Center for Molecular Modeling - S. Cottenier

Crystallographic control of hydrogen ingress in bcc-iron: Insights from ab initio simulations

lmeier — Tue, 06 Jan 2026 15:07:27 +0000

L. Meier, A.I. Bhatti, L. A. I. Kestens, S. Cottenier

International Journal of Hydrogen Energy

201, 152840

2026

Abstract

Hydrogen uptake into body-centered cubic (bcc) iron as a root cause for subsequent hydrogen embrittlement, is initiated at the surface. In this paper, we quantify how readily H diffuses from the surface into the bulk. We consider a set of 10 different Fe surfaces and treat H-permeation as a two-step process. First, density-functional calculations determine the adsorption energy of an isolated H atom at every crystallographically distinct surface site. Second, for each adsorption site we map the minimum-energy pathway between the surface and the lattice. Across all orientations studied, a clear trend emerges: sites that bind hydrogen most weakly are the starting point of the lowest-barrier diffusion channels into the metal interior. Thus, the least-favorable adsorption pockets act as “gateways” for subsurface penetration. This insight provides a practical design rule: minimizing exposure of such high-energy adsorption motifs should make bcc-iron components less susceptible to hydrogen uptake and the associated embrittlement.

Gold Open Access

DOI

https://doi.org/10.1016/j.ijhydene.2025.152840

Surface-to-bulk hydrogen transport in BCC iron: a computational review of adsorption and diffusion mechanisms

lmeier — Thu, 13 Mar 2025 11:00:35 +0000

L. Meier, A.I. Bhatti, S. Cottenier

Critical Reviews in Solid State and Materials Sciences

2024

Abstract

Hydrogen embrittlement poses a significant challenge in various engineering applications. In this context, the iron/hydrogen system serves as a crucial prototype for examining the interaction between hydrogen and steel. Despite the critical importance of this topic, there is a notable lack of knowledge regarding the influence of surface characteristics on the penetration of hydrogen into materials. To address this gap, we have conducted an extensive review of the existing literature, particularly focusing on how different surface orientations of body-centered cubic (bcc) iron affect the adsorption, diffusion, and subsequent penetration of hydrogen into an iron crystal. The review primarily focuses on computational methods, incorporating experimental data for comparative analysis wherever feasible. This comprehensive synthesis of scattered information leads to several key conclusions. First, there is a systematic relationship between surface geometry and adsorption energy that has previously been overlooked. Second, bulk diffusion characteristics are recovered just a few atomic layers beneath the surface, emphasizing the importance of the initial surface layers in determining initial penetration. Third, penetrating through the surface layers is generally more challenging than further diffusion through bulk iron, with the specifics heavily dependent on the surface orientation. Studies on high-index surfaces are limited. We identify this as an area needing further research, and this review provides a solid foundation for such studies.

This work has been performed as part of the NOHENTRY project, funded by the Energy Transition Fund (Energietransitiefonds) of the Directorate-General Energy (Algemene Directie Energie) of the Federal Public Service for the Economy (FOD Economie) of Belgium. S.C. acknowledges financial support from OCAS NV by an OCAS-endowed chair at Ghent University. The computational resources and services used in this work were provided by the VSC (Flemish Supercomputer Center), funded by the Research Foundation - Flanders (FWO) and the Flemish Government - department EWI.

Gold Open Access

DOI

https://doi.org/10.1080/10408436.2024.2416435

Hyperfine properties at Zr sites of Zr-based compounds. A DFT FP-LAPW and GIPAW study

leen — Mon, 29 Jan 2024 12:13:35 +0000

A. V. Gil Rebaza, A. M. Mudarra Navarro, M. A. Taylor, A. Errico, S. Cottenier

Physica B: Condensed Matter

Volume 657, article number 414757

2023

Abstract

We report Density Functional Theory calculations for the atomic positions and the electric-field gradients (EFG) at Zr sites in a series of Zr compounds, with the FP-LAPW and the GIPAW methods. These data are used to obtain a value for the nuclear quadrupole moments of 90Zr and 91Zr, of which the precision and reliability with respect to tabulated values is discussed. An error bar on our suggested values is provided. Good agreement is obtained between the (faster) GIPAW method and (slower yet established) FP-LAPW method, especially when identical atomic positions are imposed. This increases the confidence in GIPAW calculations for electric-field gradient and nuclear quadrupole moment determination.

