Phonon dispersions in random alloys: a method based on special quasi-random structure force constants

Wang, Yi; Zacherl, Chelsey L.; Shang, Shun‐Li; Chen, Lei; Liu, Zhe

doi:10.1088/0953-8984/23/48/485403

Cited by 27 publications

(24 citation statements)

References 36 publications

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“…A similar approach has recently been employed to study thermodynamic properties of other refractory alloys (HfNbZr, HfNbTiZr, and HfNbTaTiZr) [32]. Note that despite recent progress in the computation of phonons for disordered binary alloys [33,34], these methods have not yet been advanced to the stage where they are applicable to multi-componen alloys.…”

Section: Resultsmentioning

confidence: 99%

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

Körmann

Sluiter

2016

Entropy

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Refractory high entropy alloys (HEA), such as BCC NbMoTaW, represent a promising materials class for next-generation high-temperature applications, due to their extraordinary mechanical properties. A characteristic feature of HEAs is the formation of single-phase solid solutions.For BCC NbMoTaW, recent computational studies revealed, however, a B2(Mo,W;Nb,Ta)-ordering at ambient temperature. This ordering could impact many materials properties, such as thermodynamic, mechanical, or diffusion properties, and hence be of relevance for practical applications. In this work, we theoretically address how the B2-ordering impacts thermodynamic properties of BCC NbMoTaW and how the predicted ordering temperature itself is affected by vibrations, electronic excitations, lattice distortions, and relaxation energies.

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Section: Resultsmentioning

confidence: 99%

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

Körmann

Sluiter

2016

Entropy

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“…Previous works addressing phonons in disordered alloys have been mostly limited to binaries. [22][23][24][25][26][27] A few works have been devoted to vibrational properties of multi-component alloys, 16,[28][29][30][31] but were mainly focused on integrated quantities such as the phonon density of states 28 or thermodynamic properties such as lattice specific heat, typically derived from simplified Debye-like models. 29,30 Phonon spectra and in particular mass and force constant induced phonon broadening remain unexplored.…”

Section: Introductionmentioning

confidence: 99%

Phonon broadening in high entropy alloys

et al. 2017

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Refractory high entropy alloys feature outstanding properties making them a promising materials class for next-generation hightemperature applications. At high temperatures, materials properties are strongly affected by lattice vibrations (phonons). Phonons critically influence thermal stability, thermodynamic and elastic properties, as well as thermal conductivity. In 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 broadening. Despite their importance, phonon scattering and broadening have so far only scarcely been investigated for high entropy alloys. We 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 phonons. We find that it is crucial to include both mass and force constant fluctuations. If one or the other is neglected, qualitatively wrong results can be obtained such as artificial phonon band gaps. We analyze how the results obtained for the phonons translate into thermodynamically integrated quantities, specifically the vibrational entropy. Changes 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 considerations. The set of studied alloys includes MoTa, MoTaNb,

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“…Even though the Additional information discrepancies on lattice stability between the classic CALPHAD modeling and DFTbased first-principles calculations still exist [123] progresses have been made to narrow the differences such as bcc Ti [124] and fcc W [125], even for liquid solution phases [44]. The efficient special quasirandom structures (SQS) approach [126][127][128] is particularly useful in predicting the enthalpy and entropy of mixing in solid solution phases using phonon or Debye models [129,130]. Consequently, the thermodynamic model parameters of all individual phases can be evaluated solely from DFT-based first-principles calculations.…”

Section: Espeimentioning

confidence: 99%

The development of phase-based property data using the CALPHAD method and infrastructure needs

Campbell

Kattner

Liu

2014

Integr Mater Manuf Innov

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Initially, the CALPHAD (Calculation of Phase Diagrams) method was established as a tool for treating thermodynamics and phase equilibria of multicomponent systems. Since then the method has been successfully applied to diffusion mobilities in multicomponent systems, creating the foundation for simulation of diffusion processes in these systems. Recently, the CALPHAD method has been expanded to other phase-based properties, including molar volumes and elastic constants, and has the potential to treat electrical and thermal conductivity and even two-phase properties, such as interfacial energies. Advances in the CALPHAD method or new information on specific systems frequently require that already assessed systems be re-assessed. Therefore, the next generation of CALPHAD necessitates data repositories so that when new models are developed or new experimental and computational information becomes available the relevant low-order (unary, binary, and ternary) systems can be re-assessed efficiently to develop the new multicomponent descriptions. The present work outlines data and infrastructure needs for efficient CALPHAD assessments and updates, highlighting the requirement for data repositories with flexible data formats that can be accessed by a variety of tools and that can evolve as data needs change. Within these repositories, the data must be stored with the appropriate metadata to enable the evaluation of the confidence of the stored data.Keywords: CALPHAD; Thermodynamics; Diffusion; Property data; Data and file repositories; Materials data infrastructure ReviewThe first efforts using computational methods to describe Gibbs energy functions to represent the phases and describe phase equilibria were made more than 60 years ago as reviewed in [1]. However, only after computers became available did these efforts become systematic. In 1970, Kaufman and Bernstein [2] presented a collection of analytical thermodynamic descriptions of the Gibbs energy of the phases of binary and ternary systems as functions of temperature and concentration. These descriptions could be used for the calculation of phase equilibria and thermochemical properties in a large number of systems. This collection established the CALPHAD method as a valuable tool for the treatment of multicomponent a phase equilibria and spawned the development of several software packages and databases with collections of thermodynamic descriptions of multicomponent systems [1]. However, it soon became

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Phonon dispersions in random alloys: a method based on special quasi-random structure force constants

Cited by 27 publications

References 36 publications

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

Interplay between Lattice Distortions, Vibrations and Phase Stability in NbMoTaW High Entropy Alloys

Phonon broadening in high entropy alloys

The development of phase-based property data using the CALPHAD method and infrastructure needs

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