TY - CONF A1 - Hickel, Tilmann T1 - Design of finite temperature materials properties enabled by digital concepts N2 - Since the function of materials is controlled by properties and processes on the atomic scale, ab initio based high-throughput methods are valuable strategies in materials design. For computational efficiency, they are however often restriction to T=0K calculations, while many technologically relevant materials properties and thermodynamic stabilities change when going from low to high temperatures. On the other hand, the constantly increasing performance of digital tools for simulation and data-driven science enables more targeted material development including these kinds of finite-temperature effects. A flexible infrastructure, including data management and workflow solutions is required to make this symbiosis user-friendly efficient. Within this presentation, examples from ab initio thermodynamics for the design of phase stabilities in hard-magnetic alloys and defect-phases in advanced high-strength steels will be demonstrated. We will discuss physical concepts with a focus at the impact of magnetic excitations. At the same time, the examples will be used to derive requirements and present solutions for a digital infrastructure. An outlook will be given to current strategies with the NDFI initiative NFDI-MatWerk. T2 - HetSys Seminar Warwick University CY - Warwick, UK DA - 16.01.2023 KW - Digital Infrastructure KW - Workflows KW - Ab initio thermodynamics KW - Compositionally complex alloys KW - Hard magnets PY - 2023 AN - OPUS4-58856 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Research data infrastructures as enablers for materials design N2 - Suitable material solutions are of key importance in designing and producing components for engineering systems – either for functional or structural applications. Materials data are generated, transferred, and introduced at each step along the complete life cycle of a component. A reliable materials data space is therefore crucial in the digital transformation and an important prerequisite for machine learning in materials science. Therefore, the consortium NFDI MatWerk aims to develop a sustainable infrastructure for the standardized digital representation of materials science and engineering (MatWerk). The goal is to seamlessly integrate decentralized data and metadata, experimental and computational workflows, and a materials ontology to maximize interoperability and reproducibility of materials data processing. To this end, data use profiles of participant projects from different sub-disciplines are analyzed to identify the most relevant scientific scenarios within MatWerk. Similarly, the Plattform MaterialDigital (PMD) is committed to provide a prototypical infrastructure for the digitalization of materials in an industrial context implemented by decentralized data servers, semantic data schemas and digital workflows. The standards, methods, and tools developed within the PMD are deployed and consolidated within the context of currently more than 20 BMBF-funded academic and industrial research consortia. Scientific workflow environments represent a major focus area, including efforts to improve the definition and representation of digital workflows, as well as their distribution in form of a workflow store. In this presentation we will describe the overarching visions behind these initiatives, their status, and progress of dissemination with a focus on the workflow activities and the connection to machine learning applications. Following the philosophy of both consortia, specific examples will be used to demonstrate innovative and pragmatic solutions. T2 - MLEdays TUHH 2023 CY - Hamburg, Germany DA - 25.09.2023 KW - Digital Infrastructure KW - Workflows KW - Integrated Development Environment PY - 2023 AN - OPUS4-58853 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Constructing defect phase diagrams from ab initio calculations N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored microstructures. On the other hand, recent progress in experimental atomic-scale characterization techniques allows one to study the local chemical composition at individual defects such as interfaces, grain boundaries, dislocations and surfaces. They show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams, using chemical potentials as thermodynamics variables, provide a natural route to study these chemically driven defects. Our results show, however, that the direct application of thermodynamic approaches can fail to reproduce the experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We use ab initio calculations based on density functional theory to quantify the extension of regions where defect formation is expected. We successfully applied this concept to explain the formation of large concentrations of planar defects in supersaturated Fe2Nb Laves phases. In addition, we identify in a joint study with experiments conditions and structures in Mg-Al-Ca alloys for defect phase occurrence. The concept offers new avenues for designing materials with tailored defect structures. T2 - 6th MoD-PMI 2023 Workshop CY - Aachen, Germany DA - 29.05.2023 KW - Ab initio simulations KW - Defects KW - Phase diagrams PY - 2023 AN - OPUS4-58854 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sözen, H.I. A1 - Ener, S. A1 - Maccari, F. A1 - Fayyazi, B. A1 - Gutfleisch, O. A1 - Neugebauer, J. A1 - Hickel, Tilmann T1 - Combined ab initio and experimental screening of phase stabilities in the Ce-Fe-Ti-X system (X = 3d and 4d metals) N2 - One of the main challenges for the synthesis and application of the promising hard-magnetic compound CeFe11Ti is the formation of Laves phases that are detrimental for their thermodynamic stability and magnetic properties. In this paper, we present an ab initio based approach to modify the stability of these phases in the Ce-Fe-Ti system by additions of 3d and 4d elements. We combine highly accurate free-energy calculations with an efficient screening technique to determine the critical annealing temperature for the formation of Ce(Fe,X)11Ti. The central findings are the dominant role of the formation enthalpy at T = 0 K on chemical trends and the major relevance of partial chemical decompositions. Based on these insights, promising transition metals to promote the stability of the hard-magnetic phase, such as Zn and Tc, were predicted. The comparison with suction casting and reactive crucible melting experiments for Ce-Fe-Ti-X (X = Cu, Ga, Co, and Cr) highlights the relevance of additional phases and quaternary elements. KW - Density functional theory KW - Phase stability KW - Energy materials PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-568850 DO - https://doi.org/10.1103/PhysRevMaterials.7.014410 SN - 2475-9953 VL - 7 SP - 1 EP - 15 AN - OPUS4-56885 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Sözen, H.I. A1 - Mendive-Tapia, E. A1 - Hickel, Tilmann A1 - Neugebauer, J. T1 - Ab initio investigations of point and complex defect structures in B2-FeAl N2 - We study single-site and two-site defect structures in B2-type Fe-Al alloys by means of density functional theory supercell calculations. The defect formation energies are calculated as functions of the chemical potential, which are used to obtain the dependence of the defect concentrations on Al content at different temperatures. We also examine the converging behavior of the formation energies with respect to the supercell size to study the corresponding limit of dilute defects. The effect of magnetism is investigated by considering nonmagnetic, ferromagnetic, and paramagnetic states, calculations for the latter showing that the magnitude of the local magnetic moments strongly impacts the defect formation energies. The methodological studies are used to provide explanations for the wide spread of defect formation energies reported by experiments and other theoretical investigations. Based on these insights, the stability of the B2-FeAl structure as a function of Al concentration is obtained and discussed. KW - Atomistic models KW - Defects KW - Thermodynamics PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-546956 DO - https://doi.org/10.1103/PhysRevMaterials.6.023603 SN - 2475-9953 VL - 6 IS - 2 SP - 1 EP - 11 PB - APS CY - College Park, MD AN - OPUS4-54695 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Wang, Ning A1 - Hammerschmidt, Thomas A1 - Hickel, Tilmann A1 - Rogal, Jutta A1 - Drautz, Ralf T1 - Influence of spin fluctuations on structural phase transitions of iron N2 - The effect of spin fluctuations on the α(bcc)-γ(fcc)-δ(bcc) structural phase transitions in iron is investigated with a tight-binding (TB) model. The orthogonal d-valent TB model is combined with thermodynamic integration, spin-space averaging, and Hamiltonian Monte Carlo to compute the temperature-dependent free-energy difference between bcc and fcc iron. We demonstrate that the TB model captures experimentally observed phonon spectra of bcc iron at elevated temperatures. Our calculations show that spin fluctuations are crucial for both the α−γ and γ−δ phase transitions but they enter through different mechanisms. Spin fluctuations impact the α−γ phase transition mainly via the magnetic/electronic free-energy difference between bcc and fcc iron. The γ−δ phase transition, in contrast, is influenced by spin fluctuations only indirectly via the spin-lattice coupling. Combining the two mechanisms, we obtain both the α−γ and γ−δ phase transitions with our TB model. The calculated transition temperatures are in very good agreement with experimental values. KW - Structural phase transition KW - Magnetism KW - Spin-lattice coupling PY - 2023 DO - https://doi.org/10.1103/PhysRevB.107.104108 SN - 2469-9950 VL - 107 IS - 10 SP - 1 EP - 9 PB - American Physical Society (APS) AN - OPUS4-58790 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tehranchi, Ali A1 - Hickel, Tilmann A1 - Neugebauer, J. T1 - Hydrogen enhanced dislocation cross-slip in polycrystalline nickel N2 - Hydrogen embrittlement (HE), degradation of the mechanical properties of metals due to the presence of hydrogen, is