Short-range order and compositional phase stability in refractory high-entropy alloys via first-principles theory and atomistic modeling: NbMoTa, NbMoTaW, and VNbMoTaW

Abstract

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Interplay between magnetism and short-range order in medium- and high-entropy alloys: CrCoNi, CrFeCoNi, and CrMnFeCoNi

“…One notable disagreement between our results and those of earlier works is described in the recent study by Ghosh et al [35], which predicted MoPt 2 -like order emerging at 975 K in CrCoNi. Simulations using low-rank interatomic potentials have previously been in good agreement with results obtained using our approach when modelling refractory HEAs [13,45], so this discrepancy is surprising. We note that a recent experimental study by Li et al [19] performed annealing of CrCoNi at a variety of temperatures, including one sample annealed at 673 K for 500 h. They found evidence of increasing ASRO in their samples, but no evidence of a long-range ordered state was reported.…”

“…The inclusion of these effects is similar to the approach taken in Density Functional Perturbation Theory (DFPT) [42,43], used to describe lattice dynamics ab initio and response functions for phonons, etc. Full details of our theory and extensive discussion can be found in earlier works [41,44,45]. Our calculations assume a fixed ideal lattice, face-centred cubic (fcc) for the alloys studied in this paper, which represent the averaged atomic positions in the solid solution.…”

“…The site-wise chemical potentials serve as Lagrange multipliers in the linear response theory, but as their variation is not considered to be relevant to the underlying physics, terms involving these derivatives are dropped [41,44,45]. The symmetry of the high-temperature, homogeneous state -the solid solution -and the requirement that any imposed fluctuation conserves the overall concentrations of each chemical species ensures that the first-order term vanishes.…”

“…αα (k) by means of a backwards Fourier transform, with the mapping from reciprocal-space to real-space and fixing of the gauge degree of freedom as specified in earlier works [41,44,45].…”

Interplay between disorder and electronic correlations in compositionally complex alloys

“…However, the substantial deviation from the experimental value of 105 µΩcm could be influenced by potential short-range ordering [54][55][56] , which has been experimentally shown increase resistivity 57 . Such mechanisms are not included within the CPA framework and need to be captured with more sophisticated methodologies like non-local CPA 58,59 . The localization mechanism must also be considered.…”