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 - CONF A1 - Hickel, Tilmann T1 - Defect-hydrogen interaction in Al alloys: Challenges and benefits revealed by ab initio calculations N2 - Climate change motivates the search for light-weight materials for transportation and energy storage solutions. As one of the challenges, the deleterious effect of hydrogen on the mechanical properties of metallic alloys is known to reduce the applicability of metallic alloys, motivating the characterization and simulation of hydrogen-defect interactions in these materials. In this work, the interaction of hydrogen with planar defects in aluminium has been investigated by means of ab initio simulations. On the one hand, two distinct types of GBs have been considered – the Σ11(113) [011] with a close-packed interface structure and the Σ5(210) [001] with a more open interface structure – in order to reveal the mechanisms governing the H segregation energetics. The investigations are afterwards extended to the impact of solutes in the Al alloy. Two scenarios are compared: Their segregation to the grain boundaries and their binding in precipitates. We therewith gained insights into the role of the solute size on the structural and chemical embrittlement in absence and presence of hydrogen. A thermodynamic assessment of the impact of solutes onto H chemisorption in the interfacial vicinity is provided by performing a high-throughput analysis for potential alloying candidates. The identified trends of the solute-H interactions are used to examine the relative importance of changes in hydrogen enhanced decohesion as a thermodynamic effect. On the other hand, the interaction of hydrogen with defects can be beneficial for the formation of metal hydrides. To enhance the formation and stability of such often highly volatile hydrides we have consider a novel concept: tailoring and employing the negative pressure of microstructural and structural defects to enhance H solubility and thus hydride formation. Using systematic ab initio and atomistic simulations, we demonstrate that an enhancement in the formation of hydrides at the negatively pressurized crack tip region 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. Based on these insights we derive strategies for enhancing the capability of metals as H-storage materials. T2 - International hydrogen conference 2023 CY - Park City, Utah, USA DA - 17.09.2023 KW - Ab initio simulations KW - Hydrogen embrittlement KW - Grain boundaries KW - Hydride formation PY - 2023 AN - OPUS4-58851 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - CONF A1 - Hickel, Tilmann T1 - Hydrogen enhances cross-slip of dislocations in the vicinity of grain boundaries N2 - Extensive experimental observations indicate the presence of nano-voids and the increase of free volume along 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. To this end, the interaction of the screw dislocations with a variety of symmetric tilt grain boundaries in H-charged and H-free bicrystalline nickel specimens is examined. The presence of segregated hydrogen 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 crossslip of dislocations facilitates the formation of jogs. These jogs can form vacancies during the glide process. This mechanism shows nano-scale evidence of enhanced vacancy formation and subsequent increase in the free volume along the grain boundaries in the presence of H. This increase of the free-volume along the grain boundary dmaages the material and induce further embrittlement in addition to the direct effect of hydrogen in decreasing the fracture energy. T2 - International hydrogen conference 2023 CY - Park City, Utah, USA DA - 17.09.2023 KW - Atomistic model KW - Hydrogen embrittlement KW - Dislocation cross slip KW - Hydrogen enhanced vacancy formation PY - 2023 AN - OPUS4-58850 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 - Sreekala, L. A1 - Dey, P. A1 - Hickel, Tilmann A1 - Neugebauer, J. T1 - Unveiling nonmonotonic chemical trends in the solubility of H in complex Fe-Cr-Mn carbides by means of ab initio based approaches N2 - The microstructure of advanced high-strength steels often shows a sensitive dependence on alloying. For example, adding Cr to improve the corrosion resistance of medium-Mn steels also enhances the precipitation of carbides. The current study focuses on the behavior of H in such complex multicomponent carbides by employing different methodological strategies. We systematically analyze the impact of Cr, Mn, and Fe using density functional theory (DFT) for two prototype precipitate phases, M3C and M23C6, where M represents the metal sublattice. Our results show that the addition of these alloying elements yields strong nonmonotonic chemical trends for the H solubility. We identify magnetovolume effects as the origin for this behavior, which depend on the considered system, the sites occupied by H, and short- vs long-range interactions between H and the alloying elements. We further show that the H solubility is directly correlated with the occupation of its nearest-neighbor shells by Cr and Mn. Based on these insights, DFT data from H containing binary-metal carbides are used to design a ridge regression based model that predicts the solubility of H in the ternary-metal carbides (Fe-Cr-Mn-C). KW - Hydrogen KW - High-strength steel KW - Carbide KW - Ab initio KW - Complexity PY - 2022 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-542271 DO - https://doi.org/10.1103/PhysRevMaterials.6.014403 SN - 2475-9953 VL - 6 IS - 1 SP - 1 EP - 14 PB - American Physical Society (APS) CY - College Park, MD AN - OPUS4-54227 LA - eng AD - Bundesanstalt fuer Materialforschung und -pruefung (BAM), Berlin, Germany ER - TY - JOUR A1 - Chakraborty, P. A1 - Mouton, I. A1 - Gault, B. A1 - Tehranchi, Ali A1 - Neugebauer, J. A1 - Hickel, Tilmann T1 - Effect of Sn on stacking fault energies in zirconium and its hydrides N2 - Hydrogen embrittlement in Zr-alloy fuel cladding is a primary safety concern for water-based nuclear reactors. Here we investigated the stabilization of planar defects within the forming hydrides by Sn, the primary alloying element of Zircaloy-4 used in the cladding. In order to explain the formation of hydrides and planar defects observed in our experiments, we performed atomic-scale ab initio calculations focusing on the solute interactions with generalized stacking faults in hcp 𝛼-Zr and fcc zirconium hydrides. Our calculations showed that an increase in Sn concentration leads to a stabilization of stacking faults in both the 𝛼-Zr and hydride phases. However, the solution enthalpy of Sn is lower in the 𝛼-Zr as compared to the other hydride phases, indicative of two competing processes of Sn depletion/enrichment at the Zr hydride/matrix interface. This is corroborated by experimental findings, where Sn is less soluble in hydrides and is mostly found trapped at interfaces and planar defects, indicative of stacking faults inside the hydride phases. Our systematic investigation enables us to understand the presence and distribution of solutes in the hydride phases, which provides a deeper insight into the microstructural evolution of such alloy's properties during its service lifetime. KW - Defects KW - First-principles calculations KW - Interface and surface thermodynamics KW - Microstructure KW - Hydrides KW - Structural properties PY - 2024 UR - https://nbn-resolving.org/urn:nbn:de:kobv:b43-618044 DO - https://doi.org/10.1103/PhysRevMaterials.8.033605 SN - 2475-9953 VL - 8 IS - 3 SP - 1 EP - 9 PB - APS AN - OPUS4-61804 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 -