a persistent problem that has been attracting the attention of the material science community for about fifteen decades. Extensive experimental observations indicate the presence of nanovoids and the increase of free volume at the grain boundaries in hydrogen contaminated metals. This rate-dependent phenomenon motivates theoretical investigations of the underlying mechanisms. Here, a hydrogen enhanced cross-slip (HECS) mechanism in the close vicinity of the grain boundaries is demonstrated by direct molecular dynamics simulations and theoretical calculations. To this end, the interaction of screw dislocations with a variety of symmetric tilt grain boundaries in H-charged and H-free bicrystalline nickel is examined. The presence of segregated H atoms at the grain boundaries induces a stress field in their vicinity, and thus,- the barrier for cross-slip of screw dislocations considerably decreases. The enhanced cross-slip of dislocations facilitates the formation of jogs on bowedout dislocations. These jogs can form vacancies during the glide process. This mechanism of defect production shows nanoscale evidence of enhanced vacancy formation and subsequent increase in the free volume along the grain boundaries in the presence of H. KW - Hydrogen embrittlement KW - Dislocation KW - Grain boundary KW - Void formation PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-649858 DO - https://doi.org/10.1103/7l8f-3fbm SN - 2475-9953 VL - 9 IS - 12 SP - 1 EP - 16 PB - American Physical Society (APS) AN - OPUS4-64985 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Janssen, Jan A1 - George, Janine A1 - Geiger, Julian A1 - Bercx, Marnik A1 - Wang, Xing A1 - Ertural, Christina A1 - Schaarschmidt, Joerg A1 - Ganose, Alex M. A1 - Pizzi, Giovanni A1 - Hickel, Tilmann A1 - Neugebauer, Joerg T1 - A Python workflow definition for computational materials design N2 - Numerous Workflow Management Systems (WfMS) have been developed in the field of computational materials science with different workflow formats, hindering interoperability and reproducibility of workflows in the field. To address this challenge, we introduce here the Python Workflow Definition (PWD) as a workflow exchange format to share workflows between Python-based WfMS, currently AiiDA, jobflow, and pyiron. This development is motivated by the similarity of these three Python-based WfMS, that represent the different workflow steps and data transferred between them as nodes and edges in a graph. With the PWD, we aim at fostering the interoperability and reproducibility between the different WfMS in the context of Findable, Accessible, Interoperable, Reusable (FAIR) workflows. To separate the scientific from the technical complexity, the PWD consists of three components: (1) a conda environment that specifies the software dependencies, (2) a Python module that contains the Python functions represented as nodes in the workflow graph, and (3) a workflow graph stored in the JavaScript Object Notation (JSON). The first version of the PWD supports directed acyclic graph (DAG)-based workflows. Thus, any DAG-based workflow defined in one of the three WfMS can be exported to the PWD and afterwards imported from the PWD to one of the other WfMS. After the import, the input parameters of the workflow can be adjusted and computing resources can be assigned to the workflow, before it is executed with the selected WfMS. This import from and export to the PWD is enabled by the PWD Python library that implements the PWD in AiiDA, jobflow, and pyiron. KW - Automation KW - Workflows KW - Materials Design KW - Multi-scale simulation KW - Digitalization PY - 2025 DO - https://doi.org/10.5281/zenodo.15516179 PB - Zenodo CY - Geneva AN - OPUS4-63233 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Bayerlein, Bernd A1 - Waitelonis, Jörg A1 - Birkholz, Henk A1 - Jung, Matthias A1 - Schilling, Markus A1 - v. Hartrott, Philipp A1 - Bruns, Marian A1 - Schaarschmidt, Jörg A1 - Beilke, Kristian A1 - Mutz, Marcel A1 - Nebel, Vincent A1 - Königer, Veit A1 - Beran, Lisa A1 - Kraus, Tobias A1 - Vyas, Akhilesh A1 - Vogt, Lars A1 - Blum, Moritz A1 - Ell, Basil A1 - Chen, Ya‐Fan A1 - Waurischk, Tina A1 - Thomas, Akhil A1 - Durmaz, Ali Riza A1 - Ben Hassine, Sahar A1 - Fresemann, Carina A1 - Dziwis, Gordian A1 - Beygi Nasrabadi, Hossein A1 - Hanke, Thomas A1 - Telong, Melissa A1 - Pirskawetz, Stephan A1 - Kamal, Mohamed A1 - Bjarsch, Thomas A1 - Pähler, Ursula A1 - Hofmann, Peter A1 - Leemhuis, Mena A1 - Özçep, Özgür L. A1 - Meyer, Lars‐Peter A1 - Skrotzki, Birgit A1 - Neugebauer, Jörg A1 - Wenzel, Wolfgang A1 - Sack, Harald A1 - Eberl, Chris A1 - Portella, Pedro Dolabella A1 - Hickel, Tilmann A1 - Mädler, Lutz A1 - Gumbsch, Peter T1 - Concepts for a Semantically Accessible Materials Data Space: Overview over Specific Implementations in Materials Science N2 - This article describes advancements in the ongoing digital transformation in materials science and engineering. It is driven by domain‐specific successes and the development of specialized digital data spaces. There is an evident and increasing need for standardization across various subdomains to support science data exchange across entities. The MaterialDigital Initiative, funded by the German Federal Ministry of Education and Research, takes on a key role in this context, fostering collaborative efforts to establish a unified materials data space. The implementation of digital workflows and Semantic Web technologies, such as ontologies and knowledge graphs, facilitates the semantic integration of heterogeneous data and tools at multiple scales. Central to this effort is the prototyping of a knowledge graph that employs application ontologies tailored to specific data domains, thereby enhancing semantic interoperability. The collaborative approach of the Initiative's community provides significant support infrastructure for understanding and implementing standardized data structures, enhancing the efficiency of data‐driven processes in materials development and discovery. Insights and methodologies developed via the MaterialDigital Initiative emphasize the transformative potential of ontology‐based approaches in materials science, paving the way toward simplified integration into a unified, consolidated data space of high value. KW - Semantic Interoperability KW - Data Spaces KW - Integration Workflows KW - MaterialDigital PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-622952 DO - https://doi.org/10.1002/adem.202401092 SN - 1527-2648 SP - 1 EP - 25 PB - Wiley-VCH CY - Weinheim AN - OPUS4-62295 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Esakkiraja, N. A1 - Vishwakarma, A. A1 - Makineni, S. K. A1 - Jayaram, V. A1 - Hickel, Tilmann A1 - Divinski, S. V. A1 - Paul, A. T1 - Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bondcoats and Ni-based single crystal superalloy N2 - Pt-modified NiAl bond coats are used to extend the lifetime of blades in gas turbine engine applications. However, they suffer from the growth of deleterious precipitates within the interdiffusion zone. Partial substitution of Pt by Pd is advantageous in reducing the interdiffusion zone thickness between the bond coat and the superalloy, providing comparable oxidation properties, and critically reducing the propensity to form brittle (Pt,Ni)Al2 precipitates. In this study, we utilize the pseudo-binary diffusion couple method to estimate the interdiffusion coefficients of Ni and Al in Pd, Pd-Pt and Pt-modified nickel aluminides. Additionally, the main and cross-interdiffusion coefficients are estimated in the ternary diffusion couples. The estimated diffusion coefficients in the 𝛽-NiAl phase reflect on the thickness of the 𝛽 phase in the superalloy bond coat interdiffusion zone. Pd reduces the pseudo-binary interdiffusion coefficients of Ni–Al and also decreases the main and cross-ternary interdiffusion coefficients. This correlates with the reduction of the interdiffusion zone thickness by Pd. The diffusion process is strongly assisted by point defects in this phase. Ab initio-informed defect calculations are done to explain diffusion retardation in the presence of Pd (compared to Pt) with decreased defect concentrations. Furthermore, through in-depth microstructure characterization performed by electron probe micro analyser, transmission electron microscopy, and atom probe tomography, the presence of 𝜎, 𝑅 and 𝜇 phases as TCP precipitates in the interdiffusion zone are identified. The results give insights into the coatings’ diffusional properties that influence the service life of the product. KW - Interdiffusion KW - Bondcoat KW - Topologically close pack (TCP) phase KW - Transmission electron microscopy KW - Atom probe tomography PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618091 DO - https://doi.org/10.1016/j.actamat.2024.119687 SN - 1359-6454 VL - 266 SP - 1 EP - 14 PB - Elsevier CY - Amsterdam AN - OPUS4-61809 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhu, L. A1 - Srinivasan, P. A1 - Gong, Y. A1 - Hickel, Tilmann A1 - Grabowski, B. A1 - Körmann, Fritz A1 - Neugebauer, J. T1 - Melting properties of the refractory metals V and W and the binary VW alloy fully from first principles N2 - We investigate the melting properties of the bcc refractory metals V and W, and the disordered equiatomic VW alloy from first principles. We show that thermal vibrations have a large impact on the electronic density of states (DOS) and thus considerably affect the electronic contribution to the free energy. For W, the impact of vibrations on the electronic free energy of solid and liquid is different. This difference substantially impacts the computed melting point and also triggers a large electronic heat capacity difference between solid and liquid. For V, although vibrations likewise affect the electronic free energy, the effect on the melting properties cancels out to a large degree. For the binary VW alloy we observe a similar impact as for W, but slightly weaker. The underlying physics is explained in terms of the electronic DOS of the solid and liquid phases. Based on our accurate first-principles results, we reveal critical limitations of