Role of vacancies in structural thermalization of binary and high-entropy alloys

13 June 2023, Version 1
This content is a preprint and has not undergone peer review at the time of posting.


Vacancy assisted atomic self-diffusion is a major structural thermalization mechanism in bulk metal alloys. Depending on alloy composition, the local atomic environments might stabilize vacancies to such extent that the vacancies become trapped and the atomic self-diffusion part of the thermalization process stalls. The consequence is that such alloys get kinetically trapped in disordered structures. In this study, we investigate equimolar AgAu, CuPt, AgPdPtIr, and AgAuCuPdPt alloy thermalizing using Metropolis Monte Carlo simulations in two approaches, one where the alloy structure changes through vacancy migration and one where the structure changes by swapping atomic pairs. By comparing the two approaches, we find that the vacancy is less effective at thermalizing alloys with more elements (i.e. AgPdPtIr and AgAuCuPdPt), more heterogeneous configurational energy distributions (i.e. CuPt and AgPdPtIr), and strong interactions between certain elements, e.g. Ir-Ir interactions in AgPdPtIr. In the case of AgPdPtIr, the vacancy cannot thermalize Ir-Ir neighbors even when the vacancy is mobile, because the vacancy has difficulty breaking individual Ir-Ir pairs apart.


Computational thermodynamics
Atomistic simulations
Ab initio calculations
Theory and modeling
out of equilibrium modeling

Supplementary materials

Supplementary material to Role of vacancies in structural thermalization of binary and high-entropy alloys
Average energy of Gaussian distributed energy states, DFT settings for calculating alloy formation energies, details regarding the chi-squared test and P-values, average energy is plotted as <E>/σ, and energies along the MC trajectories.


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