Long-ranged interactions in bcc NbMoTaW high-entropy alloys

Figures & data

Figure 1. Pair interactions in the HEA NbMoTaW in [001] (circles), [011] (triangles) and [111] (squares) direction for (a) Mo-Ta, (b) Mo-Nb and (c) Ta-W. Long-ranged chemical interactions in [111] are highlighted in subfigure (a). First nearest-neighbor interactions are not shown to facilitate visualization.

Figure 2. The ground state of the HEA NbMoTaW consists of B2(Mo;Ta) (blue and yellow) and B32(Nb;W) (red and silver). The simulation box contained 27,648 atoms.

Figure 3. Specific heat capacity (a)–(d) and site occupation (e)–(h) for different scenarios of included pair interactions. The B2 ordering temperature is decreased by almost a factor of 2 if long-ranged interactions are taken into account. For nearest-neighbor interactions (p_max = 1), the computed site occupancies (e) are compared with previous results obtained in [15].

Figure 4. B2 ordering energies depending on the range of included interactions for MoTa (a), MoNb and TaW both (b) The suppression of the B2 order–disorder transition temperature is directly related to the increase in the B2 ordering energies of the individual dominant ordering pairs.

Figure 5. Pairwise short-range order parameter in the HEA at 1300 K computed from Monte Carlo simulations. (a) SRO reveals signatures of the B2(Mo,W;Ta,Nb) ordering. Ta-Mo pairs show the strongest SRO tendencies. (b) SRO parameters for TaMo for various scenarios of included chemical interactions reveal the necessity of including long-ranged interactions.

Huhn WP. Thermodynamics from first principles: prediction of phase diagrams and materials properties using density functional theory [dissertations]. 2014.

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