DOI

http://dx.doi.org/10.1016/j.physb.2023.414757

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On the feasibility of online terbium extraction at ISOL@MYRRHA

leen — Mon, 29 Jan 2024 12:05:15 +0000

B. Leenders, A. Aerts, T. E. Cocolios, S. Cottenier, D. Houngbo, L. Popescu

Nuclear Instruments and Methods in Physics Research Section B: Beam Interactions with Materials and Atoms

Volume 541, Page 249-252

2023

Abstract

Terbium is an element that has four isotopes with interesting properties for medical applications, 149, 152, 155, 161Tb. These radioisotopes are however far from being sufficiently accessible, thereby hindering the pursuit of research on radiolabelling as well as clinical or preclinical investigations. Their lack of market availability is explained by difficulties in producing these radioisotopes with high purity and specific activity. While 161Tb can be produced using neutron capture in nuclear reactors, for 149, 152, 155Tb, a production route involving the ISOL technique is under study within the Tb-IRMA-V project. The ongoing R&D towards the production and extraction of these isotopes from an ISOL target at the ISOL@MYRRHA facility is reported in this contribution.

DOI

http://dx.doi.org/10.1016/j.nimb.2023.05.034

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How to verify the precision of density-functional-theory implementations via reproducible and universal workflows

leen — Thu, 18 Jan 2024 07:21:36 +0000

E. Bosoni, L. Beal, M. Bercx, P. Blaha, S. Blügel, J. Bröder, M. Callsen, S. Cottenier, A. Degomme, V. Dikan, K. Eimre, E. Flage-Larsen, M. Fornari, A. Garcia, L. Genovese, M. Giantomassi, S. P. Huber, H. Janssen, G. Kastlunger, M. Krack, G. Kresse, T. D. Kühne, K. Lejaeghere, G. K. H. Madsen, M. Marsman, N. Marzari, G. Michalicek, H. Mirhosseini, T. M. A. Müller, G. Petretto, C. J. Pickard, S. Poncé, G.-M. Rignanese, O. Rubel, T. Ruh, M. Sluydts, D. E. P. Vanpoucke, S. Vijay, M. Wolloch, D. Wortmann, A. V. Yakutovich, J. Yu, A. Zadoks, B. Zhu, G. Pizzi

Nature Reviews Physics

6, 1, 45-58

2024

Abstract

Density-functional theory methods and codes adopting periodic boundary conditions are extensively used in condensed matter physics and materials science research. In 2016, their precision (how well properties computed with different codes agree among each other) was systematically assessed on elemental crystals: a first crucial step to evaluate the reliability of such computations. In this Expert Recommendation, we discuss recommendations for verification studies aiming at further testing precision and transferability of density-functional-theory computational approaches and codes. We illustrate such recommendations using a greatly expanded protocol covering the whole periodic table from Z = 1 to 96 and characterizing 10 prototypical cubic compounds for each element: four unaries and six oxides, spanning a wide range of coordination numbers and oxidation states. The primary outcome is a reference dataset of 960 equations of state cross-checked between two all-electron codes, then used to verify and improve nine pseudopotential-based approaches. Finally, we discuss the extent to which the current results for total energies can be reused for different goals.

Verification efforts of density-functional theory (DFT) calculations are of crucial importance to evaluate the reliability of simulation results. In this Expert Recommendation, we suggest metrics for DFT verification, illustrating them with an all-electron reference dataset of 960 equations of state covering the whole periodic table (hydrogen to curium) and discuss the importance of improving pseudopotential codes.

Verification efforts are critical to assess the reliability of density-functional theory (DFT) simulations and provide results with properly quantified uncertainties.Developing standard computation protocols to perform verification studies and publishing curated and FAIR reference datasets can greatly aid their use to improve codes and computational approaches.The use of fully automated workflows with common interfaces between codes can guarantee uniformity, transferability and reproducibility of results.A careful description of the numerical and methodological details needed to compare with the reference datasets is essential; we discuss and illustrate this point with a dataset of 960 all-electron equations of state.Reference datasets should always include an explanation of the target property for which they were generated, and a discussion of their limits of applicability.Further extensions of DFT verification efforts are needed to cover more functionals, more computational approaches and the treatment of magnetic and relativistic (spin-orbit) effects. They should also aim at concurrently delivering optimized protocols that not only target ultimate precision, but also optimize the computational cost for a target accuracy.

DOI

http://dx.doi.org/10.1038/s42254-023-00655-3

Twofold rattling mode-induced ultralow thermal conductivity in vacancy-ordered double perovskite Cs2SnI6

leen — Thu, 08 Dec 2022 10:47:22 +0000

U.-G. Jong, Y.-S.Kim, C.-H. Ri, Y.-H. Kye, C.-J. Pak, S. Cottenier, C.-J. Yu

Chemical Communications

Volume 58, Issue 26, Page 4223-4226

2022

Abstract

We report a first-principles study of lattice vibrations and thermal transport in Cs2SnI6, the vacancy-ordered double perovskite. Twofold rattlers of Cs atoms and SnI6 clusters in Cs2SnI6, being different from CsSnI3 with only Cs atom rattlers, largely scatter heat-carrying acoustic phonons strongly coupled with low-lying optical phonons and lower phonon group velocity. Using renormalized phonon dispersions at finite temperatures, we reveal that anharmonicity and twofold rattling modes induce an ultralow thermal conductivity at room temperature.