the Sommerfeld approximation in predicting the electronic heat KW - Crystal melting KW - Thermodynamics KW - Metals KW - Ab initio molecular dynamics KW - Density functional theory PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618100 DO - https://doi.org/10.1103/PhysRevB.109.094110 SN - 2469-9950 VL - 109 IS - 9 SP - 1 EP - 18 PB - American Physical Society (APS) AN - OPUS4-61810 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Janssen, J. A1 - Makarov, E. A1 - Hickel, Tilmann A1 - Shapeev, A.V. A1 - Neugebauer, J. T1 - Automated optimization and uncertainty quantification of convergence parameters in plane wave density functional theory calculations N2 - First principles approaches have revolutionized our ability in using computers to predict, explore, and design materials. A major advantage commonly associated with these approaches is that they are fully parameter-free. However, numerically solving the underlying equations requires to choose a set of convergence parameters. With the advent of high-throughput calculations, it becomes exceedingly important to achieve a truly parameter-free approach. Utilizing uncertainty quantification (UQ) and linear decomposition we derive a numerically highly efficient representation of the statistical and systematic error in the multidimensional space of the convergence parameters for plane wave density functional theory (DFT) calculations. Based on this formalism we implement a fully automated approach that requires as input the target precision rather than convergence parameters. The performance and robustness of the approach are shown by applying it to a large set of elements crystallizing in a cubic fcc lattice. KW - Ab initio simulations KW - High throughput KW - convergence parameter PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618632 DO - https://doi.org/10.1038/s41524-024-01388-2 VL - 10 IS - 1 SP - 1 EP - 11 PB - Springer Science and Business Media LLC AN - OPUS4-61863 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhou, X. A1 - Mathews, P. A1 - Berkels, B. A1 - Delis, W. A1 - Saood, S. A1 - Alhassan, A. A1 - Keuter, P. A1 - Schneider, J. A1 - Korte-Kerzel, S. A1 - Sandlöbes, S. A1 - Raabe, D. A1 - Neugebauer, j. A1 - Dehm, G. A1 - Hickel, Tilmann A1 - Scheu, C. A1 - Zhang, S. T1 - Materials Design by Constructing Phase Diagrams for Defects N2 - Phase transformations and crystallographic defects are two essential tools todrive innovations in materials. Bulk materials design via tuning chemicalcompositions is systematized using phase diagrams. It is shown here that thesame thermodynamic concept can be applied to manipulate the chemistry atdefects. Grain boundaries in Mg–Ga system are chosen as a model system,because Ga segregates to the boundaries, while simultaneously improving thestrength and ductility of Mg alloys. To reveal the role of grain boundaries,correlated atomic-scale characterization and simulation to scope and buildphase diagrams for defects are presented. The discovery is enabled bytriggering phase transformations of individual grain boundaries through localalloying, and sequentially imaging the structural and chemical changes usingatomic-resolution scanning transmission electron microscopy. Ab initiosimulations determined the thermodynamic stability of grain boundaryphases, and found out that increasing Ga content enhances grain boundarycohesion, relating to improved ductility. The methodology to trigger, trace,and simulate defect transformation at atomic resolution enables a systematicdevelopment of defect phase diagrams, providing a valuable tool to utilizechemical complexity and phase transformations at defects. KW - Automatic pattern recognition KW - Defect phase diagram KW - Density functional theory KW - Grain boundary complexion KW - Transmission electron microscopy PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618063 DO - https://doi.org/10.1002/adma.202402191 SN - 1521-4095 SP - 1 EP - 9 PB - Wiley AN - OPUS4-61806 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Hickel, Tilmann A1 - Richter, Silke A1 - Bitzek, E. A1 - Ávila Calderón, Luis A1 - Gedsun, A. A1 - Forti, M. A1 - Hammerschmidt, T. A1 - Olbricht, Jürgen A1 - Skrotzki, Birgit T1 - NFDI-MatWerk/IUC02 Definition for Reference Data of Materials N2 - This definition was agreed within the infrastructure use case IUC02 “Framework for curation and distribution of reference datasets” of the consortium NFDI-MatWerk. It is broadly formulated to cover experimental and simulation MSE data and will be developed further in agreement with the MSE community. KW - Referenzdaten KW - Digitalisierung KW - NFDI-MatWerk KW - Research Data Management KW - Reference Data PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-611688 DO - https://doi.org/10.5281/zenodo.11667673 PB - Zenodo CY - Geneva AN - OPUS4-61168 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mendive Tapia, Eduardo A1 - Patrick, Christopher E A1 - Hickel, Tilmann A1 - Neugebauer, Jörg A1 - Staunton, Julie B T1 - Quantification of electronic and magnetoelastic mechanisms of first-order magnetic phase transitions from first principles: application to caloric effects in La(FexSi1-x)(13) N2 - La(FexSi1−x)13 and derived quaternary compounds are well-known for their giant, tunable, magneto- and barocaloric responses around a first-order paramagnetic-ferromagnetic transition near room temperature with low hysteresis. Remarkably, such a transition shows a large spontaneous volume change together with itinerant electron metamagnetic features. While magnetovolume effects are well-established mechanisms driving first-order transitions, purely electronic sources have a long, subtle history and remain poorly understood. Here we apply a disordered local moment picture to quantify electronic and magnetoelastic effects at finite temperature in La(FexSi1−x)13 from first-principles. We obtain results in very good agreement with experiment and demonstrate that the magnetoelastic coupling, rather than purely electronic mechanisms, drives the first-order character and causes at the same time a huge electronic entropy contribution to the caloric response. KW - Caloric effects KW - Ab initio thermodynamics KW - Magnetoeleastic couplin PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-587882 DO - https://doi.org/10.1088/2515-7655/acd027 SN - 2515-7655 VL - 5 IS - 3 SP - 1 EP - 16 PB - IOP Publishing AN - OPUS4-58788 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Fareed, Adnan A1 - Rosalie, Julian A1 - Kumar, Sourabh A1 - Kar, S. A1 - Hickel, Tilmann A1 - Fähler, S. A1 - Maaß, Robert T1 - Constrained incipient phase transformation in Ni-Mn-Ga films: A small-scale design challenge N2 - Ni-Mn-Ga shape-memory alloys are promising candidates for large strain actuation and magnetocaloric cooling devices. In view of potential small-scale applications, we probe here nanomechanically the stress-induced austenite–martensite transition in single crystalline austenitic thin films as a function of temperature. In 0.5 μm thin films, a marked incipient phase transformation to martensite is observed during nanoindentation, leaving behind pockets of residual martensite after unloading. These nanomechanical instabilities occur irrespective of deformation rate and temperature, are Weibull distributed, and reveal large spatial variations in transformation stress. In contrast, at a larger film thickness of 2 μm fully reversible transformations occur, and mechanical loading remains entirely smooth. Ab-initio simulations demonstrate how an in-plane constraint can considerably increase the martensitic transformation stress, explaining the thickness-dependent nanomechanical behavior. These findings for a shape-memory Heusler alloy give insights into how reduced dimensions and constraints can lead to unexpectedly large transformation stresses that need to be considered in small-scale actuation design. KW - Shape-memory alloys KW - Nanoindentation KW - Incipient plasticity KW - NiMaGa PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-581422 DO - https://doi.org/10.1016/j.matdes.2023.112259 VL - 233 SP - 1 EP - 8 PB - Elsevier B.V. AN - OPUS4-58142 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tehranchi, Ali A1 - Chakraborty, Poulami A1 - López Freixes, Martí A1 - McEniry, Eunan J. A1 - Gault, Baptiste A1 - Hickel, Tilmann A1 - Neugebauer, Jörg T1 - Tailoring negative pressure by crystal defects: Microcrack induced hydride formation in Al alloys N2 - Climate change motivates the search for non-carbon-emitting energy generation and storage solutions. Metal hydrides show promising characteristics for this purpose. They can be further stabilized by tailoring the negative pressure of microstructural and structural defects. Using systematic ab initio and atomistic simulations, we demonstrate that an enhancement in the formation of hydrides at the negatively pressurized tip region of the microcrack is feasible by increasing the mechanical tensile load on the specimen. The theoretical predictions have been used to reassess and interpret atom probe tomography experiments for a high-strength 7XXX-aluminium alloy that show a substantial enhancement of hydrogen concentration at structural defects near a stress-corrosion crack tip. These results contain important implications for enhancing the capability of metals as H-storage materials. KW - Physics and Astronomy (miscellaneous) KW - Hydrogen storage KW - Ab initio Simulation KW - Microcracks PY - 2023 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-587878 DO - https://doi.org/10.1103/PhysRevMaterials.7.105401 SN - 2475-9953 VL - 7 IS - 10 SP - 105401-1 EP - 105401-12 PB - American Physical Society (APS) AN - OPUS4-58787 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - INPR A1 - Janssen, Jan A1 - George, Janine A1 - Geiger, Julian A1 - Bercx, Marnik A1 - Wang, Xing A1 - Ertural, Christina A1 - Schaarschmidt, Joerg A1 - Ganose, Alex M. A1 - Pizzi, Giovanni A1 - Hickel, Tilmann A1 - Neugebauer, Joerg T1 - A Python workflow definition for computational materials design N2 - Numerous Workflow Management Systems (WfMS) have been developed in the field of computational materials