<i>Ab initio</i>
 surface free energies of tungsten with full account of thermal excitations

Forslund, Axel; Ruban, Andrei V.

doi:10.1103/physrevb.105.045403

Cited by 12 publications

(10 citation statements)

References 46 publications

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“…Thermodynamic properties to the melting point for other systems such as Cu, Ni, Al, and W have also been calculated using TU-TILD in previous works. The results show remarkable agreement to experimental data [26,27].…”

Section: Introductionsupporting

confidence: 89%

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Thermodynamics up to the melting point in a TaVCrW high entropy alloy: Systematic ab initio study aided by machine learning potentials

et al. 2022

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Multi-principal-component alloys have attracted great interest as a novel paradigm in alloy design, with often unique properties and a vast compositional space auspicious for materials discovery. High entropy alloys (HEAs) belong to this class and are being investigated for prospective nuclear applications with reported superior mechanical properties including high-temperature strength and stability compared to conventional alloys. Computational materials design has the potential to play a key role in screening such alloys, yet for high-temperature properties, challenges remain in finding an appropriate balance between accuracy and computational cost. Here we develop an approach based on density-functional theory (DFT) and thermodynamic integration aided by machine learning based interatomic potential models to address this challenge. We systematically evaluate and compare the efficiency of computing the full free energy surface and thermodynamic properties up to the melting point at different stages of the thermodynamic integration scheme. Our new approach provides a ×4 speed-up with respect to comparable free energy approaches at the level of DFT, with errors on high-temperature free energy predictions less than 1 meV/atom. Calculations are performed on an equiatomic HEA, TaVCrW-a low-activation composition and therefore of potential interest for next generation fission and fusion reactors.

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Section: Introductionsupporting

confidence: 89%

“…In order to account fully for anharmonicity, we performed TU-TILD calculations from each of the references up to DFT. According to the conventional TU-TILD formalism that has been well established for known systems in the literature [23,[26][27][28], the free energy difference between the reference and full DFT energy is given by…”

Section: Tu-tildmentioning

confidence: 99%

Thermodynamics up to the melting point in a TaVCrW high entropy alloy: Systematic ab initio study aided by machine learning potentials

et al. 2022

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“…The socalled moment tensor potentials (MTPs) 28 have proved to be one of the most efficient machine-learning potentials [29][30][31] . The application of MTPs within the TU-TILD formalism has further improved the efficiency of free-energy calculations 18,32 .…”

Section: Introductionmentioning

confidence: 99%

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

et al. 2023

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Accurate prediction of thermodynamic properties requires an extremely accurate representation of the free-energy surface. Requirements 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 far. Here, 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 vibrations. The improved methodology has a five-times speed-up compared to state-of-the-art methods. We 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 Nb. The introduced procedure paves the way for the development of ab initio thermodynamic databases.

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“…We applied the two-stage up-sampled thermodynamic integration using Langevin dynamics method, which treats the interatomic potential as an intermediate reference potential in the thermodynamic integration. The thermodynamic integration is split in two stages: first, from the harmonic to the reference potential and, secondly, from the reference potential to full DFT [38]. In the framework of this study, a modified version of the original TU-TILD method was utilized.…”

Section: B Anharmonic Free Energy Calculationsmentioning

confidence: 99%

“…Here we report the calculated free energies of the ( 111) and ( 110) ceria surfaces at temperatures up to 2100 K. The values were calculated with the extended two-stage upsampled thermodynamic integration using Langevin dynamics (TU-TILD) method [31,32]. This method was previously applied in the free energy calculations of various metallic systems, including vacancy formation free energies [33], stacking fault free energies [31] as well as the surface free energy of TiN [34] and W [35]. In the current study TU-TILD was combined with machine-learning potentials, in particular, the moment tensor potentials (MTP) [36], which were trained on the results of ab initio molecular dynamics (AIMD) calculations [37].…”

Section: Introductionmentioning

confidence: 99%

Temperature dependence of (111) and (110) ceria surface energy

et al. 2023

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High temperature properties of ceria surfaces are important for many applications. Here we report the temperature dependences of surface energy for the ( 111) and (110) CeO2 obtained in the framework of the extended two-stage upsampled thermodynamic integration using Langevin dynamics (TU-TILD). The method was used together with machinelearning potentials called moment tensor potentials (MTPs), which were fitted to the results of the ab initio MD calculations for ( 111) and (110) CeO2 at different temperatures. The parameters of MTPs training and fitting were tested and the optimal algorithm for the ceria systems was proposed. We found that the temperature increases from 0 K to 2100 K led to the decrease of the Helmholtz free energy of (111) CeO2 from 0.78 J/m 2 to 0.64 J/m 2 . The energy of (110) CeO2 dropped from 1.19 J/m 2 at 0 K to 0.92 J/m 2 at 1800 K. We show that it is important to take anharmonicity into account as simple consideration of volume expansion gives wrong temperature dependences of the surface energies.I.

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Ab initio surface free energies of tungsten with full account of thermal excitations

Cited by 12 publications

References 46 publications

Thermodynamics up to the melting point in a TaVCrW high entropy alloy: Systematic ab initio study aided by machine learning potentials

Thermodynamics up to the melting point in a TaVCrW high entropy alloy: Systematic ab initio study aided by machine learning potentials

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

Temperature dependence of (111) and (110) ceria surface energy

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