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npj Computational Materials 2022年第1期8卷 107-112页

作者： Ivan Novikov Blazej Grabowski fritz körmann Alexander Shapeev Skolkovo Institute of Science and Technology Skolkovo Innovation CenterNobel St.3Moscow143026Russia Institute for Materials Science University of StuttgartPfaffenwaldring 5570569StuttgartGermany Computational Materials Design Max-Planck-Institut für Eisenforschung GmbHD-40237DüsseldorfGermany Materials Science and Engineering Delft University of Technology2628 CDDelftThe Netherlands

We present the magnetic Moment Tensor Potentials(mMTPs),a class of machine-learning interatomic potentials,accurately reproducing both vibrational and magnetic degrees of freedom as provided,e.g.,from first-principles calculations.The accuracy is achieved by a two-step minimization scheme that coarse-grains the atomic and the spin space.The performance of the mMTPs is demonstrated for the prototype magnetic system bcc iron,with applications to phonon calculations for different magnetic states,and molecular-dynamics simulations with fluctuating magnetic moments.

关键词： magnetic fluctuating states

Exploration of chromene-based BioAIEgens

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National Science Review 2024年第3期11卷 47-48页

作者： fritz E.kühn Department of Chemistry&Catalysis Research Center School of Natural Sciences Technical University of Munich

Photoemission efficiency is usually higher in solution than in solid state.Some compounds however, display a reverse behavior. Such a behavior is called aggregation-induced emission(AIE).

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Effect of solid-solution strengthening on deformation mechanisms and strain hardening in medium-entropy V_(1-x)Cr_(x)CoNi alloys

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Journal of Materials Science & Technology 2022年第13期108卷 270-280页

作者： Hyun Chung Dae Woong kim Woo Jin Cho Heung Nam Han Yuji Ikeda Shoji Ishibashi fritz körmann Seok Su Sohn Department of Materials Science and Engineering Korea UniversitySeoul 02841South Korea Center for High Entropy Alloys Pohang University of Science and TechnologyPohang 37673South Korea Department of Materials Science and Engineering and Research Institute of Advanced Materials Seoul National UniversitySeoul 08826South Korea Institute for Materials Science University of StuttgartPfaffenwaldring 55Stuttgart 70569Germany Computational Materials Design Max-Planck-Institut für Eisenforschung GmbHMax-Planck-Strabe 1Düsseldorf 40237Germany Research Center for Computational Design of Advanced Functional Materials(CD-Fmat) National Institute of Advanced Industrial Science and Technology(AIST)TsukubaIbaraki 305-8568Japan Department of Materials Science and Engineering Delft University of TechnologyMekelweg2Delft 2628 CDthe Netherlands

High-and medium-entropy alloys(HEAs and MEAs)possess high solid-solution strength.Numerous investigations have been conducted on its impact on yield strength,however,there are limited reports regarding the relation between solid-solution strengthening and strain-hardening rate.In addition,no attempt has been made to account for the dislocation-mediated plasticity;most works focused on twinning-or transformation-induced plasticity(TWIP or TRIP).In this work we reveal the role of solidsolution strengthening on the strain-hardening rate via systematically investigating evolutions of deformation structures by controlling the Cr/V ratio in prototypical V_(1-x)Cr_(x)CoNi alloys.Comparing the TWIP of CrCoNi with the dislocation slip of V_(0.4)Cr_(0.6)CoNi,the hardening rate of CrCoNi was superior to slip-band refinements of V_(0.4)Cr_(0.6)CoNi due to the dynamic Hall-Petch effect.However,as V content increased further to V_(0.7)Cr_(0.3)CoNi and VCoNi,their rate of slip-band refinement in V_(0.7)Cr_(0.3)CoNi and VCoNi with high solid-solution strength surpassed that of CrCoNi.Although it is generally accepted in conventional alloys that deformation twinning results in a higher strain-hardening rate than dislocation-mediated plasticity,we observed that the latter can be predominant in the former under an activated huge solid-solution strengthening effect.The high solid-solution strength lowered the cross-slip activation and consequently retarded the dislocation rearrangement rate,i.e.,the dynamic recovery.This delay in the hardening rate decrease,therefore,increased the strain-hardening rate,results in an overall higher strain-hardening rate of V-rich alloys.