science with different workflow formats, hindering interoperability and reproducibility of workflows in the field. To address this challenge, we introduce here the Python Workflow Definition (PWD) as a workflow exchange format to share workflows between Python-based WfMS, currently AiiDA, jobflow, and pyiron. This development is motivated by the similarity of these three Python-based WfMS, that represent the different workflow steps and data transferred between them as nodes and edges in a graph. With the PWD, we aim at fostering the interoperability and reproducibility between the different WfMS in the context of Findable, Accessible, Interoperable, Reusable (FAIR) workflows. To separate the scientific from the technical complexity, the PWD consists of three components: (1) a conda environment that specifies the software dependencies, (2) a Python module that contains the Python functions represented as nodes in the workflow graph, and (3) a workflow graph stored in the JavaScript Object Notation (JSON). The first version of the PWD supports directed acyclic graph (DAG)-based workflows. Thus, any DAG-based workflow defined in one of the three WfMS can be exported to the PWD and afterwards imported from the PWD to one of the other WfMS. After the import, the input parameters of the workflow can be adjusted and computing resources can be assigned to the workflow, before it is executed with the selected WfMS. This import from and export to the PWD is enabled by the PWD Python library that implements the PWD in AiiDA, jobflow, and pyiron. KW - Automation KW - Workflow KW - Materials Design KW - Multi-scale simulation KW - Digitalization PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-632328 DO - https://doi.org/10.48550/arXiv.2505.20366 SP - 1 EP - 12 AN - OPUS4-63232 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Tehranchi, Ali A1 - Zhang, S. A1 - Zendegani, A. A1 - Hickel, Tilmann A1 - Neugebauer, J. A1 - Scheu, C. T1 - Metastable defect phase diagrams as roadmap to tailor chemically driven defect formation N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored properties. Recent experimental studies show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams in combination with density functional theory provide a natural route to study these chemically driven defects. Our results reveal, however, that direct application of equilibrium bulk thermodynamics can fail to reproduce experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We apply this concept to successfully explain the formation of large concentrations of planar defects in supersaturated Fe-Nb solid solutions. We then utilize it to design suitable conditions for synthesis, which we subsequently realized experimentally, successfully validating the formation of the predicted defects in Mg-Al-Ca alloys. The concept offers new avenues for the design of materials performance by tailoring defect structures. KW - Metastable defect phase diagram KW - Ab initio thermodynamics KW - Chemical potential KW - Laves phases KW - Transmission electron microscopy PY - 2024 DO - https://doi.org/10.1016/j.actamat.2024.120145 SN - 1359-6454 VL - 277 SP - 1 EP - 9 PB - Elsevier Ltd. AN - OPUS4-61803 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Research data infrastructures as enablers for materials design N2 - Suitable material solutions are of key importance in designing and producing components for engineering systems – either for functional or structural applications. Materials data are generated, transferred, and introduced at each step along the complete life cycle of a component. A reliable materials data space is therefore crucial in the digital transformation and an important prerequisite for machine learning in materials science. Therefore, the consortium NFDI MatWerk aims to develop a sustainable infrastructure for the standardized digital representation of materials science and engineering (MatWerk). The goal is to seamlessly integrate decentralized data and metadata, experimental and computational workflows, and a materials ontology to maximize interoperability and reproducibility of materials data processing. To this end, data use profiles of participant projects from different sub-disciplines are analyzed to identify the most relevant scientific scenarios within MatWerk. Similarly, the Plattform MaterialDigital (PMD) is committed to provide a prototypical infrastructure for the digitalization of materials in an industrial context implemented by decentralized data servers, semantic data schemas and digital workflows. The standards, methods, and tools developed within the PMD are deployed and consolidated within the context of currently more than 20 BMBF-funded academic and industrial research consortia. Scientific workflow environments represent a major focus area, including efforts to improve the definition and representation of digital workflows, as well as their distribution in form of a workflow store. In this presentation we will describe the overarching visions behind these initiatives, their status, and progress of dissemination with a focus on the workflow activities and the connection between theoretical predictions and experimental solutions. Following the philosophy of both consortia, specific examples will be used to demonstrate innovative and pragmatic solutions. T2 - FLAIR Colloquium CY - Darmstadt, Germany DA - 10.06.2024 KW - MaterialDigital KW - NFDI-MatWerk KW - Workflows KW - Defect phase diagrams PY - 2024 AN - OPUS4-62720 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Solute induced defect phase transformations in Mg alloys N2 - The study of defect phases is important for designing nanostructured metals and alloys. Grain boundaries (GBs) form one class of defects that directly influence materials properties, such as deformability and strength. At the same time, alloying can introduce GB phase transformations and can therewith alter mechanical performance. In this work, we will discuss the concept of GB phase diagrams for several examples. The focus will be on the defect phases of a Σ7 (12¯30) [0001] 21.78◦ symmetric tilt GB in hcp Mg. Ab-initio simulations as a function of stress and temperature (using quasi-harmonic approximation) are performed, and different types of phase transformations are revealed. To this end, the influence of the chemical degree of freedom on the defect phases is studied for the example of Ga addition, using an efficient screening approach that combines empirical potentials and accurate ab-initio calculations. By exploiting the concept of defect phase diagrams, a phase transformation from the T to the A structural type and as well as a systematic transition of the segregation site preference is revealed. The results qualitatively agree well with experimental observations from scanning transition electron microscopy. The underlying physical mechanisms have an impact on grain-boundary engineering in metallic alloys. T2 - Calphad 2024 Conference CY - Karlsruhe, Germany DA - 26.05.2024 KW - Ab initio simulations KW - Grain boundaries KW - Defect phase diagram KW - Segregation PY - 2024 AN - OPUS4-62719 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Application of Density Functional Theory in the Context of Phase Diagram Modelling N2 - An important pillar for the modelling of phase diagrams is the availability of accurate thermodynamic data for the individual phases. While experimental calorimetry is a powerful technique, a prediction of materials behavior solely on the computer, i.e. complementary to experimental investigations, has its own advantages. It allows one to resolve uncertainties in experimental data, to develop physical thermodynamic models and to determine free energies of phases that are not stable in reality. For this purpose, density functional theory (DFT), which does not require any experimental or empirical fit parameters, is the method of choice. Its advantage is to take the quantum-mechanical solution for the electronic wave functions as a starting point, when determining the chemical bonding of atoms. In the first part of the talk, I will speak about enthalpies of formation resulting from this approach, the underlying approximations, the achievable accuracies, as well as the typical incorporation into Calphad assessments. We note, however, that a disadvantage of DFT is the restriction of the method to T = 0 K in their original formulation. Phase stabilities of real materials, on the other hand, are often dominated by processes that are due to finite temperatures. To include temperature effects in DFT, a significant method development was necessary in the last decade. In the second part of this talk, I will therefore provide the basic concepts for the calculation of vibrational, electronic, and magnetic entropy contributions. I will also highlight some recent methodological achievements in this field and show how these methods opened new routes in understanding and characterizing materials. At the end a few examples of ab initio based phase diagrams will be discussed. The focus will be on phase stabilities and microstructure formation in Ni-based materials. The advantages of combining theoretical, experimental and Calphad concepts will be particularly emphasized. T2 - MSIT Winter School on Materials Chemistry CY - Tegernsee, Germany DA - 21.01.2024 KW - Ab initio simulations KW - CALPHAD KW - Thermodynamics KW - Free energies PY - 2024 AN - OPUS4-62729 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - GEN A1 - Esakkiraja, N. A1 - Vishwakarma, A. A1 - Makineni, S. K. A1 - Jayaram, V. A1 - Hickel, Tilmann A1 - Divinski, S. V. A1 - Paul, A. T1 - Corrigendum to "Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bond coats and Ni-based single crystal superalloy" [Acta Mater. 