (led by M. Setvin) and the Technical University of Vienna (led by G. Parkinson and U. Diebold), supported by theoretical interpretations at the University of Vienna (C. Franchini), reveals unusual polaron transport behavior in hematite crystals. Contrary to expectations, doping hematite results in enhanced conductivity, suggesting that dopants do not serve as trapping centers for electrons. Computer aided  simulations performed by M. Reticcioli and F. Ellinger at the University of Vienna reveal peculiar mechanisms at play that shed light on the experimental measurements. While polaron diffusion is typically dominated by hopping of the localized charge carriers towards nearest neighbor sites, in hematite transport seems to occur preferentially via a transient delocalized charge state. The preference for this mechanism, known as random flight, can be understood by considering the particularly shallow polaronic eigenstates, lying only a few meV below the conduction band of hematite. The analysis of the density of states, clearly show a tendency of the shallow polaronic states towards the transient delocalized states.

These findings identify the random flight as an important type of electron-polaron diffusion in hematite, and the methodology introduced here may open a new way to understanding fundamental charge transport mechanism.

This work was developed within the special research program TACO (Taming Complexity in Materials Modeling), granted by the Austrian Science Fund FWF.

Original article:

Jesus Redondo et al. Real-space investigation of polarons in hematite Fe₂O₃.Sci. Adv.10,eadp7833(2024). DOI:10.1126/sciadv.adp7833

New publication:
Interplay of superexchange and vibronic effects in the hidden order of Ba2⁢MgReO6 from first principles

In heavy transition metal oxides, electronic correlation and strong spin-orbit coupling can give rise to “hidden order”, with multipolar order parameters. Here, the authors investigate the origin of the unusual quadrupolar and magnetic phases in the double perovskite Ba2MgReO6. They derive its low-energy Hamiltonian from first principles and show that its antiferroic order of x2-y2 quadrupoles and a low-temperature canted antiferromagnetic phase emerge from the interplay between electron-lattice coupling and multipolar superexchange interactions.
https://link.aps.org/doi/10.1103/PhysRevB.110.L201101

Marco Corrias winner of the poster session at Zaragoza conference
_{IUVSTA-ZCAM Metal-Oxide Ultrathin Films and Nanostructures}

New publication and cover picture:

Temperature-Dependent Anharmonic Phonons in Quantum Paraelectric KTaO₃ by First Principles and Machine-Learned Force Fields, Luigi Ranalli et al Adv Quantum Technol. 2023, 6, 2200131

New publication

Automated real-space lattice extraction for atomic force microscopy images,, Marco Corrias et al 2023 Mach. Learn.: Sci. Technol. 4 015015