关键词： Medium-entropy alloy Tensile property Solid-solution strength Strain-hardening rate Stacking fault energy

Modern internet search analytics and thyroidectomy:What are patients asking?

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World Journal of Otorhinolaryngology-Head and Neck Surgery 2024年第1期10卷 49-58页

作者： Neeraj Suresh Christian fritz Emma De Ravin karthik Rajasekaran Department of Otorhinolaryngology–Head&Neck Surgery University of PennsylvaniaPhiladelphiaPennsylvaniaUSA Perelman School of Medicine at the University of Pennsylvania PhiladelphiaPennsylvaniaUSA Leonard Davis Institute of Health Economics University of PennsylvaniaPhiladelphiaPennsylvaniaUSA

Objectives:Thyroidectomy is among the most commonly performed head and neck surgeries,however,limited existing information is available on topics of interest and concern to patients.Study Design:Observational.Setting:Online.Methods:A search engine optimization tool was utilized to extract metadata on Google‐suggested questions that“People Also Ask”(PAA)pertaining to“thyroidectomy”and“thyroid surgery.”These questions were categorized by Rothwell criteria and topics of interest.The Journal of the American Medical Association(JAMA)benchmark criteria enabled quality assessment.Results:A total of 250 PAA questions were analyzed.Future‐oriented PAA questions describing what to expect during and after the surgery on topics such as postoperative management,risks or complications of surgery,and technical details were significantly less popular among the“thyroid surgery”group(Pkely to educate them on what to expect during and after surgery,as compared to patients with higher health literacy who search with the term“thyroidectomy.”This suggests that the content of PAA questions differs based on the presumed health literacy of the internet user.

关键词： information quality online health education search analytics thyroid surgery thyroidectomy

Impact of lattice relaxations on phase transitions in a high-entropy alloy studied by machine-learning potentials

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npj Computational Materials 2019年第1期5卷 670-676页

作者： Tatiana kostiuchenko fritz körmann Jörg Neugebauer Alexander Shapeev Skolkovo Institute of Science and Technology Skolkovo Innovation CenterNobel St.3Moscow 143026Russia Computational Materials Design Max-Planck-Institut für Eisenforschung GmbH40237 DüsseldorfGermany Materials Science and Engineering Delft University of Technology2628 CD DelftThe Netherlands

Recently,high-entropy alloys(HEAs)have attracted wide attention due to their extraordinary materials properties.A main challenge in identifying new HEAs is the lack of efficient approaches for exploring their huge compositional space.Ab initio calculations have emerged as a powerful approach that complements experiment.However,for multicomponent alloys existing approaches suffer from the chemical complexity involved.In this work we propose a method for studying HEAs computationally.Our approach is based on the application of machine-learning potentials based on ab initio data in combination with Monte Carlo simulations.The high efficiency and performance of the approach are demonstrated on the prototype bcc NbMoTaW HEA.The approach is employed to study phase stability,phase transitions,and chemical short-range order.The importance of including local relaxation effects is revealed:they significantly stabilize single-phase formation of bcc NbMoTaW down to room temperature.Finally,a so-far unknown mechanism that drives chemical order due to atomic relaxation at ambient temperatures is discovered.