266 (2024) 119687] N2 - This is a corrigendum to the original article "Diffusion-controlled growth and microstructural evolution between Pt and Pd containing B2-NiAl bond coats and Ni-based single crystal superalloy" that was published in the journal "Acta Materialia", vol. 266 (2024), article 119687. PY - 2024 DO - https://doi.org/10.1016/j.actamat.2024.120219 SN - 1359-6454 VL - 277 SP - 1 PB - Elsevier CY - Amsterdam AN - OPUS4-63519 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Constructing defect phase diagrams from ab initio calculations N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored microstructures. On the other hand, recent progress in experimental atomic-scale characterization techniques allows one to study the local chemical composition at individual defects such as interfaces, grain boundaries, dislocations and surfaces. They show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams, using chemical potentials as thermodynamics variables, provide a natural route to study these chemically driven defects. Our results show, however, that the direct application of thermodynamic approaches can fail to reproduce the experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We use ab initio calculations based on density functional theory to quantify the extension of regions where defect formation is expected. We successfully applied this concept to explain the formation of large concentrations of planar defects in supersaturated Fe2Nb Laves phases. In addition, we identify in a joint study with experiments conditions and structures in Mg-Al-Ca alloys for defect phase occurrence. The concept offers new avenues for designing materials with tailored defect structures. T2 - Materials Science Colloquium CY - Uppsala, Sweden DA - 25.04.2024 KW - Ab initio simulations KW - Grain boundaries KW - Defect phase diagram KW - Laves phases KW - Workflow PY - 2024 AN - OPUS4-62731 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Interoperable workflows combining software tools along the process chain of materials N2 - Material science problems have intrinsically multiscale and multiphysics characters, and require us to employ a combination of methods on different time and length scales to resolve critical features. Normally creating workflows that connect data in multiple scales and various methods is a cumbersome task. Pyiron, an integrated development environment (IDE) for material science, contains modules for the atomistic as well as continuum scale that make a seamless connection possible. To this end, it provides a high-level coherent language in a unified workflow platform to study materials, for example, with LAMMPS simulations in the same framework as crystal plasticity codes such as DAMASK. The latter is integrated such that all required input files can be generated, the analysis can be executed and the routines of the DAMASK post-processing library can be employed. One example of a multi-scale workflow is the simulation of a multi-stage cold rolling process using pyiron. As with every DAMASK simulation, pre-processing includes the creation of the representative volume element and the material definition. It contains elastic properties that are obtained from LAMMPS calculations. To simulate the actual rolling process, the rolling subclass was implemented in the pyiron-job class. Since the total height decrease in technical rolling processes can be very large, the implementation provides for optional regridding between rolling passes. This is also required for the coupling with OpenPhase for simulating recrystallization using pyiron. To ensure interoperability between evaluation and simulation tools, work was done on a semantic representation of pyiron workflows. T2 - MSE Conference 2024 CY - Darmstadt, Germany DA - 24.09.2024 KW - Steel KW - Workflows KW - Multiscale simulation KW - Ontology PY - 2024 AN - OPUS4-62728 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Syed, F. W. A1 - Saikia, Ujjal A1 - Sun, B. A1 - Kiranbabu, S. A1 - Tehranchi, Ali A1 - Hickel, Tilmann A1 - Zaefferer, S. A1 - Ponge, D. T1 - Interfacial segregation of carbon atoms: the competition between grain boundaries and phase boundaries N2 - The microstructure of a two-phase medium manganese steel is decorated by interfaces whose character is defined by crystallography and the misorientation between adjacent grains, which in turn influences elemental segregation and shapes the resulting decorations. This study investigates how adjacent grain and phase boundaries impact a boundary’s segregation behavior, with a focus on the competition for carbon (C) enrichment in a laminated ferrite (α)- austenite (γ) microstructure subjected to a series of heat treatments. It was found that semicoherent α-γ Kurdjumov-Sachs (KS) phase boundaries show less carbon segregation than general γ grain boundaries. Furthermore, when a γ grain boundary is present at a junction with the phase boundaries, it acts as an extracting agent for C. DFT calculations support these observations, demonstrating that carbon segregation is energetically more favorable at the γ grain boundary compared to the α/γ phase boundary, due to the more negative segregation energy at the former. KW - Defects PY - 2025 DO - https://doi.org/10.1016/j.scriptamat.2025.116842 SN - 1359-6462 VL - 268 SP - 1 EP - 6 PB - Elsevier Inc. AN - OPUS4-63840 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Shanmugam, Sankaran A1 - Peterlechner, Martin A1 - Iskandar, Mohamad Riza A1 - Saikia, Ujjal A1 - Kulitckii, Vladislav A1 - Lipińska-Chwałek, Marta A1 - Mayer, Joachim A1 - Rösner, Harald A1 - Hickel, Tilmann A1 - Divinski, Sergiy V. A1 - Wilde, Gerhard T1 - Coherent twin-oriented Al3Sc-based precipitates in Al matrix N2 - Al3(Sc,Zr,Ti) nanoparticles with an ideal twin-type orientation relationship to Al host matrix were found in cold-rolled and subsequently annealed Al-based alloy. Atomic-scale investigations using high-resolution scanning transmission electron microscopy identified particles that form prominent coherent (111) twin-type interfaces along their longer facets and semi-coherent twin interfaces on their shorter facets. Ab-initio calculations showed that a coherent Al/Al3Sc twin-like phase boundary corresponds to a local energy minimum. A model is proposed explaining the formation of the twin orientation relationship of an Al3Sc nanoparticle with the Al host matrix. KW - Al-based alloy KW - Precipitation KW - Twin orientation relationship KW - Ab initio calculations KW - Transition electron microscopy PY - 2023 DO - https://doi.org/10.1016/j.scriptamat.2023.115351 SN - 1359-6462 VL - 229 SP - 1 EP - 6 PB - Elsevier BV AN - OPUS4-58789 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Design of finite temperature materials properties enabled by digital concepts N2 - Since the function of materials is controlled by properties and processes on the atomic scale, ab initio based high-throughput methods are valuable strategies in materials design. For computational efficiency, they are however often restriction to T=0K calculations, while many technologically relevant materials properties and thermodynamic stabilities change when going from low to high temperatures. On the other hand, the constantly increasing performance of digital tools for simulation and data-driven science enables more targeted material development including these kinds of finite-temperature effects. A flexible infrastructure, including data management and workflow solutions is required to make this symbiosis user-friendly efficient. Within this presentation, examples from ab initio thermodynamics for the design of phase stabilities in hard-magnetic alloys and defect-phases in advanced high-strength steels will be demonstrated. We will discuss physical concepts with a focus at the impact of magnetic excitations. At the same time, the examples will be used to derive requirements and present solutions for a digital infrastructure. An outlook will be given to current strategies with the NDFI initiative NFDI-MatWerk. T2 - FEMS Euromat Conference 2023 CY - Frankfurt/Main, Germany DA - 03.09.2023 KW - Ab initio simulations KW - Workflows KW - Chemically complex alloys KW - Hard magnetic materials KW - Thermodynamics PY - 2023 AN - OPUS4-58848 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Constructing defect phase diagrams from ab initio calculations N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored microstructures. On the other hand, recent progress in experimental atomic-scale characterization techniques allows one to study the local chemical composition at individual defects such as interfaces, grain boundaries, dislocations and surfaces. They show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams, using chemical potentials as thermodynamics variables, provide a natural route to study these chemically driven defects. Our results show, however, that the direct application of thermodynamic approaches can fail to reproduce the experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We use ab initio calculations based on density functional theory to quantify the extension of regions where defect formation is expected. We successfully applied this concept to explain the formation of large concentrations of planar defects in supersaturated Fe2Nb Laves phases. In addition, we identify in a joint study with experiments conditions and structures in Mg-Al-Ca alloys for defect phase occurrence. The concept offers new avenues for designing materials with tailored defect structures. T2 - Birmingham University, Seminar in physical chemistry CY - Birmingham, UK DA - 21.07.2023 KW - Atomistic models KW - Phase transitions KW - Defects PY - 2023 AN - OPUS4-58843 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Constructing defect phase diagrams from ab initio calculations N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored microstructures. Recent experimental studies show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams in combination with density functional theory provide a natural route to study these chemically driven defects. Our results show, however, that direct application of thermodynamic approaches can fail to reproduce the experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We successfully applied this concept to explain the formation of large concentrations of planar defects in supersaturated Fe-Nb solid solutions and to identify in a joint study with experiments conditions in Mg-Al-Ca alloys for defect phase occurrence. The concept offers new