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High-accuracy thermodynamic properties to the melting point from ab initio calculations aided by machine-learning potentials

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npj Computational Materials 2023年第1期9卷 2310-2321页

作者： Jong Hyun Jung Prashanth Srinivasan Axel Forslund blazej Grabowski Institute for Materials Science University of StuttgartPfaffenwaldring 5570569 StuttgartGermany

Accurate prediction of thermodynamic properties requires an extremely accurate representation of the free-energy *** are twofold—first,the inclusion of the relevant finite-temperature mechanisms,and second,a dense volume–temperature grid on which the calculations are performed.A systematic workflow for such calculations requires computational efficiency and reliability,and has not been available within an ab initio framework so ***,we elucidate such a framework involving direct upsampling,thermodynamic integration and machine-learning potentials,allowing us to incorporate,in particular,the full effect of anharmonic *** improved methodology has a five-times speed-up compared to state-of-the-art *** calculate equilibrium thermodynamic properties up to the melting point for bcc Nb,magnetic fcc Ni,fcc Al,and hcp Mg,and find remarkable agreement with experimental data.A strong impact of anharmonicity is observed specifically for *** introduced procedure paves the way for the development of ab initio thermodynamic databases.

关键词： harmonic point prediction

Magnetic Moment Tensor Potentials for collinear spin-polarized materials reproduce different magnetic states of bcc Fe

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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 *** accuracy is achieved by a two-step minimization scheme that coarse-grains the atomic and the spin *** 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

A machine learning approach to model solute grain boundary segregation

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npj Computational Materials 2018年第1期4卷 130-137页

作者： Liam Huber Raheleh Hadian blazej Grabowski Jörg Neugebauer Max-Planck-Institut für Eisenforschung GmbH D-40237 DüsseldorfGermany

Even minute amounts of one solute atom per one million bulk atoms may give rise to qualitative changes in the mechanical response and fracture resistance of modern structural *** changes are commonly related to enrichment by several orders of magnitude of the solutes at structural defects in the host *** underlying concept—segregation—is thus fundamental in materials *** include it in modern strategies of materials design,accurate and realistic computational modelling tools are ***,the enormous number of defect configurations as well as sites solutes can occupy requires models which rely on severe *** the present study we combine a high-throughput study containing more than 1 million data points with machine learning to derive a computationally highly efficient framework which opens the opportunity to model this important mechanism on a routine basis.

关键词： grain solute boundary

A Raman laser system for multi-wavelength satellite laser ranging

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Science China(Physics,Mechanics & Astronomy) 2004年第6期47卷 737-743页

作者： K.Hamal I.Prochazka J.blazej Czech Technical University in Prague CzechCzech Technical University in PragueCzechCzech Technical University in PragueCzech

In order to develop a laser system for multi-wavelength satellite laser ranging, the joint group of the Shanghai Astronomical Observatory and the Czech Technical University has studied the conversion efficiency of the Raman-shifting beam and its spatial characteristics. We adopted a 0.53 μm laser with pulse width of 35 ps and peak energy of 35 mJ, the second harmonic of a Nd:YAG actively and passively mode-locked laser, to pump a one-meter-long Raman tube which is full of H2 with high pressure at the Prague-based laboratory. We get the first Stokes laser (0.68 μm): 7 mJ (single pulse) with beam divergence of 40″ (arcsecond) and spatial wobbling of less than 4″; and the first anti-Stokes laser (0.43 μm): 2 mJ (single pulse) with divergence of 56″ and spatial wobbling of less than 4″. The emitting beam from the Raman cell also includes 0.53 μm: 10 mJ (single pulse) with divergence of 40″ and spatial wobbling of less than 7″. According to the radar link equation and based on the above obtained multi-wavelength’s energy, we can estimate the detection probabilities for three colors respectively. It is shown by the result that the developed multi-wavelength Raman laser system has the capability of satellite ranging. The Raman laser system will be installed at the laser station in Shanghai Astronomical Observatory to research the multi-wavelength satellite laser ranging.

关键词： multi-wavelength satellite laser ranging, Raman laser, atmosphere correction, detection probability.

THE ENERGY FUNCTION WITH RESPECT TO THE ZEROS OF THE EXCEPTIONAL HERMITE POLYNOMIALS

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Acta Mathematica Scientia 2017年第5期37卷 1483-1496页

作者： Agota P.horvath Department of Analysis Budapest University of Technology and EconomicsEgry J.u 1-3BudapestHungary

We examine the energy function with respect to the zeros of exceptional Hermite polynomials. The localization of the eigenvalues of the Hessian is given in the general *** some special arrangements we have a more precise result on the behavior of the energy function. Finally we investigate the energy function with respect to the regular zeros of the exceptional Hermite polynomials.