关键词： alloy relaxation entropy

Chemically induced local lattice distortions versus structural phase transformations in compositionally complex alloys

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npj Computational Materials 2021年第1期7卷 312-319页

作者： Yuji Ikeda konstantin Gubaev Jörg Neugebauer Blazej Grabowski fritz körmann Institute for Materials Science University of StuttgartStuttgartGermany Max-Planck-Institut für Eisenforschung GmbH DüsseldorfGermany Department of Materials Science and Engineering Delft University of TechnologyDelftThe Netherlands

Recent experiments show that the chemical composition of body-centered cubic(bcc)refractory high entropy alloys(HEAs)can be tuned to enable transformation-induced plasticity(TRIP),which significantly improves the ductility of these alloys.This calls for an accurate and efficient method to map the structural stability as a function of composition.A key challenge for atomistic simulations is to separate the structural transformation between the bcc and theωphases from the intrinsic local lattice distortions in such chemically disordered alloys.To solve this issue,we develop a method that utilizes a symmetry analysis to detect differences in the crystal structures.Utilizing this method in combination with ab initio calculations,we demonstrate that local lattice distortions largely affect the phase stability of Ti–Zr–Hf–Ta and Ti–Zr–Nb–Hf–Ta HEAs.If relaxation effects are properly taken into account,the predicted compositions near the bcc–hcp energetic equilibrium are close to the experimental compositions,for which good strength and ductility due to the TRIP effect are observed.

关键词： alloys ductility distortion

Temperature-dependent phonon spectra of magnetic random solid solutions

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npj Computational Materials 2018年第1期4卷 606-612页

作者： Yuji Ikeda fritz körmann Biswanath Dutta Abel Carreras Atsuto Seko Jörg Neugebauer Isao Tanaka Department of Materials Science and Engineering Kyoto UniversityKyoto 606-8501Japan Center for Elements Strategy Initiative for Structural Materials(ESISM) Kyoto UniversityKyoto 606-8501Japan Max-Planck-Institut für Eisenforschung GmbH D-40237 DüsseldorfGermany Department of Materials Science and Engineering Delft University of TechnologyMekelweg 22628 CD DelftNetherlands Precursory Research for Embryonic Science and Technology(PRESTO) Japan Science and Technology Agency(JST)Kawaguchi 332-0012Japan Center for Materials Research by Information Integration National Institute for Materials Science(NIMS)Tsukuba 305-0047Japan Nanostructures Research Laboratory Japan Fine Ceramics CenterNagoya 456-8587Japan

A first-principles-based computational tool for simulating phonons of magnetic random solid solutions including thermal magnetic fluctuations is developed.The method takes fluctuations of force constants due to magnetic excitations as well as due to chemical disorder into account.The developed approach correctly predicts the experimentally observed unusual phonon hardening of a transverse acoustic mode in Fe–Pd an Fe–Pt Invar alloys with increasing temperature.This peculiar behavior,which cannot be explained within a conventional harmonic picture,turns out to be a consequence of thermal magnetic fluctuations.The proposed methodology can be straightforwardly applied to a wide range of materials to reveal new insights into physical behaviors and to design materials through computation,which were not accessible so far.

关键词： magnetic random phonon

A simulation study on spatial and time resolution for a cost-effective positron emission particle tracking system

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Particuology 2024年第5期88卷 312-322页

作者： Josephine Oppotsch Matthias Steinke Miriam Fritsch fritz-Herbert Heinsius Thomas Held Nikoline Hilse Viktor Scherer Ulrich Wiedner Ruhr-Universität Bochum Institut für Experimentalphysik I44801 BochumGermany Ruhr-Universität Bochum Lehrstuhl für Energieanlagen und Energieprozesstechnik44801 BochumGermany

This work is the second part of a simulation study investigating the processing of densely packed and moving granular assemblies by positron emission particle tracking (PEPT).Since medical positron emission tomography (PET) scanners commonly used for PEPT are very expensive,a PET-like detector system based on cost-effective organic plastic scintillator bars is being developed and tested for its capabilities.In this context,the spatial resolution of a resting positron source,a source moving on a freely designed model path,and a particle motion given by a discrete element method (DEM) simulation is studied using Monte Carlo simulations and the software toolkit Geant4.This not only extended the simulation and reconstruction to a moving source but also significantly improved the spatial resolution compared to previous work by adding oversampling and iteration to the reconstruction algorithm.Furthermore,in the case of a source following a trajectory developed from DEM simulations,a very good resolution of about 1 mm in all three directions and an average 3D deviation between simulated and reconstructed events of 2.3 mm could be determined.Thus,the resolution for realistic particle motion within the generic grate system (which is the test rig for further experimental studies) is well below the smallest particle size.The simulation of the dependence of the reconstruction accuracy on tracer particle location revealed a nearly constant efficiency within the entire detector system,which demonstrates that boundary effects can be neglected.