avenues for designing materials with tailored defect structures. T2 - Fritz-Haber-Institut Seminar CY - Berlin, Germany DA - 23.03.2023 KW - Ab initio simulations KW - Defects KW - Phase diagrams PY - 2023 AN - OPUS4-58849 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - The Platform MaterialDigital (PMD) and the goal of a Materials Data Space N2 - Suitable material solutions are of key importance in designing and producing components for engineering systems – either for functional or structural applications. Materials data are generated, transferred, and introduced at each step along the complete life cycle of a component. A reliable materials data space is therefore crucial in the digital transformation of an industrial branch. Therefore, the “Innovation Platform MaterialDigital (PMD) funded by the German Federal Ministry of Education and Research (BMBF), aims to develop a sustainable infrastructure for the standardized digital representation of materials science and materials engineering. With its partners (KIT, Fraunhofer IWM, FIZ, Leibnitz IWT, BAM, MPIE), the PMD is committed to build up a materials science data space. To achieve this the PMD provides a prototypical infrastructure for the digitalization of materials implemented by decentralized data servers, standardized data schemas and digital workflows. Following the FAIR principles, it will promote the semantic interoperability across the frontiers of materials classes. Standards, methods, and tools developed within the platform are deployed and consolidated within the context of currently near 20 BMBF-funded academic and industrial research consortia and made available to the material science community in general. In this context scientific workflows represent a major focus area, represented within the platform by the workflow frameworks pyiron and SimStack. In consequence, the platform is building up a digital library in form of a workflow store along with common standards for the definition and representation of digital workflows. In this presentation we will describe the status of our Platform MaterialDigital with a focus on the workflow activities. The current status and the vision for dissemination of the solutions developed in the PMD within the community are provided. T2 - 4th EMMC International Workshop 2023 CY - Vienna, Austria DA - 26.04.2023 KW - Platform MaterialDigital KW - Workflows KW - Data Management PY - 2023 AN - OPUS4-58846 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Ab initio Thermodynamics of defect phases in metals N2 - Thermodynamic bulk phase diagrams have become the roadmap used by researchers to identify alloy compositions and process conditions that result in novel materials with tailored microstructures. On the other hand, recent progress in experimental atomic-scale characterization techniques allows one to study the local chemical composition at individual defects such as interfaces, grain boundaries, dislocations and surfaces. They show that changes in the alloy composition can drive not only transitions in the bulk phases present in a material, but also in the concentration and type of defects they contain. Defect phase diagrams, using chemical potentials as thermodynamics variables, provide a natural route to study these chemically driven defects. Our results show, however, that the direct application of thermodynamic approaches can fail to reproduce the experimentally observed defect formation. Therefore, we extend the concept to metastable defect phase diagrams to account for kinetic limitations that prevent the system from reaching equilibrium. We use ab initio calculations based on density functional theory to quantify the extension of regions where defect formation is expected. We successfully applied this concept to explain the formation of large concentrations of planar defects in supersaturated Fe2Nb Laves phases. In addition, we identify in a joint study with experiments conditions and structures in Mg-Al-Ca alloys for defect phase occurrence. The concept offers new avenues for designing materials with tailored defect structures. T2 - 19th Int. Conference on Diffusion in Liquids and Solids CY - Heraklion, Greece DA - 26.06.2023 KW - Density functional theory KW - Defects KW - Phase diagrams KW - Mg alloys PY - 2023 AN - OPUS4-58845 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Integration of multi-scale workflows into the pyiron IDE N2 - Material science problems have intrinsically multiscale and multiphysics characters, and require us to employ a combination of methods on different time and length scales to resolve critical features. Normally creating workflows that connect data in multiple scales and various methods is a cumbersome task. Pyiron, an integrated development environment (IDE) for material science, contains modules for the atomistic as well as continuum scale that make a seamless connection possible. To this end, it provides a high-level coherent language in a unified workflow platform to study materials, for example, with density functional theory (DFT) simulations in the same framework as with the finite element method (FEM). In this work, in addition to the introduction of different features in pyiron and its continuum module, a couple of exemplary workflows are demonstrated, bridging the scales in pyiron. One such workflow is analyzing the elastoplastic response of metallic alloys, where the elastic properties of the system are dependent on the atomistic composition and structure of the alloy. We use pyiron atomistics to model the dependence of elastic moduli on the atomistic composition of Al-Mg alloys. Benefiting from the integration of DAMASK in the continuum module of pyiron, the model can be used as an input to simulate the elastoplastic response of the alloy under various loadings. In addition, finite element simulations using the FEniCS package are currently integrated into the continuum module and will be demonstrated in the presentation. T2 - FEMS Euromat Conference 2023 CY - Frankfurt/Main, Germany DA - 03.09.2023 KW - Platform MaterialDigital KW - Workflows KW - Multiscale simulation PY - 2023 AN - OPUS4-58847 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - High-throughput segregation analysis at ferritic Fe grain boundaries: from first principles N2 - Understanding segregation to grain boundaries, and eventually their defect phase diagrams, is critical to enable rational grain boundary engineering for alloys design. Here, we discuss the progress and challenges one may face when generating such a database of defect-solute interactions, in the context of studying of grain boundary segregation of solutes and impurities in Fe GBs. To compute the large number of relevant defect-solute interactions we have performed high-throughput ab initio calculations using efficient and highly automated workflows using pyiron. We study has been performed across a representative set of coincident-site-lattice (CSL) type tilt GBs. Based on the large ab-initio datasets, we extract and analyse the chemical and structural trends observed in the solute segregation behaviour across the periodic table. The features which are most important in evaluating site segregation are presented and discussed. T2 - DPG Frühjahrstagung der Sektion Kondensierte Materie CY - Dresden, Germany DA - 26.03.2023 KW - Ab initio simulations KW - Defects KW - Phase diagrams PY - 2023 AN - OPUS4-58844 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Zhang, X. A1 - Zhang, J. A1 - Wang, H. A1 - Rogal, J: A1 - Li, H.-Y. A1 - Wei, S.-H. A1 - Hickel, Tilmann T1 - Defect-characterized phase transition kinetics N2 - Phase transitions are a common phenomenon in condensed matter and act as a critical degree of freedom that can be employed to tailor the mechanical or electronic properties of materials. Understanding the fundamental mechanisms of the thermodynamics and kinetics of phase transitions is, thus, at the core of modern materials design. Conventionally, studies of phase transitions have, to a large extent, focused on pristine bulk phases. However, realistic materials exist in a complex form; their microstructures consist of different point and extended defects. The presence of defects impacts the thermodynamics and kinetics of phase transitions, but has been commonly ignored or treated separately. In recent years, with the significant advances in theoretical and experimental techniques, there has been an increasing research interest in modeling and characterizing how defects impact or even dictate phase transitions. The present review systematically discusses the recent progress in understanding the kinetics of defect-characterized phase transitions, derives the key mechanisms underlying these phase transitions, and envisions the remaining challenges and fruitful research directions. We hope that these discussions and insights will help to inspire future research and development in the field. KW - Kinetics KW - Atomistic models KW - Phase transitions KW - Defects PY - 2022 DO - https://doi.org/10.1063/5.0117234 SN - 1931-9401 VL - 9 IS - 4 SP - 1 EP - 42 PB - AIP CY - New York, NY AN - OPUS4-56507 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Pierce, D.T. A1 - Benzing, J.T. A1 - Jiménez, J.A. A1 - Hickel, Tilmann A1 - Bleskov, I. A1 - Keum, J. A1 - Raabe, D. A1 - Wittig, J.E. T1 - The influence of temperature on the strain-hardening behavior of Fe-22/25/28Mn-3Al-3Si TRIP/TWIP steels N2 - The influence of temperature and stacking fault energy (SFE) on the strain-hardening behavior and critical resolved shear stress for twinning was investigated for three Fe–22/25/28Mn–3Al–3Si wt.