DOI

http://dx.doi.org/10.1039/d2cc00258b

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Towards accurate processing-structure-property links using deep learning

jelle — Fri, 14 Jan 2022 20:20:44 +0000

M. Larmuseau, K. Theuwissen, K. Lejaeghere, L. Duprez, T. Dhaene, S. Cottenier

Scripta Materialia

211, 114478

2022

DOI

https://doi.org/10.1016/j.scriptamat.2021.114478

A new ab initio equation of state of hcp-Fe and its implication on the interior structure and mass-radius relations of rocky super-Earths

leen — Thu, 09 Dec 2021 13:59:56 +0000

K. Hakim, A. Rivoldini, T. Van Hoolst, S. Cottenier, J. Jaeken, T. Chust, G. Steinle-Neuman, G. Steinle-Neumann

Icarus

Volume 313, pages 61-78

2018

Abstract

More than a third of all exoplanets can be classified as super-Earths based on radius (1-2 R-circle plus)) and mass (

DOI

http://dx.doi.org/10.1016/j.icarus.2018.05.005

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Alternative approach to populate and study the Th-229 nuclear clock isomer

leen — Thu, 09 Dec 2021 13:54:56 +0000

M. Verlinde, S. Kraemer, J. Moens, K. Chrysalidis, J.G. Correia, S. Cottenier, H. De Witte, D.V. Fedorov, V.N. Fedosseev, R. Ferrer, L.M. Fraile, S. Geldhof, C.A. Granados, M. Laatiaoui, T.A.L. Lima, P.-C. Lin, V. Manea, B.A. Marsh, I. Moore, L.M.C. Pereira, S. Raeder, P. Van den Bergh, P. Van Druppen, A. Vantomme, E. Verstraelen, U. Wahl, S.G. Wilkins

Physical Review C

100, 2

2019

Abstract

A new approach to observe the radiative decay of the Th-229 nuclear isomer, and to determine its energy and radiative lifetime, is presented. Situated at a uniquely low excitation energy, this nuclear state might be a key ingredient for the development of a nuclear clock or a nuclear laser and, the search for time variations of fundamental constants like the fine structure constant. The isomer's gamma decay towards the ground state will be studied with a high-resolution vacuum ultraviolet (VUV) spectrometer after its production by the beta decay of Ac-229. The novel production method presents a number of advantages asserting its competitive nature with respect to the commonly used U-233 alpha-decay recoil source. In this paper, a feasibility analysis of this new concept, and an experimental investigation of its key ingredients, using a pure Ac-229 ion beam produced at the ISOLDE radioactive beam facility, is reported.

DOI

http://dx.doi.org/10.1103/PhysRevC.100.024315

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Structural and electrochemical trends in mixed manganese oxides Na-x(M0.44Mn0.56)O-2 (M = Mn, Fe, Co, Ni) for sodium-ion battery cathode

leen — Thu, 09 Dec 2021 09:45:02 +0000

C.-J. Yu, Y.-C. Pak, C.-H. Kim, J.-S. Kim, K.-C. Ri, K.-H. Ri, S.H. Choe, S. Cottenier

Journal of Power Sources

511, article number: 230395

2021

Abstract

Developing cost-effective and high performance sodium-ion batteries (SIBs) relies mostly on advanced cathode materials with high electrode voltage, high capacity and fast sodium-ion diffusion. Here, we propose mixed sodium manganese oxides Nax(M0.44Mn0.56)O-2 (M = Mn, Fe, Co, Ni) as improved potential cathode materials for SIBs based on first-principles calculations. Our calculations reveal that these materials have relatively low volume expansion rates below 5%, and are thermodynamically stable. We find that the binding strength between the host and inserted Na atom gradually decreases as increasing the Na content x from 0.11 to 0.67 for each mixed compound, whereas it increases as going Mn -> Fe -> Co -> Ni at each value of Na content. Identifying the intermediate phases during Na insertion/extraction, we find a slight increase of electrode voltage with remarkably higher specific capacities by mixing due to extending the lower limit of Na content. We also investigate the sodium-ion diffusion by identifying plausible pathways , determining the activation barriers and diffusion coefficients , find fast migration within the S-shaped tunnel and moderate one within the small-sized tunnel. Through analysis of density of states, we find that these compounds exhibit half-metallic behaviour, demonstrating an enhancement of metallicity by mixing with higher valent transition metal atoms. Our calculation results show that these mixed compounds can be advanced cathode materials for high performance SIBs.

DOI

http://dx.doi.org/10.1016/j.jpowsour.2021.230395

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