关键词： Positron emission particle tracking Monte Carlo method Time-of-flight Plastic scintillators Silicon photomultipliers(SiPMs)

A simulation study for a cost-effective PET-like detector system intended to track particles in granular assemblies

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Particuology 2024年第1期84卷 117-125页

作者： Josephine Oppotsch Antonios Athanassiadis Miriam Fritsch fritz-Herbert Heinsius Thomas Held Nikoline Hilse Viktor Scherer Matthias Steinke Ulrich Wiedner Ruhr-Universität Bochum Institut für Experimentalphysik I44801 BochumGermany Ruhr-Universität Bochum Lehrstuhl für Energieanlagen und Energieprozesstechnik44801 BochumGermany

Since many industrial applications rely on the processing of densely packed and moving granular ma-terial,obtaining bulk internal information on the particle movement inside the reactors is of great importance.Such information can be delivered by Positron Emission Particle Tracking(PEPT).By marking pellets with a positron-emitting radioisotope,the position of these tracer particles can be determined via the time-of-flight differences of the emitted gamma-ray pairs.The current paper proposes a PET-like detector system based on cost-effective organic plastic scintillators instead of the more common but expensive inorganic scintillators.This system is currently under construction and was tested for its resolution and efficiency in this simulation study.Using Monte Carlo simulations and the software toolkit Geant4,three different geometries(an empty glass box,a generic grate system,and a cubic box of 1 m3 completely filled with pellets)were investigated,leading to a spatial resolution in the millimeter range and an efficiency,defined as the ratio of reconstructed decay locations to simulated decays,of 2.7%,1.4%,and 0.3%.

关键词： Positron emission particle tracking Geant4 Monte Carlo method Time-of-flight Plastic scintillators Silicon photomultipliers(SiPMs)

Ab initio vibrational free energies including anharmonicity for multicomponent alloys

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npj Computational Materials 2019年第1期5卷 454-459页

作者： Blazej Grabowski Yuji Ikeda Prashanth Srinivasan fritz körmann Christoph Freysoldt Andrew Ian Duff Alexander Shapeev Jörg Neugebauer Institute of Materials Science University of StuttgartPfaffenwaldring 5570569 StuttgartGermany Department for Computational Materials Design Max-Planck-Institut für Eisenforschung GmbHMax-Planck-Str.140237 DüsseldorfGermany Department of Materials Science and Engineering Delft University of TechnologyMekelweg 22628 CD DelftNetherlands Scientific Computing Department STFC Daresbury LaboratoryHartree CentreWarringtonUK Skolkovo Institute of Science and Technology Skolkovo Innovation CenterNobel St.3Moscow 143026Russia

The unique and unanticipated properties of multiple principal component alloys have reinvigorated the field of alloy design and drawn strong interest across scientific disciplines.The vast compositional parameter space makes these alloys a unique area of exploration by means of computational design.However,as of now a method to compute efficiently,yet with high accuracy the thermodynamic properties of such alloys has been missing.One of the underlying reasons is the lack of accurate and efficient approaches to compute vibrational free energies—including anharmonicity—for these chemically complex multicomponent alloys.In this work,a density-functional-theory based approach to overcome this issue is developed based on a combination of thermodynamic integration and a machine-learning potential.We demonstrate the performance of the approach by computing the anharmonic free energy of the prototypical five-component VNbMoTaW refractory high entropy alloy.

关键词： alloys alloy thermodynamic