关键词： exceptional Hermite polynomials system of minimal energy energy function partitioned matrices

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 *** 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 *** solve this issue,we develop a method that utilizes a symmetry analysis to detect differences in the crystal *** 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 *** 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

Phonon broadening in high entropy alloys

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npj Computational Materials 2017年第1期3卷 154-162页

作者： Fritz Kormann Yuji Ikeda blazej Grabowski Marcel H.F.Sluiter Materials Science and Engineering Delft University of Technology2628 CD DelftThe Netherlands Center for Elements Strategy Initiative for Structural Materials Kyoto UniversityKyoto 606-8501Japan Computationals Materials Design Max-Planck-Institut fur Eisenforschung GmbH40237 DusseldorfGermany

Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation hightemperature *** high temperatures,materials properties are strongly affected by lattice vibrations(phonons).Phonons critically influence thermal stability,thermodynamic and elastic properties,as well as thermal *** contrast to perfect crystals and ordered alloys,the inherently present mass and force constant fluctuations in multi-component random alloys(high entropy alloys)can induce significant phonon scattering and *** their importance,phonon scattering and broadening have so far only scarcely been investigated for high entropy *** tackle this challenge from a theoretical perspective and employ ab initio calculations to systematically study the impact of force constant and mass fluctuations on the phonon spectral functions of 12 body-centered cubic random alloys,from binaries up to 5-component high entropy alloys,addressing the key question of how chemical complexity impacts *** find that it is crucial to include both mass and force constant *** one or the other is neglected,qualitatively wrong results can be obtained such as artificial phonon band *** analyze how the results obtained for the phonons translate into thermodynamically integrated quantities,specifically the vibrational *** in the vibrational entropy with increasing the number of elements can be as large as changes in the configurational entropy and are thus important for phase stability *** set of studied alloys includes MoTa,MoTaNb,MoTaNbW,MoTaNbWV,VW,VWNb,VWTa,VWNbTa,VTaNbTi,VWNbTaTi,HfZrNb,HfMoTaTiZr.

关键词： alloys entropy high

Robust Fault-tolerant Iterative Learning Control for Discrete Systems via Linear Repetitive Processes Theory

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International Journal of Automation and computing 2015年第3期12卷 254-265页

作者： Jian Ding blazej Cichy Krzysztof Galkowski Eric Rogers Hui-Zhong Yang Key Laboratory of Advanced Process Control for Light Industry (Ministry of Education) Jiangnan University Institute of Control and Computation Engineering University of Zielona Gora Department of Electronics and Computer Science University of Southampton

This paper addresses the problem of robust iterative learning control design for a class of uncertain multiple-input multipleoutput discrete linear systems with actuator faults. The stability theory for linear repetitive processes is used to develop formulas for gain matrices design, together with convergent conditions in terms of linear matrix inequalities. An extension to deal with model uncertainty of the polytopic or norm bounded form is also developed and an illustrative example is given.

关键词： Iterative learning control linear repetitive processes linear matrix inequality(LMI) discrete linear systems fault-tolerant cont

Performance of two complementary machine-learned potentials in modelling chemically complex systems

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npj Computational Materials 2023年第1期9卷 1008-1022页

作者： Konstantin Gubaev Viktor Zaverkin Prashanth Srinivasan Andrew Ian Duff Johannes Kästner blazej Grabowski Institute for Materials Science University of StuttgartPfaffenwaldring 5570569 StuttgartGermany Institute for Theoretical Chemistry University of StuttgartPfaffenwaldring 5570569 StuttgartGermany Scientific Computing Department STFC Daresbury LaboratoryWarrington WA44ADUK Present address:NEC Laboratories Europe GmbH Kurfürsten-Anlage 3669115 HeidelbergGermany

Chemically complex multicomponent alloys possess exceptional properties derived from an inexhaustible compositional *** complexity however makes interatomic potential development *** explore two complementary machine-learned potentials—the moment tensor potential(MTP)and the Gaussian moment neural network(GM-NN)—in simultaneously describing configurational and vibrational degrees of freedom in the Ta-V-Cr-W alloy *** models are equally accurate with excellent performance evaluated against *** achieve root-mean-square-errors(RMSEs)in energies of less than a few meV/atom across 0 K ordered and high-temperature disordered configurations included in the *** for compositions not in training,relative energy RMSEs at high temperatures are within a few meV/***-temperature molecular dynamics forces have similarly small RMSEs of about 0.15 eV/Åfor the disordered quaternary included in,and ternaries not part of *** achieve faster convergence with training size;GM-NNs are faster in *** learning is partially beneficial and should be complemented with conventional human-based training set generation.

关键词： alloy faster complex