% transformation- and twinning-induced plasticity (TRIP/TWIP) steels. The SFEs were calculated by two different methods, density functional theory and statistical thermodynamic modeling. The dislocation structure, observed at low levels of plastic deformation, transitions from “planar” to “wavy” dislocation glide with an increase in temperature, Mn content, and/or SFE. The change in dislocation glide mechanisms from planar to wavy reduces the strain hardening rate, in part due to fewer planar obstacles and greater cross slip activity. In addition, the alloys exhibit a large decrease in strength and ductility with increasing temperature from 25 to 200 °C, attributed to a substantial reduction in the thermally activated component of the flow stress, predominate suppression of TRIP and TWIP, and a significant increase in the critical resolved shear stress for mechanical twinning. Interestingly, the increase in SFE with temperature had a rather minor influence on the critical resolved shear stress for mechanical twinning, and other temperature dependent factors which likely play a more dominant role are discussed. KW - TWIP Steel KW - TRIP Steel KW - Stacking fault energy KW - Plasticity mechanism KW - Twinning PY - 2022 DO - https://doi.org/10.1016/j.mtla.2022.101425 SN - 2589-1529 VL - 22 SP - 1 EP - 13 PB - Elsevier B.V. AN - OPUS4-56508 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Application of density functional theory in the context of phase diagram modelling N2 - In this presentation the fundamentals of density functional theory are explained in the context of phase diagram modelling. A special focus is on the Ni-Mg phase diagram. T2 - 7th MSIT Winter School CY - Kreuth, Germany DA - 12.03.2023 KW - Ab initio simulations KW - Thermodynamics KW - Phase diagrams PY - 2023 AN - OPUS4-58855 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Research data infrastructures as enablers for materials design N2 - Suitable material solutions are of key importance in designing and producing components for engineering systems – either for functional or structural applications. Materials data are generated, transferred, and introduced at each step along the complete life cycle of a component. A reliable materials data space is therefore crucial in the digital transformation, both in academia and industry. Therefore, the consortium NFDI MatWerk aims to develop a sustainable infrastructure for the standardized digital representation of materials science and engineering (MatWerk). The goal is to seamlessly integrate decentralized data and metadata, experimental and computational workflows, and a materials ontology to maximize interoperability and reproducibility of materials data processing. To this end, data use profiles of participant projects from different sub-disciplines are analyzed to identify the most relevant scientific scenarios within MatWerk. Similarly, the Plattform MaterialDigital (PMD) is committed to provide a prototypical infrastructure for the digitalization of materials in an industrial context implemented by decentralized data servers, semantic data schemas and digital workflows. The standards, methods, and tools developed within the PMD are deployed and consolidated within the context of currently more than 20 BMBF-funded academic and industrial research consortia. Scientific workflow environments represent a major focus area, including efforts to improve the definition and representation of digital workflows, as well as their distribution in form of a workflow store. In this presentation we will describe the overarching visions behind these initiatives, their status, and progress of dissemination with a focus on the workflow activities. Following the philosophy of both consortia, specific examples will be used to demonstrate innovative and pragmatic solutions. T2 - MCIC 2023 – 5th Materials Chain International Conference CY - Bochum, Germany DA - 31.08.2023 KW - Digital Infrastructure KW - Workflows KW - Integrated Development Environment PY - 2023 AN - OPUS4-58852 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Darvishi Kamachali, Reza A1 - Wallis, Theophilus A1 - Ikeda, Yuki A1 - Saikia, U. A1 - Ahmadian, A. A1 - Liebscher, C. A1 - Hickel, Tilmann A1 - Maaß, Robert T1 - Giant segregation transition as origin of liquid metal embrittlement in the Fe-Zn system N2 - A giant Zn segregation transition is revealed using CALPHAD-integrated density-based modeling of segregation into Fe grain boundaries (GBs). The results show that above a threshold of only a few atomic percent Zn in the alloy, a substantial amount of up to 60 at.% Zn can segregate to the GB. We found that the amount of segregation abruptly increases with decreasing temperature, while the Zn content in the alloy required for triggering the segregation transition decreases. Direct evidence of the Zn segregation transition is obtained using high-resolution scanning transmission electron microscopy. Base on the model, we trace the origin of the segregation transition back to the low cohesive energy of Zn and a miscibility gap in Fe-Zn GB, arising from the magnetic ordering effect, which is confirmed by ab-initio calculations. We also show that the massive Zn segregation resulting from the segregation transition greatly assists with liquid wetting and reduces the work of separation along the GB. The current predictions suggest that control over Zn segregation, by both alloy design and optimizing the galvanization and welding processes, may offer preventive strategies against liquid metal embrittlement. KW - CALPHAD KW - Microstructure Design KW - Grain boundary engineering KW - Steels KW - Density-based Model KW - Segregation Engineering PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-584292 DO - https://doi.org/10.1016/j.scriptamat.2023.115758 SN - 1359-6462 SN - 1872-8456 VL - 238 SP - 1 EP - 5 PB - Elsevier CY - Amsterdam AN - OPUS4-58429 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hickel, Tilmann A1 - Divinski, S. A1 - Starikov, S. A1 - Soisson, F. A1 - Mény, C. A1 - Hegde, O. A1 - Gerlitz, M. A1 - Magnifouet, G. A1 - Schneider, A. A1 - Barreteau, C. A1 - Mirebeau, I. A1 - Tran, V.T. A1 - Förster, G. A1 - Front, A. A1 - Egorov, A. A1 - Wilde, G. A1 - Amara, H. A1 - Hammerschmidt, T. A1 - Mrovec, M. A1 - Pierron-Bohnes, V. A1 - Drautz, R. A1 - Fu, C. T1 - Magnetism in iron alloys: methodological advances for thermodynamics, defects, and kinetics N2 - Steels are among the technologically and economically most relevant materials. Key innovations in important sectors of human society such as mobility, energy and safety, are currently based on alloying of Fe with other transition-metal elements such as Mn, Cr, or Co. Due to strong impacts and conceptual challenges related to magnetism, however, the fundamental understanding and the ability to computationally design these steels in high-throughput approaches lags behind other classes of alloys. In this article, we will provide a substantial review of the role of magnetism, magnetic excitations and transformations for alloy thermodynamics, point defects, interfaces and kinetics. This will be achieved by combining insights from different methods: Ab initio simulations have the advantage that the magnetic ground state is intrinsic part of the electronic minimization. Due to the coarsening of the many-electron structures and therewith magnetic interactions, tight-binding methods can handle larger system sizes. Effective interaction models provide the freedom to exploit more sophisticated magnetic interactions. The performance of these methods in terms of magnetic properties of Fe alloys will be evaluated by providing state-of-the-art results for their sensitivity to magnetism. Furthermore, dedicated experiments will be discussed to complete the understanding of magnetic effects in Fe alloys and to validate the modeling strategy. KW - Magnetic excitations KW - Defects KW - Diffusion KW - Density functional theory KW - Tight-binding KW - Effective interaction models PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-634530 DO - https://doi.org/10.1515/ijmr-2023-0225 SN - 1862-5282 VL - 60 IS - 99 SP - 1 EP - 14761 PB - Walter de Gruyter GmbH AN - OPUS4-63453 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Ávila Calderón, Luis A1 - Shakeel, Y. A1 - Gedsun, A. A1 - Forti, M. A1 - Hunke, S. A1 - Han, Ying A1 - Hammerschmidt, T. A1 - Aversa, R. A1 - Olbricht, Jürgen A1 - Chmielowski, M. A1 - Stotzka, R. A1 - Bitzek, E. A1 - Hickel, Tilmann A1 - Skrotzki, Birgit T1 - Management of reference data in materials science and engineering exemplified for creep data of a single-crystalline Ni-based superalloy N2 - The identification of process-structure-property relationships of materials inevitably requires the combination of research data from different measurements. Therefore, the concepts related to FAIR (findable, accessible, interoperable, reusable) data handling, increasingly reported in literature, are particularly important in the materials science and engineering domain. However, they have not yet been integrated into a single, overarching methodological framework, particularly for reference data. Here, we introduce such a framework. Our concept covers data generation, documentation, handling, storage, sharing, data search and discovery, retrieval, and usage. Furthermore, we prototypically implement it using a real dataset with creep data of a single-crystal CMSX-6 Ni-based superalloy. The presented implementation is traceable and permanently accessible through open repositories. The individual elements considered in the framework ensure the functionality and usability of the data and, thus, the adherence to the FAIR principles. In conjunction with this, we present a definition for reference data of materials. Our definition underlines particularly the importance of a comprehensive documentation, e.g., on material provenance, data processing procedures, and the software and hardware used, including software-specific input parameters, as these details enable data users or independent parties to assess the quality of the datasets and to reuse and reproduce the results. Reference data that is managed according to the proposed framework can be used to advance knowledge in the materials science and engineering domain, e.g., by identifying new process-structure-property relations. KW - Referenzdaten KW - NFDI-MatWerk KW - Data schema KW - Research Data Management KW - Reference Data PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-625047 DO - https://doi.org/10.1016/j.actamat.2025.120735 VL - 286 SP - 1 EP - 15 PB - Elsevier Inc. AN - OPUS4-62504 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Mai, H. L. A1 - Cui, X.-Y, A1 - Hickel, Tilmann A1 - Neugebauer, J. A1 - Ringer, S. P. T1 - A high-throughput ab initio study of elemental segregation and cohesion at ferritic-iron grain boundaries N2 - Segregation of alloying elements and impurities at grain boundaries (GBs) critically influences material behaviour by affecting cohesion. In this study, we present an ab initio high-throughput evaluation of segregation energies and cohesive effects for all elements up to Z=92 in the periodic table (Z = 1–92, H–U) across the substitutional sites in six model ferritic iron GBs using density functional theory (DFT). From these data, we construct comprehensive elemental maps for solute segregation tendencies and cohesion at GBs, providing guidance for segregation engineering. We systematically assess the cohesive effects of different elements in all segregating positions along multiple fracture paths with a quantum-chemistry bond-order method as well as a modified Rice–Thomson–Wang theory of interfacial cohesion. The effects of segregants on the cohesion of GBs are shown to vary drastically as a function of site character, and hence their induced cohesive effects must be considered as a thermodynamic average over the spectral energy distribution. Thus, models that overlook these aspects may fail to accurately predict the impacts of varying alloying concentrations, thermal processing conditions, or GB types. The insights presented here, along with our accompanying dataset, are expected to advance our understanding of GB segregation in steels and other materials. KW - Defects PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-638397 DO - https://doi.org/10.1016/j.actamat.2025.121288 SN - 1359-6454 VL - 297 SP - 1 EP - 16 PB - Elsevier Inc. AN - OPUS4-63839 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Janssen, Jan A1 - George, Janine A1 - Geiger, Julian A1 - Bercx, Marnik A1 - Wang, Xing A1 - Ertural, Christina A1 - Schaarschmidt, Jörg A1 - Ganose, Alexander Miguel A1 - Pizzi, Giovanni A1 - Hickel, Tilmann A1 - Neugebauer, Jörg T1 - A Python workflow definition for computational materials design N2 - Numerous Workflow Management Systems (WfMS) have been developed in the field of computational materials science with different workflow formats, hindering interoperability and reproducibility of workflows in the field. To address this challenge, we introduce here the Python Workflow Definition (PWD) as a workflow exchange format to share workflows between Python-based WfMS, currently AiiDA, jobflow, and pyiron. This development is motivated by the similarity of these three Python-based WfMS, that represent the different workflow steps and data transferred between them as nodes and edges in a graph. With the PWD, we aim at fostering the interoperability and reproducibility between the different WfMS in the context of Findable, Accessible, Interoperable, Reusable (FAIR) workflows. To separate the scientific from the technical complexity, the PWD consists of three components: (1) a conda environment that specifies the software dependencies, (2) a Python module that contains the Python functions represented as nodes in the workflow graph, and (3) a workflow graph stored in the JavaScript Object Notation (JSON). The first version of the PWD supports directed acyclic graph (DAG)-based workflows. Thus, any DAG-based workflow defined in one of the three WfMS can be exported to the PWD and afterwards imported from the PWD to one of the other WfMS. After the import, the input parameters of the workflow can be adjusted and computing resources can be assigned to the workflow, before it is executed with the selected WfMS. This import from and export to the PWD is enabled by the PWD Python library that implements the PWD in AiiDA, jobflow, and pyiron. KW - Worklows KW - FAIR Workflows KW - Automation KW - Materials Acceleration Platforms PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-643325 DO - https://doi.org/10.1039/D5DD00231A SN - 2635-098X SP - 1 EP - 14 PB - Royal Society of Chemistry (RSC) AN - OPUS4-64332 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Roters, F. A1 - Aslam, A. A1 - Bai, Y. A1 - Büschelberger, M. A1 - Bulert, K. A1 - Butz, A. A1 - Hickel, Tilmann A1 - Jogi, T. A1 - Klitschke, S. A1 - Martin, M. A1 - Meyer, L.-P. A1 - Morand, L. A1 - Nahshon, Y. A1 - Radtke, N. A1 - Saikia, Ujjal A1 - Trondl, A. A1 - Wessel, A. A1 - Zierep, P. A1 - Helm, D. T1 - StahlDigital: Ontology-Based Workflows for the Steel Industry N2 - The innovative strength of the steel industry is based on the mastery of microstructure–property relationships. Digital workflows can largely contribute to this aim by making the complexity of workflows reproducible and their execution user independent. In this work, the tools and workflows developed in the project StahlDigital as part of the German MaterialDigital initiative are presented and application examples are provided. A steel ontology builds the foundation for data collection and storage as well as for the semantic description of experimental and simulation data processing workflows. A dataspace powered by the Dataspace Management System (DSMS) digitally represents such workflows and manages data along them in a Findable, Accessible, Interoperable, Reusable manner aiming to derive new knowledge. Experimental data processed via DSMS can be further evaluated and used as input for simulation workflows. The simulations included in such workflows are run by the workflow system pyiron, which has been semantically extended in StahlDigital for this purpose. KW - Steel KW - Rolling KW - Multiscale simulation KW - Ontology KW - Workflow PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-627187 DO - https://doi.org/10.1002/adem.202402148 SN - 1527-2648 SP - 1 EP - 13 PB - Wiley VHC-Verlag AN - OPUS4-62718 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Hickel, Tilmann A1 - Waske, Anja A1 - Tehranchi, Ali A1 - Bhattacharya, Biswajit A1 - Stawski, Tomasz M. A1 - Fellinger, Tim-Patrick A1 - Mehmood, Asad A1 - Witt, Julia A1 - Ozcan, Ozlem A1 - Guilherme Buzanich, Ana A1 - Kumar, Sourabh A1 - Mishra, Rajesh Kumar A1 - Holzer, Marco A1 - Stucchi de Camargo, Andrea Simone A1 - Agudo Jácome, Leonardo A1 - Manzoni, Anna A1 - Fantin, Andrea A1 - John, Elisabeth A1 - Hodoroaba, Vasile-Dan A1 - Bührig, Sophia A1 - Murugan, Jegatheesan A1 - Marschall, Niklas A1 - George, Janine A1 - Darvishi Kamachali, Reza A1 - Maaß, Robert A1 - Emmerling, Franziska T1 - Chemically complex materials enable sustainable high-performance materials N2 - Chemically complex materials (CCMats) 􀀀 including high-entropy alloys, oxides, and related multi-principal element systems 􀀀 offer a paradigm shift in materials design by leveraging chemical diversity to simultaneously optimize functional, structural, and sustainability criteria. The vastness of the compositional and structural space in CCMats propels the field into an expanding exploratory state. To reconcile functional and structural performance across this immense parameter space remains an open challenge. This Perspective evaluates the opportunities and challenges associated with harnessing chemical complexity across a broad spectrum of applications, such as hydrogen storage, ionic conductors, catalysis, magnetics, dielectrics, semiconductors, optical materials, and multifunctional structural systems. It is delineated how three central design strategies: targeted substitution (SUB), defect engineering (DEF), and diversity management (DIV) enable the reconciliation of high functional performance with long-term structural stability and environmental responsibility. Advances in computational thermodynamics, microstructure simulations, machine learning, and multimodal characterization are accelerating the exploration and optimization of CCMats, while robust data infrastructures and automated synthesis workflows are emerging as essential tools for navigating their complex compositional space. By fostering cross-disciplinary knowledge transfer and embracing data-driven design, CCMats are poised to deliver next-generation materials solutions that address urgent technological, energy, and environmental demands. KW - Chemically complex materials KW - Structural stability KW - Functional performance KW - Design strategies KW - Sustainability PY - 2026 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655598 UR - https://www.sciencedirect.com/science/article/pii/S1359028626000033?via%3Dihub DO - https://doi.org/10.1016/j.cossms.2026.101256 SN - 1359-0286 VL - 42 SP - 1 EP - 26 PB - Elsevier Ltd. CY - Amsterdam AN - OPUS4-65559 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Kumar, Sourabh A1 - Hickel, Tilmann T1 - Grain Boundary Transformation Induced by Boron Segregation N2 - Boron enhances the hardenability of low-alloyed steel and reduces embrittlement at low temperatures, at parts-per-million concentration levels. Ist effectiveness arises from segregation to grain boundaries (GBs)-planar defects- between crystals-yet atomic-scale evidence remains limited.We addressed this gap by synthesizing GBs with controllable geometry and orientation, enabling reproducible comparison with and without boron segregation. Differential phase-contrast imaging directly reveals boron at iron GBs, and in-situ TEM heating (20 °C to 800 °C) allows us to track the dynamic evolution of GB structures. We found that boron segregation induces local structural changes and triggers GB phase transformations, as corroborated by calculated GB defect phase diagrams spanning broad ranges of carbon and boron content. Our findings not only bridge a gap in understanding the interplay between GB structure and chemistry but also lay the groundwork for targeted design and passivation strategies in steel, potentially transforming its resistance to hydrogen embrittlement, corrosion, and mechanical failure. KW - Steel KW - Defect Phases KW - Grain Boundary PY - 2025 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-655812 DO - https://doi.org/10.1038/s41467-025-62264-1 VL - 16 SP - 1 EP - 14 PB - Nature Communications AN - OPUS4-65581 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER -